The vitamin B complex is a family of eight water-soluble vitamins essential for the health of your nervous system, skin, eyes and hair. As normal levels of B complex vitamins promote healthy hair, taking too much or too little of these vitamins affects the strength and thickness of your hair. While hair loss is a common sign of a B vitamin deficiency, using excessive amounts of B vitamins to correct this may further increase your hair loss.
Vitamin B Complex
The eight vitamins in the vitamin B complex are thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, biotin, folic acid and vitamin B12, or cobalamins. As these vitamins are all water-soluble, your body readily excretes excess B vitamins in your urine. While this results in a very low risk of toxicity, excessive use of B vitamin supplements can lead to toxic effects. According to the Linus Pauling Institute, the Office of Dietary Supplements and the University of Maryland Medical Center, these effects include nerve damage, stomach upset, diarrhea, sensitive eyes and skin blemishes. None of these agencies notes hair loss; excessive intake of the full vitamin B complex does not have a noticeable effect on the health of your hair.
Deficiencies and Supplements
While hair loss is not among the side effects of toxic vitamin B complex levels, it is a common symptom of a B vitamin deficiency. Once you determine which B vitamin is the cause of your hair loss, increasing your intake of that vitamin may correct brittle or thinning hair. As levels of each B vitamin affect others, however, you need to be careful not to overdo your supplementation. According to the University of Maryland Medical Center, excessive use of any individual B vitamin supplement reduces your body's levels of other B vitamins. As such, taking too much of one B vitamin can cause deficiencies in other B vitamins, potentially leading to brittle and thinning hair.
Biotin and Inositol
According to the Linus Pauling Institute, the use of biotin to treat or prevent hair loss is common. However, they note that there is no scientific evidence supporting these uses of biotin. In his 2003 book "The Encyclopedia of Nutrition and Good Health," Dr. Robert Ronzio notes that inositol is effective at preventing hair loss in animals. Although otherwise known as vitamin B8, inositol is not officially an essential vitamin due to your body's ability to produce adequate amounts without dietary sources.
Hair Loss Causes
MayoClinic.com list a number of potential dietary causes of hair loss. Aside from B vitamins, hair loss is also an effect of insufficient levels on a number of macro and micronutrients. While your high B vitamin levels may not be the direct cause, hair loss can arise from interactions between these vitamins and other nutrients or medications. If you are taking large amounts of B complex vitamins as part of a treatment, your hair loss is likely a side effect of that disease or condition. Hair loss also arises from nondietary sources, such as excessive stress, emotional or physical disturbances, hereditary conditions and even the way in which you style your hair. As such, you should explore all possible causes with your doctor before reducing or ceasing your use of vitamin B complex supplements.