Iron comes in two forms in the diet: heme and nonheme. Heme iron is from animal tissues and is readily absorbed when eaten. Nonheme iron is from plants (and in some animal tissues) and is not easily absorbed because this iron has phytic or oxalic acid that binds iron to itself. Because humans lack special enzymes to break apart the bind, the iron passes through the digestive tract and is excreted.
Men require about 8 mg a day of iron while women who are menstruating need between 15 to 18 mg a day.
Seafood
Oysters have one of the highest amounts of iron per serving (3 oysters provide 7 mg of iron) as well as other shellfishes like mussels and clams.
Fish―particularly cold-water fish like salmon, trout and tuna―also provide high iron amounts as well as omega-3 fatty acids and vitamin D.
Meats
Meats, such as poultry, beef, and pork, contain a rich source of heme iron. A 3-ounce sirloin steak (about the size of a deck of playing cards) contains about 4.0 mg which makes up 20% of your daily recommendation. Be sure to consume the lean cuts of meats to minimize your saturated fat intake.
Whole Grains and Other Plant Sources
Whole grains provide mainly nonheme iron which are not easily absorbed into your body. These foods include wheat germ, oatmeal, millet, brown rice, and fortified cereals and breads.
Other sources of plant sources of iron include leafy vegetables (spinach), broccoli, green peas, kidney beans, prunes, raisins, apricots, lima beans, tofu and almonds.
Improving Iron Absorption
To make iron more easily absorbed in the small intestine, you can cook some of these foods to break the tough phytic or oxalic acid bond in nonheme iron.
Eating foods that are rich in vitamin C also helps in absorption because vitamin C donates an electron to iron in its ferric form (+3 charge), yielding the ferrous form (+2 charge). Vitamin C then forms a complex called a chelate with ferrous iron, enhancing absorption rate. Ferrous iron absorbs better than ferric iron because it can pass the mucous layer of the small intestines to reach the intestinal absorptive cells.
By combining iron-rich foods with vitamin C-rich foods, you can increase your iron intake, especially for women. An example meal would be a 4-oz. steak, half a cup of steamed spinach with ginger and garlic, a whole wheat bun, and a fresh fruit cup for dessert. If you are vegetarian, then your meal may be noodles with baby bok choy, tofu, onions, carrots and edamame.
References
- "Ultimate Sports Nutrition"; Ellen Coleman; 2004
- "Perspectives in Nutrition;" Gordon Wardlaw and Margaret Kessel; 2002
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