Milk, fish, and eggs are sources of vitamin B12

A bout 20 percent of people over age 60 have low levels of vitamin B12, yet many of them don’t know it. You need B12 to help make red blood cells, nerves, and DNA, so the effects of a deficiency can show up in many ways. The symptoms—fatigue, weakness, shortness of breath, constipation, tingling and numbness in the feet and/or hands, memory loss, disorientation, paranoia, and irritability—can be caused by many conditions. They also can develop over time, and people who are short on B12 experience only a few of them. That makes recognizing a vitamin B12 deficiency tricky.

Doctors don’t always have B12 at the front of their minds when a patient is having symptoms like these, according to Joshua Miller, Ph.D., professor and chair of the Department of Nutritional Sciences, School of Environmental and Biological Sciences at Rutgers University. But if not caught in time, some of the symptoms of vitamin B12 deficiency may be irreversible. 

How Deficiencies Develop

Not getting enough B12 in your diet—you need 2.4 micrograms per day—is obviously one reason people become deficient. B12 is found naturally in animal products—dairy, meat, fish, and eggs. Vegans and vegetarians, along with those who have cut back on animal foods for health reasons, may fall short. 

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But even those who take in adequate amounts of the vitamin may be at risk. Ten to 30 percent of older people have trouble absorbing vitamin B12 from food, according to the Institute of Medicine, because stomach acid production declines with age. The type 2 diabetes drug metformin and acid controllers such as omeprazole (Prilosec) and ranitidine (Zantac) can also interfere with B12 uptake. People with celiac or Crohn’s disease or those who’ve had weight-loss surgery may not absorb B12; they require lifelong high-dose supplementation.

Pernicious anemia, an autoimmune disorder that blocks B12 absorption and is one of the most common causes of severe deficiencies, is often found in people over 65 (although it can occur at any age). What’s more, anyone who has any autoimmune disorder may be at risk for this type of anemia because having one autoimmune condition increases the likelihood of having another, Miller says. 

Testing and Treatment

If you have symptoms like the ones listed above, you should have a blood test for total vitamin B12. Results often fall into a gray zone (between 100 and 300 picograms/milliliter), even in those who are very deficient.

That’s why a second test, for methylmalonic acid—which rises if B12 levels are low—is commonly done to confirm, according to hematologist Sally Stabler, M.D., professor of medicine at the University of Colorado School of Medicine. Miller suggests a B12 test for long-term users of drugs that inhibit B12 absorption, even if they have no symptoms. But testing may be a good idea for all older adults. “I think the evidence is strong enough that you could ask your doctor for one to see where you are,” he says.

Supplements will correct a low B12 level, with the dosage dependent upon the degree of deficiency. Those with pernicious anemia, for example, will need to be on a lifelong schedule of high-dose shots or daily high-dose oral supplements. People who have malabsorption problems from age or medication will require less. Diet shortfalls can be reversed with a low-dose supplement (2 micrograms), along with fortified foods such as breakfast cereals. Vitamin B12 from supplements or fortification may be absorbed even when B12 from foods that naturally contain it isn’t. Check with your doctor before taking vitamin B12 supplements.

Editor’s Note: This article also appeared in the June 2019 issue of Consumer Reports On Health.