Any dietary or drug treatment with high doses of micronutrients may override the body's own control mechanisms; therefore, micronutrient therapies may be associated with potential side effects and toxicities. High-dosed micronutrients should not be used without medical supervision.
Pernicious anemia occurs when stomach cells are not able to produce a certain protein (‘intrinsic factor’), needed by the body to absorb vitamin B12. Symptoms include weakness, pale skin, diarrhea, weight loss, fever, numbness or a tingling sensation in the hands and feet, loss of balance, confusion, memory loss, and irritability.
Patients with lack of intrinsic factor secretion can be effectively treated using oral vitamin B12 but require lifetime vitamin B12 therapy. When used alone, oral doses of at least 150 micrograms (mcg) per day are necessary, although single weekly oral doses of 1000 mcg have proved satisfactory in some cases (22).
Several studies indicate that high blood levels of homocysteine appear to promote mortality and cardiovascular disease as well as stroke, Alzheimer's disease, birth defects, recurrent pregnancy loss, and eye disorders. Keeping homocysteine at levels associated with lower rates of disease seems to require adequate B12, vitamin B9 (folic acid) and vitamin B6 intake (23).
A small study suggested that people in a state of physical and mental weariness (‘fatigue’) who were not deficient in vitamin B12 might gain more energy from vitamin B12 injections (24). One preliminary study indicated that people with chronic fatigue syndrome might benefit from B12 injections. More research is needed to confirm these observations.
Studies suggest that vitamin B12 supplements may improve sperm counts and sperm mobility (25). In infertile couples, a low serum level of cobalamin was prevalent in 39% of all men with an abnormal semen analysis (45). However, the evidence is weak. Further studies are needed to determine whether B12 has any real beneficial effect.
Authored by Dr Peter Engel in 2010, reviewed and revised by Angelika Friedel on 29.06.2017