Vitamin B is not a single vitamin, but rather a group of vitamins consisting of eight members: Thiamine, riboflavin, niacin, pantothenic acid, B-6, biotin, B-12 and folate. (ref 1) B vitamins are water soluble, which means if you get too much the excess is excreted in your urine and unlikely to cause health problems. (ref 2, paras 1 -4) However, a deficiency in any of the B vitamins can cause troubling symptoms, including hair loss. If you think you are deficient in the B vitamins, speak to your doctor about boosting your blood levels.
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Excess Water-Soluble B Vitamins
Unlike the fat-soluble vitamins A, E, D and K, water-soluble B vitamins don't build up in your body. (ref 2) This means you can take quite a lot without experiencing any negative symptoms. Yet, there are some. Take too much vitamin B6 from supplements and you may experience nerve damage, painful skin patches, sensitivity to sunlight, nausea and heartburn. (ref 3, Can vitamin B6 be harmful?) Take too much niacin and you can experience flushing, and liver damage, although it is rare. (ref 4, Niacin Toxicity) Too much folate may increase the risk of certain cancers. (ref 5, Can folate be harmful?) But there is no evidence that an excess of any of the B vitamins causes hair loss.
More likely to cause hair loss is a deficiency in one of the B vitamins. According to the University of Maryland Medical Center website, all of the B vitamins support healthy hair. (ref 6, para 1) In fact, the UMMC recommends eating foods rich in B vitamins, such as whole grains, if you experience hair disorders including hair loss. (ref 7, Nutrition and Supplements) Guidelines on hair loss in adult women by the University of Texas at Austin, School of Nursing, note that for hair loss accompanied by malnutrition or a gastrointestinal or absorptive disorder, increasing vitamin B-12 levels may be part of the treatment plan. (ref 8, #5 under Diagnosis)
Other Nutrients and Hair Loss
One vitamin that does pose problems for your hair when taken in excess is vitamin A. Hypervitaminosis A, or excess vitamin A, can cause hair loss when taken in excess of 50,000 international units per day, according to Huntington College of Health Sciences. (ref 9, pg 1) It would be difficult to get that much from food, but taking megadoses of supplements could put you over the limit. Your problem could result from a deficiency in any number of other vitamins or minerals that support hair growth. Huntington College of Health Sciences notes vitamins C and E and the minerals calcium, selenium, zinc and iodine as being important for healthy hair growth. (ref 9)
What To Do About Hair Loss
See your doctor to rule out any nutrient deficiencies or excess levels of vitamin A.While hair loss is often hereditary, there are methods to slow hair loss or maintain the hair that you have. (ref 10, paras 11 - 14) A healthy diet rich in fresh fruits and vegetables, whole grains, lean protein, low-fat dairy and nuts and seeds in moderation will help provide all the nutrition you need to maintain a healthy nutrient status. The UMMC recommends being tested for food sensitivities and eating plenty of antioxidant-rich foods such as blueberries, tomatoes and squashes, avoiding refined foods like white bread and pasta, using healthy oils like olive oil in your cooking and reducing your intake of trans fats found in commercial baked goods. (ref 7, Nutrition and Supplements)