Adequate Levels of Vitamin B12 May Prevent Brain Shrinkage, Alzheimer's

Low levels of vitamin B12 are strongly associated with brain shrinkage, a condition common in people with Alzheimer's disease. Conversely, adequate intake of the vitamin, from foods or supplements, may have a protective effect.

Writing in the journal Neurology, Anna Vogiatzoglou, MSc, of Oxford University and her colleagues wrote that "risk factors for cognitive impairment may be present years before clinical dementia and Alzheimer’s disease (AD) can be diagnosed; therefore, it is important to identify individuals at risk of developing dementia. Brain atrophy is associated with confirmed AD and is a marker of disease progression."

Vogiatzoglou tracked the health of 107 men and women for five years. The participants ranged from 61 to 87 years of age, and none showed signs of cognitive impairment when the study began.

She and her colleagues used magnetic resonance imaging (MRI) scans to measure brain size, and blood tests to measure levels of vitamin B12 and folic acid, as well as homocysteine and methylmalonic acid to indirectly measure activity of the vitamins.

Although all of the subjects had vitamin B12 levels in the normal range, people with lower levels of the vitamin were six times more likely to experience brain shrinkage during the five years of the study. The researchers also reported that low levels of holotranscobalamin, a marker of vitamin B12 activity, were also related to a six time greater risk of brain shrinkage.

Folic acid, homocysteine, and methylmalonic acid levels were not related to brain shrinkage.

Vogiatzoglou and her colleagues wrote that vitamin B12 levels “may be an early marker of brain atrophy and thus a potentially important modifiable factor for cognitive decline in the elderly.”

Other studies have also found an association between low levels of vitamin B12 and cognitive impairment. Some cases of pseudo-Alzheimer’s disease have been reversed with vitamin B12 supplements or injections.

Last year, researchers reported that African Americans taking histamine-2 receptor antagonists (e.g., Tagamet and Zantac) – drugs that interfere with vitamin B12 absorption – were about two and one-half times more likely to experience cognitive impairment.

Reference: Vogiatzoglou A, Refsum H, Johnston C, et al. Vitamin B12 status and rate of brain volume loss in community-dwelling elderly. Neurology, 2008;71:826- 832. See also: Boustani M, Hall KS, Lane KA, et al. The association between cognition and histamine-2 receptor antagonists in African Americans. Journal of the American Geriatric Society, 2007; 55:1248-1253.