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Low B12 Intake Can Affect Brain Volume, Memory Skills


Vitamin B12 deficiency is one of the most common nutritional deficiencies in the developing world. Those at particular risk include the elderly, especially those with atrophic gastritis, a thinning of the stomach lining. B12 deficiency is known to cause neurological damage, affecting memory and balance. New research shows that older adults with low blood levels of the vitamin are also more likely to have lower brain volumes.

Christine C. Tangney, PhD, associate professor in the department of clinical nutrition at Rush University Medical Center, and lead author of the study, followed 121 older residents (over 65 years) of the South side of Chicago who were a part of the large, ongoing Chicago Health and Aging Project (CHAP). Each participant had blood drawn to measure levels of vitamin B12 and B12-related markers. The volunteers also took tests that measured memory and other cognitive skills.

An average of four-and-one-half years later, the same subjects had MRI scans of the brain to measure total volume and to look for other signs of brain damage.

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Those with high levels of four out of five markers for vitamin B12 deficiency were more likely to test lower on cognitive tests and had smaller brain volumes. Total serum vitamin B12 may not reliably indicate true vitamin B12 stores, so more sensitive tests of vitamin status include holoTC, methylmalonic acid (MMA), and homocysteine. For each increase of one micromole per liter of homocysteine, for example, cognitive scores decreased by 0.03 standardized units.

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Brain imaging scans confirmed that higher levels of homocysteine was linked to white matter lesions and cerebral infarcts and MMA was associated with brain atrophy.

“Our findings definitely deserve further examination,” said Dr. Tangney, “(but) lend support for the contention that poor vitamin B12 status is a potential risk factor for brain atrophy and may contribute to cognitive impairment. It’s too early to say whether increasing vitamin B12 levels in older people through diet or supplements could prevent these problems, but it is an interesting question to explore.”

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Vitamin B12, also known as cobalamin, is a water soluble vitamin that plays a key role in normal nervous system functioning and brain development. Because the vitamin is found primarily in animal foods such as meats, fish, shellfish, and dairy products, vegetarians and vegans are also at risk for a B12 deficiency. Vegetarian sources of B12 include fortified cereals, fortified soymilks or meat analogues, and nutritional yeast.

The Institute of Medicine already recommends B12 supplements for seniors, co-author Martha Clare Morris, ScD, director of nutrition at Rush University Medical Center, noted in an interview. “As we get older, our stomachs produce less of the acid that breaks down the vitamin to make it available for absorption,” explains Dr. Tangney. “Older people also take more drugs that inhibit absorption such as metformin.”

Journal reference:
Tangney CC, et al "Vitamin B12, cognition, and brain MRI measures: A cross-sectional examination" Neurology 2011; 77: 1276–1282.

Additional reference:
Herrmann W. et al. “Functional vitamin B12 deficiency and determination of holotranscobalamin in populations at risk.” Clin Chem Lab Med. 2003 Nov;41(11):1478-88.