People who follow a vegetarian or vegan diet often have vitamin B12 deficiencies, as it is virtually found only in animal sources, such as meat, poultry, liver, brewer's yeast, clams, eggs, herring, mackerel, kidneys, milk, dairy products, and seafood.
A deficiency of B12 can cause a general decline in mental function, problems with walking and balance, weakness, confusion, and in advanced cases, dementia. Supplementing with B12 has been shown to help in the treatment of Alzheimer's disease, as those who are treated with the vitamin within six months of onset of symptoms find that many symptoms disappear and mental clarity improves.
Severe vitamin B12 depletion eventually manifests as pernicious anemia, characterised by immature, abnormally large red blood cells (macrocytes), which are very inefficient at carrying oxygen, and by white blood cells with abnormal nuclei. Lack of oxygen in the cells causes impaired functioning and feelings of weakness and tiredness.
However, long before anemia develops, other conditions may manifest, such as neurological problems like numbness, the sensation of pins and needles, burning in the feet, shaking, muscle fatigue, sleep disorders, memory loss, irrational anger, and impaired mental function, or psychological conditions such as dementia, depression, psychosis or obsessive-compulsive behavior.
Getting a sufficient amount of sleep is also necessary in order for us to feel our most energetic. Low levels of vitamin B12 can lead to a deficiency in melatonin, the hormone responsible for regulating your circadian rhythm, which allows you to get a good night's sleep. It also reduces stress levels in the body by working with serotonin receptors in the brain, producing an overall feeling of calm, allowing you to fall asleep.
And as we get older we are more likely to have suboptimal levels of B12 in our bodies, as our digestive systems find it increasingly more difficult to absorb the vitamin. The stomach lining gradually loses the ability to produce sufficient amounts of hydrochloric acid, which is necessary in order to release the B12 that is bound to the protein in food. The widespread use of antacids also lowers the production of this important substance, thus reducing B12 absorption even more.
It is recommended that those over 50 take an oral supplement to ensure adequate levels of B12. The form and type of B12 taken is important in order to receive the maximum level of absorption. The body does not easily absorb B12 at any age, even when consuming foods containing plentiful amounts of it. Its absorption is a complex process in which problems can arise at several points during its metabolism.
In order for vitamin B12 to ultimately be absorbed into the bloodstream at the end of the small intestine, it needs to go through a number of chemical processes involving pepsin, hydrochloric acid, R-protein, pancreatic enzymes, intrinsic factor (a protein), calcium, and cell receptors. A deficiency in any of these things can lead to B12 deficiency through blocked absorption.
At this point, transport proteins in the bloostream bind to B12 in order to deliver it to the cells, where enzymes liberate the B12 from the protein complex and convert it to its two coenzyme forms, methylcobalamin and adenosylcobalamin. A deficiency in these required enzymes can interfere with this conversion.
The only living things able to manufacture B12 are bacteria. Bivalves such as clams, mussels and oysters are high in B12 because of the large quantities of vitamin B12-synthesizing microorganisms they siphon from the sea.
Unfortunately, while eggs contain B12, they also contain substances that block its absorption. Plant foods said to be sources of B12 actually contain cobamides (B12 analogs), which are substances that block the uptake of true B12 and actually increase the body's need for the vitamin. Bacterial overgrowth in the small intestines can also produce cobamides. The use of antibiotics, or a typical western diet high in refined carbohydrates, can encourage the proliferation of bacterial overgrowth, leading to B12 deficiencies.
Multivitamins can actually cause more problems with B12 absorption than they solve. A noted B12 researcher, the late Victor Herbert, believed that many multivitamin products contain spurious and even dangerous analogs of vitamin B12, possibly due to crystalline B12 interacting with other nutrients in multivitamin products, such as vitamin C, iron and copper. Most multivitamins contain 100-20 mcg of B12, however, even with an intake of 500 mcg you would only absorb about 1.8 mcg of that amount.
The liver stores a considerable amount of B12, and the body has the ability to recycle an amazing 75 percent of the B12 it uses, which is why deficiency may not show up until our later years, or until some time after beginning a vegetarian or vegan diet.
The two most common types of vitamin B12 supplement are cyanocobalamin and methylcobalamin. The cheapest and most common is cyanocobalamin, however, the liver must convert cyanocobalamin to methylcobalamin before the body can use it. To be sure you get the most absorption from your B12 supplement, methylcobalamin is the better choice. In either type, look for the sublingual form of the supplement that is allowed to dissolve under the tongue. In this way the vitamin is absorbed by the blood vessels under the tongue and doesn't have to run the gauntlet of the stomach and intestine in order to be absorbed.