Vitamin B12 deficiency is relatively common.
About 7% of the total population is deficient in vitamin B12. Vegans and vegetarians need to be especially careful because the foods that naturally contain B12 are animal-based, including dairy products, eggs, fish, meat, and poultry. Thirty percent of older adults have atrophic gastritis, which means that they don’t produce enough intrinsic factor to dismantle and absorb the vitamin from food. Instead, they require vitamin B12 supplements and fortified foods, which don’t need intrinsic factor for absorption.
Vitamin B12 deficiency can have catastrophic health effects.
Vitamin B12 deficiency can cause irreversible nerve damage that results in tingling or numbness in the hands and feet and difficulty walking, heart disease, and vision loss. Milder deficiency can cause depression, weakness, fatigue, heart palpitations, shortness of breath, pale skin, a smooth tongue and mouth soreness, loss of appetite, weight loss, gastrointestinal upset, confusion, and memory loss.
Commonly used lab testing for vitamin B12 deficiency is useless.
The most widely used lab test for determining a person’s vitamin B12 status, the serum B12 test, had been criticized for several reasons. The serum B12 test is a late indicator of deficiency. By the time that levels register as low, a person may have clinical symptoms, including irreversible peripheral neuropathy. The serum B12 test measures how much of the vitamin is circulating in the blood, but much of the B12 dissolved in the blood can’t be used by the body; between 70 and 90% of the vitamin B12 in the serum is bound to protein and inaccessible. Even if the serum test was accurate, there are no universally established criteria for defining vitamin B12 deficiency.
Folate masks vitamin B12 deficiency.
If someone is taking a lot of folate supplements or eating a lot of folate-fortified food, a B12 deficiency might be masked, which is why folic acid intake from fortified foods and supplements should total no more than 1,000 mcg daily for healthy adults.
Vitamin B12 supplements won’t turn you into a superhero.
Contrary to the labels on hundreds of food products and supplement bottles, there is no evidence that vitamin B12 will make you a better athlete or boost your energy level. Your body needs small amounts of vitamin B12 to oxidize glucose and produce energy from it. Small amounts of vitamin B12 are necessary to produce the kind of energy that your cells need to carry out essential functions – not the sort of “energy” defined as the opposite of fatigue.