Vitamin B12 (Cobalamin)

Vitamin B₁₂, also known as cobalamin, is a water-soluble vitamin that is a crucial nutrient for human health. It plays a vital role in brain function and the production of DNA and red blood cells. Vitamin B₁₂ is notable for its contribution to the proper maintenance of neurological function and is involved in the metabolism of every cell of the human body, especially affecting DNA synthesis and regulation, fatty acid synthesis, and energy production.

Sources of Vitamin B₁₂

The primary sources of Vitamin B₁₂ are animal products, including fish, meat, poultry, eggs, milk, and milk products. It is generally not present in plant foods, but fortified breakfast cereals and nutritional yeasts are often a source of B₁₂ for vegetarians and vegans. Due to its scarcity in plant-based foods, Vitamin B₁₂ deficiency is particularly common among strict vegetarians and vegans unless they take supplements or consume B₁₂-fortified foods.

Absorption and Bioavailability

Vitamin B₁₂ absorption is a complex process and requires a protein produced by the stomach, called intrinsic factor, to be absorbed in the small intestine. Once absorbed, it is stored in the liver. The bioavailability of Vitamin B₁₂ from dietary supplements is higher than that from food sources, making supplementation an effective way to prevent deficiency.

Importance for Longevity

Emerging research suggests that Vitamin B₁₂ may have a role in slowing the aging process. It is essential for protecting the telomeres, the protective caps on the ends of chromosomes, which are linked with longevity. Telomeres shorten with age, and B₁₂ helps maintain their length. Additionally, adequate levels of Vitamin B₁₂ are associated with lower blood levels of homocysteine, a compound that can contribute to cardiovascular disease when elevated.

Deficiency and Health Risks

Vitamin B₁₂ deficiency can lead to anemia and neurological problems. Symptoms of deficiency include fatigue, weakness, constipation, loss of appetite, weight loss, and neurological changes such as numbness and tingling in the hands and feet. Prolonged B₁₂ deficiency can result in severe neurological damage.

Because the body stores about 1 to 5 mg vitamin B12 (or about 1,000 to 2,000 times as much as the amount typically consumed in a day), the symptoms of vitamin B12 deficiency can take several years to appear.

There are several groups that have a higher risk of Vitamin B₁₂ deficiency. Relevant for the longevity commuity are: Vegetarians, vegans, older adults (age ≥ 50) and people taking Metformin.

See Vitamin B12 Deficiency

Toxicity

Vitamin B₁₂ is a water-soluble vitamin, so any unused amount will exit the body through the urine. Generally, up to 1000 mcg a day of an oral tablet to treat a deficiency is considered safe. The Institute of Medicine states “no adverse effects have been associated with excess vitamin B₁₂ intake from food and supplements in healthy individuals.” However, it is important not to start a high-dosage supplement of any kind without first checking with your doctor.

Supplementation and Recommendations

For most adults, the recommended dietary allowance (RDA) for Vitamin B₁₂ is 2.4 micrograms, though higher doses can be found in supplements. Those who might benefit from supplementation include older adults, individuals with gastrointestinal disorders like Crohn's disease or celiac disease, and those who have had gastrointestinal surgeries.

Research and Future Directions

Current research is investigating the potential of Vitamin B₁₂ as a modulator of gut microbiota and its possible impact on obesity and metabolic syndrome. Studies are also examining whether B₁₂ supplementation can improve cognitive function in the elderly and reduce the risk of neurodegenerative diseases.

See Also

• Wikipedia - Vitamin B₁₂
• National Institutes of Health - Office of Dietary Supplements - Vitamin B12 Fact Sheet for Consumers / Fact Sheet for Health Professionals
• Vitamin B12 MedlinePlus®
• Harvard School of Public Health - The Nutrition Source: Vitamin B12