Does Coffee Block Iron Absorption?

Your body conserves iron and recycles most of it. Since it is difficult to excrete iron once in your body, you maintain balance primarily by controlling the rate of absorption, according to Eleanor Whitney, Ph.D., and Sharon Rolfes, M.S., R.D., in "Understanding Nutrition." You absorb more iron when your iron stores are low and you absorb less iron when you have plenty.

The bioavailability of iron from your food is influenced by whether it comes from animals or plants and several other factors that either inhibit or enhance its absorption. Heme iron is found only in animal-derived foods, such as meat, fish and poultry. Nonheme iron comes from both plant-derived and animal-derived foods. Approximately 25 percent of heme iron and 10 percent of nonheme iron is absorbed, depending on your needs and other dietary factors.

Iron Absorption

A specialized protein, ferritin, takes iron from your digestive tract and stores it in mucous membrane cells of your small intestine. When your body needs iron, another protein, transferrin, transports it throughout your body. During their brief three-day lifespan, your intestinal cells temporarily hold iron so they can release it to your body if needed or carry it out as waste when their lifespan is over.

Absorption-Inhibiting Factors

Dietary factors that inhibit the absorption of iron include phytates and fibers found in grains and vegetables, phosphates in cola drinks, oxalates found in spinach, calcium and phosphorus found in milk, EDTA found in food additives and tannic acid and other polyphenols found in tea and coffee. The tannins in coffee consumed with a meal might cause a 50 percent reduction in iron uptake and tea can reduce iron absorption by 60 percent, according to the Colorado University Extension. Lack of iron might lead to tiredness, shortness of breath, reduced physical performance and reduced immune function, according to MayoClinic.com.

Absorption-Enhancing Factors

Meat, fish and poultry contain easily absorbed heme iron and MFP, a factor associated with the digestion of meat, fish and poultry. MFP also enhances the absorption of nonheme iron from foods included in the same meal. Citric acid and lactic acid from foods and hydrochloric acid from your stomach enhance nonheme iron absorption. Vitamin C enhances nonheme iron absorption by keeping the iron in its ready-to-absorb ferrous chemical form. Sugars also enhance nonheme iron absorption.

Individual Variation

Your health, iron status and life cycle stage also influence your rate of iron absorption. When you need more iron, for instance in pregnancy, or in healthy growing children, iron absorption increases. People with a gastrointestinal disease might absorb very little iron.

Dietary Factor Combinations

Due to the many factors that affect iron bioavailability, their combined influence can be difficult to predict. Factors that have a strong influence individually might combine with other factors in the same meal to produce a less-pronounced effect. The factors most relevant overall, according to Whitney and Rolfes, include the enhancers MFP and vitamin C, and the phytate inhibitors. Although coffee, in isolation, does significantly inhibit the absorption of iron, it might not have as pronounced an effect when interacting with other inhibiting or enhancing absorption factors in a given meal and within the context of individual variation.