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What Are the Dangers of Excess B6 & B12?

By Christine Gray

Vitamins B6 and B12 are both water-soluble B-complex vitamins, and while the body normally excretes excesses of water-soluble vitamins through urination, it has the capacity to store excess vitamin B12 in the liver for future use. Vitamin B6 is essential to protein metabolism, hemoglobin production and oxygenation, neurological and immune function and the conversion of tryptophan to niacin. Vitamin B12 plays a vital role in DNA production, red blood cell formation, neurological function and fat and protein metabolism.

Recommended Dietary Allowances

The daily recommended dietary allowance, or RDA, of vitamin B6 is 1.3 mg for men and women age 19 to 50, 1.5 mg for women over age 50, 1.7 mg for men over age 50, 1.9 mg for pregnant women and 2 mg for lactating women, according to the National Institutes of Health Office of Dietary Supplements. Fortified cereals, potatoes, chicken, pork, beef, beans, seeds and nuts are all excellent sources of vitamin B6. The RDA of vitamin B12 is 2.4 mcg for those over age 14, except for pregnant and lactating women, who should consume 2.6 mcg and 2.8 mcg of vitamin B12 daily, respectively. Fortified cereals, beef liver, clams, fish and dairy products all provide significant amounts of vitamin B12. Mushrooms are the only known non-animal product food that contains naturally occurring vitamin B12.

Risks of Deficiency

Vitamin B6 deficiency is unusual in the industrialized world, but can cause inflammation of the skin, a sore tongue, nausea, anemia, kidney stones, irritability, depression, confusion and convulsions. Vitamin B12 deficiencies are characterized by megaloblastic anemia, fatigue, weakness, constipation, anorexia, weight loss, loss of coordination, confusion, memory loss, dementia, soreness of the mouth or tongue, and tingling or numbness in the extremities.

Risks of Toxicity

The Food and Nutrition Board of the Institute of Medicine set the upper tolerable intake level for vitamin B6, or the largest daily dose than can be taken safely, at 100 mg for adults. Larger doses can cause nerve damage to the arms and legs. Nerve damage has been reported in doses below 500 mg per day.The National Institutes of Health Office of Dietary Supplements reports there are no known side effects from excessive vitamin B12 consumption. Studies have shown no toxic effects in individuals who took over 400 times the recommended dietary allowance for up to five years.

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