Iron Supports Immunity, Grows Hair and Builds Bone For Postmenopausal Women
By Michael Mooney
With the currrent trend of vilifying iron as a "toxic" nutrient coming from several purported "experts" there is a need for science-based counterpoint to this incorrect notion.
Iron is an essential nutrient, required for life and health, and like other essential nutrients, you can get too little or too much of it. Like vitamin A and D, iron has a narrow "safety index."
That is, the Recommended Daily Value for iron is not as greatly different from its Lowest Observed Adverse Effect Level (LOAEL), as some other nutrients. For instance, vitamin C, folic acid and various B-vitamins have wide safety indexes, with little potential for toxicity.
The LOAEL is a dose where toxicity can occur "...rarely, but for some sensitive subgroups it does occur..." when taken over a period of time, such as three months.
Iron's LOAEL is 100 mg a day. The Recommended Daily Value is 10 mg for men and 18 mg for women, so iron can cause toxicity at only 5 to 10 times the amount that is required to keep you healthy.
So while iron can cause toxicity, it takes a much higher dosage than we get from our daily multivitamins to cause problems.
Iron is not toxic in the doses found in dietary supplements in the United States.
In the appropriate safe dosage range iron delivers several important health benefits.
1. Iron is important for energy in its role as a component of red blood cells;
2. Iron has an important role in supporting immune function, with the first large nutritional study of HIV+ men showing that those whose daily iron intake from food and supplements was 54 mg/day took twice as long to progress to a diagnosis of full-blown AIDS those whose iron intake was 36 or 18 mg a day;
3. A study of healthy postmenopausal women showed that 48 percent were deficient in iron, while having half as efficient immune function, as well as other symptoms of iron deficiency, such as low energy and breathlessness;
4. Iron has an important role in healthy hair. People with ferritin levels (a measure of iron storage in the body) below 40 ng/dL are likely to experience hair loss;
5. And finally, the study below showed that iron intake was associated with better bone density, while intake of 20 mg of iron or more per day combined with calcium at 800 to 1,200 mg was associated with greater bone density in five types of bone.
It seems with all these important findings of the value of supplemental and food sources of iron that recommendations that post-menopausal women (or men) should not take iron is contrary to the goal of optimal health.
The decision to take iron or not take iron is most prudently decided based on the blood tests called "ferritin" and "transferrin saturation."
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Harris MM, et al. Dietary iron is associated with bone mineral density in healthy postmenopausal women Journal of Nutrition, November 2003. 133:3598-3602
Healthy nonsmoking postmenopausal women (n = 242; ages 40–66 y) were included in the Bone, Estrogen, and Strength Training (BEST) Study. Bone mineral density (BMD) was measured at five sites (lumbar spine L2-L4, trochanter, femur neck, Ward's triangle and total body) using dual energy X-ray absorptiometry (DXA). Mean nutrient intakes were assessed using a 3-d diet record. Regression models were calculated using each BMD site as the dependent variable and iron as the independent variable. Covariates included in the models were years past menopause, fat-free mass, fat mass, use of hormone replacement therapy, total energy intake and dietary intake of protein and calcium. Using linear models, iron was associated with greater BMD at all sites (P 0.01), even after adjusting for protein and/or calcium. Increasing levels of iron intake (>20 mg) were associated with greater BMD at several bone sites among women with a mean calcium intake of 800-1200 mg/d. Elevated iron intake was not associated with greater BMD among women with higher (>1200 mg/d) or lower calcium intakes (<800 mg/d). Dietary iron may be a more important factor in bone mineralization than originally thought and, its combined effect with calcium on BMD warrants exploration in future studies.