Vitamin B12 deficiency is relatively uncommon in the young.
There’s a good chance that you take a supplement containing vitamin B12 every day, but only about 6% of the total population below the age of 60 is deficient in this vitamin. According to the NIH, the prevalence grows significantly in older adults; the rate hovers around 20% in those older than 60. As you age, you lose the intrinsic factor in your stomach, which means that you aren’t able to absorb the vitamin from food. Instead, you require supplements and fortified foods.
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.
Deficiency can have catastrophic health effects.
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:
- heart palpitations
- shortness of breath
- pale skin
- a smooth tongue and mouth soreness
- loss of appetite
- weight loss
- gastrointestinal upset
- memory loss.
Commonly used lab testing for vitamin B12 deficiency is useless.
The most widely used lab test for determining a person’s status, the serum B12 test, had been criticized for several reasons. The test is a late indicator of deficiency. By the time that levels register as low, a person may have clinical symptoms, including irreversible nerve damage. The 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 deficiency.
Folate masks deficiency.
If you take a lot of folate supplements or eat a lot of folate-fortified food, a B12 deficiency might be masked. You should consume no more than 1,000 mcg of folic acid daily from fortified foods and supplements.
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. 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.