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WASHINGTON - To meet the
body's daily energy and nutritional needs while minimizing risk
for chronic disease, adults should get 45 percent to 65 percent of
their calories from carbohydrates, 20 percent to 35 percent from fat,
and 10 to 35 percent from protein, says the newest report on
recommendations for healthy eating from the National Academies'
Institute of Medicine. To maintain cardiovascular health at a
maximal level, regardless of weight, adults and children also should
spend a total of at least one hour each day in moderately intense
physical activity, which is double the daily goal set by the 1996
Surgeon General's report.
Because carbohydrates, fat, and protein all serve as energy sources
and can substitute for one another to some extent to meet caloric
needs, the recommended ranges for consuming these nutrients should be
useful and flexible for dietary planning. Earlier guidelines
called for diets with 50 percent or more of carbohydrate and 30
percent or less of fat; protein intake recommendations remain
unchanged. The new acceptable ranges for children are similar to
those for adults, except that infants and younger children need a
slightly higher proportion of fat -- 25 percent to 40 percent of their
caloric intake, said the panel that wrote the report.
"We established ranges for fat, carbohydrates, and protein
because they must be considered together," says panel chair
Joanne Lupton, professor of nutrition, Texas A&M University,
College Station. "Studies show that when people eat very
low levels of fat combined with very high levels of carbohydrates,
high-density lipoprotein cholesterol concentration, or "good
cholesterol," decreases. Conversely, high-fat diets can
lead to obesity and its complications if caloric intake is increased
as well, which is often the case. We believe these ranges will
help people make healthy and more realistic choices based on their own
food preferences."
The report stresses the importance of balancing diet with exercise,
recommending total calories to be consumed by individuals of given
heights, weights, and genders for each of four different levels of
physical activity. For example, a 30-year-old woman who is 5
feet 5 inches tall and weighs 111 to 150 pounds should consume between
1,800 and 2,000 calories per day if she lives a sedentary lifestyle.
However, if she is a very active person, her recommended total caloric
intake increases to 2,500 to 2,800 calories per day. If her
lifestyle fits the moderately active category as defined in the
report, which is the minimum level of activity to decrease risk of
chronic disease, she should eat between 2,200 and 2,500 calories per
day. Using grams for the recommended ranges of intake, she
should consume 55 to 97 grams of fat and 285 to 375 grams of
carbohydrates per day.
The new one-hour-a-day-total exercise goal stems from studies of how
much energy is expended on average each day by individuals who
maintain a healthy weight. Energy expenditure is cumulative,
including both low-intensity activities of daily life, such as
stair-climbing and housecleaning, and more vigorous exercise like
swimming and cycling. Someone in a largely sedentary occupation
can achieve the new exercise goal by engaging in a moderate-intensity
activity, such as walking at 4 miles per hour, for a total of 60
minutes every day, or engaging in a high-intensity activity, such as
jogging for 20 to 30 minutes four to seven days per week.
New Dietary Recommendations
Since the publication of the U.S.
Recommended Dietary Allowances in 1989 and the Canadian Recommended
Nutrient Intakes in 1990, new information has emerged about nutrient
requirements that warrants the development of updated guidelines.
This report, the sixth in a series, develops new guidelines for the
United States and Canada for the consumption of energy, carbohydrates,
fiber, fat, fatty acids, cholesterol, protein, and amino acids,
collectively known as macronutrients.
In the past,
recommended dietary allowances or RDAs have served as the benchmarks
of nutritional adequacy in the United States. The new Dietary
Reference Intakes, or DRIs, are established using an expanded concept
that includes indicators of good health and the prevention of chronic
disease, as well as possible adverse effects of over consumption.
The panel assessed thousands of scientific studies linking excessive
or inadequate consumption of fats, carbohydrates, and protein with
increased risk for dietary deficiency diseases, obesity, heart
disease, diabetes, and other chronic illnesses. The DRIs include
not only recommended intakes, intended to help individuals meet their
daily nutritional requirements, but also Tolerable Upper Intake Levels
(ULs) that help them avoid harm from consuming too much of a nutrient.
The DRIs are designed to meet the needs of individuals who are healthy
and free of specific diseases or conditions that may alter their daily
nutritional requirements. It is expected that people known to
have specific conditions or chronic diseases will get nutritional
advice from their health professionals that is tailored to their
special needs.
Concern About Added Sugars
Both children and adults should consume at
least 130 grams of carbohydrates each day, the report says.
However, this newly set RDA is based on the minimum amount of
carbohydrates needed to produce enough glucose for the brain to
function, and most people regularly consume far more.
The report suggests that Added sugars should comprise no more than 25
percent of total calories consumed. Added sugars are
distinguished from natural sugars, such as lactose found in milk and
fructose found in fruits. Added sugars are those incorporated
into foods and beverages during production. Major sources
include candy, soft drinks, fruit drinks, pastries, and other sweets.
The suggested maximum level stems from the evidence that people whose
diets are high in added sugars have lower intakes of essential
nutrients.
Are All Fats Bad?
Fat is a major source of energy for the body
and aids in the absorption of essential vitamins. Some foods
that are major contributors of fat in the diet include butter,
margarine, vegetable oils, visible fat on meat and poultry, whole
milk, egg yolks, nuts, and baked goods. High-fat diets usually
mean increased intakes of saturated fat, which can raise the level of
low-density lipoprotein, or "bad" cholesterol, in the
bloodstream of some individuals and heightens their risk for heart
disease. Meats and bakery and full-fat dairy products are the
main sources of saturated fat in most diets. Because saturated
fat and cholesterol provide no known beneficial role in preventing
chronic diseases, they are not required at any level in the diet, the
report says. Recognizing that completely eliminating saturated
fat and cholesterol from the typical diet in the United States or
Canada and would make it very difficult to meet other nutritional
guidelines, the panel recommended keeping consumption as low as
possible while maintaining a nutritionally adequate diet.
Monounsaturated and
polyunsaturated fatty acids, also present in fat, reduce blood
cholesterol levels and thus lower the risk of heart disease when they
replace saturated fats in the diet. People must get two types of
polyunsaturated fatty acids, known as alpha-linolenic acid (an omega-3
fatty acid) and linoleic acid (an omega-6 fatty acid), from the foods
they consume since neither is synthesized in the body. A lack of
either one will result in symptoms of deficiency, including scaly skin
and dermatitis, although these deficiencies are extremely rare in the
United States and Canada. The report sets recommended intakes
for linoleic acid, present in high levels in vegetable oils such as
safflower oil or corn oil, at 17 grams per day for men and 12 grams
per day for women based on average intakes in the United States.
For alpha-linolenic acid, found in milk and some vegetable oils such
as soybean and flax seed oils, the recommendations are 1.6 and 1.1
grams per day for men and women, respectively.
Partially hydrogenated vegetable oils, such as those used in many
margarines and shortenings, contain a particular form of unsaturated
fat known as trans fatty acids. Trans fatty acids have physical
properties generally resembling saturated fatty acids, and their
presence tends to harden oils. The report's findings and
recommendations on trans fatty acids were released in early July at
the request of the Food and Drug Administration as an important step
in its process to determine whether trans fat should be listed on
nutrition labels. Often found in cookies, crackers, dairy
products, meats, and fast food, trans fatty acids increase the risk of
heart disease by boosting levels of bad cholesterol. Because
they are not essential and provide no known health benefit, there is
no safe level of trans fatty acids and people should eat as little of
them as possible while consuming a nutritionally adequate diet.
Because trans fatty acids occur in so many types of food, an all-out
ban is impractical and would make it extremely difficult to get a
nutritional adequate diet, the panel added.
New Facts on Fiber
The report contains the first recommended
intake levels for fiber from the Food and Nutrition Board. The
fiber recommendations are based on studies that show an increased risk
for heart disease when diets low in fiber are consumed. Although
there is some evidence to suggest that fiber in the diet may also help
to prevent colon cancer and promote weight control, the data are
inconclusive at this point. The recommended intake for total
fiber for adults 50 years and younger is set at 38 grams for men and
25 grams for women, while for men and women over 50 it is 30 and 21
grams per day, respectively, due to decreased consumption of food.
Recommended intakes are also provided for children and teenagers.
Many new food products are marketed as containing fiber, but the lack
of a uniform definition of fiber for regulatory purposes casts doubts
on the usefulness of some content claims. Therefore, the report
provides a specific definition of what should be called fiber in food.
It defines "total fiber" as the combination of
"dietary" and "functional" fiber. Dietary
fiber is the edible, non-digestible component of carbohydrates and
lignin naturally found in plant food. Some foods with dietary
fiber include cereal bran, flaked corn cereal, sweet potatoes,
legumes, and onions. Functional fiber refers to those fiber
sources that are shown to have similar health benefits as dietary
fiber, but are isolated or extracted from natural sources or are
synthetic. An example would be pectin extracted from citrus peel
and used as a gel that is the basis for jams and jellies. The
definition of functional fiber aims to exclude fiber-like products,
whether extracted or synthesized, that cannot be shown to have proven
health benefits. It is hoped that regulatory bodies in both the
United States and Canada will work toward adopting these definitions.
Recommended Levels for Protein
The report
establishes age-based requirements for the first time for all nine of
the essential amino acids found in dietary protein. Values are
included for pregnant women, infants, and children based on their
special needs. Using new data, the report reaffirms previously
established recommended levels of protein intake, which is 0.8 grams
per kilogram of body weight for adults. Recommended intake of
protein during pregnancy also is increased. Because data on the
potential for high-protein diets to produce chronic or other diseases
are often conflicting or inadequate, tolerable upper intake levels for
consumption could not be determined for protein or for the individual
amino acids. However, given the lack of data on over consumption
for some of these amino acids and protein, caution is warranted in
consuming levels significantly above that normally found in foods.
This study was sponsored
by the U.S. Department of Health and Human Services Office of Disease
Prevention and Health Promotion; Health Canada; U.S. Food and Drug
Administration; National Institutes of Health; Centers for Disease
Control and Prevention; U.S. Department of Agriculture; Department of
Defense; Institute of Medicine; the Dietary Reference Intakes Private
Foundation Fund, including the Dannon Institute and the International
Life Sciences Institute-North America; and the Dietary Reference
Intakes Corporate Donors' Fund, contributors to which include Roche
Vitamins Inc., Mead Johnson Nutrition Group, and M&M Mars.
The study was undertaken by scientists from the United States and
Canada under the auspices of the Institute of Medicine's Food and
Nutrition Board, which has been responsible for developing RDAs for
United States for the last 60 years. The Institute of Medicine
is a private, nonprofit organization that provides health policy
advice under a congressional charter granted to the National Academy
of Sciences.
_Copies of Dietary Reference Intakes for Energy, Carbohydrate,
Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids are
available from the National Academy Press; tel. (202) 334-3313 or
1-800-624-6242 or on the Internet at http://www.nap.edu.
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