Scientists warn that current vitamin B12 guidelines may be putting your brain at risk

Vitamin B12 is best known for helping the body make DNA, red blood cells, and healthy nerve tissue. But research suggests that simply meeting the current minimum standard may not always be enough, especially for older adults. A UCSF led study found that healthy older people with lower vitamin B12 levels, even when those levels still fell within the accepted normal range, showed signs of subtle neurological and cognitive problems.

The findings raise a provocative possibility: some people may be told their B12 status is fine while their brains are already showing early signs of strain. The study, published in Annals of Neurology , looked at older adults who did not have dementia or mild cognitive impairment. Even in this relatively healthy group, lower levels of active B12 were linked to slower thinking, slower visual processing, and more visible injury in the brain's white matter. White matter is made up of the nerve fibers that allow different parts of the brain to communicate. The work was led by senior author Ari J. Green, MD, of the UCSF Departments of Neurology and Ophthalmology and the Weill Institute for Neurosciences. Green and his colleagues said the results call attention to a possible weakness in current B12 guidelines. The minimum threshold used to define deficiency may not capture early functional changes in the nervous system. "Previous studies that defined healthy amounts of B12 may have missed subtle functional manifestations of high or low levels that can affect people without causing overt symptoms," said Green, noting that clear deficiencies of the vitamin are commonly associated with a type of anemia. "Revisiting the definition of B12 deficiency to incorporate functional biomarkers could lead to earlier intervention and prevention of cognitive decline." Researchers enrolled 231 healthy participants through the Brain Aging Network for Cognitive Health (BrANCH) study at UCSF. The participants had an average age of 71, and none had dementia or mild cognitive impairment. Their average blood B12 level was 414.8 pmol/L, far above the U.S.

Key points

• The findings raise a provocative possibility: some people may be told their B12 status is fine while their brains are already showing early signs of strain.
• The study, published in Annals of Neurology , looked at older adults who did not have dementia or mild cognitive impairment.
• Even in this relatively healthy group, lower levels of active B12 were linked to slower thinking, slower visual processing, and more visible injury in the brain's white matter.
• White matter is made up of the nerve fibers that allow different parts of the brain to communicate.
• The work was led by senior author Ari J.