Many foods, drinks, and supplements have been shown to affect the absorption of iron.¹⁰³

Foods, drinks and supplements that interfere with iron absorption include

• Green tea (Camellia sinensis).^{104, 105, 106, 107} This effect may be desirable for people with iron overload diseases, such as haemochromatosis. The inhibitory effect of green tea on iron absorption was 26% in one study.¹⁰⁸

• Coffee (Coffea arabica, C. robusta).^{109, 110, 111}

• Red wine, particularly the polyphenol component (also found in tea).^{112, 113} 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 biscuits; in wheat germ, oats, nuts, cacao powder, vanilla extract, beans, and many other foods, and in IP-6 supplements.^{114, 115, 116}

• Whole wheat bran, independent of its phytate content, has been shown to inhibit iron absorption.¹¹⁷

• Calcium from food and supplements interferes with haem-iron absorption.^{118, 119}

• Soya protein.^{120, 121}

• Eggs.^{122, 123}

Foods and supplements that increase iron absorption include

• Meat, poultry, and fish.^{124, 125, 126, 127, 128}

Although vitamin C increases iron absorption,^{129, 130, 131, 132} the effect is relatively minor.¹³³

Taking vitamin A with iron helps treat iron deficiency, since vitamin A improves the absorption and/or utilization of iron.^{134, 135}

Although soy protein has been shown to decrease iron absorption (see above), certain soya-containing foods (e.g. tofu, miso, tempeh) have significantly improved iron absorption.¹³⁶ Some soya sauces may also enhance iron absorption.¹³⁷

Alcohol, but not red wine, has been reported to increase the absorption of ferric, but not ferrous, iron.^{138, 139}

Iron has been reported to potentially interfere with manganese absorption. In one trial, women with high iron status had relatively poor absorption of manganese.¹⁴⁰ In another trial studying manganese/iron interactions in women, increased intake of "non-haem iron"--the kind of iron found in most supplements--decreased manganese status.¹⁴¹ These interactions suggest that taking multiminerals that include manganese may protect against manganese deficiencies that might otherwise be triggered by taking isolated iron supplements.