Ask the Doctors

Dear Doctor: One of my resolutions for the new year was to become a vegan, and now my girlfriend is saying I'll have to take supplements to get enough vitamin B12. Why can't I get B12 in my diet, and what will happen if I fall short?

Dear Reader: Your girlfriend has done her homework -- vitamin B12 is a nutrient that is essential to human health. And while it occurs naturally in a wide range of animal foods, B12 is not found in any plant foods. As a vegan, you're now going to have to rely on supplements to be sure you get enough B12.

Why is it so important?

Vitamin B12 is a bit of a workhorse. Not only does it play a key role in the proper functioning of the brain and the nervous system, it's crucial to the production of red blood cells in the bone marrow. As though that wasn't enough, B12 also aids in DNA and RNA synthesis, and is involved in the metabolism of carbohydrates, fats and proteins. Research shows that B12 also has a hand in maintaining mood and memory.

The body does not store B12, so you need to ingest it every day. Beef liver and clams have the highest concentrations of the nutrient. It is also present in varying quantities in red meat, eggs, poultry, shellfish, milk and milk products. Many breakfast cereals and some dairy products are fortified with B12. For vegans, there are non-dairy milks, meat substitutes and nutritional yeast products to which B12 has been added. Dietary supplements are widely available.

What happens when B12 is in short supply?

Considering all the roles the nutrient plays in health and well-being, the list of symptoms is long and sometimes quite serious. People with a B12 deficiency may feel weak and tired, the result of the vitamin's role in producing the red blood cells that carry oxygen throughout the body. Since B12 helps maintain the protective sheath around your nerves, a lack of the vitamin can lead to strange sensations like numbness or tingling, as well as problems with balance or walking. Mood and memory may also suffer.

In extreme cases, B12 deficiency can lead to megaloblastic anemia, a blood disorder in which the red blood cells produced in the bone marrow are unusually large, malformed and immature.

And while your girlfriend is right about your need for vigilance in getting enough B12, she may do well to examine her own B12 status. Recent studies suggest that up to 40 percent of the population, vegan or not, may be flirting with B12 insufficiency. Due to physiological changes associated with aging, the elderly are at increased risk of vitamin B12 deficiency. Individuals who have undergone weight-loss surgery must also make a special effort to get enough of the nutrient.

As for you, a newly minted vegan, we recommend that you seek professional advice, preferably from your family doctor, to be certain that you forge a wise nutritional course.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095.)

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