Diet and Obesity: The Role of Carbohydrates
David S. Ludwig
Children's Hospital, Boston; Associate Professor, Harvard Medical School
Reduction in dietary fat has been widely advocated for the prevention and treatment of
obesity. However, the efficacy of low fat diets has been questioned in recent years.
One potential adverse effect of a low fat diet is a compensatory increase in consumption
of high glycemic index (GI) carbohydrate, principally refined starchy foods and
concentrated sugar. Such foods can be rapidly digested or transformed into glucose,
causing a large increase in postprandial blood glucose and insulin. Mechanisticallyoriented studies suggest that consumption of a high GI diet elicits hormonal changes
that limit availability of metabolic fuels, with important consequences for energy intake
and expenditure. There are over 50 clinical trials and epidemiological studies of GI in
the medical literature, a majority of which has found beneficial effects of a reduced GI
diet on outcomes related to obesity, diabetes mellitus and cardiovascular disease.
Ongoing inconsistency in findings among published studies likely arises from lack of
consensus on proper methodology. Based on available evidence, a low GI diet may be
an optimal compromise between the low fat diet at one end of the spectrum, and the
very low carbohydrate (Atkins’) diet at the other.
Communication about starch: fairy tales, diets and science
Birgitte Sloth and Arne V. Astrup
Department of Human Nutrition, Centre for Advanced Food Studies, The Royal
Veterinary and Agricultural University, Frederiksberg, Denmark, bsl@kvl.dk.
In recent years starch has been made the culprit for obesity and related diseases by
many popular low carbohydrate diets. It is the higher glycemic and insulinemic response
following a starch rich meal that is hypothesized to result in increased risk of developing
obesity, diabetes and cardiovascular disease. However, different starches can result in
very different glycemic responses. The glycemic index (GI) was introduced 25 years ago
in order to rank different carbohydrate rich foods according to their glycemic response.
GI is defined as the incremental area under the 2 hour blood glucose response curve
after ingestion of a 50 g carbohydrate portion of the test food. This is expressed in
percentage of the same area under the curve following the intake of 50 g carbohydrate
from a reference food ingested by the same subject. The GI should be tested in 10
subjects, and the reference food should be repeated 3 times in each subject.
Although the GI was introduced 25 years ago, the effect of low GI diets on body weight
is still much debated. Many studies have been performed, but they are often biased by
confounding factors such as fiber content and macronutrient composition, making it
difficult to draw conclusions regarding the effects of the GI per se. Current official
dietary recommendations of USDA, Australia and the Nordic countries advise high
intake of fruit and fiber, low intake of added sugar, and some recommend whole grain.
The question is whether these recommendations might benefit from utilizing GI.
Another question is whether the GI is a feasible dietary recommendation. Although the
latest international table offers GI values for more than 750 different types of food, the
use of these tables to predict the GI of food and meals has proven difficult. This is due
to the fact that many different factors influence glycemic response. Testing and labeling
of each food seems therefore to be necessary if the public are to be able to choose low
GI foods.
An alternative approach to the GI is to focus on individual food factors, such as the
effect of whole grain including intact grains, resistant starch and energy density. This
would allow for more tightly controlled trials, with simpler conclusions and less
confounding factors, and eventually lead to simpler dietary advice with assured efficacy.
2
Introduction of EUROSTARCH and scope of the symposium
Roel J. Vonk and Marion G. Priebe
University Medical Center Groningen, Groningen, The Netherlands
Starch is the most important source of energy. In spite of that, the information about the
metabolic quality of starchy foods is scarce.
Much of the discussions about the metabolic quality of starchy food is focused on the
discussion about the glycaemic response and the from it derived glycaemic index (GI).
The glycaemic response is not only determined by the characteristics of the starch, but
also by other meal components, the gastric emptying rate, the endogenous glucose
synthesis and the characteristics of a previous meal. An objection in the use of the GI as
parameter of the metabolic quality of food is that a low GI not necessarily needs to be
the result of the digestive characteristics of the starch, but can also be achieved by
addition of fat which is not compatible with a healthy nutritional profile. Another objection
is its limited reflection of the metabolic effects of starchy foods. A low influx of glucose
over a long period as compared to a high and short influx results not only in lower
glycemia but also in differences in insulinemia, suppression of endogenous glucose
synthesis and other metabolic parameters which are likely to be relevant for the
prevention of disease.
We conclude that the GI can be useful for characterization of starchy foods, labeling of
food products, nutritional epidemiology and communication about health. However, to
establish the overall metabolic quality of starchy foods and to investigate in detail
physiological and metabolic effects related to various starchy foods more specific
parameters reflecting starch characteristics are needed as well as knowledge of other
relevant metabolic parameters.
In the EUROSTARCH project the dual isotope technique was applied which comprises a
continuous D-[6,6-2H2]glucose infusion and the ingestion of a starchy meal labeled with
the stable isotope 13C. With this technique the rate of appearance of exogenous glucose
can be estimated, reflecting the net rate of intestinal glucose absorption. 13C-labeled
starchy foods were produced from wheat cultured under 13CO2 atmosphere. This
method was applied in several of our studies and we analysed the relation between the
net influx rate of glucose to other metabolic parameters like lipid metabolism and incretin
response.
To study biological effects like cognitive function and mental performance experiments
were conducted using test meals differing in post meal glycaemia.
We also developed methods to analyse the fermentation of 13C-labelled resistant starch.
Health aspects in relation to the fermentation of starchy foods are colon cancer, which
we did not address, as well as obesity and type 2 diabetes. In relation with this we
investigated the improvement of the glucose tolerance caused by a previous low GI
meal rich in resistant starch and dietary fiber. 13C-labelled barley was produced for
fermentation studies measuring 13C- short chain fatty acids in plasma.
Accumulation of evidence for health benefits of slowly digestible starch could also be
useful to convince food industry to alter the processing technique, which will be
discussed.
We expect that the results of the EUROSTARCH project will contribute to efficient
discussions about the metabolism of starch and its relevance for health and disease.
3
The glycaemic index concept: past and future
Cyril W.C. Kendall and David J. A. Jenkins
Department of Nutritional Sciences, Faculty of Medicine, University of Toronto;
Clinical Nutrition & Risk Factor Modification Center, St. Michael’s Hospital;
Toronto, Ontario, Canada M5S
Fiber-rich foods to a reduced risk of type 2 diabetes and coronary heart disease in
epidemiological studies. The “fiber hypothesis” suggested that this was a direct effect of
fiber. The glycemic index concept is an extension of the fiber hypothesis suggesting
that fiber would reduce the rate of nutrient influx from the gut. It has particular relevance
to those chronic Western diseases associated with central obesity and insulin
resistance. However, other properties and components of food other than its fiber
content contribute to the glycemic and endocrine responses postprandially. The aim of
the glycemic index classification of foods was therefore to assist in the physiological
classification of carbohydrate foods which, it was hoped, would be of relevance in
prevention and treatment of chronic diseases such as diabetes.
Early studies demonstrated starchy carbohydrate foods had very different effects
on postprandial blood glucose and insulin responses in healthy and diabetic subjects
depending on the rate of digestion. A range of factors associated with foods, including
soluble fiber, were shown to alter the rate of glucose absorption and the subsequent
glycemic and insulinemic responses. Carbohydrate rich foods were tested and the
resulting glycemic index classification of foods provided a numeric physiological
classification of carbohydrate foods of relevance in prevention and treatment of
diseases such as diabetes.
More recently, low glycemic index diets have been reported to improve glycemic
control in diabetic subjects, to reduce serum lipids in hyperlipidemic subjects and
possibly to aid in weight control. In large cohort studies, low glycemic index or glycemic
load diets (glycemic index multiplied by total carbohydrate) have also been associated
with higher levels of high-density lipoprotein cholesterol (HDL-C), reduced C-reactive
protein (CRP) concentrations and with decreased risk of developing diabetes and
cardiovascular disease. More recently, some case-control and cohort studies have also
found positive associations between dietary glycemic index and the risk of colon, breast
and other cancers.
While the glycemic index concept continues to be debated and there remain
inconsistencies in the data, sufficient positive findings have emerged to suggest that the
glycemic index is an aspect of diet of potential importance in the treatment and
prevention of chronic diseases.
4
Effect of food processing on the digestibility of cereal products
Gwenaelle FUZELLIER, Alexandra MEYNIER, Stéphanie LOYER, Vincent
LANG, Sophie VINOY
Nutrivaleur, Danone Vitapole, Palaiseau, France
Altering the carbohydrates quality of cereal products is likely to have an effect in
nutrition, as they are the main source of energy. Analytical procedures have been
developed to characterise dietary carbohydrates with respect to chemical composition
and likely gastrointestinal fate (Englyst et al., 1992; Englyst et al, 1999). Rapidly (RAG)
and Slowly available glucose (SAG) describe the likely rate at which glucose from starch
and sugars becomes available for absorption from the small intestine. The aim of the
project was 1) to evaluate the impact of food processing on the digestibility of cereal
products by measuring the change in the composition of glycaemic carbohydrates
during processing and 2) to evaluate the influence of lipids on the GI of processed
cereal products.
METHODS : i) in part 1, three cereal products (1 plain biscuit (PB), a white bread (WB)
and a ready to eat cereal (RTEC) differing by their food process (baking, soft baking in
high moisture conditions and extrusion) were analyzed for their SAG content (Englyst et
al. 2000) at each stage of food processing, ii) in part 2, seven cereal products (1 PB
containing 12 g/100 g lipids, 3 RTEC and 3 toasted bread (TB) containing 2, 6 or 12
g/100 g lipids) were analyzed for their SAG content and their GI according to the
FAO/WHO method (1998). For each level of fat, the amounts of the other
macronutrients were similar.
RESULTS : In part 1, the dough contains the same quantity of SAG for the 3
technologies (51-56% of SAG/Total CHO), whereas a dramatic decrease of SAG
occurred during extrusion process (high pressure) and during soft baking process (high
humidity). In the final product, PB had the highest level of SAG (17.2g/100g) compared
to the RTEC (1.3g/100g) and the WB (0.5g/100g). In part 2, for both TB and RTEC,
increasing fat content (from 2 to 12 g/100g) has only a moderate effect on the decrease
of GI values (-11 and -7 GI units for TB and RTEC, respectively). Moreover, for
comparable level of fat (12 g/100 g), the PB with the highest SAG content displayed the
lowest GI value (GI = 41) which was 16 and 29 GI units lower than TB (GI= 57) and
RTEC (GI = 70) respectively.
CONCLUSION : Food processing influences the quality of the carbohydrates content.
Plain biscuits manufacturing led to high SAG products, minimally processed foods, while
soft baking in high moisture conditions or extrusion led to very low SAG products. These
results confirmed that fat content has only a minor influence on the GI compared to the
digestibility of carbohydrates in processed cereal products in this range of fat content.
5
Metabolic effects of Low or High Glycaemic Index starch : can
we go further than the GI concept
M. Laville1, A. De Rougemont1, M. Desage1, V. Sauvinet1, J.A. Nazarre1, S.
Vinoy2, S. Normand1
1
CRNH Rhône-Alpes, Lyon, France, 2Danone Vitapole, Palaiseau, France
The glycaemic index has been developed in order to classify food according to the
glycaemic response after ingestion. Although this parameter is of interest, especially for
people prone to glucose intolerance, some limitations could be underlined.
First, it is limited to the ingestion of the food alone which is not a physiological
condition.
Second, it is limited to 2 hours post prandial, whereas physiological phenomena
last much longer.
Third, it is limited to glycaemia, however glucose metabolism is more complex
involving insulin secretion, stimulation of glucose utilisation, inhibition of
endogenous glucose production.
Forth, glycaemic response could be manipulated by adding to food different
product: fructose, fat, fibres with large differences in metabolic consequences
and potential health benefit and these parameters should be taken into account
in addition to GI.
We will show the evolution of the different parameters of glucose metabolism after the
ingestion of glucose compared to pasta with or without fat. This will highlight that
glucose metabolism events last much more than 2 hours and that the evolution of
endogenous glucose production is able to modulate the glycaemic response.
During the EUROSTARCH project, glucose metabolism of a High GI breakfast has
been compared to a Low GI one in overweight subjects. These breakfasts were similar
in calories and macronutrients content but resulted from different technological process:
flakes vs biscuits and exhibited differences in Rapid Available Glucose and Slow
available Glucose. When using 13C labelled starch we were able to show important
differences in exogenous glucose appearance between the HGI and the LGI breakfast.
Differences in glycaemia were also found but they were less pronounced due to a
modulation by endogenous glucose production which was less inhibited during LGI
breakfast. Differences between acute and chronically ingestion have also been found.
In conclusion, GI is useful to classify starches but could not resume all the metabolic
properties of the food. The metabolic results could be modulated by the others
components of the meal and late metabolic events have also to be taken into account.
6
Systemic rate of appearance of starch derived glucose and the
secretion of incretin hormones
Renate E. Wachters-Hagedoorn*, Marion G. Priebe*, Janneke A.J.
Heimweg*, A. Marius Heiner*, Klaus N. Englyst**, Jens. J. Holst#, Frans
Stellaard*, Roel J. Vonk*
*Department of Pediatrics, Laboratory Nutrition and Metabolism. University Medical
Center Groningen, Groningen, The Netherlands, **Englyst Carbohydrates – Research
and Services, Southampton, UK, #Department of Medical Physiology, University of
Copenhagen, Copenhagen, Denmark.
Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide
(GIP) play a role in the control of glucose homeostasis and GIP is implicated in the
regulation of energy storage. The capacity of carbohydrates to induce secretion of these
incretin hormones, could be one of the factors determining the metabolic quality of
different types of carbohydrates.
We aimed to analyze the correlation between the rate of intestinal absorption of (starch
derived) glucose and plasma concentrations of GLP-1 and GIP after ingestion of
glucose and starchy foods with different content of rapidly and slowly available glucose.
In a crossover study glucose, insulin, GLP-1 and GIP concentrations were monitored
during 6 h following consumption of glucose, uncooked corn starch (UCCS) or corn
pasta in 7 healthy male volunteers. All test meals were naturally labeled with 13C. Using
a primed-continuous D-[6,6-2H2]glucose infusion, the rate of appearance of exogenous
glucose (RaEx) was estimated, reflecting the rate of intestinal glucose absorption.
GLP-1 concentrations were significantly increased during 180 to 300 min after ingestion
of UCCS - the starch product with a high content of slowly available glucose. A high GIP
response in the early postprandial phase (15 - 90 min) was observed after consumption
of glucose. There was a strong positive within-subject correlation between RaEx and
GIP concentrations (r = 0.73, P < 0.01) across the test meals.
Rapidly and slowly digestible carbohydrates have been shown to differ considerably in
their potency to stimulate secretion of incretin hormones; the metabolic consequences
of which need to be explored.
7
Influence of low GI cereal food on postprandial metabolism
S. Vinoy1, A. Meynier1, G. Fuzellier1, S. Normand2, M. Laville2, V. Lang1
1
Danone Vitapole, Palaiseau, France, 2CRNH Rhône-Alpes, Lyon, France
The metabolic effects of carbohydrate-rich foods is very much influenced by their quality
(Jenkins et al.1981; Ludwig et al. 2002). Low glycemic index (GI) meals based on slowly
available glucose (SAG) digestibility may have some beneficial postprandial metabolic
effects. The aim of the work was to review three studies which evaluated the
postprandial effects of cereal products differing in the CHO digestibility and their GI
values on 1) their glycemic, insulin and gastric inhibitory peptide (GIP) responses 2)
because of different exogenous appearance rate of glucose (RaE), when the cereal
products are consumed within a meal.
METHODS. Each of the three clinical trials were conducted on 12 to 13 healthy subjects
in a randomised cross over design (total 37 subjects). Two breakfasts per study were
tested with the same principle : the meals had similar quantities of macronutrients, and
represented around 20% of daily energy intake. The only difference between the
breakfasts was the quality of the carbohydrates of the cereal products: either a low GI
biscuit containing high quantity of SAG (15-16g/100g) (“low GI breakfast”), either
medium to high GI extruded cereals containing low quantity of SAG (<2g/100g) (“high GI
breakfast”). For the measurement of the RaE, the carbohydrates of both cereal products
were specifically labelled with 13C-glucose. Blood parameters such as glycaemia,
insulinemia, GIP concentrations, and RaE, total appearance rate of glucose (RaT),
exogenous disappearance rate of glucose (RdE) were measured during the postprandial
period (270 min).
RESULTS. Low GI biscuits included in a breakfast induced significant lower glycemic
and insulin response in two clinical trials : -43% and –29% reduction of the area under
the curve between T0-T120min (AUC0-120) for glycemia; -26% and -29% reduction of the
AUC0-120 of insulin response, compared to the high GI breakfast. The GIP response was
significantly lower in the first part of the morning after the Low GI breakfast. Moreover,
AUCi for GIP tended to be higher after the low GI breakfast, compared to the high GI
breakfast on the second part of the morning (120-270 min.; p = 0.08). The RaE after low
GI breakfast decreased significantly at T90, T120, T150 and increased at T210
compared to high GI breakfast. Furthermore, the total amount of exogenous
carbohydrates, based on the AUC calculation, was significantly lower after the low GI
breakfast during all the morning.
CONCLUSION. Low GI cereal products included in realistic breakfasts, with low GI and
high SAG content induced a slow release of carbohydrates during the morning, which
led to reduced glycemic, insulinemic and GIP responses in the first part of the morning
and especially at the peak of glucose and insulin concentrations. These results confirm
the important role of slow digestible CHO on metabolism and show that more insights
are necessary in order to settle recommendations based on CHO digestibility for public
health.
8
Modulating the glycaemia of starchy foods; acute and semi-acute
effects
Inger Björck, Anne Nilsson, Elin Östman
Applied Nutrition and Food Chemistry, Department of Food Technology, Engineering
and Nutrition, Lund University, Sweden
Introduction
A diet characterised by a low Glycaemic Index (GI) is increasingly being implicated as
protective in relation to development of type 2 diabetes, myocardial infarction and
dysmetabolic syndrome. Additionally, there are strong epidemiological evidence that
whole grain food protects against heart disease and type 2 diabetes. Apart from being
rich in cereal fibre, whole grain products are rich in associated bioactive compounds
such as phytochemicals and micronutrients, with potential metabolic impact. Certain
whole grain cereals also display a lower GI. Thus, a new generation cereal products
should preferably be whole grain and of low GI.
Objective
Food factors that could be utilized for design of low GI whole grain foods will be
discussed, and tools for quality assurance of the GI features will be addressed.
Results and conclusion
Most low GI cereal products improve glucose tolerance in the perspective from
breakfast to lunch in healthy subjects, which might contribute to the long term benefits
with low GI diets. This phenomenon probably relates to the lente features per se. A low
GI evening meal consisting of boiled barley kernels also reduced glucose response and
insulin demand at a subsequent standardized breakfast. In contrast, whole meal barley
porridge was not effective, suggesting that the low GI of the barley kernels and/or some
other entity connected to the preservation of the botanical structure was involved.
Results from the EUROSTARCH project indicate that colonic fermentation of resistant
starch and dietary fibre present in the barley kernels and formation of short chain fatty
acids at the time of the breakfast meal suppress free fatty acid levels at this time point
thus improving glucose tolerance in the perspective from evening meal to breakfast.
More knowledge in this area may provide additional tools for design of low GI whole
grain cereal foods with optimal long-term metabolic benefits.
9
Metabolic and physiologic impact of starch fermentation
Martine Champ, Henri Dumon, Véronique Ferchaud-Roucher, Michel
Krempf, Lucile Martin Catherine Michel, Jean Ménanteau, Noëlle Moreau,
Jean-Pierre Segain
Human Nutrition Research Centre, Nantes, France
The fraction of starch which is fermented in the colonic lumen of human by the microbial
flora is qualified of ‘resistant starch’ (RS). Indeed RS is defined as ‘the sum of starch
and products of starch degradation not absorbed in the small intestine of healthy
individuals’. This definition includes different types of starch that (1) are physically
inaccessible, usually due to an encapsulation in intact cell walls, or (2) are naturally
resistant to endogenous α-amylase, or (3) have been modified by hydrothermic
treatments then retrograded or (4) chemically modified with a high degree of reticulation
or substitution.
As for any dietary fibre or fermentable carbohydrate, the fermentation of RS produces,
short chain fatty acids (SCFA, mainly acetate, propionate and butyrate) but also other
organic acids, such as lactic acid, and gases. Among SCFA, butyrate plays an important
physiological role in maintaining the health and integrity of the colonic mucosa. It
provides the primary energy source for the colonic epithelium and also regulates
epithelial cell growth and differentiation. Numerous studies have shown that butyrate
may be an important protective agent in colonic carcinogenesis. Anti-tumour effects
include inhibition of cell proliferation, stimulation of cell differentiation, and induction of
apoptosis. The underlying molecular mechanisms of these pleiotropic effects seem to
mainly involve the regulation of gene transcription by inhibiting histone deacetylase
activity. Thus, a growing interest for the consumption of RS has been observed in the
last decades, mostly due to its capacity to produce a large amount of butyrate in the
colon. However, until now, no results of the ongoing intervention trials on RS and cancer
risk have been published but animal studies revealed apparently contradictory results
depending on the animal model and the type of the RS used. RS is recognized by some
authors as a prebiotic stimulating intestinal lactic acid producing bacteria (i.e. mainly
bifidobacteria and lactobacilli). This property is probably associated to its ability to acidify
colonic lumen which is thought to be favourable to the proliferation of deleterious
microrganisms. It is also proposed that a lower pH in the colon induced by RS
fermentation may inhibit enzyme activities involved in the conversion of molecules such
as bile acids or nitrate into harmful compounds which have been implicated in
carcinogenesis.
More recently, new impacts of fermentation have been identified. Indeed fermentability
of dietary fibre is now evoked to explain the efficiency of dietary fibre consumption on
satiety and glycemia. The release of gut peptides such as glucagon-like-peptide-1 (GLP1) and/or gastric inhibitory polypeptide (GIP) appears to be associated with enhanced
postprandial carbohydrate handling the following day upon ingestion of a control meal.
This possible mechanism has been investigated in the case of RS by several authors.
Many studies have been performed to evaluate and to understand the potential benefits
of RS consumption. A lot is known but more research are necessary to be able to adapt,
quantitatively and qualitatively, RS intake to the requirements of different populations
such as patients with inflammatory disease or colon cancer, those who are in remission
phase or simply ‘at risk’ for such diseases and finally for the general healthy population.
The metabolic benefits of RS consumption in the prevention of insulin resistance
syndrome still require a lot of investigation to optimize its use with this objective.
10
Colon – Adipose Tissue Interactions
M Denise Robertson
School of Biomedical and Molecular Sciences, University of Surrey, Guildford GU2 7XH
UK.
Introduction: Insulin resistance (IR) and type 2 diabetes (T2DM) are becoming
increasingly common in Westernised societies in-line with the increased incidence of
obesity. In the UK, current figures estimate that 24 % of adult men are obese but of
greater concern, 14 % of children under the age of 10 years are also classified as
obese, with the implications this will have co-morbidity and mortality rates for the future.
The end-point of IR is a disorder of impaired glucose metabolism leading ultimately to
T2DM, however, for many the starting point for IR is as a disorder of fatty acid
metabolism and adipose tissue (AT) dysfunction. Lifestyle factors such as the increased
consumption of insoluble dietary fibres have been shown to be beneficial in improving
IR, however, the mechanisms, especially in terms of their effects upon the cause of IR,
AT dysfunction, were unknown.
Methods: We employed an integrative approach incorporating a dietary intervention,
measurements of insulin sensitivity, flux-rates of metabolites across peripheral tissues in
situ (skeletal muscle and AT) and biopsies to look at underlying changes in gene
expression. Ten healthy subjects underwent a randomized-crossover study where they
supplemented their habitual diet with either 30g/ day type 2 RS or a matched placebo
supplement for 4 weeks. At the end of the intervention insulin sensitivity was measured
by a hyperinsulinaemic-euglycaemic clamp and metabolite flux rates were measured
during a meal tolerance test (MTT). During the MTT, veins draining subcutaneous
abdominal AT and skeletal muscle were cannulated and arterio-venous concentrations
across tissues were calculated combined with measurements of tissue blood flow.
Tissue biopsies from both muscle and AT were analysed for mRNA expression of key
genes involved with glucose and lipid metabolism.
Results: As expected from our earlier studies, RS supplementation significantly
increased insulin sensitivity. There was a significant reduction in AT lipolysis; with a
reduction in both fatty acid and glycerol output from adipose tissue. There was a 3-fold
increase in the uptake of glucose by AT, however there was no effect on adipose tissue
blood flow directly. There were significant increases in plasma levels of the SCFA,
acetate and propionate, however, butyrate concentrations remained unaltered and at the
level of detection. With this A-V sampling technique we have been able to demonstrate
the uptake of both acetate and propionate into both muscle and adipose tissue. In AT
specifically there was a 15 % fractional extraction rate of acetate which appeared to be
a function of the arterial concentration, propionate however had a fractional extraction
rate of 14 % with the placebo, increasing to 35 % following RS supplementation,
implying a degree of AT adaptation.
Conclusion: RS significantly affects AT function, independently from other lifestyle
factors, however further work is required to determine the specific mechanisms involved.
11
Non-invasive measurement of exogenous acetate production
T.Preston1 and D. J. Morrison1, T.Preston@suerc.gla.ac.uk
Stable Isotope Biochemistry Laboratory, SUERC, Rankine Avenue, East Kilbride, G75
0QF, UK
Introduction: Acetate is quantitatively the most important short chain fatty acid (SCFA)
produced in the colon, principally by bacterial fermentation of non-digestible
carbohydrates (NDC). Portal acetate promotes hepatic lipogenesis; propionate may
reduce hepatic lipogenesis and cholesterologenesis; butyrate may improve bowel
health; SCFA may modulate gut motility and may moderate the glycaemic response to a
meal. Improved methodology is required to quantify the production of each SCFA.
Methods using stable isotope-labelled tracers have been applied to quantify total acetate
production and to derive exogenous acetate production by difference1. Tracer materials
produced by chemical synthesis (extrinsic labelling) have been termed simple
metaprobes2.
Previous methodology applied intravenous infusions of simple
metaprobes with blood sampling. A different approach is described here where
metaprobes are used orally in combination with urine sampling. This permits noninvasive measurement of acetate production over extended (~24 hours) periods typical
of NDC fermentation. When combined with improved analytical methods that we have
developed in parallel3, the approach can now be applied to measure low enrichments of
13C metaprobes with accuracy. Recent developments have included simultaneous
measurement of propionate and acetate production, of great relevance to studies of the
metabolic syndrome.
Methods: Initial validation studies in two healthy adult males were undertaken using
plasma sampling over 8 hours and urine sampling over 24 hours. This was to determine
i), that urine could be used where multiple blood samples had previously been used and
ii), that an oral metaprobe bolus could be used where previously a primed constant i.v.
infusion had been used. To facilitate this, 1-13C-acetate and 2H3-acetate were used.
Initial experiments confirmed tracer equivalence. Next, urine sampling showed that the
area under the curve of urinary tracer excretion yields essentially the same result as
plasma plateau–derived acetate production. This also showed a bolus tracer dose to be
equivalent to a 'pseudo' constant infusion (multiple oral doses). The new method was
then applied to the study of total acetate production in two subjects using test biscuits
baked with and without NDC (Table 1). The most recent experiment demonstrated that
propionate production can be estimated simultaneously with acetate.
Results: Total acetate and propionate production data in two healthy adults is given in
Table 1.
Treatment
Subject 1
mol/kg/min
1) NDC-free diet
2) As above with 20g Raftilose®
Exogenous acetate (difference)
3) As above with 20g raw potato starch
Exogenous acetate (difference)
2) Propionate production
Subject 2
mol/kg/min
13.2
23.1
9.9
17.8
4.6
5.5
27.9
37.7
9.8
32.7
4.8
3.3
Conclusions: A non-invasive method employing modest oral doses of 13C-labelled
SCFA and urine sampling has been developed to measure total acetate production. It
has also been applied to study acetate production from 13C-labelled resistant starch4.
12
The new method will be applied to measure total acetate and total propionate production
in relation to metabolic syndrome variables. Finally, as metaprobe delivery to the site of
SCFA production is preferred, future work will test oral formulations that deliver simple
metaprobes to the colon5.
References: 1Pouteau E, Piloquet H, Maugeais P, Champ M, Dumon H, Nguyen P, Darman D &
M Krempf (1996) Am J Physiol 271: E58-E64. 2Young VR & AM Ajami (2001) Metabolism 2000:
the emperor needs new clothes Proc Nutr Soc 60(1): 27-44. 3Morrison DJ, Cooper K, Waldron S,
Slater C, Weaver LT & T Preston (2004) Rapid Communications in Mass Spectrometry 18: 25932600. 4Small AC, Preston T, Dodson B, Priebe M & K Verbeke (2006) Production of Complex
Metaprobes: 13C-labelled Cereals Abstracts of the Eurostarch final conference, Groningen, April
2006. 5Morrison DJ, Ward M, Edwards CA, Preston T, Dodson B & LT Weaver (2006) Novel
Strategies for Colonic Provision of Short Chain Fatty Acids Abstracts of the Eurostarch final
conference, Groningen, April 2006.
13
Colonic nitrogen metabolism
K. Verbeke, K. Geboes, V. De Preter
Department of Gastrointestinal Research, UZ Gasthuisberg, K.U.Leuven, B-3000
Leuven, Belgium
Introduction: It is generally accepted that fermentation of carbohydrates in the colon
results in beneficial effects for the host because of the generation of short chain fatty
acids (SCFA, mainly acetate, propionate and butyrate) whereas colonic fermentation of
proteins by the microbiota is considered much less favourable. Besides SCFA and
branched chain fatty acids, a number of potentially toxic metabolites is formed such as
ammonia, sulphur compounds, indoles and phenolic compounds. As a consequence,
most dietary interventions targeting the colon (such as pre- and probiotic administration)
aim at increasing the saccharolytic activity of the colonic microbiota and decreasing the
proteolytic activity.
Aim: We have developed a stable isotope labelled biomarker, lactose[15N, 15N]ureide, to
monitor the colonic nitrogen metabolism and have investigated (i) whether pre- and
probiotic administration effectively resulted in a decreased generation of ammonia and
(ii) whether is was possible to measure this effect in a quantitative way.
Results: Upon oral administration of lactose[15N, 15N]ureide, the bond between the
sugar and ureide moiety of this molecule resists enzymatic degradation during passage
through the small intestine whereas it is hydrolysed upon arrival in the colon by the
activity of specific bacteria. The [15N, 15N]urea generated in this way is consequently
rapidly hydrolysed to [15N]NH3. Ammonia can be taken up by the bacteria for their own
metabolism followed by faecal excretion or can be absorbed through the colonic mucosa
and after conversion in the liver to urea be urinary excreted. Hence, the ratio between
faecal and urinary excretion of 15N reflects the fate of ammonia in the colon.
Using this biomarker, we have evaluated the influence on colonic ammonia metabolism
of a number of prebiotic substrates (lactulose, inulin, resistant starch) and probiotic
substrates (Lactobacillus casei Shirota, Bifidobacterium breve (Yakult strain) and
Saccharomyces boulardii) in healthy volunteers. The results of these experiments have
clearly indicated that (i) the colonic ammonia metabolism was significantly influenced
after administration of some of the tested substrates, (ii) that the observed effects were
substrate-dependant and (iii) that the observed effects could be quantitatively expressed
using the biomarker. Limitations of the biomarker identified during the execution of the
experiments include the absorption of a fraction of glucose[15N, 15N]ureide from the
small bowel and the fact that the biomarker seems to reflect only the processes in the
proximal colon.
Conclusions: Lactose[15N, 15N]ureide is a useful biomarker to quantitatively measure
the influence of pre- and probiotic substrates on the colonic nitrogen metabolism.
14
Methodological development for 13C-acetate plasma analysis
V. Ferchaud-Roucher1, M. Champ2.
1
Centre de Recherche en Nutrition Humaine, INSERM U539, Hôtel-Dieu, 44093 Nantes,
France. veronique.ferchaud-roucher@univ-nantes.fr
2
INRA, Unité des Fonctions Digestives et Nutrition Humaine, rue de la Géraudière BP
71627, 44316 Nantes, France. champ@nantes.inra.fr
Breath tests are currently used to qualitatively assess colonic fermentation but no
quantitative estimations were available for human studies. In the present work, methods
were developed to determine acetate turnover in human subjects using stable isotopes.
Our procedure for the analysis of plasma acetate concentrations (in µM) and isotopic
enrichments (in MPE) by GC/MS consisted in a deproteinisation of plasma, an extraction
with diethyl ether and a derivatization with TBDMS agent. This method was used to
assess the effect of colonic fermentation from lactulose (non-digested disaccharide) on
fatty acid metabolism in overweight volunteers with insulin resistance. Eight overweight
adults (89.6  7.2 kg) were infused with a primed constant intravenous infusion of [113C]acetate and of [1,1,2,3,3-2H ]glycerol for 9 h. After 3 h of tracer infusion, subjects
5
ingested 30 g of pure lactulose, or a saline solution. Isotopic enrichment of plasma
acetate and glycerol were measured by GC-MS (EI and SIM to monitor ions m/z 118,
117 and 145, 148, respectively). Before saline or lactulose intake, plasma [M+1]acetate
enrichments were similar (5.3 MPE). The acetate turnovers were 11.4  2.4 with saline
versus 10.7  1.4 µmol.kg-1.min-1 with lactulose, indicating no significant difference (NS).
After lactulose ingestion, acetate enrichments decreased significantly (P < 0.05).
Acetate turnover became significantly higher, 15.5  2.2 µmol.kg-1.min-1 (lactulose)
compared to 10.3  2.2 µmol.kg-1.min-1 (Saline, P  0.001). A significant increase of
acetate concentration in the plasma (P  0.001).
GC/MS is a powerful analytical tool for the stable isotope studies but requires high
isotopic enrichments of 13C-labelled SCFA ( 1MPE) in the plasma sample. To measure
low isotopic enrichments of 13C-SCFA (or natural abundance < 1 MPE), we have
developed a method in GC-C-IRMS using a Solid Phase Micro-Extraction (SPME). After
removal of plasma proteins, the SPME fiber was plunged in the liquid sample during 40
min at 40°C. Then, acetate was directly desorbed into GC-C-IRMS. The accuracy of
isotopic enrichment measurement was determined using plasma spiked with 13C-acetate
and 13C-butyrate solution from 0 to 1 Mol Percent Excess (MPE). Good linearity and
repeatability (RSD < 5%) were obtained for acetate and butyrate. Plasma acetate,
propionate and butyrate concentrations were also determined relative to 3Methylvalerate (Internal Standard). Good linearity and repeatability were observed from
0 to 400 µM for acetate, from 0 to 20 µM for propionate and from 0 to 10 µM for
butyrate. This method was applied to determine plasma acetate production obtained
from the lactulose fermentation in one healthy volunteer over 3 hours. A 50% increase
of acetate production was measured 2 hours after oral lactulose intake. These results
are in agreement with those measured by GC/MS in healthy and overweight adults
following a lactulose intake by using higher amount of labelled tracers.
Using the GC/MS method, particular attention needs to be paid to minimizing
contaminations of acetate during extraction and derivatization steps and to reporting
consistent and reproducible measurements. GC-C-IRMS method presented here is a
very sensitive method but only one analyze per adsorption onto the SPME fiber is
possible in GC-C-IRMS.
15
In conclusion, analytical methods were developed to assess the colonic fermentation in
human and allow to measure high (> 1 MPE, GC/MS method) and very low isotopic
enrichment (< 1 MPE, GC-C-IRMS) within the physiological concentration measured in
human plasma.
16
Bacterial short chain fatty acid interconversions and their
significance for measuring colonic production
D. J. Morrison1, W. G. Mackay2, C. A. Edwards2, T. Preston1, B. Dodson3 and
L. T. Weaver2
1
Stable Isotope Biochemistry Laboratory, SUERC, Scottish Enterprise Technology Park,
East Kilbride, G75 0QF, UK. 2Division of Developmental Medicine, University of
Glasgow, Royal Hospital for Sick Children, Yorkhill, Glasgow, G3 8SJ, UK. 3School of
Science and Technology, Bell College of Technology, Hamilton, ML3 0JB, UK.
Introduction: Short chain fatty acids (SCFAs) are produced in the colon by bacterial
fermentation of, mainly, non-digestible carbohydrates. They have important local
beneficial effects and may have systemic health benefits. Measuring their production
can be effected by delivering isotopically labelled SCFA to the colon and subsequent
measurement of SCFA isotopic dilution in urine. However, measurement of the major
SCFAs simultaneously in any protocol may be complicated by interconversion reactions
that introduce errors when using the same isotopic tracer.
Methods: The interconversion of acetate, propionate, butyrate and lactate were
investigated in vitro using faecal batch culture systems from healthy adult volunteers
(n=5). Briefly, each substrate was incubated at physiological concentrations and high
enrichment (~50 MPE) and the complete isotopomer envelope of each SCFA were
measured by GCMS. Mean rates of production of product from precursor were
calculated using fractional synthesis rates and absolute pool size to derive absolute
synthesis rates in mol.hr-1. In addition, oligofructose was incubated to determine the
contribution of acetate and lactate conversion to the butyrogenic nature of oligofructose.
Results: The interconversions observed are detailed in the table.
Product
Acetate
Propionate
Butyrate
Lactate
Precursor
2H -acetate
3
-
X

X
2H -propionate
5
X
-
X
X
2H -butyrate
7
X
X
-
X
13C -lactate
3

‡

Precursors incubated separately; X – no conversion detected (< 1.5
‡ only observed in 2 subjects.
-
mol.hr-1);
The most significant interconversions observed were acetate conversion to butyrate and
lactate conversion to acetate, propionate and butyrate. Butyrate production from acetate
and lactate precursors was quantitatively significant. Upon addition of oligofructose, an
increase of acetate and lactate conversion to butyrate occurred. These pathways
combined represented nearly 80% of butyrate produced during oligofructose
fermentation.
Conclusions: Extracellular or luminal acetate and lactate are major precursor pools for
butyrate and propionate synthesis and interconversion reactions largely explain butyrate
production from oligofructose even though it is selectively fermented by non-butyrate
17
producing bacteria. The consequences of these interconversion reactions for using
colonic delivery of isotopically labelled SCFAs to measure production by isotope dilution
are two-fold:
1) Different isotope labelled species are required to measure production of acetate,
propionate and butyrate simultaneously e.g. 13C acetate, 13C propionate and 2H
butyrate because of the relatively large flux of acetate to butyrate
2) Using different isotopically labelled SCFAs may facilitate the quantitation of both
total production and the fractional contribution of interconversion simultaneously
to produce a global picture of SCFA production.
18
Influence of resistant starch on colonic metabolism
K. Verbeke, L. Cloetens, J. De Loor, V. De Preter, P. Rutgeerts
Department of Gastrointestinal Research, UZ Gasthuisberg, K.U.Leuven, B-3000
Leuven, Belgium
Introduction: The effects of resistant starch (RS) in the colon are mainly attributed to
the generation of short-chain fatty acids and especially butyric acid. In this study, we
have investigated whether RS (type 3) also influences other colonic metabolic pathways,
particularly protein fermentation and the ammonia metabolism. Secondly, it was
investigated whether the effects of RS as such were different from the effects of RS
combined with wheat bran. Lactose [15N, 15N’]-ureide was used as a biomarker to
evaluate the fate of colonic ammonia whereas the urinary concentration of p-cresol was
considered as a marker of protein fermentation in the colon1.
Methods: Ten healthy volunteers participated in a randomized placebo-controlled crossover study in which they received either RS (2 x 15g/d) or placebo (maltodextrine) for 2
weeks followed by a 2-weeks wash-out and a second period of 2 weeks during which
they received the opposite treatment. Ten other volunteers performed a similar study in
which they received either RS (2 x 15g/d) or RS combined with wheat bran (2 x 6g/d). At
the start and at the end of each intake period, the volunteers consumed a pancake test
meal labeled with 75 mg lactose [15N, 15N’]-ureide after which they performed a
fractionated 48-h urine collection. Urinary 15N content was measured using total
combustion-IRMS and expressed as % of administered dose and the urinary p-cresol
excretion was determined using GC-MS and expressed as total p-cresol content (mg).
Results: Administration of RS for 2 weeks resulted in a significant decrease in 15Nexcretion over 48h (from 50.93 ± 14.41% at baseline to 38.65 ± 12.04 after RS intake).
The effect on the cumulative 15N-excretion was mainly due to a decrease in the 6 - 24h
fraction. The effect of RS administration was significantly different from that of placebo
intake whereas no difference could be found between RS and RS+WB. Only a tendency
towards a more pronounced effect with RS was observed.
On the other hand, p-cresol excretion at baseline (55.6 ± 42.0 mg) was not significantly
different from the excretion after administration of RS (59.0 ± 37.7 mg).
Conclusions: It was found that administration of RS type 3 resulted in a decreased
urinary excretion of 15N, indicating that either a lower amount of ammonia was
generated in the colon or that a higher amount was removed through bacterial
incorporation followed by faecal excretion. On the contrary, no influence on the protein
metabolism was observed.
1De
Preter V et al. Br J Nutr 2004; 92:439-446.
19
Food and behaviour: the role of carbohydrates
David Benton, d.benton@swansea.ac.uk
University of Wales Swansea, U.K.
Initially two mechanisms are reviewed by which carbohydrate is commonly said to
influence behaviour. It has been suggested that some people eat carbohydrates foods
not for their taste but because of a ‘pharmacological’ action; that is it improves mood. A
meal almost exclusively carbohydrate will increase the tryptophan / long-chain neutral
amino-acid ratio in blood. It is proposed that the tryptophan is transported into the brain
where it is converted to mood-enhancing serotonin. However, it appears that this is
probably a laboratory artefact as even small amount of protein in a meal will nullify this
mechanism. The basic information was obtained from rats and there is doubt whether
similar mechanisms exist in primates.
Secondly it has been often suggested that a meal high in carbohydrate may after
several hours produce a hypoglycaemic reaction. The associated release of insulin
removes glucose from the blood stream. Very low levels of blood glucose disrupt the
functioning of the brain so vision can be blurred, speech slurred and thinking slowed.
Such a view results from the use of the Glucose Tolerance Test in which blood glucose
is monitored following the consumption of 50g of glucose. However, when the same
quantity of carbohydrate is consumed with protein and fat only rarely do very low levels
of blood glucose result. Although reactive hypoglycaemia can occur it is rare and does
not commonly cause behavioural problems.
Finally some recent findings are outlined in which the amount and nature of
carbohydrate eaten for breakfast, and its interaction with other macro-nutrients, were
studied. In adults a high glycaemic load disrupted memory in the late morning although
blood glucose levels were not low enough to be described as hypoglycaemic. In
contrast carbohydrate that results in a slow release of glucose into the blood was
associated with better memory in the late morning. A combination of carbohydrate with
other macro-nutrients that slow the release of glucose was associated with better
memory. There was an interaction with glucose tolerance. Individuals with better, but
not poorer glucose tolerance, benefited from a meal of a low glycaemic load.
There have been fewer studies of children and the picture may differ from the adult. In
children a small breakfast disrupted the ability to stay on task in the late morning. The
consumption of snacks or carbohydrate containing drinks or can help functioning,
depending on previous meals.
20
Carbohydrates and satiety, physiological aspects
Anton Scheurink1, Gertjan van Dijk1 and Bauke Buwalda2
Department of Neuroendocrinology1 and Behavioral Physiology2, University of Groningen,
The Netherlands
Differences in diet choice are accompanied with differences in physiology and behavior.
The brain areas that initiate the intake of either carbohydrate-rich or fat-rich food are
different and the satiety factors that are released by a high carbohydrate or a high fat
meal are different. these items will be discussed in the introductory part of the
presentation.
Concentrating on the health benefits, we investigated the effects of high carbohydrate or
high fat feeding on stress responsiveness and metabolic functioning. We used the high
carbohydrate chow diet as the golden standard and found that rats on a high fat diet
generally overeat and develop a mild insulin resistance, reflected by somewhat elevated
levels of insulin and (sometimes) glucose during an intravenous glucose tolerance test.
We then focussed on the diet-induced effects on the behavioral and physiological
effects of social stress and found that high fat feeding significantly changed the
responses that are normally observed during and after stress. First, the stress-induced
reduction in body weight was attenuated in rats on a high fat diet. Second, high-fat fed
rats showed a faster recovery of body temperature after several stressors including
social defeat and an injection of the 5HT1a agonist 8-OH-DPAT or lipopolysaccharide
(LPS). These data suggest that a high fat diet seems to have a protective, anti-stress
like effect.
However, there was a price for this. The seemingly beneficial effects of the high fat diet
on short term stress-responsiveness were accompanied with negative long term effects
on metabolism. Rats on a high fat diet develop mild insulin resistance. This pathological
condition is remarkably affected by social stress. After a social defeat insulin resistance
is increased and glucose tolerance is impaired. In other words, we found that social
stress made the rats more susceptible for the development of insulin resistance on a
high fat diet.
21
Effects of differences in postprandial glycaemia on cognitive
functions
Anne Nilsson, Elin Östman , Inger Björck
Applied Nutrition and Food Chemistry, Department of Food Technology, Engineering
and Nutrition, Lund University, Sweden
Introduction
Glucose is the main fuel of the brain and number of studies has demonstrated positive
effects on cognitive functions of a glucose drink or a breakfast meal compared with
fasting state. However, due to a number of food factors, carbohydrate rich foods differ in
the delivery rate of glucose to the blood. After foods with high glycaemic index (GI),
plasma glucose, and hence, also the insulin concentrations rise rapidly. The high insulin
surge will favour an increased rate of glucose disposal. The result may even be an
undershoot in blood glucose to a level below the fasting value. On the other hand, lowGI foods result in a smaller blood glucose increment directly after a meal and instead
usually maintain a higher blood glucose increment in the late postprandial phase.
Consequently, due to significant differences in postprandial blood glucose appearance
after a high-GI meal compared with a low-GI meal, cognitive functions during the
postprandial phase may differ depending on the quality of the food ingested. In addition,
it is evident that type II diabetes is associated with an increased risk of cognitive
dysfunction and it has been suggested that an improved glycaemic control may
enhance cognitive functions in elderly type II diabetic patients. An accumulating body of
data also shows a relation between glucose tolerance and cognitive functions in healthy
adults, especially in elderly.
Objective
The aim of the presently described project within EUROSTARCH was to evaluate
potential differences in cognitive functions after test meals differing in post meal
glycaemia.
Methods
Methods for estimation of working memory and selective attention were developed and
applied in the postprandial phase in healthy elderly subjects. Glycaemic responses
simulating high- or low Glycaemic Index features, respectively, were achieved by varying
the time schedule for oral administration of glucose (50 g).
Results and conclusion
The cognitive tools developed allowed detection of differences in cognitive performance
related to the postprandial blood glucose level; higher glycaemia in the late postprandial
phase resulting in improved cognitive function. The results also indicate that even in
healthy elderly subjects, there was a significant difference in cognitive performance
related to the efficiency in blood glucose regulation; where subjects with less efficient
blood glucose regulation displayed lower scores in the cognitive tests.
22
Potential health benefits of Low GI starchy foods
M. Laville1, A De Rougemont1, M Sothier1, M Skilton1, JA Nazarre1, S. Vinoy2,
S. Normand1
1
CRNH Rhône-Alpes, Lyon, France, 2Danone Vitapole, Palaiseau, France
The effects of either low- (LGI) or high-glycemic index (HGI) starch were studied on
weight control and cardiovascular risk factors in overweight subjects.
Design: The study was a parallel, randomized 5-week intervention, matched group trial.
The 38 subjects (BMI: 27.3 ±1.5 kg/m²) were given dietary advice to replace ad libitum
usual starch by either LGI or HGI starch.
Results: The diet groups did not differ in total energy or macronutrient intakes. Dietary
goals were reached in the LGI diet group (mean GI= 46.3 ±0.4 %, p<0.0001) with a
significant difference in GI between groups (p<0.0001). Mean body weight decrease
was significant in the LGI diet group (-1.1 ±0.3 kg, p=0.004) and this decrease was
significantly greater than in the HGI group (-0.3 ±0.2 kg, p=0.04 between groups). No
significant differences in body fat mass were observed. However, neither diet altered
fasting insulin, QUICKI, HOMA-IR, lipid profile and substrate oxidations. The LGI diet
decreased total cholesterol by 9.6% (p<0.001), HDL cholesterol by 2.5% (p=0.04), LDL
cholesterol by 8.6% (p=0.01) and both LDL to HDL ratio (10.1%, p=0.003) and total to
HDL cholesterol ratio (8.5%, p=0.001). No significant changes in lipid parameters were
observed in the HGI group.
Conclusions: A 5-week LGI diet decreased body weight and improved cardiovascular
risk factors including total cholesterol, LDL cholesterol, and LDL/HDL ratio without any
significant improvement in insulin sensitivity.
23
Communication of EUROSTARCH messages to the nonscientific community - what messages can we give?
Diane McCrea, diane@mccrea1.demon.co.uk
Food Consultancy (dmc) Ltd, Cardiff, UK
Introduction
The aims of the EUROSTARCH project were to investigate the health-related properties
of different starchy food and to find out more about how, by choosing the right types of
starchy foods, it might be possible to reduce dietary risk factors and how these might
contribute to the prevention and treatment of obesity and type 2 diabetes.
Against a background of media hype about ‘miracle diets’ consumers are often
confused about diet and health and about making appropriate food choices, especially
about starchy foods. Low carbohydrate diets, including ‘the Atkins diet’, have been very
popular in recent years, yet it seems that these have now fallen out of favour. In
contrast there is growing emphasis on the ‘GI diet’, as witnessed from the consumer
press particularly in Sweden, France and the UK.
EUROSTARCH project work packages have undertaken specific research to find out
more about low GI, starchy foods and what they can specifically contribute to satiety,
weight maintenance, and cognitive performance, as well as to a healthy nutritional
profile and the reduction of diet related health risks. This presentation sets the research
results into the broader consumer context. It will consider how scientific messages can
be translated into the public domain and what messages can be communicated - what
we know, what we don’t know, and why we might change our views as a result of future
research and new information.
Results
The main messages from EUROSTARCH research confirm that substituting high GI
starchy foods with low GI starchy foods has a positive effect on satiety, and that there is
also a positive effect on weight loss. However, while at this stage there is no conclusive
evidence related to cognitive performance, there is an indication of an association with
glycaemic response.
Low GI, starchy foods can contribute to a healthy nutritional profile in several ways.
While there can be many different food choices when selecting a ‘low GI’ diet, in
whatever way this is achieved, it must also be in line with a healthy nutritional profile.
This is an important consumer message. Our research has also confirmed that
substituting high GI starchy foods with low GI starchy foods leads to a better lipid profile,
and better blood glucose regulation, also at the subsequent meal.
In conclusion:
This presentation will review the messages that can be communicated to consumers,
and the challenges for scientists of communicating accurate concise messages from
their research, especially when faced with the media’s seemingly insatiable demand for
‘quick fix’ miracle diets and ‘headline grabbing’ messages.
24