& Alan Titchenal Tuesday, July 17, 2012
Vitamin B12 deficiency harms memory and nerves
The effects of essential nutrient deficiencies can range from mild physiological dysfunction that is reversible to permanent, irreversible damage or even death. One nutrient deficiency that causes great concern, especially for older people, is vitamin B12 deficiency.
QUESTION: What are the symptoms of B12 deficiency?
ANSWER: Severe vitamin B12 deficiency has clear signs of fatigue and anemia, making it relatively easy to diagnose. However, symptoms of marginal deficiency are less obvious and might go unnoticed for a long time. Since B12 deficiency is known to damage the nervous system and cause permanent impairment of short-term memory if not treated in a timely fashion, medical researchers are seeking better methods to identify marginal (subclinical) B12 status before serious damage takes place.
B12-deficient individuals can develop confusion and depression, but the specific problems can vary from one person to another. Some of the symptoms are similar to those of Alzheimer's disease. Since older people are at greater risk of developing both B12 deficiency and Alzheimer's disease, it is important to be careful to distinguish between the two conditions. The symptoms of B12 deficiency can be reversible if treated within six to 12 months. However, if left untreated, B12 deficiency can cause irreversible damage.
Q: If a person consumes B12 food sources like meat and dairy products, can they still become B12 deficient?
A: Yes. After age 50 many people experience changes in stomach function that decrease their ability to absorb B12 from foods. However, the form of B12 put into supplements and fortified foods can still be well absorbed by most of these people.
Q: How is B12 deficiency diagnosed?
A: A variety of blood tests are used to evaluate B12 status. Each has strengths and weaknesses. The single test most likely to catch a B12 deficiency early is a blood test for methylmalonic acid level. Adding a blood test for serum B12 level increases the diagnostic accuracy.
Q: Does a person diagnosed with B12 deficiency require monthly B12 injections?
A: The traditional medical treatment has been to give monthly injections of B12. For many older people, B12 shots generally continue throughout their lives, and this seems to be the most reliable method of treatment. However, the need for injections has been challenged by a number of studies that found high dose oral supplements of 500 to 2,000 micrograms per day to be effective.
Q: Are there ways to prevent B12 deficiency, and if so, which is the best?
A: Dietary supplements can be taken as a preventive measure, especially for vegetarians and older people. B12 supplements are available as regular pills, sublingual (under the tongue) pills and in liquid "shots," to name a few forms sold. Although the name "shots" might imply an injectable form, these are like the small energy "shot" products sold in small bottles and are not the same as the injected form of B12. There is little evidence any of these special forms are more effective than the inexpensive standard pill forms. Most B12 supplements are rather tasteless and could be taken sublingually by letting it dissolve under the tongue, if desired.
Vitamin B12 is considered to be nontoxic, but over time, high daily doses like 1,000 micrograms can accumulate in cells. This is currently thought to be harmless, but the potential effect of years of high intake remains to be studied.
Joannie Dobbs, PhD, CNS and Alan Titchenal, PhD, CNS
are nutritionists in the Department of Human Nutrition, Food and Animal Sciences,
College of Tropical Agriculture and Human Resources, UH-Manoa.Dr. Dobbs also works with the University Health Service
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