Lean red meat best source of iron in food
Many people suffer from iron deficiency, yet this essential nutrient can be toxic if excess accumulates in the body. A small fraction of the population has a gene that predisposes it to iron overload, but most people just absorb less iron when the body has plenty.
Question: What foods are good sources of iron?
Answer: What appears to be a simple question is anything but simple to answer. There are two key factors that need to be considered: the amount of iron in a food and the amount of iron that is available to the body.
Q: Why isn't the amount of iron in a food all the information that is needed?
A: There are numerous lists of food sources of iron posted on the Internet. Generally these sites simply rank foods based on which foods contain the greatest quantity of iron. But, listing foods only by iron content fails to account for how much of the iron will actually be absorbed into the body and become available for needed functions.
For example, a half-cup of cooked spinach and three ounces of cooked lean beef contain similar amounts of iron, but the body absorbs about 10 times as much iron from the beef. So, it really takes five cups of the spinach to match the three ounces of beef.
Q: How much food iron is available (bioavailable) to the body?
A: The World Health Organization estimates that people eating an all-plant food diet absorb only 5 percent of the iron in their food. Adding small amounts of meat, poultry and fish to the plant food diet raises iron absorption to about 10 percent, and adding moderate amounts of animal foods increases iron absorption to about 15 percent.
Q: What other food factors enhance iron absorption?
A: Vitamin C and beta-carotene found mostly in green and orange fruits and vegetables increase iron absorption.
Q: What food components inhibit iron absorption?
A: Numerous food factors inhibit iron absorption. These components, however, are often beneficial for other functions of the body. For example, calcium strongly inhibits iron absorption from both plant and animal iron sources. Other foods that inhibit iron absorption include bran, many whole-grain foods, tea, coffee, red wines, beans (especially red beans) and some vegetables like spinach.
Q: What foods are good sources of well-absorbed iron?
A: The most readily absorbed iron is found in lean red meats that are not overcooked. Other animal foods like chicken and fish have less iron, but even small amounts of them increase iron absorption from plant foods when consumed together.
Are iron-fortified foods and iron supplements good iron sources? See this column in two weeks for the answers.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S. are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii-Manoa. Dr. Dobbs also works with University Health Services.