Report Offers New
Eating, Exercise Guidelines
to Reduce Risk of Chronic Disease
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 percent 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 are the same. 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," said 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 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 daily 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 daily. 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
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
overconsumption. 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.
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, and nuts.
High-fat diets usually mean increased intakes of saturated
fat, which can raise the amount of low-density lipoprotein
and the level of "bad" cholesterol in the
bloodstream of some individuals and heightens their risk
for heart disease. Meats, baked goods, 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 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 flaxseed 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 daily 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. The report also
provides recommended intakes 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, nondigestible 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
overconsumption for some of these amino acids and protein,
caution is warranted in consuming levels significantly
above those 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; U.S. 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.
Source: National Academy of Sciences Press Release -
September 2002
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