Special Diets

Many foods, beverages, and supplements have been shown to affect the absorption of iron.²⁹

Foods, beverages and supplements that interfere with iron absorption include

• Green tea (Camellia sinensis).^{30, 31, 32, 33} This effect may be desirable for people with iron overload diseases, such as hemochromatosis. The inhibitory effect of green tea on iron absorption was 26% in one study.³⁴

• Coffee (Coffea arabica, C. robusta).^{35, 36, 37}

• Red wine, particularly the polyphenol component (also found in tea).^{38, 39} Since wine is also a dietary source of iron, it is not clear whether drinking red wine would lead to a deficiency of iron.

• Phytate (phytic acid), found in unleavened wheat products such as matzoh, pita, and some rye crackers; in wheat germ, oats, nuts, cacao powder, vanilla extract, beans, and many other foods, and in IP-6 supplements.^{40, 41, 42}

• Whole wheat bran, independent of its phytate content, has been shown to inhibit iron absorption.⁴³

• Calcium from food and supplements interferes with heme-iron absorption.^{44, 45}

• Soy protein.^{46, 47}

• Eggs.^{48, 49}

Foods and supplements that increase iron absorption include

• Meat, poultry, and fish.^{50, 51, 52, 53, 54}

Although vitamin C increases iron absorption,^{55, 56, 57, 58} the effect is relatively minor.⁵⁹

Taking vitamin A with iron helps treat iron deficiency, since vitamin A improves the absorption and/or utilization of iron.^{60, 61}

Although soy protein has been shown to decrease iron absorption (see above), certain soy-containing foods (e.g. tofu, miso, tempeh) have significantly improved iron absorption.⁶² Some soy sauces may also enhance iron absorption.⁶³

Alcohol, but not red wine, has been reported to increase the absorption of ferric, but not ferrous, iron.^{64, 65}

Iron has been reported to potentially interfere with manganese absorption. In one trial, women with high iron status had relatively poor absorption of manganese.⁶⁶ In another trial studying manganese/iron interactions in women, increased intake of “non-heme iron”—the kind of iron found in most supplements—decreased manganese status.⁶⁷ These interactions suggest that taking multiminerals that include manganese may protect against manganese deficiencies that might otherwise be triggered by taking isolated iron supplements.