Side Effects of Vitamin Supplements: Vitamin B6 and Vitamin B12

B vitamins, such as vitamin B6 and vitamin B12, are essential to the human body. Most of our B vitamin requirements can be reached through a eating a balanced diet of healthy foods, but occasionally vitamin supplements are required. While vitamin supplements are generally considered safe, the risk of side effects does exist.

Vitamin B6: Daily Recommendations and Side Effects
Vitamin B6 is used by the body in over 100 metabolic processes. The body uses Vitamin B6 to help the immune system produce antibodies, maintain nerve function, form red blood cells, break down proteins, and synthesize neurotransmitters. It also aids in the absorption of vitamin B12. A deficiency in vitamin B6 can lead to a deficiency in vitamin B12.

Vitamin B6 is water soluble, which means the body cannot store it. It is therefore important to ingest vitamin B6 through food sources (whole grains, meat, beans, nuts, fortified breads and cereals) or a balanced multi-vitamin or B-complex formula when dietary restrictions are involved.

The recommended daily dosages for Vitamin B6 are:
Ages 0-6 months - 0.1 milligrams
Ages 7-12 months - 0.3 milligrams
Ages 1-3 years - 0.5 milligrams
Ages 4-8 years - 0.6 milligrams
Ages 9-13 years - 1 milligram
Ages 14-18 years - 1.3 milligrams (boys) and 1.2 milligrams (girls)
Ages 19-50 years - 1.3 milligrams
Ages 51 years and up - 1.7 milligrams (men) and 1.5 milligrams (women)
Pregnant teens and adults - 1.9 milligrams
Breastfeeding teens and adults - 2 milligrams

Side effects of Vitamin B6 include acne or other skin reactions, photosensitivity (an allergic reaction to sunlight, which can lead to sun poisoning), nausea, vomiting, abdominal pain, breast soreness, headache, and loss of appetite.

Research studies have had mixed results in discovering the toxic level of vitamin B6, ranging anywhere from 200 milligrams to 500 milligrams. This has led the Food and Nutrition Board (FNB) of the U.S. Institute of Medicine of the National Academy of Sciences to set the upper tolerance level of vitamin B6 rather low.

Ages 1-3 years - 30 milligrams
Ages 4-8 years - 40 milligrams
Ages 9-13 years - 60 milligrams
Ages 14-18 years - 80 milligrams
Ages 19 years and up - 100 milligrams
The upper tolerance level for babies during their first year is unknown. Infants should only receive the amount of B6 provided by their food, breast milk or formula.

Toxic level side effects of vitamin B6 include drowsiness, numbness, tingling of the skin or extremities, poor coordination, trouble walking, seizures, and sensory neuropathy (a degeneration of the sensory nerves). Respiratory distress has been reported as a toxic side effect in infants.

Research has shown no side effects from food sources of vitamin B6, only from vitamin supplements. It is therefore best to use food as your source of vitamin B6 and consult with a doctor or pharmacist before taking a supplement.

Vitamin B6 can reduce the effectiveness of anticonvulsant medications, such as phenobarbital (Luminal) and phenytoin (Dilantin), as well as the anti-parkinsonism effects of levodopa (Sinemet). Several prescription medications cause photosensitivity as one of their side effects and vitamin B6 can increase this reaction. Always tell your doctor or pharmacist if you are using a supplemental form of vitamin B6.

Vitamin B12: Daily Recommendations and Side Effects
Vitamin B12 is an essential vitamin for the proper functioning of the body. It aids in metabolism, the formation of red blood cells, and the proper functioning of the central nervous system. The body stores several years' worth of the vitamin in the liver. A deficiency of vitamin B12 is rare, though the elderly and vegetarians may experience it due to not absorbing the required amounts from their food.

The recommended daily dosages for Vitamin B12 are:
Ages 0-6 months - 0.4 micrograms
Ages 7-12 months - 0.5 micrograms
Ages 1-3 years - 0.9 micrograms
Ages 4-8 years - 1.2 micrograms
Ages 9-13 years - 1.8 micrograms
Ages 14 years and up - 2.4 micrograms
Pregnant teens and adults - 2.6 micrograms
Breastfeeding teens and adults - 2.8 micrograms

Side effects of vitamin B12 include diarrhea, itching, and rash. In the case of a severe reaction to vitamin B12, the rash may remain for up to four months.

Vitamin B12 is generally handled well by most people and research has shown very little in the way of side effects or toxicity. Due to this fact, the Food and Nutrition Board has not set an upper tolerance level dosage for vitamin B12.

People who are recovering from angioplasty or a coronary stent should not take supplemental B12 (or B6) due to the risk of a renarrowing of the artery. Speak to your doctor before taking a multi-vitamin containing B vitamins or a B-complex formula.

Vitamin B12 should not be used by people with Leber's disease, a hereditary condition that causes optic nerve atrophy, as the speed of atrophy can be greatly increased.

The Side Effects of Other Vitamin Supplements
For additional information on the side effects of vitamin supplements, check out the following articles here on Associated Content:

Side Effects of Vitamin Supplements (Vitamin C, Vitamin E, Calcium and Zinc)

Side Effects of Vitamin Supplements: Vitamin A and Vitamin D

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Sources:
Linus Pauling Institute's Micronutrient Information Center, Oregon State University:
Vitamin B6
Vitamin B12

National Institutes of Health National Library of Medicine - Medline Plus:
Vitamin B6
Vitamin B12

Drugs.com:
Vitamin B6
Vitamin B12

Nutritional Supplement Educational Centre:
Vitamin B6
Vitamin B12 (Cobalamin)