Iron: The Double-Edged Sword

The Physicians Committee

Iron: The Double-Edged Sword

Iron encourages the formation of cancer-causing free radicals. Of course, the body needs a certain amount of iron for healthy blood cells. But beyond this rather small amount, iron becomes a dangerous substance, acting as a catalyst for the formation of free radicals. Because of this, research studies have shown that higher amounts of iron in the blood mean higher cancer risk.

Once excess iron is absorbed by the digestive tract, the body stores it. Most of us accumulate much more iron than we need. In spite of the advertising from iron supplement manufacturers, "iron overload" is much more common in America than iron deficiency. Studies have shown that major contributors to iron excess are taking vitamin and mineral supplements that contain iron, excess consumption of red meat, and, to some extent, eating manufactured foods that have had iron added artificially. The iron present in these sources is highly absorbable. The iron in red meat, in particular, is a highly absorbable form (heme iron); however, iron from vegetarian food sources (nonheme iron) may prove to be a better choice because, while it isn’t absorbed as well as heme iron, it is sufficient to promote adequate iron levels without encouraging iron stores above the recommended range. A diet of grains, vegetables, fruits, and beans provides adequate iron, without the risk of overload.

It is easy to check whether your body has accumulated too much stored iron. The following set of tests will check for both iron deficiency and iron overload. The more general hemoglobin and hematocrit tests are not sufficient. Although general guidelines are given here, the tests should be interpreted by your doctor:

  • Serum ferritin (normal values are 15-60 mcg/l of serum). This test may require interpretation by your doctor, but is the most reliable guide to the amount of iron in your body.2

  • Serum iron

  • Total iron binding capacity (TIBC)

Doctors divide the serum-iron value by the TIBC. The result should be 16 to 50 percent for women and 16 to 62 percent for men. This test is usually administered to detect iron deficiency, levels below normal values.  Results above these norms indicate excess iron.  TIBC results may fall within the normal range even when body iron measured by ferritin is considerably elevated. Therefore, further tests may be required as this test is not definitive. 

A test sometimes used to check for iron deficiency is the red cell protoporphyrin test. A result greater than 70 units is considered abnormal. If two of these three values (serum ferritin, serum iron/TIBC, and red cell protoporphyrin) are normal, iron-deficiency anemia is not likely. Serum iron and TIBC should be measured after fasting overnight.

In a recent six-year study of 1,277 Veterans Administration Hospital patients with vascular disease, but no history of cancer, half the patients were randomly assigned to standard of care and half to the same care plus measured blood drawing to reduce iron levels to those present normally in premenopausal women and children. Analysis showed a 37 percent reduction in overall cancer incidence with iron reduction and reduced cancer-specific and all-cause mortality among patients who developed cancer in the iron-reduction arm compared with those in the control arm.2

Unfortunately, the body has no way to rid itself of excess iron. However, iron accumulation to levels that produce cancer can be prevented by avoiding excess iron in the diet (as indicated above) and by giving blood. This altruistic act of giving blood can have health benefits for the donor as well.  Menstruating women lose iron-rich blood monthly and have ferritin levels that average about 25 mcg/l. Delayed iron accumulation because of menstruation is believed to explain why women generally live longer than men. It also explains why cancer risk is lower in premenopausal women compared to men of similar age and why cancer risk soars in women following menopause when iron levels rise dramatically. Men and women who live to very old age characteristically have body iron levels closer to those in menstruating women, presumably because of lifelong, relatively low dietary iron intake.

1. Lauffer RB. Iron Balance. New York, NY: St. Martin's Press, 1991.
2. Zacharski L, Chow B, Howes P, et al. Decreased Cancer Risk After Iron Reduction in Patients With Peripheral Arterial Disease: Results From a Randomized Trial. J Natl Cancer Inst. 2008;100:1-7.