B12 (also known as cobalamin) is essential for keeping your brain and nerves healthy and for making DNA and red blood cells. B12 also helps lower levels of homocysteine, an amino acid linked (in high levels) to dementia, heart disease, stroke, and osteoporosis. 

B12 is an essential supplement for those on a plant-based diet – particularly vegans - because it is not possible to extract from plants. 

We typically get B12 through diet. Rich sources include beef, liver, clams, poultry, fish, fortified cereals, eggs, cheese, yogurt, milk, and fortified plant milks (like soy, almond, or rice milks). 

An estimated 3.2% of adults ages 50 or older have very low B12 levels, and up to 20% may have borderline deficiency. Aging is often the causeWe tend to produce less stomach acid as we get older. That makes it harder to extract B12 from food, says Dr. Meir Stampfer, a professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health. 

Other causes of B12 deficiency include: 

  • taking heartburn medications that suppress stomach acid 
  • weight loss surgery 
  • autoimmune diseases that attack the stomach lining or gastrointestinal tract. 

PS: unlike Vitamins A and D, there are no known harmful side effects from taking too much B12.