IIFET 2000 Proceedings
Communicating Health Messages about N-3FA
Joyce A. Nettleton, DSc, RD, Elmhurst, Illinois, USA
Abstract. Dietary advice to the public about fat consumption has consistently emphasized the reduction of total fat,
saturated fat and cholesterol. Against a background of conflicting and changing messages about how much and what type of
fat to consume, updated messages have emerged that emphasize the fatty acid profile of the fat, e.g. Dietary Guidelines for
Americans, 2000. General scientific agreement supports the recommendation to increase omega-3 fatty acid (n-3FA)
consumption and reduce omega-6 (n-6FA) intake. Specific quantitative recommendations for n-3FA intake, however, vary
widely among countries and expert groups and have not yet been included among the National Academy’s Recommended
Dietary Allowances. Unresolved questions remain about safe limits for infants, patients with certain health risks and
interactions between n-6FA and n-3FA. Complexities about different fatty acid classes and n-3FA in particular further
complicate communications efforts to provide concise and accurate guidance for public health. Food sources of n-3FA are
limited and new ways of incorporating these fatty acids into foods need to be developed. Biotechnology and food technology
are likely to be important in enhancing n-3FA intake for all segments of the population. Communications challenges
presented by emerging and conflicting science about different classes of fatty acids and the health benefits of n-3FA are
discussed in detail.
Keywords: health messages, n-3 fatty acids, communications, dietary fat
BACKGROUND
For the past two decades or more, dietary
recommendations regarding fat intake have consistently
focused on reducing consumption of total fat, saturated fat
and cholesterol as a means of lowering blood low-density
lipoprotein (LDL) and cholesterol levels and avoiding
excess calorie intake (Dietary Guidelines Advisory
Committee 1985-1995, National Research Council, 1989,
National Cholesterol Education Program 1993). Fat has
principally been viewed as the major culprit in overweight
and the development of heart disease and other chronic
diseases. In spite of increasing awareness of the complex
contribution to health of individual fatty acids and fatty
acid classes, general advice to the public has emphasized
restriction of certain classes of fatty acid – saturates and
trans fatty acids – and limitation of calories from fat to no
more than 30% total energy. The health-promoting
attributes of fats have largely been overlooked.
Recognition of the complex and sometimes contradictory
effects of individual fatty acids in the reduction of disease
risk has made it exceedingly difficult to craft health
messages for the public without enhancing the confusion
about dietary fat that already exists (Food and Agriculture
Organization, 1994).
As new knowledge accrues,
guidance on dietary fat is likely to become more complex.
The most recent edition of the Dietary Guidelines for
Americans released in May 2000, reflects these issues
(Dietary Guidelines Advisory Committee, 2000). Better
understanding of the complexities of fatty acid
metabolism creates new opportunities to develop health
messages that are targeted to specific audiences, focused
on health promotion, compatible with disease prevention
and are attuned to consumer behavior. Health messages
to the public encouraging consumption of n-3FA and
tempering n-6FA intake present unique challenges and
opportunities.
Scope of Health Effects of n-3FA
It is now clear that the n-3 long chain fatty acids
eicosapentaenoic acid (EPA) and docosahexaenoic acid
(DHA) have direct and indirect effects on the heart that
are protective against heart disease. They consistently
lower triacyglycerol levels in normal and hyperlipidemic
subjects, reduce platelet aggregation, usually reduce
cholesterol levels, modestly increase LDL and high
density lipoprotein (HDL) levels, modulate endothelial
activation, and reduce cardiac arrhythmias (Connor 2000,
von Schacky 2000). In addition, they have been shown to
reduce blood pressure, risk of sudden death, mortality
from coronary heart disease in subjects with a previous
myocardial infarction, modulate endothelial activation
and improve vasodilation and blood rheology (Burr et al.
1989, Nettleton 1995, Albert et al. 1998, De Caterina et
al. 2000, von Schacky 2000). In addition to their effects
in protecting against heart disease, n-3FA act as
immunomodulators, reducing the immune and
inflammatory responses in immune-based diseases such
as arthritis, psoriasis and asthma and in autoimmune
disorders such as lupus and nephropathy (Connor 2000,
James et al. 2000, Kremer 2000). N-3FA may also be
beneficial in multiple sclerosis, certain cancers,
peroxisomal disorders and in enhancing resistance to
infection (Nettleton 1995, Ip 1997, Gogos et al. 1998,
Harbige 1998, Martinez et al. 2000). A recent frontier
where n-3FA appear beneficial is certain neuropsychiatric
illnesses such as bipolar disorder, schizophrenia and
depression (National Institutes of Health 1998, Stoll et al.
1999).
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Benefits of n-3FA in infant nutrition
N-3FA are considered essential nutrients for fetal and
infant development (Innis 1991, Uauy and Hoffman
2000), although absolute requirements have not been
defined (Gibson and Makrides 2000). DHA is the
required fatty acid, though infants can synthesize DHA
from alpha-linolenic acid (ALA) and EPA.
Recommended levels of n-3FA for infant formulae vary
among countries and controversy exists about the
supplementation of formulae with EPA and DHA (Scott
et al. 1998). All agree that at a minimum ALA is
appropriate. Interactions with n-6FA, particularly
arachidonic acid, are an important consideration if fatty
acid imbalances are to be avoided. Infant nutrition may be
enhanced if effective ways to boost the consumption of n3FA by pregnant and nursing women can be found.
Recognition of the desirability of such an approach is a
first step.
Fats and that some foods are unhealthy any time (Center
for Science in the Public Interest 2000). Vegetable fats
may be preferable to animal fats, but what about tropical
vegetable oils and margarine? If saturated fatty acids are
the dietary villains in raising blood cholesterol levels,
does that mean everything else is okay?
The history of health messages about butter, margarine
and spreads is illustrative of both changing science and
consumer confusion (Katan 2000). Originally, margarine
was promoted as superior to butter because of its lower
saturated fatty acid content.
Differences among
margarines were minimized in the belief that the net
effect would be lower saturated fatty acid intake. With
the realization that some margarines, particularly stick
types, may contain tropical oils rich in saturated fatty
acids and partially hydrogenated oils rich in trans fatty
acids, and might actually be less healthful than butter,
margarine became suspect (Mensink and Katan 1990,
Lichtenstein et al. 1999). As concern about the health
advantages of margarines changed, emphasis shifted to
soft margarines over stick versions, but inevitably the
popular press returned to the comparison with butter.
Recent product developments include margarines free of
trans fatty acids and specialty soft margarines enhanced
with phytosterols to control blood cholesterol levels.
Focus solely on soft margarine still leaves open the
question for consumers of which functionally desirable
(solid) fats are nutritionally suitable for baking. Add the
plethora of brand and composition differences among
products and consumers still have reason to be confused.
COMMUNICATIONS ISSUES
While the public has been reminded to limit fat intake to
combat heart disease, diverse targets have been suggested.
The Dietary Guidelines for Americans, the American
Heart Association and others have recommended total
energy intakes that comprise no more than 30% calories
from fat, with saturated fat not exceeding 10% calories.
Very low fat diets with no more than 15% calories from
fat have been promoted as an antidote to heart disease and
a way to reduce weight (Ornish et al. 1990). The most
recent edition of the Dietary Guidelines describes a diet
limited to 30% calories from fat as “moderate.” This
subtle shift in language recognizes that people have
difficulty adhering to diets with less fat and that the
benefits of consuming less fat have been questioned. The
public, however, has heard conflicting messages in
translating numbers to foods. Examples of these mixed
messages are shown in Table 1. There may not be any
good or bad foods, but some say there are good and bad
Similar evolution is occurring among vegetable oils
except that the emphasis has shifted from encouraging
consumption of high linoleic acid polyunsaturated oils to
those with predominantly monounsaturated fatty acids.
Simple identity may be obscured with the development of
vegetable oils having markedly different fatty acid
profiles from the original product, e.g. high oleic acid soy
and sunflower oils. Product labels alert the consumer to
these changes, but consumers can no longer rely on the
food source or shorthand nomenclature such as
“vegetable” to indicate the predominant fatty acid classes.
Diversity of fatty acid profile from the same plant source,
e.g. soy, canola and sunflower, arguably a consumer
benefit from biotechnology, changes the way consumer
education messages must be crafted and demands that
nutritionists, physicians and health educators stay abreast
of such important changes in the food supply. This
oversimplistic example illustrates the difficulty faced by
those developing simple, food-based messages for the
general public.
Whether relatively simple dietary
messages about fat can ever be effective or meaningful
will need to be evaluated.
Table 1. Mixed messages about dietary fat.
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Eat a low fat diet – 30% calories from fat
Very low fat diets may reverse coronary heart disease
Choose a diet moderate in fat
No good foods/bad foods
Good fats and bad fats
Vegetable fats are better than animal fats
Avoid tropical oils and shortening
Saturated fatty acids are the villains in heart disease
Trans fatty acids are worse than saturates
Margarine is better than butter
Some margarines are no better than butter
Some margarines help lower blood cholesterol
Some vegetable oils are healthier than others
Both fatty fish and lean fish are good for you
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that the news media excel and public interest thus
generated makes it compelling that health messages from
scientists stay current.
SCIENTIFIC ISSUES
Both scientists and consumers confront new and changing
information. Nutritionists have responded to new data
and emerging understanding about fatty acid metabolism
by modifying dietary advice to the public, paying greater
attention to the interactions and complexities of dietary
fatty acids and putting greater effort into quantifying
minimal and safe levels of intake. Thus, the most recent
Dietary Guidelines for Americans, emphasize moderate
fat intake and consumption of monounsaturated fatty
acids, with acknowledgment of the diverse effects among
polyunsaturated fatty acids. While many scientists admit
that n-6FA intakes may be excessive, not all would
advocate reducing their consumption. Official mention in
dietary advice to the public of the value of fish oils and n3FA has been long in arriving (Holman 1998).
Table 2. Recommended intakes of n-3 fatty acids*.
Source
WHO
Sweden
Japan
Masters
COMA (UK)
BNF
NATO
USA
Canada
Sweden
WHO
It may be said that nutrition scientists generally agree
about the desirability of a low intake of saturated and
trans fatty acids, the relatively benign effect of
monounsaturates (Feldman 1999), and the potential for
excess n-6FA intake to be detrimental. There is also
general agreement about the essentiality of n-3FA for
infant development, the cardio-protective effects of n3FA and the desirability of increasing n-3FA intake by
the general population (Simopoulos et al. 1999). By how
much intake should increase is unsettled and ways to
effect such change present challenges. For people with
certain diseases, questions of dose, therapeutic effects and
duration of treatment are unresolved. Consumption of n3FA may have contradictory effects. The benefit of n3FA among Type 2 diabetics whose risk of heart disease
may be reduced perhaps at some cost to their glucose
control is an example. Further, the inherent complexities
about n-3FA themselves makes resolution of these
questions particularly difficult. To what extent can ALA
substitute for EPA and DHA? To what extent does high
intake of n-6FA compromise the benefit of n-3FA
consumption?
Ratio ALA EPA+DHA Total
n-6:n-3
n-3FA
5-10:1
5:1
2:1
2.3:1
2.4
2.2
g/day
0.2
1.2
0.8
0.65
1.2-1.6
1.7
2.8
*
Source: Kris-Etherton et al. 1999; WHO: World Health
Organization, COMA: Committee on the Medical Aspects
of Foods, BNF: British Nutrition Foundation, NATO:
North Atlantic Treaty Organization
FUTURE COMMUNICATIONS
As awareness of the health benefits of n-3FA increases, the
need to quantify and refine dietary fat messages will
become more urgent. The need to diversify food sources of
n-3FA will become pressing. EPA and DHA are most
concentrated in fatty fish: salmon, tuna, rainbow trout,
sardines, mackerel, Atlantic bluefish, herring and
anchovies, while ALA is found mainly in canola, soy and
flaxseed oils. Other avenues for furnishing n-3FA include
fish oil supplements, purified fatty acids, algal sources and
functional foods with micro-encapsulated n-3FA
(Lovegrove et al. 1997, Newton 1998, Kris-Etherton
2000). Genetically engineered seed oils with enhanced n3FA or their precursors may also be promising (Ursin
2000). Poultry and eggs have become important sources in
the U.S. diet because fish meal is fed to chickens and
substantial amounts of chicken are consumed (Huang et al.
1990, Raper and Exler 1991). Awareness of diverse food
sources of n-3FA will need to increase.
A summary of the different recommendations for n-3FA
intake is shown in Table 2 (Simopoulos et al. 1999, KrisEtherton 2000). These recommendations reflect not only
differences in units – ratios, grams, percent total energy –
but in quantity. Figures shown for the U.S. have not been
adopted officially. Differences in recommendations
between the U.K. and Sweden, 1.5% and 4.0% energy
respectively, show how widely national recommendations
can vary.
Acknowledgement of the differences in effectiveness
between plant and animal sources of n-3FA may be
important. In order to encourage interest in and adoption
of dietary fat guidance, it is desirable to explain the
benefits beyond changes in blood cholesterol levels. For
the greater public health, it will likely become even more
important to emphasize preventive health strategies rather
than therapeutic approaches. Communication about n3FA can also capitalize on the public’s strong interest in
Finally, it is useful to note that the emergence of new
nutrition knowledge can have the paradoxical effect of
refining dietary guidelines and discouraging the
incorporation of new information into health messages
until more precise information becomes available. It is in
announcing and interpreting new findings for the public
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diet and health, organic and natural foods and innovative
products that encourage modification of dietary habits.
The success of the food industry in developing low fat
foods shows that food manufacturers are responsive to
consumer trends. Applications from genomics and
biotechnology are promising for developing more
healthful foods with enhanced n-3FA content.
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Effective communications strategies take into account
specific audiences, the need to tailor the message to the
audience, and simplicity. Updated health information
about fat, however, is complex, competes in an
environment laden with conflicting messages and reaches
audiences already mystified by food fats, oils and
margarines. Moreover, the effects of dietary change
occur over the long term and may not be sensed by the
individual. Against this daunting background is the
enduring popularity of food and the pleasure of eating, the
power and potential of n-3FA themselves, people’s
interest in their own health and popular fascination with
promising science. Surely a wager on the side of n-3FA
is a winning bet.
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