Vitamin B12

Vitamin B12 is important for metabolism. Metabolism within the body includes the processes of energy generation and use; including nutrition, digestion, absorption, elimination, respiration, circulation, and temperature regulation.

You'll only find vitamin B-12 in animal-based foods, and Alaskan cod is one of the best sources. A 3-ounce serving has 1.96 micrograms, which gives you 81 percent of the recommended daily intake. Vitamin B-12 is essential for the normal development of red blood cells and hemoglobin, and it keeps your nerves working properly. It may also keep your heart healthy by removing the amino acid homocysteine from the blood; high levels of homocysteine are associated with cardiovascular disease.

Good sources of vitamin B12:

• Sardines
• Salmon
• Tuna
• Cod
• Lamb
• Scallops
• Shrimp
• Beef
• Yogurt
• Cow's milk

B12 deficiency is associated with cognitive impairment, memory loss, dementia, and psychosis. However, vitamin B supplementation has been shown to reduce the rate of brain atrophy in older people with mild cognitive impairment (MCI).

In the United States, B12 deficiency is defined as a total blood level of less than 148 pmol/L, which is three standard deviations below the population average. Due to a lack of agreement on what blood levels constitute a B12 deficiency, clinical features are often considered a better indication for supplementation.

B12 absorbed from the gastrointestinal tract is bound to transport proteins in the blood, including haptocorrin (HC) and transcobalamin (TC). The B12-TC complex (Holo-TC) is the only bioactive form of this vitamin, as B12 bound to HC (Holo-HC) is unavailable for cell uptake and is considered inactive.