of the National Academy of Sciences decided that an
expanded set of reference values was needed to incor-
porate this new research and provide better nutrition
guidance to both health professionals and consumers.
In 1997, in cooperation with nutrition authorities in
Canada, they began replacing RDAs (and RNIs in
Canada) with the first Dietary Reference Intakes or
DRIs.
Components of the DRIs
DRIs cover micronutrients (e.g., vitamins and
minerals) essential to human health. Dietary guidance
in a different form is also given formacronutrients
(e.g.,protein,carbohydrates,andfats). The DRIs for
vitamins and minerals consist of four values that
reflect both the lower and upper daily intake limits
beyond which adverse health effects may occur. They
also include and an average or recommended daily
value meets the health needs of most of the
population.
DRIs are intended to apply only to people who
appear healthy. They are calculated based on the nutri-
tional needs of each age group and gender: infants 0–6
months and 6–12 months; children ages 1–3 years, 4-8
years, and 9–13 years; adolescents 14–18 years, and
adults. The adult group is subdivided into women who
are pregnant, women who arebreastfeeding,andsome-
times into younger and older adults, depending on the
nutrient. The values for each nutrient are measured
against a specific reference goal. Examples of these
goals include preventing symptoms of a nutrient defi-
ciency disease, maintaining normal growth, maintaining
a specific level of the nutrient circulating in the blood, or
preventing symptoms associated with nutrient excess.
Four reference values make up the DRI for
micronutrients:
Estimated Average Requirement (EAR). The EAR is
the average daily intake of a nutrient that will meet
the nutritional needs of half the individuals in the
group. In other words, if half the healthy children
between ages four and eight received the EAR for
iron for their age group, about 50% would show
signs of iron deficiency and 50% would not.
Recommended Dietary Allowance (RDA). The RDA
is the amount of a nutrient that meets the needs of 97–
98% of all healthy individuals within the group. For
example, if all children ages 4–8 years old were receiv-
ing the RDA for iron for their age group, only one or
two of every hundred children would be iron deficient.
The RDA is calculated using the EAR and the
amount of variability (standard deviation [SD]) of
the need for the nutrient within each group. Mathe-
matically RDA = EAR + (2 x SD of the nutrient).
Average Intake (AI). Calculating the RDA requires
that enough information is available to calculate the
EAR. This information is not always available
because of practical and ethical limitation on exper-
imenting with humans. When insufficient information
is available to calculate the RDA, an estimate of the
average daily intake is made. Just like the RDA, the
AI expected to meet or exceed the nutritional need of
almost everyone in the group. Although both the
RDA and the AI are intended to give guidance
about how much of a particular nutrient a healthy
individual in a specific group should, on average, get
daily, the AI is an estimate based on experimental
evidence and observation, not a defined calculation
like the RDA.KEY TERMS
Amino acid—Molecules that are the basic building
blocks of proteins.
Bioavailability—The degree to which a compound
can be absorbed and used by the body.
Dietary supplement—A product, such as a vitamin,
mineral, herb, amino acid, or enzyme, that is
intended to be consumed in addition to an individ-
ual’s diet with the expectation that it will improve
health.
Fatty acids—Complex molecules found in fats and
oils. Essential fatty acids are fatty acids that the
body needs but cannot synthesize. Essential fatty
acids are made by plants and must be present in the
diet to maintain health.
Macronutrient—A substance needed in large
quantities to maintain growth and health such as
the energy-producing molecules that come from
proteins, carbohydrates, and fats.
Micronutrient—Substances that are needed in very
small, even trace, amounts to maintain normal
growth and health.
Mineral—An inorganic substance found in the
earth that is necessary in small quantities for the
body to maintain health. Examples include zinc,
copper, iron.
Toxic—Harmful or poisonous to the body.
Vitamin—A nutrient that the body needs in small
amounts to remain healthy but that the body cannot
manufacture for itself and must acquire through
diet.Dietary reference intakes