physical exercise. Interactive food guide pyramid
models are accessible at the USDA’s Web site
(www.mypyramid.gov). The USDA publication
Dietary Guidelines for Americans 2005includes dis-
cussion of the food guide pyramids and other
nutritional information.
Since the 1940s the standard of appropriate
nutritional intake for individual nutrients has
been the recommended dietary allowance (RDA),
which quantifies how much of a nutrient a person
should consume to prevent deficiency of that
nutrient. Through the decades since, new knowl-
edge and understanding have resulted in the
emergence of additional standards that attempt to
quantify the normal levels of nutrients necessary
for health as well as the lower and upper limits
beyond which health problems arise. These now
fall collectively under the umbrella term dietary
reference intake (DRI). Because most people do not
consume the “daily” amount of a nutrient every
day the DRI system also takes into consideration
variations in eating patterns and nutrient con-
sumption, using formulas that look at nutritional
needs over the long term and establishing aver-
ages that meet them.
For further discussion of nutritional needs,
please see the overview section “Nutrition and
Diet.”
See also AGING, NUTRITION AND DIETARY CHANGES
THAT OCCUR WITH; ANTIOXIDANT; LIFESTYLE AND HEALTH;
MINERALS AND HEALTH; VITAMINS AND HEALTH.
nutritional supplements Products that provide
additional NUTRIENTS and dietary substances
beyond those that enter the body via food con-
sumption. The most commonly taken nutritional
supplements, also called dietary supplements, are
vitamins and minerals, which are available in
combination formulas (multivitamin supplements,
multimineral supplements, and multivitamin with
mineral supplements) as well as products that
contain single nutrients. Some products combine
vitamins and minerals with herbal and botanical
substances, for example vitamin C with ECHINACEA.
The choices among products are nearly endless;
the nutritional supplement industry remains a key
player in the American economy, with annual
sales exceeding $19 billion.
In the United States federal law classifies vita-
min and mineral supplements and most MEDICINAL
HERBS AND BOTANICALSas dietary supplements. This
removes these products from the jurisdiction of
the US agency charged with oversight of DRUG
safety and EFFICACY, the US Food and Drug Admin-
istration (FDA). Though various federal laws regu-
late matters of safety and efficacy as well as
advertising claims of health benefits, testing of
supplement products shows wide variation of
quality standards across manufacturers and prod-
ucts. This can result in inconsistent doses and
effectiveness.
The intent of nutritional supplements should be
to augment, not replace, dietary nutrients. Vita-
mins, minerals, and botanicals do not deliver
energy nutrients, though other kinds of nutri-
tional supplements (such as protein supplements)
do. Health experts disagree on whether the effect
of supplements, especially vitamins and minerals,
in the body is the same as that when the same
nutrients enter the body from food sources. Some
research studies investigating antioxidants, for
example, show much higher levels of activity from
consumed foods compared to supplements. Other
studies show no measurable difference. A com-
mon philosophy among nutritionists is “stay close
to the earth” because the highest concentrations
of nutrients come from fresh fruits, vegetables,
and whole grains.
People who have chronic health conditions or
take regular prescription medications should
check with the doctor or pharmacist before taking
nutritional supplements of any kind, as the risk
for DRUG INTERACTIONis high. As well, some chronic
health conditions or the medications taken to treat
them have specific effects on how the body
absorbs and metabolizes nutrients, increasing or
decreasing the need for those nutrients. For such
people, doctors may recommend therapeutic
nutritional supplementation. For others, most
health experts recommend obtaining nutrients
from the diet to the extent possible and using
nutritional supplements, including vitamins and
minerals, only when there are clear and specific
reasons to supplement dietary intake. However,
research continues to generate new knowledge
and understanding of how nutrients affect health196 Nutrition and Diet