Doctor’s Tip: New recommendations for Vitamin B12 supplementation |

Doctor’s Tip: New recommendations for Vitamin B12 supplementation

Editor’s note: This column was corrected Tuesday, Dec. 29.

Vitamins are substances that the body can’t make that are necessary in trace amounts for normal metabolic functioning. Vitamin B12 is made by bacteria in dirt, and as humans were evolving over millions of years they ate plenty of dirt. In modern times though, with treated water and pre-washed produce, most of us don’t eat much dirt.

Animals get some dirt in what they eat, and B12 is stored in their flesh. So most people who eat animal products (fish included) get enough B12, with the following exceptions: 1) people over age 50, because they don’t absorb B12 as well; 2) people with the rare autoimmune disease pernicious anemia, that destroys intrinsic factor which is needed for B12 absorption; 3) people who have had obesity surgery that affects the part of the intestine where B12 is absorbed; 4) people with diseases that affect intestinal health, such as celiac disease and Crohn’s disease; 5) people who take the diabetes drug metformin; 6) people on long-term drugs that prevent the stomach from making acid, such as Nexium, Prilosec, Pepcid, and Zantac.

B12 is involved in the function of every cell in the human body. In particular, it is necessary for brain, nervous system, and red blood cell health. Low B12 levels can result in the following problems: 1) anemia, associated with abnormally large red blood cells; 2) fatigue; 3) numbness and tingling in hands and feet and poor balance—both of which can be irreversible; 4) poor memory, depression, psychosis, and dementia; 5) elevated homocysteine, which is a risk factor for cardiovascular disease.

In the absence of eating dirt, vegans (no animal products) and vegetarians (small amounts of animal products) tend to become B12 deficient, and MUST take a supplement. It is possible to get enough B12 “naturally” through products such as nutritional yeast, which is usually—depending on the brand—fortified with B12. But it’s so important not to become deficient that experts such as Dr. Greger (, “How Not to Die”) recommend supplements instead.

B12 levels can be measured through a blood test, the most accurate test being methylmalonic acid. However, B12 tests can be falsely negative, and there have been cases of symptomatic B12 deficiency in people with normal B12 blood tests. Dr. Greger does not recommend checking B12 levels as long as people follow his guidelines, except in pregnant and breast-feeding women, people with unexplained neurologic symptoms, and people with abnormally large red blood cells.

There are 2 types of B12 supplements, and Dr. Greger recommends cyanocobalamin, which can be found at any pharmacy and most grocery stores. He recommends getting tablets and chewing them, because absorption is markedly improved with interaction of the B12 supplement with your saliva and mouth microbiome. Taking B12 simultaneously with other vitamins as in multivitamins can interfere with it, so Dr. Greger recommends taking it separately. Dr. Greger’s latest B12 recommendations are somewhat complicated and in some cases confusing, but you can’t go wrong if you go with the following:

  • vegan children ages 6 months to 3 years: 5 micrograms (mcg) a day
  • vegan children ages 4 to 10 years: 25 mcg. a day
  • vegan children above 10 years: 50 mcg. a day
  • non-vegan and vegan pregnant and lactating women: 50 mcg. a day (adequate B12 levels in the mother is necessary for adequate brain development in the fetus and infant).
  • vegetarians, vegans, and meat eaters age 50 and above: 50 mcg. a day
  • vegetarians and vegans, and meat eaters 65 and older 1000 mcg. a day.

People on metformin or stomach acid-blockers should take 50 mcg. People with celiac disease, Crohn’s disease, or history of obesity surgery should take sublingual B12 preparations or consider injections. B12 injections are not recommended otherwise, because of the inconvenience, the extra cost, and the fact that high blood levels associated with injection aren’t “natural” and in one person out of 10 can cause acne.

Greg Feinsinger, M.D., is a retired family physician with a special interest in heart disease and diabetes prevention and reversal, ideally though lifestyle changes. He’s available for free, one-hour consultations — call 379-5718.

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