Your B12 Levels May Be “Normal” – But Your Brain Could Still Be At Risk! Here's How

A new study suggests that older adults with lower levels of vitamin B12—even within the normal range—may experience cognitive decline and brain damage. Researchers found that these people had slower thinking speeds and increased brain lesions, which are associated with dementia.

Why B12 Matters for Brain Health

Vitamin B12 is essential for making DNA, producing red blood cells, and maintaining healthy nerve function. It plays a key role in brain health, helping to protect neurons and support cognitive function. While it is well known that a severe deficiency in B12 can cause anaemia and nerve problems, this study suggests that even slightly lower levels could have negative effects on the brain.

Study Findings: Slower Thinking and More Brain LesionsThe study, conducted by researchers at the University of California, San Francisco (UCSF), examined 231 healthy adults over the age of 70. All participants had B12 levels within the normal range, averaging 414.8 pmol/L—well above the U.S. minimum of 148 pmol/L. Despite this, those with lower B12 levels showed signs of brain decline.

Key findings from the study include:

These results suggest that even when B12 levels are considered "normal," they might not be optimal for brain health.

Should B12 Guidelines Be Updated?

Dr Ari J. Green, senior author of the study and a professor at UCSF, believes current B12 recommendations may need to be revised. He explains that past studies may have overlooked subtle brain-related effects of lower B12 levels.

"Many people with 'normal' B12 levels may still be at risk for cognitive decline," Dr Green said. "We need to consider new ways of defining B12 deficiency by incorporating functional biomarkers to identify early signs of cognitive problems before they become serious."

The study's findings suggest that the definition of a healthy B12 level might not be sufficient for preventing brain decline, particularly in older adults.

Who Is at Risk?

While this study focused on older adults, researchers believe the impact of lower B12 levels could extend to a larger group than previously thought.

Co-first author Alexandra Beaudry-Richard, MSc, from UCSF and the University of Ottawa, explained, "Lower B12 levels may affect brain function more than we realized. It’s possible that many people could be experiencing mild cognitive effects without knowing it."

As people age, their ability to absorb B12 decreases, making older adults particularly vulnerable. B12 is found naturally in animal-based foods like meat, dairy, and eggs, so vegetarians and vegans are also at a higher risk of deficiency.

Should You Take B12 Supplements?

While more research is needed, the findings suggest that older adults with neurological symptoms—such as memory loss, slower thinking, or balance issues—may benefit from B12 supplementation, even if their levels are within the normal range.

"In addition to redefining B12 deficiency, doctors should consider B12 supplements for older patients experiencing neurological symptoms," Beaudry-Richard said.

To maintain healthy B12 levels, experts recommend:

This study shows the importance of B12 for brain health, even in people who do not have an obvious deficiency.

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