Tolerable Upper Intake Level (UL). The UL is the
highest daily amount that is unlikely to cause adverse
(negative) risks to health in almost all of the members
of the group. In other words, if all the children ages
4–8 were taking the UL for iron, most of them would
remain healthy, but over time one or two per hun-
dred might show signs of iron excess. The higher the
amount of nutrient consumed above the UL, the
higher the risk of adverse health effects. Some micro-
nutrients such as folic acid, niacin, and magnesium,
have ULs that apply only to dietary supplements and
not the quantity of the nutrient obtained from food.
The inclusion of a UL value for the first time
acknowledges that too much of a nutrient can be
toxic and harmful to health.
Macronutrients are what most people call food—
nutrients that provide calories (energy). These include
carbohydrates, fat, fatty acids, cholesterol, protein,
and amino acids.Fiberis an included nutrient but it
does not provide energy. In the body, carbohydrates,
proteins, and fats can in some cases be used inter-
changeably. In addition, it is not possible to link
specific quantities of these macronutrients to the pre-
vention or development of chronic diseases such as
diabetes and cardiovascular disease. In place of
DRIs, the Institute of Medicine has developed Accept-
able Macronutrient Distribution Ranges (AMDRs)
for energy-yielding nutrients. AMDRs are expressed,
not as absolute numbers, but as a percentage of total
energy (calorie) intake.Controversies about DRIsThe four components of the DRI are intended to
provide more guidance than a single number alone
would provide. However, they are not without their
critics. Some criticism stems from statistical assump-
tions made in the calculations. Other criticism is based
on the fact that different forms of certain nutrients have
a different bioavailability. For example,ironin meat is
more easily absorbed than iron in plant foods, and the
vitamin Ein dietary supplements is more biologically
active than vitamin E in food. Although this should not
be a source of confusion to healthcare professionals, it
can be confusing to the average consumer.
The greatest controversies among experts are over
the UL. These center around four areas:
Very little experimental data is available about the upper
limit of certain nutrients in special populations such as
children, pregnant women, and elderly individuals.
Some experts are not comfortable with the way the
Institute of Medicine derived UL values. Experts
point out that in some cases the UL for one subgroupoverlaps the RDA for another subgroup and that in
other cases the typical intake of certain groups
already exceeds the UL with no apparent harmful
effects (e.g., iron in young children). The vitamin C
UL appear to be especially controversial.
No distinction is made between short-term (acute)
and long-term (chronic) overdose of nutrients.
The ULs do not take into consideration genetic
diversity of the population and are much less sensi-
tive to the life stage of the individual than RDAs.
This is in part because of limited data available for
certain age groups.
Much of the data used to determine the UL is based on
short-term (a few days) intake information and there-
fore has a high degree of unreliability. Human experi-
ments with potentially toxic mega doses of nutrients is
generally unethical, making an adequate amount of
reliable data in the UL range difficult to obtain.
DRIs and AMRDs continue to be researched and
revised as more data becomes available. Despite the
controversy, they offer both healthcare professionals
and individuals some guidelines about the benefits and
dangers of nutrient consumption.Precautions
DRIs are intended as guidelines for population
groups, not individuals. Although they give values for
daily intake of nutrients, these values are intended to
apply over time. Except in cases of acute mega doses,
the effects of too much or too little of a nutrient develop
gradually over time. In any given day, an individual
may eat more or less than the DRI of a particular
nutrient and still remain healthy.
DRIs are intended to be applied to a healthy pop-
ulation. Individuals under the supervision of a health-
care professional may be advised to take more or less of
particular nutrients than the DRIs indicate. In this
situation, the advice of the healthcare professional
should be followed.
Nutrients interact with each other and with phar-
maceuticals and herbal remedies. These interactions
are not entirely understood and may affect the absorp-
tion, utilization, and excretion of various vitamins and
minerals in ways that change the RDA.
Certain population groups, such as vegans, have
dietary needs that may be satisfied only with dietary
supplements or very carefully controlled diets.Parental concerns
Parents should discuss DRIs with a healthcare
professional who can translate them into healthyDietary reference intakes