Dr.
Ann de Wees Allen
Chief of Biomedical Research
Glycemic Research Institute
Washington, D.C.
Data reviewed by Dr. M. Wessling-Resnick, Professor of Nutritional
Biochemistry, Harvard School of Public Health, 03/27/2003
For the past twenty years, researchers have warned against
the use of supplements that contain high doses of iron.
This warning is based on hundreds of studies showing that
excess iron is a primary cause of human diseases including
free radical induced degenerative disease. Iron accumulation
and oxidative injury are presently under consideration (2003)
as potential contributors to a number of neurodegenerative
diseases, such as Alzheimer's and Parkinson's disease (Pinero
et al, Cell Mol Biol. 2000;46 (4):761-776).
Dietary iron intake has been found to be related to risk of
colorectal cancer. Increased red meat consumption (which is
high in iron) raises the risk of developing colorectal cancer
by elevating increased iron in the contents of the colon.
Beef contains 2.31 mg of iron per 3 ounces of cooked meat.
High iron levels are also linked to an increase in stroke
damage (April 25, 2000 issue of Neurology, the American Academy
of Neurology's scientific journal). Researchers found that
stroke patients with elevated levels of iron are much more
likely to experience severe neurological symptoms and increased
brain damage.
Additionally, high blood iron levels are associated with increased
cardiovascular disease. Neurologist and lead study author
Antoni Davalos, M.D. states, "Blood ferritin (iron) levels
should be tested as we test cholesterol or glucose levels
in patients with cardiovascular diseases or cardiovascular
risk factors."
Iron is a key element in the metabolism of almost all living
organisms, and in humans is an essential component of hundreds
of enzymes and proteins. Iron found in food is generally not
a causal factor in iron overload, except in Hereditary Hemochromotosis
(a genetic disorder). Ribonucleotide reductase is an iron-dependent
enzyme required for DNA synthesis, thus iron is required for
vital functions, including growth, healing, reproduction,
and immune function. Iron is beneficial in humans, unless
it reaches excess levels in the blood.
Iron deficiency in humans is related to the medical conditions:
Storage Iron Depletion, Early Functional Iron Deficiency,
and Iron Deficiency Anemia. A simple blood test can identify
these forms of iron deficiencies. Typical symptoms include
fatigue, rapid heart rate, palpitations, and rapid breathing
on exertion.
Persons exhibiting mild iron deficiencies may elect to take
supplemental vitamin C instead of iron supplements, as vitamin
C strongly enhances the absorption of nonheme iron by reducing
dietary ferric iron to ferrous iron and forming an absorbable
iron-ascorbic acid complex. Soy protein inhibits iron absorption,
and should be used selectively by persons with iron deficiencies.
Supplements that contain high doses of iron, or taking too
many supplements that contain iron, are at issue, and not
normal amounts of iron found in the food chain. Acute toxicity
is potentially fatal and can occur with iron doses of 20-60
mg/kg of body weight. Medical experts conclude that "It
would be prudent for those who are not at risk of iron deficiency
to avoid excess iron intake."
The Tolerable Upper Intake Level (UL) for iron is:
| INFANTS
0-12 months |
Not
possible to establish/source of iron intake should be
from food and formula only |
| CHILDREN
1-13 years |
40
mg/day |
| ADOLESCENTS
14-18 years |
45
mg/day |
| ADULTS
19 years + |
45
mg/day |
Food and
Nutrition Board (FNB) of the Institute of Medicine
BOTTOM LINE
It has been shown that high iron stores are much more common
than iron deficiencies (Fleming et al. Am J Clin Nutr. 2001;73(3):638-646).
A supplemental dose of 18 mg of elemental iron per day, as contained
in a multi-vitamin, would be the upper limit of acceptable iron
ingested, particularly in men and postmenopausal women who are
not at risk of iron deficiency. If iron deficiency is diagnosed,
medical experts recommend determining the underlying cause,
rather than treating it with iron supplements.
The bottom line is that multi-vitamin/mineral supplements that
contain less than 18 mg of iron/day are safe and acceptable.
end report
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