UNIT V:
Integration of Metabolism
Nutrition
1. Overview
 Nutrients are the constituents of food necessary to sustain the
normal functions of the body.
 All energy is provided by three classes of nutrients: fats,
carbohydrates, protein (Figure 27.1).
 The intake of these energy-rich molecules is larger than that of
the other dietary nutrients
 Therefore, they are called the macronutrients.
 This chapter focuses on the kinds and amounts of
macronutrients that are needed to maintain optimal health and
prevent chronic disease in adults.
 Those nutrients needed in lesser amounts, vitamins and
minerals, are called the micronutrients.
2
 Figure 27.1 Essential nutrients obtained from the diet.
 [Note: Ethanol is not considered an essential component of the diet
3
but may provide a significant contribution to the daily caloric intake of
some individuals.]
2. Dietary Reference Intakes
 Dietary Reference Intakes (DRI)- estimate of the amounts of
nutrients required to prevent deficiencies and maintain optimal
health and growth.
 The DRI also establish upper limits on the consumption of
some nutrients, and incorporate the role of nutrients in lifelong
health.
4
A. Definition of the DRI
 The DRI consist of four dietary reference standards for the intake
of nutrients designated for specific age groups, physiologic states,
and gender.
5
 Figure 27.2 Components of the Dietary Reference Intakes (DRIs).
A. Definition of the DRI
1.
Estimated Average Requirement (EAR):
 The EAR is the average daily nutrient intake level estimated to
meet the requirement of one half of the healthy individuals in a
particular life stage and gender group.
 Requirements for half the healthy individuals
6
A. Definition of the DRI
2. Recommended Dietary Allowance (RDA):
 The RDA is the average daily dietary intake level that is sufficient
to meet the nutrient requirements of nearly all (97–98%) the
individuals in a life stage and gender group.
 The RDA is not the minimal requirement for healthy individuals;
rather, it is intentionally set to provide a margin of safety for most
individuals.
 The EAR serves as the foundation for setting the RDA.
 Requirement for 97–98% of all healthy individuals
7
A. Definition of the DRI
3. Adequate Intake (AI):
 The AI is set instead of an RDA if sufficient scientific evidence is
not available to calculate an EAR or RDA.
 The AI is based on estimates of nutrient intake by a group (or
groups) of apparently healthy people that are assumed to be
adequate.
 For example, the AI for young infants, for whom human milk is the
recommended sole source of food for the first four to six months,
is based on the estimated daily mean nutrient intake supplied by
human milk for healthy, full-term infants who are exclusively
breast-fed.
8
 Observed or experimentally determined
 Used when RDA is not available
A. Definition of the DRI
4. Tolerable Upper Intake Level (UL):
 The UL is the highest average daily nutrient intake level that is likely
to pose no risk of adverse health effects to almost all individuals in
the general population.
 As intake increases above the UL, the potential risk of adverse
effects may increase.
 The UL is not intended to be a recommended level of intake.
 The UL are useful because of the increased availability of fortified
foods and the increased use of dietary supplements.
 The UL applies to chronic daily use. For some nutrients, there may
be insufficient data on which to develop a UL.
 Level at which risk of harm begins to increase
9
B. Using the DRI
 Most nutrients have a set of DRI (Figure 27.3).
 Usually a nutrient has an EAR and a corresponding RDA.
 Most are set by age and gender, and may be influenced by
special factors, such as pregnancy and lactation in women.
 When the data are not sufficient to estimate an EAR (or an
RDA), then an AI is designated.
 The AI is judged by experts to meet the needs of all
individuals in a group, but is based on less data than an EAR
and RDA.
10
A. Definition of the DRI
Figure 27.3 Dietary Reference Intakes for
vitamins and minerals in individuals one year and
older. EAR = Estimated Average Requirement;
RDA = Recommended Dietary Allowance; AI =
Adequate Intake; UL = Tolerable Upper Intake
Level; — = no value established.
11
DRIs for selected nutrients
Nutrient
Age, condition
DRI
Protein
(g/day)
> 19 years
EAR
RDA
Phosphorus
(mg/day)
> 19 years
EAR
RDA
UL
580
700
4,000
3,000
580
700
4,000
3,000
AI
4,700
4,700
> 19–70 years
> 70 years
Potassium
(mg/day)
> 19 years
Women
38 g
46 g* (0.8 g/kg)
Men
46 g
56 g† (0.8 g/kg)
Institute of Medicine (http://www.iom.edu)
*Reference woman = 57 kg; †Reference man = 70 kg;
‡Dietary Guidelines for Americans, 2010
B. Using the DRI
 Intakes below the EAR need to be improved because the
probability of adequacy is fifty percent or less (Figure 27.4).
 Intakes between the EAR and RDA likely need to be
improved because the probability of adequacy is less than 98
percent, and intakes at or above the RDA can be considered
adequate.
 Intake above the AI can be considered adequate. Intakes
between the UL and the RDA can be considered to have no
risk for adverse effects.
13
B. Using the DRI
 Figure 27.4 Comparison of the components of the Dietary Reference Intakes.
EAR = Estimated Average Requirement; RDA = Recommended Dietary
Allowance; AI = Adequate Intake; UL = Tolerable Upper Intake Level.
14
3. Energy Requirement in Humans
 The Estimated Energy Requirement is the average dietary
15
energy intake predicted to maintain an energy balance (that is,
when the calories consumed are equal to the energy expended)
in a healthy adult of a defined age, gender, and height whose
weight and level of physical activity are consistent with good
health.
 Differences in the genetics, body composition, metabolism, and
behavior of individuals make it difficult to accurately predict a
person's caloric requirements.
 However, some simple approximations can provide useful
estimates: For example, sedentary adults require about 30
kcal/kg/day to maintain body weight; moderately active adults
require 35 kcal/kg/day; and very active adults require 40
kcal/kg/day.
A. Energy content of food
 The energy content of food is calculated from the heat released by the
total combustion of food in a calorimeter
 It is expressed in kilocalories (kcal, or Cal)
 The standard conversion factors for determining the metabolic caloric
value of fat, protein, and carbohydrate are shown in Figure 27.5.
16
 Figure 27.5 Average energy available from the major food
components.
B. How energy is used in the body
 The energy generated by metabolism of the macronutrients is
used for three energy-requiring processes that occur in the body:
 Resting metabolic rate,
 Thermic effect of food, and
 Physical activity
17
 Figure 27.6 Estimated total energy expenditure in a typical 20-year-
old woman, 165 cm (5 feet, 4 inches) tall, weighing 50 kg (110 lb),
and engaged in light activity.
18
B. How energy is used in the body
Resting metabolic rate:
1.
The energy expended by an individual in a resting, postabsorptive state is called the resting (formerly, basal) metabolic
rate (RMR).
It represents the energy required to carry out the normal body
functions, such as respiration, blood flow, ion transport, and
maintenance of cellular integrity.
In an adult, the RMR is about:






19
1,800 kcal for men (70 kg)
and 1300 kcal for women (50 kg)
From 50–70% of the daily energy expenditure in sedentary
individuals is attributable to the RMR (Figure 27.6).
B. How energy is used in the body
2. Thermic effect of food:
 The production of heat by the body increases as much as 30% above
the resting level during the digestion and absorption of food.
 This effect is called the thermic effect of food or diet-induced
thermogenesis.
 Over a 24–hour period, the thermic response to food intake may
amount to 5–10% of the total energy expenditure.
20
B. How energy is used in the body
3. Physical activity:
 Muscular activity provides the greatest variation in energy
expenditure.
 The amount of energy consumed depends on the duration and
intensity of the exercise.
 The daily expenditure of energy can be estimated by carefully
recording the type and duration of all activities.
 In general, a sedentary person requires about 30–50% more than
the resting caloric requirement for energy balance (see Figure
27.6), whereas a highly active individual may require 100% or more
calories above the RMR.
21
4. Acceptable Macronutrient Distribution
Ranges
 Acceptable Macronutrient Distribution Ranges (AMDR) are
defined as:
 A range of intakes for a particular macronutrient that is associated
with reduced risk of chronic disease while providing adequate
amounts of essential nutrients.
 The AMDR for adults is 45–65% of their total calories from
carbohydrates, 20–35% from fat, and 10–35% from protein
(Figure 27.7).
22
 Figure 27.7 Acceptable
macronutrient distribution ranges
in adults.

23
5. Dietary Fats
 The incidence of a number of chronic diseases is significantly
influenced by the kinds and amounts of nutrients consumed
(Figure 27.8)
 Dietary fats most strongly influence the incidence of
coronary heart disease (CHD); evidence linking dietary fat
and the risk for cancer or obesity is much weaker.
 In the past dietary recommendations emphasized decreasing
the total amount of fat in the diet
 Research now indicates that the type of fat is more
important than the total amount of fat consumed.
24
 Figure 27.8 Influence of nutrition on some common causes of death
25
in the United States in the year 2000. Red indicates causes of death
in which the diet plays a significant role. Blue indicates causes of
death in which excessive alcohol consumption plays a part. (*Diet
plays a role in only some forms of cancer.)
A. Plasma lipids and CHD
 Plasma cholesterol may arise from the diet or from
endogenous biosynthesis.
 In either case, cholesterol is transported between the
tissues in combination with protein and phospholipids as
lipoproteins.
1. Low-density lipoprotein (LDL) and high-density
protein (HDL):
 The level of plasma cholesterol is not precisely regulated, but
rather varies in response to the diet.
 Elevated levels result in an increased risk for cardiovascular disease
(Figure 27.9).
26
 Figure 27.9 Correlation of the death rate from coronary heart
27
disease with the concentration of plasma cholesterol. [Note: The
data were obtained from a six year study of men with the death rate
adjusted for age.]
A. Plasma lipids and CHD
 The risk increases progressively with higher values for serum total
cholesterol.
 A much stronger correlation exists between the levels of blood
LDL cholesterol and heart disease
 In contrast, high levels of HDL cholesterol have been associated
with a decreased risk for heart disease.
 Abnormal levels of plasma lipids (dyslipidemias) act in
combination with smoking, obesity, sedentary lifestyle, and other
risk factors to increase the risk of CHD.
 Elevated plasma triacylglycerols are also a risk factor for CHD, but
the association is weaker than that of LDL cholesterol with CHD.
28
B. Dietary fats and plasma lipids
 Triacylglycerols are quantitatively the most important class
of dietary fats.
 The influence of triacylglycerols on blood lipids is
determined by the chemical nature of their constituent fatty
acids.
 The presence or absence of double bonds (saturated vs.
mono- and polyunsaturated), the number and location of
the double bonds (n-6 vs n-3), and the cis vs. trans
configuration of the unsaturated fatty acids are the most
important structural features that influence blood lipids.
29
B. Dietary fats and plasma lipids
1.
Saturated fat:
 Triacylglycerols composed primarily of fatty acids whose side
chains do not contain any double bonds are referred to as saturated
fats.
 Consumption of saturated fats is strongly associated with high
levels of total plasma cholesterol and LDL cholesterol, and an
increased risk of CHD.
 The main sources of saturated fatty acids are dairy and meat
products and some vegetable oils, such as coconut and palm oils
(Figure 27.10).
 Most experts strongly advise limiting intake of saturated fats.
30
B. Dietary fats and plasma lipids
Monounsaturated fats:
2.




31
Triacylglycerols containing primarily fatty acids with one double
bond are referred to as monounsaturated fat.
Unsaturated fatty acids are generally derived from vegetables and
fish.
When substituted for saturated fatty acids in the diet,
monounsaturated fats lower both total plasma cholesterol and
LDL cholesterol, but maintain or increase HDL cholesterol.
This ability of monounsaturated fats to favorably modify
lipoprotein levels may explain, in part, the observation that
Mediterranean cultures, with diets rich in olive oil (high in
monounsaturated oleic acid), show a low incidence of CHD.
.
32
 Figure 27.10 Compositions of commonly encountered dietary lipids.
B. Dietary fats and plasma lipids
3. Polyunsaturated fats:
 Triacylglycerols containing primarily fatty acids with more
than one double bond are referred to as polyunsaturated fats.
 The effects of polyunsaturated fatty acids (PUFAs) on
cardiovascular disease is influenced by the location of the
double bonds within the molecule.
a. ω-6 Fatty acids:
a.
33
These are long-chain, polyunsaturated fatty acids, with the first
double bond beginning at the sixth carbon atom (when counting
from the methyl end of the fatty acid molecule [Note: They are also
called n-6 fatty acids.]
34
B. Dietary fats and plasma lipids
 Consumption of fats containing ω-6 polyunsaturated fatty acids,
lowers plasma cholesterol when substituted for saturated fats
 Plasma LDL are lowered, but HDL, which protect against CHD,
are also lowered.
 The powerful benefits of lowering LDL are only partially offset
because of the decreased HDL
35
b. ω-3 Fatty acids:
 These are long-chain, polyunsaturated fatty acids, with the first
double bond beginning at the third carbon atom (when counting
from the methyl end of the fatty acid molecule).
 Dietary ω-3 polyunsaturated fats (Fish oil) suppress cardiac
arrhythmias, reduce serum triacylglycerols, decrease the
tendency for thrombosis, lower blood pressure, and substantially
reduce risk of cardiovascular mortality (Figure 27.12), but they
have little effect on LDL or HDL cholesterol levels.
.
 Figure 27.12 Dose responses
of physiologic effects of fish
oil intake.
36
B. Dietary fats and plasma lipids
4.
Trans fatty acids:
 Trans fatty acids (Figure 27.13) are chemically classified as
37
unsaturated fatty acids, but behave more like saturated fatty acids in
the body, that is, they elevate serum LDL (but not HDL), and they
increase the risk of CHD.
 Trans fatty acids do not occur naturally in plants, but occur in small
amounts in animals.
 However, trans fatty acids are formed during the hydrogenation of
liquid vegetable oils, for example, in the manufacture of margarine
and partially hydrogenated vegetable oil.
 Trans fatty acids are a major component of many commercial baked
goods, such as cookies and cakes, and most deep-fried foods.
 A clue to the presence of trans fatty acids in a food is the words
‘partially hydrogenated’ on the list of package ingredients.
.
 Figure 27.13 Structure of cis
and trans fatty acids
38
B. Dietary fats and plasma lipids
5.
Dietary cholesterol:
 Cholesterol is found only in animal products.
 The effect of dietary cholesterol on plasma cholesterol (Figure
27.14) is less important than the amount and types of fatty acids
consumed.
 Figure 27.14 Response of plasma
39
LDL concentrations to an increase in
dietary cholesterol intake.
40
 Figure 27.15 Effects of dietary fats.
6. Dietary Carbohydrates
 The primary role of dietary carbohydrate is to provide
energy.
 Carbohydrate consumption has significantly increased,
leading some observers to link obesity with carbohydrate
consumption.
 However, obesity has also been related to increasingly
inactive lifestyles, and to calorie-dense foods served in
expanded portion size.
 Carbohydrates are not inherently fattening.
41
 Figure 27.16 Total caloric consumption
and distribution of calories between the
macronutrients in adults.
42
A. Classification of carbohydrates
 Carbohydrates in the diet are classified as either
monosaccharides and disaccharides (simple sugars),
polysaccharides (complex sugars), or fiber.
1. Monosaccharides:



43
Glucose and fructose are the principal monosaccharides found in
food.
Glucose is abundant in fruits, sweet corn, corn syrup, and honey.
Free fructose is found together with free glucose and sucrose in
honey and fruits.
A. Classification of carbohydrates
2. Disaccharides:
 The most abundant disaccharides are:
 Sucrose (glucose + fructose), is ordinary “table sugar,” and is abundant in
molasses and maple syrup.
 Lactose (glucose + galactose) is the principal sugar found in milk.
 Maltose (glucose + glucose) is a product of enzymatic digestion of
polysaccharides.
 It is also found in significant quantities in beer and malt liquors.
 The term “sugar” refers to monosaccharides and
disaccharides.

44
A. Classification of carbohydrates
Polysaccharides:
3.



Fiber:
4.



45
Complex carbohydrates are polysaccharides (most often polymers
of glucose), which do not have a sweet taste.
Starch is an example of a complex carbohydrate that is found in
abundance in plants.
Common sources include wheat and other grains, potatoes, dried
peas and beans, and vegetables.
Dietary fiber is defined as the non-digestible carbohydrates and
lignin present in plants.
Several different terms are used to described this complex group
of compounds.
For example, functional fiber is the isolated, extracted, or
synthetic fiber that has proven health benefits.
A. Classification of carbohydrates
 Total fiber is the sum of dietary fiber and functional fiber.
 Soluble fiber refers to fibers that form a viscous gel when
mixed with a liquid.
 Insoluble fiber passes through the digestive track largely
intact.
 Dietary fiber provides little energy but has several
beneficial effects.

46
 Figure 27.17 Actions of
dietary fiber.
47
B. Dietary carbohydrate and blood glucose
 Some carbohydrate-containing foods produce a rapid rise
followed by a steep fall in blood glucose concentration, whereas
others result in a gradual rise followed by a slow decline.
 The glycemic index has been proposed to quantitate these
differences in the time course of postprandial glucose
concentrations (Figure 27.18).
 Glycemic index is defined as:
 The area under the blood glucose curves seen after ingestion of a
meal with carbohydrate-rich food, compared with the area under
the blood glucose curve observed after a meal consisting of the same
amount of carbohydrate in the form of glucose or white bread.
48
49
 Figure 27.18 Blood glucose concentrations following ingestion of
food with low or high glycemic index.
C. Requirements for carbohydrate
 Carbohydrates are not essential nutrients, because the
carbon skeletons of amino acids can be converted into
glucose
 However, the absence of dietary carbohydrate leads to
ketone body production, and degradation of body protein
whose constituent amino acids provide carbon skeletons for
gluconeogenesis.
 Adults should consume 45–65 percent of their total calories
from carbohydrates.
50
7. Dietary Protein
 Humans have no dietary requirement for protein, per se, but, the
protein in food does provide essential amino acids.
 Nine of the 20 amino acids needed for the synthesis of body
proteins are essential—that is, they cannot be synthesized in
humans.
51
A. Quality of proteins
1.
Proteins from animal sources:
 Proteins from animal sources (meat, poultry, milk, and
fish) have a high quality because they contain all the
essential amino acids in proportions similar to those
required for synthesis of human tissue proteins
52
A. Quality of proteins
2. Proteins from plant sources:
 Proteins from wheat, corn, rice, and beans have a lower quality than
53
do animal proteins.
 However, proteins from different plant sources may be combined in
such a way that the result is equivalent in nutritional value to animal
protein.
 For example, wheat (lysine-deficient but methionine-rich) may be
combined with kidney beans (methionine-poor but lysine-rich) to
produce a complete protein of improved biologic value.
 Thus, eating foods with different limiting amino acids at the same
meal (or at least during the same day) can result in a dietary
combination with a higher biologic value than either of the
component proteins
C. Requirement for protein in humans
 The amount of dietary protein required in the diet varies with its




54

biologic value.
The greater the proportion of animal protein included in the diet, the
less protein is required.
The RDA for protein is computed for proteins of mixed biologic value
at 0.8 g/kg of body weight for adults, or about 56 g of protein for a
70-kg individual.
People who exercise strenuously on a regular basis may benefit from
extra protein to maintain muscle mass; a daily intake of about 1 g/kg
has been recommended for athletes.
Women who are pregnant or lactating require up to 30 g/day in
addition to their basal requirements.
To support growth, children should consume 2 g/kg/day.
C. Requirement for protein in humans
Consumption of excess protein:
1.



55
There is no physiologic advantage to the consumption of more
protein than the RDA.
Protein consumed in excess of the body's needs is deaminated,
and the resulting carbon skeletons are metabolized to provide
energy or acetyl coenzyme A for fatty acid synthesis.
When excess protein is eliminated from the body as urinary
nitrogen, it is often accompanied by increased urinary calcium,
increasing the risk of nephrolithiasis and osteoporosis.
C. Requirement for protein in humans
The protein-sparing effect of carbohydrate:
2.




56
The dietary protein requirement is influenced by the
carbohydrate content of the diet.
When the intake of carbohydrates is low, amino acids are
deaminated to provide carbon skeletons for the synthesis of
glucose that is needed as a fuel by the central nervous system.
If carbohydrate intake is less than 130 g/day, substantial amounts
of protein are metabolized to provide precursors for
gluconeogenesis.
Therefore, carbohydrate is considered to be “protein-sparing,”
because it allows amino acids to be used for repair and
maintenance of tissue protein rather than for gluconeogenesis.
D. Protein-calorie malnutrition
 In developed countries, protein-energy (calorie)
57
malnutrition (PEM) is seen most frequently in hospital
patients with chronic illness, or in individuals who suffer
from major trauma, severe infection, or the effects of major
surgery.
 Such highly catabolic patients frequently require intravenous
(parenteral) or tube-based (enteral) administration of
nutrients.
 In developing countries, an inadequate intake of protein
and/or energy may be observed.
 Affected individuals show a variety of symptoms, including a
depressed immune system with a reduced ability to resist
infection. Death from secondary infection is common.
 Two extreme forms of PEM are kwashiorkor and marasmus.
D. Protein-calorie malnutrition
1.
Kwashiorkor:
 Kwashiorkor occurs when protein deprivation is relatively greater
than the reduction in total calories.
 Kwashiorkor is frequently seen in children after weaning at about
one year of age, when their diet consists predominantly of
carbohydrates.
 Typical symptoms include stunted growth, edema, skin lesions,
depigmented hair, anorexia, enlarged fatty liver, and decreased
plasma albumin concentration.
 Edema results from the lack of adequate plasma proteins to maintain
the distribution of water between blood and tissues.
58
59
Figure 27.22: A.Listless child with kwashiorkor. B.Child suffering with marasmus.
D. Protein-calorie malnutrition
2.
Marasmus:
 Marasmus occurs when calorie deprivation is relatively greater than
the reduction in protein.
 Marasmus usually occurs in children younger than one year of age
when the mother's breast milk is supplemented with thin watery
gruels of native cereals, which are usually deficient in protein and
calories.
 Typical symptoms include arrested growth, extreme muscle wasting
(emaciation), weakness, and anemia.
 Victims of marasmus do not show the edema or changes in plasma
proteins observed in kwashiorkor.
60
8. Chapter Summary
 Estimated Average Requirement (EAR) is the average daily nutrient
intake level estimated to meet the requirement of one half the healthy
individuals in a particular life stage and gender group.
 The Recommended Dietary Allowance (RDA) is the average daily
dietary intake level that is sufficient to meet the nutrient requirements
of nearly all (97–98%) individuals.
 Adequate Intake (AI) is set instead of an RDA if sufficient scientific
evidence is not available to calculate the RDA.
 The Tolerable Upper Intake Level (UL) is the highest average daily
nutrient intake level that is likely to pose no risk of adverse health
effects to almost all individuals in the general population.
61
8. Chapter Summary
 The energy generated by the metabolism of the
macronutrients is used for three energy-requiring processes
that occur in the body: resting metabolic rate, thermic
effect of food, and physical activity.
 Acceptable Macronutrient Distribution Ranges (AMDR)
are defined as the ranges of intake for a particular
macronutrient that is associated with reduced risk of
chronic disease while providing adequate amounts of
essential nutrients.
 Adults should consume 45–65% of their total calories from
carbohydrates, 20 –35% from fat, and 10–35% from
protein (Figure 27.22).
62
8. Chapter Summary
 Elevated levels of cholesterol or LDL cholesterol result in increased
risk for cardiovascular disease.
 In contrast, high levels of HDL cholesterol have been associated with a
decreased risk for heart disease.
 Dietary or drug treatment of hypercholesterolemia is effective in
decreasing LDL, increasing HDL, and reducing the risk for
cardiovascular events.
 Consumption of saturated fats is strongly associated with high levels of
total plasma and LDL cholesterol. When substituted for saturated
fatty acids in the diet, monounsaturated fats lower both total plasma
and LDL cholesterol, but increase HDL.
63
8. Chapter Summary
 Consumption of fats containing n-6 polyunsaturated fatty acids lowers
plasma LDL, but HDL, which protect against coronary heart disease,
are also lowered.
 Dietary n-3 polyunsaturated fats suppress cardiac arrhythmias and
reduce serum triacylglycerols, decrease the tendency for thrombosis,
and substantially reduce the risk of cardiovascular mortality.
 Carbohydrates provide energy and fiber to the diet. When they are
consumed as part of a diet in which caloric intake is equal to energy
expenditure, they do not promote obesity.
 Dietary protein provides essential amino acids. The quality of a protein
is a measure of its ability to provide the essential amino acids required
for tissue maintenance.
64
8. Chapter Summary
 Proteins from animal sources, in general, have a higher- quality




65
protein than that derived from plants. However, proteins from
different plant sources may be combined in such a way that the result
is equivalent in nutritional value to animal protein.
Positive nitrogen balance occurs when nitrogen intake exceeds
nitrogen excretion. It is observed in situations in which tissue growth
occurs, for example, in childhood, pregnancy, or during recovery
from an emaciating illness.
Negative nitrogen balance occurs when nitrogen losses are greater
than nitrogen intake. It is associated with inadequate dietary protein,
lack of an essential amino acid, or during physiologic stresses such as
trauma, burns, illness, or surgery.
Kwashiorkor is caused by inadequate intake of protein.
Marasmus results from chronic deficiency of calories.
66