The vitamin B complex includes a group of water-soluble vitamins that contribute to energy production, brain and nerve function, blood formation and the health of your liver, skin and eyes. B vitamins include thiamine, or B1; riboflavin, or B2; niacin, or B3; pantothenic acid, or B5; pyridoxine, or B6; biotin, or B7; folate, or B9; and cobalamin, or B12. Choline may also be included with the B vitamins. The University of Maryland Medical Center, or UMMC, advises that you should avoid taking supplemental doses of any single B vitamin for an extended period of time. Taking a supplement that includes all of the B vitamins will help you prevent an imbalance.
Functions
B vitamins play vital roles in metabolism, growth and development and the synthesis of DNA. Thiamine, riboflavin and niacin help your body produce energy. Niacin, B5 and B12 support your nervous system and enhance cognitive function. Niacin, folate, B6 and B12 assist with red blood cell production, vasodilation and blood flow. Dietary folate, or folic acid, may help prevent birth defects and reduce your risk of cancer, the American Cancer Society, or ACS, states. The B vitamins combat stress by supporting your immune system, according to the UMMC. Because some of the B vitamins have complementary functions, adding a B-complex multivitamin to your diet may help you take advantage of the varied benefits of this nutrient group.
Sources
You can meet most of your daily requirements for the B vitamins by eating a balanced diet that includes vegetables, fruits, grains, dairy products, meat and fish, according to the ACS. Vegetarians who exclude animal products and vegans may need to supplement their diet with cobalamin, or vitamin B12, which occurs naturally only in shellfish, meats, poultry, milk products and eggs. Some fortified grain products contain B12. Whole grains and enriched breads and cereals contain thiamine, riboflavin, niacin and folate. Pork, beef, chicken, seafood, liver and fish provide thiamine, niacin, B5 and B12. Leafy green vegetables, citrus fruits, liver, mushrooms, nuts and dried beans contain folate. Biotin, or vitamin B7, occurs in peanuts, liver, egg yolks, mushrooms and bananas and is also manufactured by bacteria in your intestinal tract. Choline is found in peanuts, meats, egg yolks and cauliflower.
Deficiencies
Severe vitamin B deficiency syndromes such as beriberi, caused by a thiamine deficiency, and pellagra, caused by a niacin deficiency, have become rare in developed countries, according to the UMMC. Vitamin B deficiencies have been associated with an increased risk of Alzheimer's disease and other neurological disorders. Vitamin B deficiencies may also cause anemia, fatigue, abdominal pain, developmental delays in children and skin irritations, according to the ACS. An inadequate intake of vitamins B6, B12 and folate may increase your levels of homocysteine, an amino acid that may contribute to heart disease and Alzheimer's disease, the UMMC notes. Women who are pregnant and breastfeeding may need to supplement their diet with folate, B6 and B12, according to the UMMC. Due to digestive changes in the elderly, older adults have difficulty absorbing vitamin B12 from foods. Older adults may have an inadequate intake of other B vitamins in their diet, as well, the UMMC notes.
Toxicity
Because the B vitamins are water-soluble and your body flushes away excess amounts in your urine, toxicities are rare, according to the UMMC. Niacin is an exception, causing low blood pressure, hot skin flushes, dizziness, digestive disturbances and visual alterations at high doses. B6 may cause nerve damage at high doses and may affect nerve development in the infants of pregnant women who take high doses, the UMMC notes.
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