> Please do forward this to the list. My main point is that the
>detrimental effects of insufficient iron have always been emphasized when
>the reverse, the detrimental effects of too much iron (and many other
>vitamins/minerals) are seldom mentioned.
Risks of iron deficiency (Yip, J Nutr 124:1479S-90S, 1994):
1) severe anemia (Hgb<50g/L) increases risk of childhood and maternal death
2) poor child cognitive development (greater effect than mild lead poison)
3) poor work performance and productivity (linear correl. with Hgb)
4) impaired immune responses (Zimmer, et al, Pediatr Nutr Hndbk, in press)
>It is extremely important to be aware that too
>much iron can cause problems (some have even linked it with an increased
>susceptibility to cancer and ischemic heart disease - although yes it is
>still controversial) and the fact that iron is involved in one of the
body's
>defense mechanisms.
Risks of iron excess:
1) increased infectious disease risk
caveat: occurs when body's iron storage/transport capacity is overloaded
2) high iron stores correlated with increased risk of cancer and CHD
caveat: not supported by Yip, et al, Am J Clin Nutr 53:30, 1991 and
Stampfer, et al, Circulation 87:11, 1993. Remains HIGHLY controversial
> For example the much larger quantities of available iron in the diet of
>iron-fortified formula-fed infants has been associated with a higher
>susceptibility to salmonellosis, botulism, and SIDS (Weinberg, 1994).
I agree. When you dump elemental iron (not complexed with lactoferrin) into
an infant with limited iron transport capcity, you can grow all kinds of
infectious organisms.
> I certainly agree that the advantage breast fed babies have has to do
>with a number of factors, of which lactoferrin is only one. However, I
>think that it is very incorrect to say that
>one of the top 5 causes of maternal mortality in childbirth worldwide is
>anemia. Anemia is a SYMPTOM not a cause. The underlying causes for
>anemia are many and varied and it is these issues that need to be
>addressed (and considered to be causes) not the symptom of anemia.
OK, mia culpa on semantics. Anemia is an effect modifier on other "causes"
of maternal mortality like obstetric hemorrhage. The "cause" of anemia in
childbearing women is multifactorial, but iron-deficiency secondary to
insufficient iron intake is the most prevalent cause of anemia in women of
childbearing age worldwide (DeMaeyer and Adiels-Tegman, World Health Stat Q,
38:302-15, 1985). Anemia is listed as a leading "indirect cause" of
maternal
mortality in the U.S. (Rochat, et al, Obstet Gynecol, 72:91-7, 1988).
Severe
anemia was listed as the "cause" of 16.4% of maternal deaths in rural
northern India (Kumar, et al, Int J Obstet Gynecol, 29:313-9, 1989).
Jacobson (Worldwatch Paper 102, 1991) states that a mother's risk of dying
in
childbirth increases four-fold with anemia and eight-fold with severe
anemia. This sampling of the evidence would indicate that iron deficiency
is
a serious concern in women planning to have a child.
>Why doesn't a woman's iron absorption rate reach 40% or 90% during
>pregnancy? Because it would be potentially very detrimental to both her
>and the embryo/fetus in terms of giving an advantage to pathogens.
If sufficient transferrin was synthesized by the mother to transport the
iron
to the tissues in need, I don't see how the pathogens could get an
advantage. The iron is in the gut already, the process of taking it up
needs
to be more efficient to reduce the risk of iron deficiency during pregnancy.
Actually, the arguement usually goes that people ate a lot more meat in
their
hunter-gatherer days and sufficient iron was stored to meet the needs of
pregnancy in advance. Since I'm not the anthropologist, I'll leave that
discussion to Drs. Dettwyler and Stuart-Macadam (I did say it was a
straw-man
arguement :).
>This brings up an interesting point that I have been wondering about
lately.
>Arthur and Isbister (1987 in Drugs 33:171-182) noted that "Other mammals
>have approximately ten times the iron loss present in humans per kilogram
>and iron absorption in humans is only one-fiftieth to one-hundreth of
>that in other mammals". Why? I would be interested to hear Dr. Zimmer's
>comments.
Humans don't "excrete" iron. Absorbed iron is either stored in the tissues
as ferritin or held in the intestinal epithelial cells until they are
sloughed off. Iron is pretty much only regulated at the level of
absorption. Not being a phylogenic specialist, I would need to read the
paper cited to make a comment.
Ok, I just looked at how long this is, and I must apologize to those who pay
for such ramblings. I'll try to summarize some of these points and make
them
relevent to maternal/child health and lactation in a follow-up message.
Kathy, have you invited Dr. Stuart-Macadam to JOIN LactNet? :)
Paul Zimmer,
Ph.D.
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