By Roberta H. Anding, MS, Baylor College of Medicine and Texas Children’s Hospital

Edited by Kate Findley and proofread by Angela Shoemaker, The Great Courses Daily

Over the years, many supplements such as vitamin E have been hyped by the media. Vitamin B₁₂, however, is worth the hype. For a variety of reasons, many of us have this vitamin deficiency. Professor Anding describes the roles of Vitamin B₁₂ and what leads to a deficiency.

Vitamin B₁₂ Roles

Vitamin B₁₂ is unique to the B vitamin family. The body can store a supply of vitamin B₁₂ up to two years in the liver, as opposed to all the other B vitamins where you need to have a consistent daily intake.

B₁₂, like folic acid, is needed in the production of red blood cells, as well as the maintenance of a normal central nervous system. It also plays a key role in the metabolism of fat, protein, and carbohydrate.

The absorption of vitamin B₁₂ requires the production of adequate stomach acid, and it also requires intrinsic factor. Intrinsic factor is secreted by the parietal cells in the stomach that unlocks vitamin B₁₂ from food.

Deficiencies

Gastric bypass, used for the management of obesity, reduces the amount of acid that the stomach produces because the stomach is now smaller, and by extension it reduces the amount of intrinsic factor that interacts with the food. The loss of the gastric juice or hydrochloric acid also occurs naturally with the aging process. About 30% of those over 50 years old can suffer from malabsorption of the vitamin. 

“When the physician told my mother that she had a problem with her red blood cells, my mother assumed that was iron because that’s what she knew,” Professor Anding said. “What she actually had was a B₁₂ deficiency, not because she doesn’t eat food sources of B₁₂, but the problem is she didn’t have enough intrinsic factor because she’s 85 years old.”

B vitamin deficiencies can take years to develop, so someone who has just experienced gastric bypass can have adequate B₁₂ in their blood on their first visit to the doctor. Over a period of time, they lose that ability to absorb adequate amounts from their diet. 

Sometimes to compensate for a deficiency, you can take injections or a large oral dose of up to 500 milligrams. However, the injections only work if you’re already B₁₂ deficient, not as a prevention strategy.

Other populations at risk include vegans because vitamin B₁₂ is found in animal products. If a vitamin B₁₂ deficiency goes on untreated, you can actually develop a form of anemia called pernicious anemia, an inappropriate immune response. 

You end up with a macrocytic anemia, a large cell anemia, and you can have irreversible nerve destruction. Recent research also suggests that a deficiency of B₁₂, as with folate, may increase the likelihood of neural tube defects, illustrating again the interaction of B vitamins. 

If you’re at risk, you must monitor your B₁₂ status carefully. Vitamin B₁₂ has no known toxicity.

Heart Disease and B Vitamins

A relationship between B vitamins and heart disease exists due to the synergy between B vitamins. B₆, folate, and B₁₂ all work closely together, and a deficiency of any one of these vitamins can increase the level of homocysteine in the blood. 

Perhaps you’ve had a homocysteine level drawn by your health care provider. An increased level of the protein homocysteine is a marker for an increased risk of heart disease. The question then becomes, is it homocysteine directly that causes an increased risk of heart disease, or is it a marker for a poor diet?

Professor Anding suggests that it is also a potential marker for these B vitamin interactions. For example, suppose you eat well, but you drink significant amounts of alcohol with your friends on the weekend. Then you must ask yourself, are increased homocysteine levels an indication that your diet is poor, or is it the effect that alcohol has on all of these B vitamins? 

“This is a wonderful example of how nutrition is all woven together, and the B vitamin family really illustrates this probably as well as anything in clinical nutrition,” Professor Anding said. 

This article was edited by Kate Findley, Writer for The Great Courses Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for The Great Courses Daily.

Professor Roberta H. Anding is a registered dietitian and Director of Sports Nutrition and a clinical dietitian at Baylor College of Medicine and Texas Children’s Hospital. She also teaches and lectures in the Baylor College of Medicine’s Department of Pediatrics, Section of Adolescent Medicine and Sports Medicine, and in the Department of Kinesiology at Rice University.