Iron and vitamin B12 are both major nutrients needed by cells in your body to function properly. Both nutrients are commonly found in foods derived from animal sources. Where they differ is that B12, a water-soluble vitamin, is easily absorbed in the body, whereas iron is not. Iron absorption can be inhibited by calcium, the tannins found in coffee and teas, excess fiber and phytates.
Function of Vitamin B12
Vitamin B12 is also commonly known as cobalamin. It is needed for energy metabolism, the formation of red blood cells and the maintenance of the central nervous system. B12 also plays an important role in the synthesis of DNA, the genetic material in all cells.
Food Sources of B12
Vitamin B12 is bound to protein in food. Good food sources of B12 are meat, fish, poultry, dairy, eggs and shellfish. B12 is not generally found in plant-based food, but fortified cereals are a good source, with high bioavailability for vegetarians. The amount of B12 in liver is 48.0 mcg per serving, salmon has 4.9mcg, beef has 2.4mcg, tuna has 1.0mcg, yogurt has 1.4mcg, milk and cheese have 0.9mcg, an egg has 0.6mcg and chicken has 0.3mcg per serving. Fortified breakfast cereals can vary in their content of B12.
Recommended Daily Allowances (RDAs)
The RDA for B12 for the adult population is 2.4mcg/day. If a woman is pregnant or lactating, it is increased to 2.6mcg/day and 2.8mcg/day respectively. It is, therefore, easy to obtain the amount of vitamin B12 needed through diet. The RDA for iron is 18mg/day for females and 8mg/day for males. Pregnant women should increase their iron intake to 27mg/day.
Function of Iron
Iron is another nutrient that is essential to all body cells. It is the carrier of oxygen in the body and is also part of hemoglobin in blood and myoglobin in muscles. There are two types of iron found in foods, Heme iron and non-heme iron. Heme iron is found in meat, fish and poultry and is more easily absorbed than non-heme iron, which can be found in fruits, vegetables, beans, nuts and grains.
Food Sources of Iron
Liver is high in iron. A serving of chicken liver has 12.8mg of heme iron, beef can range from 3.2mg to 4.6mg depending on the cut, dark meat turkey has 2.0mg, and tuna has 1.0mg. A serving of kidney beans has 3.0mg of non-heme iron, prune juice has 1.5mg, raisins and brown rice have 1.0mg, spinach has 3.2mg, dried apricots have 1.7mg, and broccoli has 1.1mg. To enhance the absorption of iron, it is often recommended to consume foods high in vitamin C with the iron-containing foods.
If B12 and iron are deficient in the diet, there are supplemental forms of both nutrients available. A more complete list of food sources for vitamin B12 and iron can be found on the U.S. Department of Agriculture's Nutrient Database Web site.
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