Vitamin B12 deficiency: Cause & Symptoms - LIVE HEALTHY


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July 12, 2020

Vitamin B12 deficiency: Cause & Symptoms

Vitamin B12 is a water-soluble B complex vitamin obtained primarily from animal sources. It is also known as cobalamin because it is a cobalt-containing compound. The body needs only tiny amounts of B12 and stores it better than the other B vitamins, but vitamin B12 deficiency because of diet or an inability to absorb it can eventually cause nervous system problems, pernicious anemia, and other ailments.

Vitamin B12 deficiency

Why is Vitamin B12 essential?

Vitamin B12 aids in energy production from fats and carbohydrates and in the production of amino acid. Nerves need B12 to maintain healthy myelin sheaths. The vitamin is also involved in the production of the mood-affecting substance S-adenosyl methionine.

Vitamin B12 works with folic acid to control blood levels of the amino acid homocysteine. It aids in the formation of red blood cells, the nucleic acids DNA and RNA, and other vitamins. Pregnant women and children need adequate B12 for normal growth and development. B12 assists immune function and melatonin secretion.

Benefits and uses

An excess of homocysteine (which vitamin B12 can help prevent) dramatically increases the risk of heart disease and perhaps osteoporosis. Many people find that B12 increases their bodily energy and prevents fatigue.

Inadequate body levels have been tied to hearing problems—one study of B12 levels in soldiers, 50 percent of whom suffered from either tinnitus or hearing loss. It was found that nearly half of the soldiers with hearing problems were deficient in vitamin B12, fewer than one in five of the soldiers with normal hearing had deficiencies, and tinnitus was most severe among those soldiers with the lowest B12 levels.

Vitamin B12 may reduce the rate of various emotional and nervous system disorders, including depression, age-related mental impairment, and multiple sclerosis. Vitamin B12 may also help prevent or treat asthma, bursitis, diabetes, hepatitis, male infertility, retinopathy, shingles, and bursitis.

Daily requirement

The NRC recently increased slightly the recommended dietary intake for B12. The adult RDI is 2.4 to 2.8 mcg.

Vitamin B12 Deficiency risk factors

After several years, vegans (vegetarians who also avoid dairy and eggs) face some risk of long-term deficiency. Many people who suffer from a vitamin B12 deficiency have a malabsorption condition, often related to lack of a stomach enzyme (intrinsic factor) needed for the small intestines to absorb B12.

Malabsorption is very common among the elderly, mainly due to autoimmune-induced atrophy of the mucous membrane that lines the stomach. People with diabetes or thyroid disorders are also at increased risk of vitamin B-12 deficiency.

Stress, alcoholism, and overuse of antacids can increase the need for B12. Deficiencies in vitamin B12 may cause neurological problems, numbness in the hands and feet, diarrhea, confusion, fatigue, depression, and memory loss.

Optimal intake

An optimal daily supplement level of B12 is 50 to 150 mcg. Larger doses (such as 1,000 to 2,000 mcg per day) are used to reverse pernicious anemia.

Vitamin B12 sources

Vitamin B12 occurs principally in animal products, as it is stored in tissues after being produced by the action of certain bacteria in the intestines. Rich sources include organ meats, beef, lamb, pork, poultry, milk, eggs, cheese, and seafood such as sardines, salmon, oysters, and tuna.

A few plant sources exist, such as tempeh, sea vegetables, brewer’s yeast, spirulina, and mushrooms, but these are less reliable compared to animal sources and may provide a form of the vitamin that is not as useful as animal-derived B12. Some breakfast cereals are fortified with B12.

Recent findings

Studies have continued to support the connection between B12 (and other B vitamins), homocysteine levels in the blood, and heart disease. A recent study, however, found that homocysteine levels may also be a risk factor for chromosomal damage.

Researchers have also determined that B12 supplementation is an affordable and nontoxic strategy for preventing irreversible neurological damage among the elderly if started early.

A two-year study found that people with vitiligo, a disorder in which patches of skin lose their color, could induce repigmentation by taking vitamins B12 and folic acid in combination with exposure to the sun.


It is non-toxic up to at least 1,000 mcg per day, much beyond the optimal level. Vitamin B12 supplements are not associated with side effects. If a person is deficient in vitamin B12 and takes 1,000 mcg of folic acid per day or more, folic acid can improve anemia caused by vitamin B12 deficiency, but not affect neurological symptoms of a vitamin B12 deficiency.

Vitamin B12 deficiencies often occur without anemia (even in people who don’t take folic acid supplements). Some doctors do not know that the absence of anemia does not rule out a B12 deficiency. If this confusion delays the diagnosis of a vitamin B12 deficiency, the patient could be permanently injured.

This problem is rare, and should not happen with doctors knowledgeable in this area using correct testing procedures. Anyone supplementing with more than 1,000 mcg per day of folic acid should seek evaluation by a nutrition-savvy medical practitioner.

Types of products available

As an individual supplement vitamin B12 comes in tablets, capsules, liquids, and lozenges; some forms are sublingual. Potency ranges from 100 to 10,000 mcg. Injectable B12 offers no advantages over oral supplements.

B12 is sometimes combined with folic acid. It is included in most B complex and multi-nutrient formulas. The most common form in supplements is cyanocobalamin; hydroxocobalamin and methylcobalamin are also found.

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