232 Introduction to Human Nutrition
to assess recent chromium exposure, but are not long-
term measures of chromium status. The only reliable
indicator of chromium status is to monitor blood
levels of glucose, insulin, lipid, and/or related vari-
ables before and after chromium supplementation. A
response in blood glucose can often be seen in 2 weeks
or less, whereas effects on blood lipids may take
longer.
Requirements and dietary sources
The dietary chromium content of foods varies widely.
The richest dietary sources of chromium are spices
such as black pepper, brewer’s yeast, mushrooms,
prunes, raisins, nuts, asparagus, beer, and wine.
Refi ning of cereals and sugar removes most of the
native chromium, but stainless-steel vessels in
contact with acidic foods may contribute additional
chromium.
There is currently no RDA set for dietary chro-
mium, instead there are AI values [which were estab-
lished by the US Food and Nutrition Board in 2001]:
infants 0.2 μg (fi rst 6 months), 5.5 μg (7–12 months),
children 11 and 15 μg (1–3 and 4–8 years, respec-
tively), teenage boys 25 and 35 μg (9–13 and 14–18
years, respectively), adult men 35 and 30 μg (19–50
years and 50 years and older, respectively), teenage
girls 21 and 24 μg (9–13 and 14–18 years, respec-
tively), adult women 25 and 20 μg (19–50 years and
51 years and older, respectively), pregnant women 29
and 30 μg (less than 18 years and 19–50 years, respec-
tively), and lactating women 44 and 45 μg (less than
18 and 19–50 years, respectively). An AI was set based
on representative dietary intake data from healthy
individuals from the Third Nutrition and Health
Examination Survey (NHANES III).
9.16 Other elements
In addition to the essential elements discussed in
this chapter, other elements in the periodic table
may emerge as being essential for human nutrition.
For 15 elements, aluminum, arsenic, boron, bromine,
cadmium, chromium, fl uorine, germanium, lead,
lithium, nickel, rubidium, silicon, tin, and vanadium,
specifi c biochemical reactions have not been defi ned
and their suspected essentiality is based on circum-
stantial evidence from data emanating from animal
models, from essential functions in lower forms
of life, or from biochemical actions consistent with
a biological role or benefi cial action in humans.
Two elements, fl uorine and lithium, have benefi cial
actions when ingested in high (pharmacological)
amounts. Lithium is used to treat bipolar disorder,
and fl uorine (as fl uoride) is discussed in Section
9.14 because of its important benefi cial actions in
preventing dental caries in susceptible population
groups. Some consider that the circumstantial
evidence for chromium is suffi ciently substantial to
warrant special attention in dietary requirement rec-
ommendations, and this element is discussed in
Section 9.15. The estimated or suspected requirement
of all of these elements (including the essential
trace elements, iodine, selenium, and molybdenum)
is usually less than 1 mg/day and they are defi ned
as ultratrace elements. Cobalt is not included in the
list of ultratrace elements because the only require-
ment for cobalt is as a constituent of preformed
vitamin B 12.
These elements are not discussed at length in this
chapter and the reader is referred to other reading
material. For completeness, three tables, on absorp-
tion, transport, and storage characteristics (Table
9.21), excretion, retention, and possible biological
roles of the ultratrace elements (Table 9.22), and
human body content and food sources (Table 9.23)
are included here.9.17 Perspectives on the future
The preceding parts of this chapter have highlighted
some issues in the area of minerals and trace elements
for which we have an incomplete understanding. In
the future, nutritional scientists, dieticians, and other
health care professionals will have to:
● obtain a greater understanding of the molecular
and cellular processes involved in the intestinal
absorption and tissue uptake of certain minerals
and trace elements
● identify functional markers of mineral and trace
element status. These markers could be defi ned as
a physiological/biochemical factor that (1) is related
to function or effect of the nutrient in target
tissue(s) and (2) is affected by dietary intake or
stores of the nutrient (which may include markers
of disease risk). Examples of such indicators
or markers are those related to risk of chronic dis-
eases, such as osteoporosis, coronary heart disease,