Vitamin B12

Vitamin B12 (cobalamin) is unique in that it is required by the body in much smaller amounts than any other B vitamin. Cobalamin was first discovered in the 1940s and was found to cure pernicious anemia — a condition in which the body can’t make enough healthy red blood cells. B12 is needed for optimal digestion and the absorption of foods, the manufacturing of protein, and the metabolism of carbohydrates and fats. It also has the ability to increase energy levels and prevent fatigue.

Eye Health

Japanese researchers conducted a study at the Nihon University School of Medicine in Tokyo where 28 glaucoma patients took 1,500 mcg/day of vitamin B12 for five years to evaluate the vitamin’s influence on vision. The patients receiving the B12 had “less measurable loss of peripheral vision, more stable visual acuity, and better control of eye fluid pressure compared to a group that did not take B12.”

In the Blue Mountains Eye Study, cobalamin was shown to benefit eye health as it provides protection to the lens which assists in the prevention of cataracts.

A lack of B12 may leave the optic nerve more susceptible to damage. In the European Journal of Internal Medicine, several months of vitamin B12 use was able to improve vision in a male with optic neuropathy (central vision loss).

Another study appearing in the Archives of Internal Medicine showed that women who took vitamin B12, B6 and folic acid for several years had a 35 percent to 40 percent lower risk of developing age-related macular degeneration than the women who took a placebo.

Brain Health

Because of cobalamin’s important nerve-protecting function, a wide variety of neurological problems have been associated with low levels of this nutrient including confusion, memory loss, decreased reflexes, loss of balance, and numbness and tingling in the arms and legs.

Low levels of vitamin B12 have been linked with poor memory in older adults at high risk for Alzheimer’s disease, according to a large study, thought to be one of the first to examine how the relationship between diet and genes can affect cognition in old age. This study, conducted at the Division of Geriatric Epidemiology and Medicine in Sweden, found that 370 subjects over 75 years old with low levels of B12 had twice the risk of developing Alzheimer’s disease over the three-year period of the study.

And a study published in the October 2010 issue of Neurology also showed that vitamin B12 may help to guard against Alzheimer’s disease, supporting the scientific debate about whether it is effective in reducing the chance of memory loss.

Research has shown that low vitamin B12 levels can be related to dementia in general. A study presented in theInternational Journal of Geriatric Psychiatry illustrated that 73 outpatients with probable Alzheimer’s disease and low vitamin B12 status was associated with irritability, disturbed behavior, and an increase in the behavioral and psychological symptoms of dementia.

An article in the Annals of Internal Medicine looked at cobalamin deficiency in the elderly population in relation to memory impairment and neuropathy. It was found that these problems were treated successfully with vitamin B12 injections or supplementation.

Vitamin B12 prevents nerve damage by preserving myelin, the fatty sheath that protects nerve fibers, helping electrical impulses to move throughout the body. When there is a deficiency of B12, the lack of healthy myelin can lead to disrupted nerve transmissions, which, in turn, may cause tingling in the fingers and the bottoms of the feet, producing multiple sclerosis-type symptoms. A study in Pediatric Radiology concluded that “myelination retardation was due to insufficient intake of vitamin B12.”


Because vitamin B12 is required to convert folate to its active form, one of the most obvious deficiency symptoms is anemia. Vitamin B12 helps prevent anemia by assisting folic acid in regulating the formation of red blood cells, and helping in the utilization of iron.

Heart Disease and Homocysteine Reduction

Another important benefit of cobalamin is its ability to lower the risk of atherosclerosis. Vitamin B12 converts homocysteine into methionine which brings down homocysteine levels. The lower your homocysteine levels, the lower your risk for heart disease.

An article appearing in the Journal of the American Medical Association showed that the incidence of adverse events from heart disease was significantly lower in patients receiving a combination of vitamin B12, B6 and folic acid therapy. The study further suggested that the benefit obtained with this homocysteine-lowering protocol was maintained one year later despite the cessation of vitamin therapy at six months. The study concluded that taking this combination of vitamin B6, B12, and folic acid was “an effective therapy for improving outcome in patients undergoing coronary angioplasty.”

Hearing Loss

Vitamin B12 deficiency has been associated with chronic tinnitus and noise-induced hearing loss. A study in theAmerican Journal of Clinical Nutrition examined the association of age-related auditory dysfunction and vitamin B12 deficiency. In the study, women with hearing dysfunction exhibited low blood levels of vitamin B12. This led these researchers to recommend that “serum levels of B12 be evaluated in persons with tinnitus, noise-induced hearing loss, or age-related hearing loss.”


The most common reason for B12 deficiency in older people is malabsorption due to low stomach acid. As we age, the ability of the intestines to perform the juggling act of absorbing vitamin B12 often diminishes. According to a study in the New England Journal of Medicine, it was found that a B12 deficiency could be a major cause of memory loss, muscle weakness, and parasthesias (abnormal skin sensations) in some elderly psychiatric patients.

The main causes of deficiency in the general population are due to conditions that affect gastrointestinal health such as celiac disease or Crohn’s disease. Other reasons for poor absorption of vitamin B12 include alcohol and drug use, being a vegetarian and being under considerable amounts of stress.


The RDA for vitamin B12 is 2 to 3 mcg per day, although supplements are available in strengths from 50 to 5,000 mcg. B12 isn’t absorbed well through the stomach, so a sublingual or time-released form is usually recommended.  Vitamin B12 injections are indicated if there is a severe deficiency. Older people may lose the ability to absorb B12 from their food and may benefit from taking supplements.

Food sources

Vitamin B12 is unique among the nutrients because it is found almost exclusively in animal flesh and animal products. Anyone who eats a reasonable amount of meat will probably have an adequate intake. People who stop consuming foods with B12 may take years to develop deficiencies. The reason this take so long is that the body recycles much of its vitamin B12 — reabsorbing it over and over again. Vegans, strict vegetarians who avoid dairy products and eggs as well as meats, are in danger of becoming B12 deficient. Foods containing vitamin B12 are liver, clams, oysters, herring, salmon, tuna, brewer’s yeast, beef, pork, poultry, eggs, milk and dairy products.  Fermented plant foods including miso (soybean paste), tempeh (fermented whole soybeans) and brewer’s yeast are good sources of B12 for the vegetarian.

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