The common wisdom is that nutritional deficiency is extremely rare because the human body stores several years’ worth of vitamin B12. However, current research suggests that depletion and deficiency are more common than previously thought.

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On Nutrition

If you’ve heard anything about vitamin B12, it’s probably that only vegetarians and vegans need to worry about it — or that vegetarians and vegans don’t need to worry about it, because we store extra B12 in our tissues. Maybe you heard that extra B12 gives you extra energy. Allow me to do some debunking.

Vitamin B12 is naturally found in animal-based foods, including fish, meat, poultry, eggs, milk and other dairy products. Some nutritional yeast products also contain vitamin B12, and many breakfast cereals are fortified with B12. You can also get vitamin B12 from over-the-counter supplements or lozenges or prescription injections.

We need vitamin B12 to form normal red blood cells, for brain and nervous system (neurological) function and for building DNA. It’s also important for bone and heart health. The common wisdom is that nutritional deficiency is extremely rare because the human body stores several years’ worth of vitamin B12. However, current research suggests that depletion and deficiency are more common than previously thought.

The Institute of Medicine (IOM) set the adequate intake of B12 for adults at 2.4 micrograms per day in 1998. Interestingly, in 2014, the European Food Safety Authority determined that the average adult needs 4 micrograms per day — that’s significantly higher. While most children and adults in the U.S. get enough B12 by IOM standards, research from the Framingham Offspring Study (an offshoot of the famous Framingham Heart Study) suggests that nearly two in five people may have B12 levels on the low side of normal. The researchers speculated that even when people technically get enough B12 from meat, poultry and fish, they may not be absorbing all of it.

When you eat foods rich in vitamin B12, your stomach acid and digestive enzymes free the B12 from the protein it’s bound to. Synthetic vitamin B12 in fortified foods and dietary supplements doesn’t require this step, because it’s already freed. A substance called intrinsic factor secreted by your stomach combines with free vitamin B12, allowing it to be absorbed in your small intestine. Some people have trouble absorbing B12 from food, but do fine with supplements. People who don’t produce enough intrinsic factor may need B12 injections.

Diagnosing deficiency

The IOM’s recommendations for vitamin B12 is based on the amount needed to prevent megaloblastic anemia (a type of anemia where the body makes fewer but larger red blood cells) and maintain normal levels in the blood. Trouble is, if someone also has iron-deficiency anemia, which makes the blood cells smaller, the net result may be normal-looking red blood cells. Plus, evidence suggests that the amount of vitamin B12 in your blood might not accurately reflect how much you have stored.

Another concern is that the neurological symptoms of vitamin B12 deficiency — numbness and tingling in the hands and feet, poor balance, depression, confusion and memory loss — can happen before levels are low enough to cause anemia, so early diagnosis and intervention is important to avoid irreversible damage. That can be challenging, because these and other symptoms — which can include hair loss, fatigue, weakness, constipation, loss of appetite and unexplained weight loss — can result from a variety of medical conditions.

People who experience fatigue due to vitamin B12 deficiency will feel more energetic when they get their levels back to normal, but extra B12 doesn’t provide extra energy in people who already have normal levels.

Elevated levels of the amino acid homocysteine in the blood could be a clue to a vitamin B12 deficiency, but low vitamin B6 or folic acid levels can also raise homocysteine. Elevated levels of methylmalonic acid (MMA) might be more precise indicator vitamin B12 deficiency.

Who’s at risk?

You are especially at risk of deficiency if you are age 50 or older; are vegetarian or vegan; take metformin; have had surgery of the upper gastrointestinal tract; are receiving chemotherapy; have hypothyroidism; or regularly take one of a number of medications, including antacids and nonsteroidal anti-inflammatory medications (aspirin, ibuprofen, naproxen).

Speaking at the annual meeting of the Academy of Nutrition and Dietetics last fall, Roman Pawlak, Ph.D., RDN, assistant professor of nutrition at East Carolina University and author of several research articles on B12 deficiency, said that recommendations should be based on age and stage of life — for example, needs are higher during pregnancy and breast feeding. “As we age, we may have problems in absorbing vitamin B12 due to changes in the gastrointestinal system. Why don’t we set the recommendation based on age, so the recommendations for people who are 70 or 80 are not the same as for people who are 20 or 25?”

While plant-based diets are good for cardiovascular health, research shows that vegetarians — or others — who have low B12 levels tend to have higher homocysteine levels, which can lead to heart disease even when cholesterol and blood-pressure levels are normal. “There’s more to heart disease than just these traditional coronary heart-disease risk factors,” Pawlak said.

Seattle dietitian Ginger Hultin, MS, RDN, CSO, a spokeswoman for the Academy of Nutrition and Dietetics and past chair of the Academy’s Vegetarian Nutrition Dietetic Practice Group, said the prevalence of B12 deficiency among vegetarians varies widely in studies — from 12 to 94 percent, depending upon several factors, including how the researchers define deficiency, what tests they use to look for it and the type of vegetarian diet.

“Vegans need to take B12 — that’s the bottom line here. Anemia, neurological damage and other signs of deficiency can and do happen,” she said. “Vegetarians who eat dairy, eggs, and fish are getting natural sources which may easily meet their daily needs unless there is an absorption issue.”

Hultin said that while vegan diets are very healthy, they simply don’t contain adequate food sources of B12, and vitamin B12 occurring naturally in non-animal foods is negligible and unreliable. “Fortified foods and supplements are the way that vegans should get their B12 and taking a supplement form is likely the safest way to ensure you are getting enough.”