Many foods, beverages, and supplements have been shown to affect the absorption of iron.¹⁰⁵

Foods, beverages and supplements that interfere with iron absorption include

• Green tea (Camellia sinensis).^{106, 107, 108, 109} 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.¹¹⁰

• Coffee (Coffea arabica, C. robusta).^{111, 112, 113}

• Red wine, particularly the polyphenol component (also found in tea).^{114, 115} 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.^{116, 117, 118}

• Whole wheat bran, independent of its phytate content, has been shown to inhibit iron absorption.¹¹⁹

• Calcium from food and supplements interferes with heme-iron absorption.^{120, 121}

• Soy protein.^{122, 123}

• Eggs.^{124, 125}

Foods and supplements that increase iron absorption include

• Meat, poultry, and fish.^{126, 127, 128, 129, 130}

Although vitamin C increases iron absorption,^{131, 132, 133, 134} the effect is relatively minor.¹³⁵

Taking vitamin A with iron helps treat iron deficiency, since vitamin A improves the absorption and/or utilization of iron.^{136, 137}

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.¹³⁸ Some soy sauces may also enhance iron absorption.¹³⁹

Alcohol, but not red wine, has been reported to increase the absorption of ferric, but not ferrous, iron.^{140, 141}

Iron has been reported to potentially interfere with manganese absorption. In one trial, women with high iron status had relatively poor absorption of manganese.¹⁴² 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.¹⁴³ These interactions suggest that taking multiminerals that include manganese may protect against manganese deficiencies that might otherwise be triggered by taking isolated iron supplements.