The B vitamin thiamine is an essential component of certain enzymatic reactions in the body. A human must get his or her thiamine from food sources as the body cannot make its own. Sources of thiamine include lean meats, nuts, and eggs, although fruit and vegetables also contain some of the vitamin.
Thiamine is also known as thiamin and used to be called Vitamin B1 or aneurine. It is soluble in water, and it is present in the body in four forms. These are free thiamine, thiamin monophosphate (TMP), thiamin pyrophosphate (TPP), and thiamin triphosphate (TTP). These forms of thiamine work inside the cells to help release energy from carbohydrates. Healthy functioning of muscles and the circulatory and nervous systems also depend on sufficient thiamine.
According to the U.S. National Institutes of Health (NIH), the recommended daily intake for thiamine is 1.1 milligrams (mg) for women over 19 and 1.2 mg for males over the age of 14. Children need less, with preteens requiring less than 1 mg per day. Pregnant and breast-feeding women need more than an average adult.
Meat is one of many dietary sources of thiamine. According to the Linus Pauling Institute in the United States, 3 ounces (about 85 grams) of lean pork contain 0.72 milligrams of thiamine. Organ meats and eggs also contain thiamine, although large eggs only contain 0.03 mg thiamine apiece. In contrast, a cup (about 240 milliliters, or ml, in volume) of milk provides 0.10 mg of thiamine.
Staple carbohydrates in many developed countries contain less thiamine than occurs naturally in the plant. This is due to the processing of grains, which removes the outer layer and polishes or refines the grain. Therefore, white rice and products such as pasta and bread that are made from white flour are commonly fortified with the vitamin.
One slice of whole wheat bread can contain 0.10 mg of thiamine, whereas an artificially fortified slice of white bread can provide 1.1 mg. One cup (about 240 ml) of unfortified cooked white rice contains only 0.04 mg compared to 0.26 mg for the same serving of fortified rice. Fortified cereal can contain from 0.5 mg up to 2.0 mg per cup (about 240 ml). Wheatgerm breakfast cereal is one of the richest sources of thiamine and can provide 4.47 mg per cup (about 240 ml).
Legumes such as peas and lentils also provide thiamine. Half a cup (about 120 ml) of cooked peas contains 0.21 mg of thiamine, and the same serving of lentils has 0.17 mg. Nuts like Brazil nuts and pecans provide about 0.17 mg of thiamine per ounce (about 28 grams).
Vegetables and fruits are not particularly rich in thiamine per volume, but the sources of thiamine all add up over a day. For example, one orange contains 0.10 mg, and a half a cup (about 120 ml) of spinach offers 0.09 mg. Thiamine supplements are also available, but the NIH recommends a varied diet as the best way to get an adequate amount of thiamine.