The Importance Of Child And Maternal Nutrition
Although the precise contribution of nutrition to maternal and
infant health cannot yet be distinguished from genetic, environmental,
or behavioural factors that affect risk, an inadequate diet during
pregnancy increases the probability of a low birth weight (LBW) infant,
who, in turn, has an increased risk of mortality. Well-nourished
mothers who gain appropriate amounts of weight during pregnancy
generally give birth to heavier, healthier babies.
The most important factor contributing to the infant mortality rate
is a low birth weight - less than 2500 g. Infant deaths and illnesses
increase sharply as birth weight declines. LBW infants are at increased
risk for developmental handicaps, birth defects, respiratory and other
infectious diseases, behaviour problems, and complications of medical
interventions.
Medical, social, behavioural, and dietary factors before and during
pregnancy contribute to the risk for LBW. Dietary factors include an
inadequate intake of calories or essential nutrients such as protein,
vitamins, and minerals. The more these risk factors are present, the
greater the risk to mother and child.
Normal pregnancy is accompanied by anatomical and physiologic
changes that are necessary to promote fetal growth and development and
prepare the mother for labor, birth, and lactation.
During both pregnancy and lactation, hormonal changes affect the
utilization of nutrients. They include an increase in cardiac output,
heart rate, and basal metabolic rate. Preparation of the mammary glands
for lactation begins during pregnancy. Lactation is initiated and
maintained by hormonal changes that occur in response to the infant's
sucking stimulus.
During pregnancy, body weight, lean body tissue, and fat increase.
After childbirth, blood volume and extracellular fluids return to
prepregnant levels.
Immediately after birth, weight is lost, but birth weight is usually
regained by the 10th day. After this time, weight increases at a rapid
but decelerating rate. Most infants double their birth weight by the
age of 4 months and triple it within a year.
The very rapid rate of growth in infancy is followed by slower
growth during the preschool and early school-age years. Children become
leaner between 6 months and 6 years, after which a gradual increase in
fat thickness occurs in both males and females untilpuberty; females
have a relatively greater body fat content than males at all stages of
development.
Extra energy and nutrients are needed to support the growth of
maternal tissues, and the increased metabolic demands of pregnancy as
well as the growth of the fetus and placenta. During lactation, the
energy and nutrients provided in the milk, and those required for its
production, must be replaced.
Maternal pregnancy weight and weight gained during pregnancy are
important determinants of infant birth weight. Inadequate weight gain
during pregnancy and low prepregnancy weight combined with low weight
gain are associated with lower than average infant birth weight and
greater risks for fetal or neonatal death and neonatal disease.
The RDA for vitamins and minerals for pregnant or lactating women include levels above those for nonpregnant women (See RDA Tables).
In healthy women with normal pregnancies, vitamin and mineral needs can
usually be met by consuming an adequate diet. Supplements, although
usually recommended, are not always associated with measurable health
improvements in this population.
The need for iron is increased during pregnancy, and the National
Research Council recommends an iron supplement of 30 to 60 mg per day
to prevent depletion of iron stores during pregnancy and lactation.
Pregnant women should be evaluated periodically to determine their
level of iron stores and should receive supplements when iron stores
are low.
The RDA for zinc includes a 5 mg per day increment during pregnancy
over the 15 mg per day recommended for nonpregnant women. The rate of
fetal malformations and other poor outcomes of pregnancy may be higher
in populations where zinc deficiency has been recognized.
Maternal age influences fetal and infant mortality rates and birth
weight. Mothers 15 years of age or younger have increased rates of
pregnancy-induced hypertension and premature delivery, are more likely
to deliver infants of low body weight, and have higher rates of fetal
loss and infant mortality. While nutrition is by no means the only
issue in caring for the pregnant adolescent, it is a controllable risk
factor that can be reduced by programs that provide support, prenatal
care, and extra food.
Pica:Pica, a persistent compulsion to eat unsuitable
substances of little or no nutritional value, is a recognized
complication of pregnancy. Inadequate absorption of iron is the hazard
most commonly attributed to pica.
Hypertension:Hypertensive conditions induced by pregnancy
are known as preeclampsia and eclampsia. Preeclampsia is characterized
by a rise in blood pressure, generalized edema that may cause sudden,
large weight gain from retained water, and loss of protein. Eclampsia
is the most severe form of the disorder, characterized by convulsions
that may lead to coma. Hypertension existing before pregnancy may also
adversely affect pregnancy.
Diabetes:Infants born to women with diabetes are at
greatly increased risk for prematurity, congenital defects, excessively
high birth weight, and other conditions that increase overall
mortality, especially when the mother's blood glucose levels remain
high during pregnancy.
Diabetes screening is indicated for pregnant women with risk factors
for overt diabetes; a previous history of gestational diabetes, a
large-for-gestational-age infant, excess amniotic fluid during
pregnancy, excretion of sugar in urine, an increase of thirst and
urination, or recurrent vaginal or urinary tract infections. Diabetes
screening can identify diabetes in mothers who may not have been
diagnosed previously and who might benefit from preventive services.
Glucose and amino acids, rather than fatty acids, are the primary
metabolic fuels for the fetus. Fetal energy requirements increase
during pregnancy to a maximum estimated 150 kcal per day. These are
modest values when compared with the mother's estimated energy
requirement of 2000 to 2800 kcal per day.
A fetus near term requires about 6 to 8 g of protein per day. Most
of this comes as small amounts of essential and nonessential amino
acids received continuously from the placental circulation. Another
source of protein occurs in amniotic fluid the fetus swallows.
Vitamin requirements of the human fetus have not been established.
Although specific vitamin deficiencies have been shown to induce
reproductive loss and developmental defects in experimental animals,
similar data for human fetuses are not available.
Mineral requirements of the fetus, estimated from studies on fetal
body composition, seem to be higher during the last few weeks of
pregnancy than at any other time during prenatal or postnatal
development. Little is known, however, about the specific needs for
individual minerals.
Excessive alcohol consumption adversely affects fetal development.
Infants born to women who were chronic alcoholics exhibit specific
abnormalities of the eyes, nose, heart, and central nervous system;
irritability and hyperactivity after birth as a result of alcohol
withdrawal; and impaired physical and mental development despite
nutritional rehabilitation. Evenone or two drinks per day are
associated with higher rates of spontaneous abortion, premature
detachment of the placenta, and LBW infants.
The nutritional requirements of normal infants have been
investigated and RDA's have been established. Infants require three to
four times greater amounts of energy per kilogram of body weight (90 to
120 kcal per day) than do adults to support their relatively high
metabolic rate and needs for growth. Energy requirements of individual
infants are determined by body size and composition, rates of physical
growth, and activity patterns. Normal infants appear to adjust intake
to needs, provided the mother is sensitive to cues of satiation; loss
of interest in food, releasing the nipple from the mouth, or turning
the head from the nipple or pushing the bottle or cup away.
Protein requirements are also proportionately greater in infants
than in adults. Dietary protein must be sufficient to support increases
in body protein. These needs can be met by protein intakes of about 2.2
g per kg for the first 6 months and 2.0 g per kg for months 7 to 12.
Because dietary fat is a concentrated source of the calories needed
to meet infants' high energy needs, infants should consume 34 to 54
percent of total calories from fat. Carbohydrate should supply 30 to 60
percent of the total daily energy intake in infancy.
Although infant requirements for micronutrients are not as well
defined as those for energy and protein, RDA's have been established
for many vitamins and minerals. Infants fed a commercially available
formula that is properly prepared should receive an adequate intake of
vitamins.
Iron deficiency is the most common nutrient deficiency in infancy.
Current recommendations are that infants begin consuming iron-fortified
cereals at 4 to 6 months of age to prevent anaemia. Because human milk
is low in fluoride and because enamel development in permanent teeth is
significant during the first year of life, a fluoride supplement may be
desirable for children who do not have access to adequately fluoridated
drinking water.
Human milk is the food of choice for infants. It provides
appropriate amounts of energy and nutrients, it contains factors that
provide protection against infection, and it rarely causes allergic
responses. Fat provides about 50 percent of the calories in human milk,
most in the form of triglyceride, with the fatty acid pattern
reflecting the maternal diet. Linoleic acid provides an average of 4
percent of the calories in human milk. The cholesterol content varies
considerably but averages 20 mg per 100 ml. Lactose (milk sugar) is the
major carbohydrate.
The concentrations of water-soluble vitamins in human milk generally
reflect the maternal dietary intake and nutritional status. Providing
folate supplementation to a women deficient inthis vitamin increases
milk folate levels. Vitamin B12 deficiency has been reported
in breast-fed infants whose mothers are strict vegetarians. Breast-fed
infants require supplemental vitamin K at birth (human milk is low in
vitamin K) and may require vitamin D supplementation if exposure to the
sun is inadequate.
Infant Formulas:The Food and Drug administration
specifies the nutrient composition of commercial infant formulas.
Manufacturers modify cow milk by replacing its fats with vegetable oils
that are well absorbed, diluting it to a more appropriate concentration
of minerals and other solutes, heating it to improve protein
digestibility, and adding vitamins and minerals. Soy-based substitutes
are available for infants who develop allergic or other sensitivities
to substances in cow milk-based formulas.
When properly prepared, commercial formulas support normal growth
and development. Errors in preparation, however, result in medical
problems. Inadequately diluted formula increases the concentrations of
calories, proteins and solutes and can increase levels of sodium and
other substances in the blood, resulting in disturbances of acid-base
balance and toxic symptoms. Overdiluting the formula reduces the level
of sodium and other salts in the blood, thereby causing adverse
reactions and does not provide adequate energy and nutrients for growth.
Imitation Milks:Substitute or imitation milks, inadequate
in calories and nutrients, are not suitable for feeding to infants.
Malnutrition has been observed in infants fed imitation milk and in
those fed nondairy creamer.
Cows Milk:Unmodified whole cow milk is inappropriate to
feed to young infants. Its lipids are less digestible than the lipids
of human milk or most vegetable oils, and its concentrations of
minerals and other solutes nearly exceed the excretory capacity of the
immature kidney.
For infants, 2-percent and nonfat milks are deficient in energy,
essential fatty acids, and certain vitamins, and they contain excessive
protein and minerals per calorie provided. They are not recommended
during the first year of life.
Goats Milk:Goats milk should not be used during infancy
because it is low in iron, folate, and vitamins B, C, and D. And it has
a solute concentration even higher than in cow milk.
Solid Foods:By the age of 4 to 6 months, infants have
usually matured enough to sit and to control movements of the head,
tongue, lips, and jaw. They can indicate when they do not want to eat.
At this point feeding pureed solid foods becomes appropriate. The
recommended routine is to introduce single-ingredient foods to the
diet, one at a time, at weekly intervals. Iron supplemented cereals are
usually the first foods added. If properly preparedand stored, pureed
foods made at home are nutritionally equivalent to those prepared
commercially. By the age of 1 year, foods should provide more than 50
percent of the energy intake of infants. Salt need not be added to food
prepared for normal infants, and sugar should be used sparingly, or not
at all. Infants should not be fed hot dogs, nuts, grapes, popcorn,
uncooked carrots, round candies, and similar foods that can cause
choking.
Infants born prematurely or after intrauterine growth retardation
are at high risk for malnutrition and may require special feeding.
Before 26 weeks of gestation, the fetus's gastrointestinal system is
too immature to digest proteins, fats, or lactose. Fully competent
digestive processes do not develop until about 36 weeks of gestation.
Infants born prior to 34 weeks of gestation may not be able to suck
effectively. The challenge is to provide adequate calories and
nutrients in a form that the immature digestive and excretory systems
can handle and that does not cause complications.
Providing 95 to 160 kcal and about 3 g of protein per kg per day, 4
percent of calories as linoleic acid, 40 to 50 percent of calories as
carbohydrate, and sufficient water to compensate for the unusually high
losses from the skin helps achieve adequate nutrition for LBW infants.
Human milk and formulas designed for full-term infants contain
insufficient calcium and phosphorus to meet the needs of LBW infants
and must be supplemented to permit adequate bone growth and
mineralization. Because iron supplements increase susceptibility to
vitamin E deficiency, recommendations for iron supplementation in the
LBW infant are cautious. Preventing bone disease in LBW infants depends
not only on adequate calcium and phosphorus, but also on an intake of
at least 500 IU of vitamin D per day. Vitamin E requirements may be
higher for LBW infants than for term infants. The recommendations for
folate in LBW is 50 ?g per 100 kcal. This vitamin must be added
separately to liquid multivitamin preparations because of its
instability.
Methods for meeting nutritional goals for LBW infants usually
include a combination of human milk; other special supplements,
formulas or products fed by mouth or tube (enteral nutrition); or
intravenous feeding (parenteral nutrition). Some LBW infants can be
nourished adequately on their mother's milk, whereas others thrive
better when provided with additional supplements. Special formulas for
LBW infants contain more protein, calcium, and phosphorus than formulas
for term infants. Although the composition of these formulas vary, all
can support growth.
The energy requirements of children are determined by their
individual basal metabolic rates, rates of growth, and activity
patterns. Therefore, appropriate intakes for children of the same age,
sex, and size vary.
Children need protein for the maintenance of body tissues, changes
in body composition, and synthesis of new muscles. During growth, the
protein content of the body increases from about 15 percent at one year
to 18 percent by four years, which is also the value for adults. The
RDA for protein decreases from 1.8 g per kg per day at one year to 0.8
g per kg per day at 18 years.
Inadequate intakes of vitamins and minerals will be reflected in
slow growth rates, inadequate mineralization of bones, and very low
reserves of micronutrients. With the relatively low prevalence of
clinical signs of vitamin and mineral deficiency in the general
population of children, there is no evidence that supplementation is
necessary for this group. Although vitamin and mineral supplements
increase the quantity of these nutrients in the diet, they have not
been shown to improve biochemical indices of nutrient status in
children who are already well nourished. For this reason,
recommendations for vitamin and mineral supplements target children at
high risk, those from socioeconomically deprived families, and those
who have poor appetites or eating habits.
Preschool children are a nutritionally vulnerable group. Their
growth rate is slower than it was in infancy and their nutritional
needs in relation to body size proportionately reduced. Thus, they
often want and eat relatively little food. Food intake can be reduced
even further by the increasing independence (expressed as refusals to
eat) and immature feeding skills that are characteristic of very young
children.
Parents continue to be the main influence on the food intake of
school-aged children, although an increasing proportion of the diet is
consumed in schools, day care centres, and fast food restaurants.
Between the ages of 4 and 6, children increase the varieties of foods
they are willing to eat. Snacks become an important source of calories
and nutrients, and may contribute as much as one-third of calories and
fat, one-fifth of the protein, and nearly one-half of the carbohydrate
10-year-old children consume. These patterns emphasize the need for
parents and schools to provide appropriate meals and snacks and
guidance in food choices.
Energy and nutrient requirements are directly related to the stage
and rate of growth, and demands are greatest during the peak velocity
of growth. For most nutrients the RDA's are similar to those for adults.
The RDA for calcium, 1200 mg per day, is higher for adolescents than
for adults and is designed to meet the needs of the adolescent who is
growing at the fastest rate. Achieving maximum bone mass during the
teens and twenties can reduce the risk of developing osteoporosis later
in life. The higher RDA for iron for adolescent males is also related
to rapid growth, which is accompanied by increases in blood volume,
muscle mass, and iron-containing enzymes. Vitamin requirements are
correlated withgrowth demands rather than age.
The growth surge of adolescence demands significant increases in
calories and nutrient intake to support the rapid growth rate and
increased body size. In early adolescence, children still depend on
their parents for food, but by the end of adolescence they are largely
independent.
Irregular eating patterns are common in adolescence, reflecting this
growing independence from the family and the teenager's increasingly
busy social life and athletic, academic, and vocational activities.
Breakfast or lunch are often skipped or eaten on the run. Snacking is
characteristic of this age group and contributes significantly to
nutrient intake. These snack foods are often higher in calories, fat
and sugar, and lower in vitamins, minerals, and fibre, than foods
consumed at family meals. Because lifetime dietary patterns are
established during these years, adolescents should be encouraged to
choose nutritious foods, to develop good eating habits, and to maintain
appropriate levels of physical activity.
Several chronic diseases have special implications in the nutrition
of infants, children, and adolescents. Childhood hyperactivity (or
attention deficit disorders) and eating disorders such as anorexia
nervosa and bulimia occur at this age. Children with chronic disease
and other handicapping conditions frequently require therapeutic diets
accompanied by intensive nutrition counselling and support.
The relationship between diet in infancy, childhood, and adolescence
and the development of adult atherosclerosis and coronary heart disease
is of great current interest. Cholesterol-lowering diets for children
with elevated blood cholesterol levels, as well as for those with
normal levels, have been recommended to prevent the onset of the adult
disease. These recommendations are that all children older than two
years adopt a diet that reduces dietary fat intake to 30 percent or
less of calories, saturated fat to less than 10 percent of calories,
and daily cholesterol intake to 250 mg or less.
Increasing evidence suggests that atherosclerosis begins in
childhood. Cholesterol concentrations rise after infants begin to be
fed, infants fed human milk or cow milk have higher blood cholesterol
levels at age 6 months than do those fed formulas containing vegetable
oils, but these differences are reduced once cholesterol-containing
foods are added to the diet. By the age of one year, blood cholesterol
levels correlate with dietary intake of saturated fat and cholesterol,
they rise rapidly during the first two years of life. Childhood blood
cholesterol levels have a strong genetic component, and children whose
parents have high levels are two or three times more likely to have
high blood cholesterol levels than children of parents with low or
normal levels.
Measurements of heart disease risk factors such as high blood
pressure or obesity are highly correlated with those made in the same
children at age seven. Thus, pediatricians have been urged to identify
and to treat children with elevated blood cholesterol levels.
The increased rate of pediatric obesity is an important public
health issue. Childhood obesity can lead to adult obesity and all its
complications.
Both genetic and environmental factors are involved, there is a
strong correlation of body weights to the weight of the biologic
parents. Lower than normal activity levels are also related to
childhood obesity. One study observed a direct relationship between the
body weight and number of hours spent watching television [Dietz,
W.H., and Gortmaker, S.L.: Do we fatten our children at the television
set Obesity and television viewing in children and adolescents.
Pediatrics 75:807-12, 1985.] .
Animal and human studies have shown that severe malnutrition during
fetal growth and early infancy retards brain cell division and alters
nerve myelination (structure of nerve fibres).
Data from population groups in which malnutrition is endemic
indicate a relationship between growth retardation of infants and young
children and low performance in mental development tests. Children with
protein-energy malnutrition in infancy who were tested at ages 5 to 11
years had poorer academic performance than children who were well
nourished in infancy, which is reflected in classroom behaviour
problems such as lack of attention, poor memory, poor motivation, and
easy distractibility.
Studies of the effects of omitting breakfast on cognitive
performance show that nutrition benefits learning. Well-nourished
children aged 9 to 10 who skipped breakfast displayed higher rates of
inaccurate responses to problem solving.
Early identification and nutrition intervention can prevent
subsequent mental retardation in infants born with many kinds of
metabolic disorders. Such children require long-term dietary
management. One example of such a disorder is phenylketonuria.
Phenylketonuria results in excessive and potentially toxic blood
levels of the amino acid phenylalanine. The goals of therapy are to
provide adequate intakes of energy and nutrients but only enough
phenylalanine to maintain normal growth and development. Meeting these
goals requires special formulas and food productswith reduced
phenylalanine content, as well as considerable support from health
professionals.
Current recommendations are to continue the phenylalanine-restricted
diet throughout the reproductive years, because experience with its
discontinuation at ages ranging from 4 to 10 years indicates
progressively decreasing cognitive functioning, learning difficulties,
poor attention span, and behavioural difficulties. Evidence suggests
also that phenylalanine restriction during pregnancy improves the
outcome for women with phenylketonuria and their infants.
Assessment of nutritional status is an integral part of maternity
care at the beginning of pregnancy and periodically throughout
pregnancy and lactation to provide continuing monitoring and recommend
appropriate intervention.
Evidence related to the role of diet in maternal and child health
indicates that well-nourished mothers produce healthier children.
Intake of sufficient energy and nutrients to attain optimal nutritional
status, including appropriate weight before pregnancy and adequate
weight gain during pregnancy, improves infant birth weight and reduces
infant mortality. Avoiding potentially toxic substances such as alcohol
or drugs during pregnancy improves birth weight and health.
Evidence related to the role of diet in infancy indicates that
breast milk is the optimal food for infants. Whenever possible and as
early as possible, health professionals should provide guidance and
support to pregnant women and new mothers on the importance of
breastfeeding and on methods for its initiation and maintenance.
Consuming the appropriate amount and form of energy and nutrients
for developmental age is important for good health, as is early
education about lifelong dietary patterns that help prevent disease.
Parents should guide their children in developing positive eating
behaviours and on age-appropriate food patterns that meet nutritional
requirements but avoid excessive intake of fat, sodium, and sugar.
Physicians, nurses, and other health professionals caring for
children and women of childbearing age should receive education and
training in nutrition assessment, nutrition intervention for prevention
of disease, and promotion of maternal and child health.
Nutrition Services:Evidence related to the role of
nutrition in maternal, infant, and child health suggests that all
health care programs for these groups should provide nutrition
services, especially to those people at special health or economic
risk. Such services includenutrition assessment, dietary counselling,
nutrition education, and referral.
Food Products:Evidence related to the role of dietary
factors in maternal and child health suggests that food manufacturers
should develop nutritious, low-fat, low-salt, low-sugar snack food
products for children and adolescents. Quality and safety of infant
formulas and other infant foods require continued monitoring to prevent
untoward health consequences. [The Surgeon General's Report on Nutrition & Health, 1988.]
Although the precise contribution of nutrition to maternal and
infant health cannot yet be distinguished from genetic, environmental,
or behavioural factors that affect risk, an inadequate diet during
pregnancy increases the probability of a low birth weight (LBW) infant,
who, in turn, has an increased risk of mortality. Well-nourished
mothers who gain appropriate amounts of weight during pregnancy
generally give birth to heavier, healthier babies.
The most important factor contributing to the infant mortality rate
is a low birth weight - less than 2500 g. Infant deaths and illnesses
increase sharply as birth weight declines. LBW infants are at increased
risk for developmental handicaps, birth defects, respiratory and other
infectious diseases, behaviour problems, and complications of medical
interventions.
Medical, social, behavioural, and dietary factors before and during
pregnancy contribute to the risk for LBW. Dietary factors include an
inadequate intake of calories or essential nutrients such as protein,
vitamins, and minerals. The more these risk factors are present, the
greater the risk to mother and child.
Pregnancy and Lactation
Normal pregnancy is accompanied by anatomical and physiologic
changes that are necessary to promote fetal growth and development and
prepare the mother for labor, birth, and lactation.
During both pregnancy and lactation, hormonal changes affect the
utilization of nutrients. They include an increase in cardiac output,
heart rate, and basal metabolic rate. Preparation of the mammary glands
for lactation begins during pregnancy. Lactation is initiated and
maintained by hormonal changes that occur in response to the infant's
sucking stimulus.
During pregnancy, body weight, lean body tissue, and fat increase.
After childbirth, blood volume and extracellular fluids return to
prepregnant levels.
Infants
Immediately after birth, weight is lost, but birth weight is usually
regained by the 10th day. After this time, weight increases at a rapid
but decelerating rate. Most infants double their birth weight by the
age of 4 months and triple it within a year.
Children and Adolescents
The very rapid rate of growth in infancy is followed by slower
growth during the preschool and early school-age years. Children become
leaner between 6 months and 6 years, after which a gradual increase in
fat thickness occurs in both males and females untilpuberty; females
have a relatively greater body fat content than males at all stages of
development.
Nutritional Needs of Pregnant and Lactating Women
Extra energy and nutrients are needed to support the growth of
maternal tissues, and the increased metabolic demands of pregnancy as
well as the growth of the fetus and placenta. During lactation, the
energy and nutrients provided in the milk, and those required for its
production, must be replaced.
Maternal pregnancy weight and weight gained during pregnancy are
important determinants of infant birth weight. Inadequate weight gain
during pregnancy and low prepregnancy weight combined with low weight
gain are associated with lower than average infant birth weight and
greater risks for fetal or neonatal death and neonatal disease.
The RDA for vitamins and minerals for pregnant or lactating women include levels above those for nonpregnant women (See RDA Tables).
In healthy women with normal pregnancies, vitamin and mineral needs can
usually be met by consuming an adequate diet. Supplements, although
usually recommended, are not always associated with measurable health
improvements in this population.
The need for iron is increased during pregnancy, and the National
Research Council recommends an iron supplement of 30 to 60 mg per day
to prevent depletion of iron stores during pregnancy and lactation.
Pregnant women should be evaluated periodically to determine their
level of iron stores and should receive supplements when iron stores
are low.
The RDA for zinc includes a 5 mg per day increment during pregnancy
over the 15 mg per day recommended for nonpregnant women. The rate of
fetal malformations and other poor outcomes of pregnancy may be higher
in populations where zinc deficiency has been recognized.
Adolescent Pregnancy
Maternal age influences fetal and infant mortality rates and birth
weight. Mothers 15 years of age or younger have increased rates of
pregnancy-induced hypertension and premature delivery, are more likely
to deliver infants of low body weight, and have higher rates of fetal
loss and infant mortality. While nutrition is by no means the only
issue in caring for the pregnant adolescent, it is a controllable risk
factor that can be reduced by programs that provide support, prenatal
care, and extra food.
Disorders During Pregnancy
Pica:Pica, a persistent compulsion to eat unsuitable
substances of little or no nutritional value, is a recognized
complication of pregnancy. Inadequate absorption of iron is the hazard
most commonly attributed to pica.
Hypertension:Hypertensive conditions induced by pregnancy
are known as preeclampsia and eclampsia. Preeclampsia is characterized
by a rise in blood pressure, generalized edema that may cause sudden,
large weight gain from retained water, and loss of protein. Eclampsia
is the most severe form of the disorder, characterized by convulsions
that may lead to coma. Hypertension existing before pregnancy may also
adversely affect pregnancy.
Diabetes:Infants born to women with diabetes are at
greatly increased risk for prematurity, congenital defects, excessively
high birth weight, and other conditions that increase overall
mortality, especially when the mother's blood glucose levels remain
high during pregnancy.
Diabetes screening is indicated for pregnant women with risk factors
for overt diabetes; a previous history of gestational diabetes, a
large-for-gestational-age infant, excess amniotic fluid during
pregnancy, excretion of sugar in urine, an increase of thirst and
urination, or recurrent vaginal or urinary tract infections. Diabetes
screening can identify diabetes in mothers who may not have been
diagnosed previously and who might benefit from preventive services.
Nutritional Needs of the Fetus
Glucose and amino acids, rather than fatty acids, are the primary
metabolic fuels for the fetus. Fetal energy requirements increase
during pregnancy to a maximum estimated 150 kcal per day. These are
modest values when compared with the mother's estimated energy
requirement of 2000 to 2800 kcal per day.
A fetus near term requires about 6 to 8 g of protein per day. Most
of this comes as small amounts of essential and nonessential amino
acids received continuously from the placental circulation. Another
source of protein occurs in amniotic fluid the fetus swallows.
Vitamin requirements of the human fetus have not been established.
Although specific vitamin deficiencies have been shown to induce
reproductive loss and developmental defects in experimental animals,
similar data for human fetuses are not available.
Mineral requirements of the fetus, estimated from studies on fetal
body composition, seem to be higher during the last few weeks of
pregnancy than at any other time during prenatal or postnatal
development. Little is known, however, about the specific needs for
individual minerals.
Excessive alcohol consumption adversely affects fetal development.
Infants born to women who were chronic alcoholics exhibit specific
abnormalities of the eyes, nose, heart, and central nervous system;
irritability and hyperactivity after birth as a result of alcohol
withdrawal; and impaired physical and mental development despite
nutritional rehabilitation. Evenone or two drinks per day are
associated with higher rates of spontaneous abortion, premature
detachment of the placenta, and LBW infants.
Nutritional Needs of Normal Infants
The nutritional requirements of normal infants have been
investigated and RDA's have been established. Infants require three to
four times greater amounts of energy per kilogram of body weight (90 to
120 kcal per day) than do adults to support their relatively high
metabolic rate and needs for growth. Energy requirements of individual
infants are determined by body size and composition, rates of physical
growth, and activity patterns. Normal infants appear to adjust intake
to needs, provided the mother is sensitive to cues of satiation; loss
of interest in food, releasing the nipple from the mouth, or turning
the head from the nipple or pushing the bottle or cup away.
Protein requirements are also proportionately greater in infants
than in adults. Dietary protein must be sufficient to support increases
in body protein. These needs can be met by protein intakes of about 2.2
g per kg for the first 6 months and 2.0 g per kg for months 7 to 12.
Because dietary fat is a concentrated source of the calories needed
to meet infants' high energy needs, infants should consume 34 to 54
percent of total calories from fat. Carbohydrate should supply 30 to 60
percent of the total daily energy intake in infancy.
Although infant requirements for micronutrients are not as well
defined as those for energy and protein, RDA's have been established
for many vitamins and minerals. Infants fed a commercially available
formula that is properly prepared should receive an adequate intake of
vitamins.
Iron deficiency is the most common nutrient deficiency in infancy.
Current recommendations are that infants begin consuming iron-fortified
cereals at 4 to 6 months of age to prevent anaemia. Because human milk
is low in fluoride and because enamel development in permanent teeth is
significant during the first year of life, a fluoride supplement may be
desirable for children who do not have access to adequately fluoridated
drinking water.
Human milk is the food of choice for infants. It provides
appropriate amounts of energy and nutrients, it contains factors that
provide protection against infection, and it rarely causes allergic
responses. Fat provides about 50 percent of the calories in human milk,
most in the form of triglyceride, with the fatty acid pattern
reflecting the maternal diet. Linoleic acid provides an average of 4
percent of the calories in human milk. The cholesterol content varies
considerably but averages 20 mg per 100 ml. Lactose (milk sugar) is the
major carbohydrate.
The concentrations of water-soluble vitamins in human milk generally
reflect the maternal dietary intake and nutritional status. Providing
folate supplementation to a women deficient inthis vitamin increases
milk folate levels. Vitamin B12 deficiency has been reported
in breast-fed infants whose mothers are strict vegetarians. Breast-fed
infants require supplemental vitamin K at birth (human milk is low in
vitamin K) and may require vitamin D supplementation if exposure to the
sun is inadequate.
Infant Formulas:The Food and Drug administration
specifies the nutrient composition of commercial infant formulas.
Manufacturers modify cow milk by replacing its fats with vegetable oils
that are well absorbed, diluting it to a more appropriate concentration
of minerals and other solutes, heating it to improve protein
digestibility, and adding vitamins and minerals. Soy-based substitutes
are available for infants who develop allergic or other sensitivities
to substances in cow milk-based formulas.
When properly prepared, commercial formulas support normal growth
and development. Errors in preparation, however, result in medical
problems. Inadequately diluted formula increases the concentrations of
calories, proteins and solutes and can increase levels of sodium and
other substances in the blood, resulting in disturbances of acid-base
balance and toxic symptoms. Overdiluting the formula reduces the level
of sodium and other salts in the blood, thereby causing adverse
reactions and does not provide adequate energy and nutrients for growth.
Imitation Milks:Substitute or imitation milks, inadequate
in calories and nutrients, are not suitable for feeding to infants.
Malnutrition has been observed in infants fed imitation milk and in
those fed nondairy creamer.
Cows Milk:Unmodified whole cow milk is inappropriate to
feed to young infants. Its lipids are less digestible than the lipids
of human milk or most vegetable oils, and its concentrations of
minerals and other solutes nearly exceed the excretory capacity of the
immature kidney.
For infants, 2-percent and nonfat milks are deficient in energy,
essential fatty acids, and certain vitamins, and they contain excessive
protein and minerals per calorie provided. They are not recommended
during the first year of life.
Goats Milk:Goats milk should not be used during infancy
because it is low in iron, folate, and vitamins B, C, and D. And it has
a solute concentration even higher than in cow milk.
Solid Foods:By the age of 4 to 6 months, infants have
usually matured enough to sit and to control movements of the head,
tongue, lips, and jaw. They can indicate when they do not want to eat.
At this point feeding pureed solid foods becomes appropriate. The
recommended routine is to introduce single-ingredient foods to the
diet, one at a time, at weekly intervals. Iron supplemented cereals are
usually the first foods added. If properly preparedand stored, pureed
foods made at home are nutritionally equivalent to those prepared
commercially. By the age of 1 year, foods should provide more than 50
percent of the energy intake of infants. Salt need not be added to food
prepared for normal infants, and sugar should be used sparingly, or not
at all. Infants should not be fed hot dogs, nuts, grapes, popcorn,
uncooked carrots, round candies, and similar foods that can cause
choking.
Low Birth Weight Infants
Infants born prematurely or after intrauterine growth retardation
are at high risk for malnutrition and may require special feeding.
Before 26 weeks of gestation, the fetus's gastrointestinal system is
too immature to digest proteins, fats, or lactose. Fully competent
digestive processes do not develop until about 36 weeks of gestation.
Infants born prior to 34 weeks of gestation may not be able to suck
effectively. The challenge is to provide adequate calories and
nutrients in a form that the immature digestive and excretory systems
can handle and that does not cause complications.
Providing 95 to 160 kcal and about 3 g of protein per kg per day, 4
percent of calories as linoleic acid, 40 to 50 percent of calories as
carbohydrate, and sufficient water to compensate for the unusually high
losses from the skin helps achieve adequate nutrition for LBW infants.
Human milk and formulas designed for full-term infants contain
insufficient calcium and phosphorus to meet the needs of LBW infants
and must be supplemented to permit adequate bone growth and
mineralization. Because iron supplements increase susceptibility to
vitamin E deficiency, recommendations for iron supplementation in the
LBW infant are cautious. Preventing bone disease in LBW infants depends
not only on adequate calcium and phosphorus, but also on an intake of
at least 500 IU of vitamin D per day. Vitamin E requirements may be
higher for LBW infants than for term infants. The recommendations for
folate in LBW is 50 ?g per 100 kcal. This vitamin must be added
separately to liquid multivitamin preparations because of its
instability.
Methods for meeting nutritional goals for LBW infants usually
include a combination of human milk; other special supplements,
formulas or products fed by mouth or tube (enteral nutrition); or
intravenous feeding (parenteral nutrition). Some LBW infants can be
nourished adequately on their mother's milk, whereas others thrive
better when provided with additional supplements. Special formulas for
LBW infants contain more protein, calcium, and phosphorus than formulas
for term infants. Although the composition of these formulas vary, all
can support growth.
Role of Dietary Factors in Child Health
The energy requirements of children are determined by their
individual basal metabolic rates, rates of growth, and activity
patterns. Therefore, appropriate intakes for children of the same age,
sex, and size vary.
Children need protein for the maintenance of body tissues, changes
in body composition, and synthesis of new muscles. During growth, the
protein content of the body increases from about 15 percent at one year
to 18 percent by four years, which is also the value for adults. The
RDA for protein decreases from 1.8 g per kg per day at one year to 0.8
g per kg per day at 18 years.
Inadequate intakes of vitamins and minerals will be reflected in
slow growth rates, inadequate mineralization of bones, and very low
reserves of micronutrients. With the relatively low prevalence of
clinical signs of vitamin and mineral deficiency in the general
population of children, there is no evidence that supplementation is
necessary for this group. Although vitamin and mineral supplements
increase the quantity of these nutrients in the diet, they have not
been shown to improve biochemical indices of nutrient status in
children who are already well nourished. For this reason,
recommendations for vitamin and mineral supplements target children at
high risk, those from socioeconomically deprived families, and those
who have poor appetites or eating habits.
Preschool children are a nutritionally vulnerable group. Their
growth rate is slower than it was in infancy and their nutritional
needs in relation to body size proportionately reduced. Thus, they
often want and eat relatively little food. Food intake can be reduced
even further by the increasing independence (expressed as refusals to
eat) and immature feeding skills that are characteristic of very young
children.
Parents continue to be the main influence on the food intake of
school-aged children, although an increasing proportion of the diet is
consumed in schools, day care centres, and fast food restaurants.
Between the ages of 4 and 6, children increase the varieties of foods
they are willing to eat. Snacks become an important source of calories
and nutrients, and may contribute as much as one-third of calories and
fat, one-fifth of the protein, and nearly one-half of the carbohydrate
10-year-old children consume. These patterns emphasize the need for
parents and schools to provide appropriate meals and snacks and
guidance in food choices.
Role of Dietary Factors in Adolescent Health
Energy and nutrient requirements are directly related to the stage
and rate of growth, and demands are greatest during the peak velocity
of growth. For most nutrients the RDA's are similar to those for adults.
The RDA for calcium, 1200 mg per day, is higher for adolescents than
for adults and is designed to meet the needs of the adolescent who is
growing at the fastest rate. Achieving maximum bone mass during the
teens and twenties can reduce the risk of developing osteoporosis later
in life. The higher RDA for iron for adolescent males is also related
to rapid growth, which is accompanied by increases in blood volume,
muscle mass, and iron-containing enzymes. Vitamin requirements are
correlated withgrowth demands rather than age.
The growth surge of adolescence demands significant increases in
calories and nutrient intake to support the rapid growth rate and
increased body size. In early adolescence, children still depend on
their parents for food, but by the end of adolescence they are largely
independent.
Irregular eating patterns are common in adolescence, reflecting this
growing independence from the family and the teenager's increasingly
busy social life and athletic, academic, and vocational activities.
Breakfast or lunch are often skipped or eaten on the run. Snacking is
characteristic of this age group and contributes significantly to
nutrient intake. These snack foods are often higher in calories, fat
and sugar, and lower in vitamins, minerals, and fibre, than foods
consumed at family meals. Because lifetime dietary patterns are
established during these years, adolescents should be encouraged to
choose nutritious foods, to develop good eating habits, and to maintain
appropriate levels of physical activity.
Role of Dietary Factors in Childhood Chronic Disease
Several chronic diseases have special implications in the nutrition
of infants, children, and adolescents. Childhood hyperactivity (or
attention deficit disorders) and eating disorders such as anorexia
nervosa and bulimia occur at this age. Children with chronic disease
and other handicapping conditions frequently require therapeutic diets
accompanied by intensive nutrition counselling and support.
Coronary Heart Disease
The relationship between diet in infancy, childhood, and adolescence
and the development of adult atherosclerosis and coronary heart disease
is of great current interest. Cholesterol-lowering diets for children
with elevated blood cholesterol levels, as well as for those with
normal levels, have been recommended to prevent the onset of the adult
disease. These recommendations are that all children older than two
years adopt a diet that reduces dietary fat intake to 30 percent or
less of calories, saturated fat to less than 10 percent of calories,
and daily cholesterol intake to 250 mg or less.
Increasing evidence suggests that atherosclerosis begins in
childhood. Cholesterol concentrations rise after infants begin to be
fed, infants fed human milk or cow milk have higher blood cholesterol
levels at age 6 months than do those fed formulas containing vegetable
oils, but these differences are reduced once cholesterol-containing
foods are added to the diet. By the age of one year, blood cholesterol
levels correlate with dietary intake of saturated fat and cholesterol,
they rise rapidly during the first two years of life. Childhood blood
cholesterol levels have a strong genetic component, and children whose
parents have high levels are two or three times more likely to have
high blood cholesterol levels than children of parents with low or
normal levels.
Measurements of heart disease risk factors such as high blood
pressure or obesity are highly correlated with those made in the same
children at age seven. Thus, pediatricians have been urged to identify
and to treat children with elevated blood cholesterol levels.
Obesity
The increased rate of pediatric obesity is an important public
health issue. Childhood obesity can lead to adult obesity and all its
complications.
Both genetic and environmental factors are involved, there is a
strong correlation of body weights to the weight of the biologic
parents. Lower than normal activity levels are also related to
childhood obesity. One study observed a direct relationship between the
body weight and number of hours spent watching television [Dietz,
W.H., and Gortmaker, S.L.: Do we fatten our children at the television
set Obesity and television viewing in children and adolescents.
Pediatrics 75:807-12, 1985.] .
Cognitive Performance
Animal and human studies have shown that severe malnutrition during
fetal growth and early infancy retards brain cell division and alters
nerve myelination (structure of nerve fibres).
Data from population groups in which malnutrition is endemic
indicate a relationship between growth retardation of infants and young
children and low performance in mental development tests. Children with
protein-energy malnutrition in infancy who were tested at ages 5 to 11
years had poorer academic performance than children who were well
nourished in infancy, which is reflected in classroom behaviour
problems such as lack of attention, poor memory, poor motivation, and
easy distractibility.
Studies of the effects of omitting breakfast on cognitive
performance show that nutrition benefits learning. Well-nourished
children aged 9 to 10 who skipped breakfast displayed higher rates of
inaccurate responses to problem solving.
Inborn Errors of Metabolism
Early identification and nutrition intervention can prevent
subsequent mental retardation in infants born with many kinds of
metabolic disorders. Such children require long-term dietary
management. One example of such a disorder is phenylketonuria.
Phenylketonuria results in excessive and potentially toxic blood
levels of the amino acid phenylalanine. The goals of therapy are to
provide adequate intakes of energy and nutrients but only enough
phenylalanine to maintain normal growth and development. Meeting these
goals requires special formulas and food productswith reduced
phenylalanine content, as well as considerable support from health
professionals.
Current recommendations are to continue the phenylalanine-restricted
diet throughout the reproductive years, because experience with its
discontinuation at ages ranging from 4 to 10 years indicates
progressively decreasing cognitive functioning, learning difficulties,
poor attention span, and behavioural difficulties. Evidence suggests
also that phenylalanine restriction during pregnancy improves the
outcome for women with phenylketonuria and their infants.
Implications for Public Health Policy
Assessment of nutritional status is an integral part of maternity
care at the beginning of pregnancy and periodically throughout
pregnancy and lactation to provide continuing monitoring and recommend
appropriate intervention.
Evidence related to the role of diet in maternal and child health
indicates that well-nourished mothers produce healthier children.
Intake of sufficient energy and nutrients to attain optimal nutritional
status, including appropriate weight before pregnancy and adequate
weight gain during pregnancy, improves infant birth weight and reduces
infant mortality. Avoiding potentially toxic substances such as alcohol
or drugs during pregnancy improves birth weight and health.
Evidence related to the role of diet in infancy indicates that
breast milk is the optimal food for infants. Whenever possible and as
early as possible, health professionals should provide guidance and
support to pregnant women and new mothers on the importance of
breastfeeding and on methods for its initiation and maintenance.
Consuming the appropriate amount and form of energy and nutrients
for developmental age is important for good health, as is early
education about lifelong dietary patterns that help prevent disease.
Parents should guide their children in developing positive eating
behaviours and on age-appropriate food patterns that meet nutritional
requirements but avoid excessive intake of fat, sodium, and sugar.
Physicians, nurses, and other health professionals caring for
children and women of childbearing age should receive education and
training in nutrition assessment, nutrition intervention for prevention
of disease, and promotion of maternal and child health.
Nutrition Programs and Services
Nutrition Services:Evidence related to the role of
nutrition in maternal, infant, and child health suggests that all
health care programs for these groups should provide nutrition
services, especially to those people at special health or economic
risk. Such services includenutrition assessment, dietary counselling,
nutrition education, and referral.
Food Products:Evidence related to the role of dietary
factors in maternal and child health suggests that food manufacturers
should develop nutritious, low-fat, low-salt, low-sugar snack food
products for children and adolescents. Quality and safety of infant
formulas and other infant foods require continued monitoring to prevent
untoward health consequences. [The Surgeon General's Report on Nutrition & Health, 1988.]
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