Many foods, drinks, and supplements have been shown to affect the absorption of iron.¹⁰²

Foods, drinks and supplements that interfere with iron absorption include

• Green tea (Camellia sinensis).^{103, 104, 105, 106} 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.¹⁰⁷

• Coffee (Coffea arabica, C. robusta).^{108, 109, 110}

• Red wine, particularly the polyphenol component (also found in tea).^{111, 112} 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.^{113, 114, 115}

• Whole wheat bran, independent of its phytate content, has been shown to inhibit iron absorption.¹¹⁶

• Calcium from food and supplements interferes with haem-iron absorption.^{117, 118}

• Soya protein.^{119, 120}

• Eggs.^{121, 122}

Foods and supplements that increase iron absorption include

• Meat, poultry, and fish.^{123, 124, 125, 126, 127}

Although vitamin C increases iron absorption,^{128, 129, 130, 131} the effect is relatively minor.¹³²

Taking vitamin A with iron helps treat iron deficiency, since vitamin A improves the absorption and/or utilization of iron.^{133, 134}

Although soya protein has been shown to decrease iron absorption (see above), certain soya-containing foods (e.g. tofu, miso, tempeh) have significantly improved iron absorption.¹³⁵ Some soya sauces may also enhance iron absorption.¹³⁶

Alcohol, but not red wine, has been reported to increase the absorption of ferric, but not ferrous, iron.^{137, 138}

Iron has been reported to potentially interfere with manganese absorption. In one trial, women with high iron status had relatively poor absorption of manganese.¹³⁹ 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.¹⁴⁰ These interactions suggest that taking multiminerals that include manganese may protect against manganese deficiencies that might otherwise be triggered by taking isolated iron supplements.