Vitamin B12 is a water-soluble vitamin, also known as Cobalamin. It is found in dietary sources to include liver, beef, pork, eggs, milk, cheese and fish. The Recommended Daily Amount for both males and females is 2.4mcg.
B12 contributes to the reduction in tiredness and fatigue, to the normal metabolism of homocysteine (a naturally occurring protein found in the blood) and functioning of the nervous system. Vitamin B12 works with folic acid in several body processes including the regulation and formation of red blood cells and the utilization of Iron, DNA synthesis and the formation of the myelin sheath, a fatty white substance that surrounds the nerve cells and assists with the transmission of nerve impulses. In order for vitamin B12 to be absorbed effectively, the stomach secretes a special protein carrier known as the intrinsic factor.
For those who may lack the intrinsic factor in the small intestine, a deficiency in B12 will develop. The classic symptom of B12 deficiency is pernicious anaemia, however deficiency also affects the brain and nervous system. Other symptoms include numbness, pins and needles or burning feet. It can also cause impaired mental function which in the elderly may mimic Alzheimer’s disease. Other symptoms may include a smooth, enlarged bright red tongue and digestive complaints such as constipation and/or diarrhea.
Cardiovascular Health– Due to the role of B12 in homocysteine metabolism, B12 is believed to play an important role in cardiovascular health; this is because high levels of homocysteine have been associated with an increase in the build-up of is plaques in the arteries, with the potential to lead to heart attack and stroke (1). According to research raised homocysteine levels are also believed to encourage the development of blood clots, impair the tone of the blood vessels and encourage the development of inflammation and plaque formation in the arteries (2), (3), (4). In particular, those following a vegetarian diet have been shown to be at an increased risk of cardiovascular disease mainly, but not exclusively, due to vitamin B12 deficiency-induced condition known as hyperhomocysteinemia (5).
Cognitive Function-Deficiencies in vitamin B12 and Folic acid as a result of raised homocysteine levels have also been associated with mental disturbances and impaired mental function (6). An accumulation of homocysteine in the blood is thought to impair the breakdown and use of chemical messengers (7). A Swedish study involving 296 elderly participants showed those who were deficient in Vitamin B12 or folic acid and raised homocysteine noticed significant clinical improvements in the severity of mental disease when supplemented with Vitamin B12 (8). Other studies have also shown that supplementation with B12 may be beneficial in reversing impaired mental function as a result of B12 deficiency (9). Furthermore, it has been shown that Alzheimer’s patients have significantly low serum levels of B12 and vitamin B12 deficiency (10), (11). It is also believed that supplementing with B12, particularly in the early stages of Alzheimer’s may be completely reversible in some patients (6).
Depression-Vitamin B12 deficiency has also been associated with depression, especially in the elderly (12). Both B12 and Folic acid have been observed in studies of depressive patients as have high homocysteine levels. In a large population study from Norway increased plasma homocysteine was associated with increased risk of depression (13).
Auditory Dysfunction- Research also suggests a link between Vitamin B12 deficiency and hearing impairment (6). An investigation involving three groups of noise-exposed subjects revealed a significant proportion of those with tinnitus and noise-induced hearing loss demonstrated B12 deficiency compared to those with normal hearing (14). A further double-blind, randomized, placebo-controlled prospective involving forty patients aged 18 to 60 who had chronic subjective tinnitus with or without sensorineural hearing loss of more than 6 months’ duration showed that seventeen (42.5%) of the total patients suffering from tinnitus were vitamin B12-deficient. The same study showed those who received vitamin B12 supplementation had a significant improvement in the severity of tinnitus. Those who did not have a B12 deficiency and those who received placebo showed no improvement in the severity of tinnitus symptoms (15).
Digestive support– Vitamin B12 contributes to normal energy yielding metabolism. Vitamin B12 is required for the correct absorption and metabolism of fats, carbohydrates and proteins, making it valuable for people whose diets are high in these nutrients. It helps support correct growth and development via the correct use of these nutrients.
Anaemia– Vitamin B12 contributes to normal red blood cell formation. This implies that a B12 deficiency could aggravate anaemia- the result of an iron deficiency. A supplement may therefore help to guard against this.
Heart health– Vitamin B12 contributes to normal homocysteine metabolism. Homocysteine is an amino acid that has been linked with increased risk of heart disease. Vitamin B12 helps in its metabolism, so may be of use when deficiency is linked to higher than normal homocysteine levels.
Stress and low mood– Vitamin B12 contributes to the normal function of the nervous system. This means it may help support cases of stress and low mood.
No adverse effects have been associated with excess vitamin B12 intake from food and supplements in healthy individuals. There is no established Tolerable Upper Intake Level for vitamin B12.