While a vast majority of Indians are severly deficient in Vit B12 and should you happen to be an outlier and have a normal levels of Vit B12 in your blood – these “apparent normal levels” may still not be sufficient to protect your brain and cognitive health.
New research suggests that a normal vitamin B12 blood test does not always mean your brain is getting enough vitamin B12.
University of California San Fransisco Study on Vit B12
That is the key finding from a new study led by researchers at the University of California, San Francisco (UCSF). The research suggests that some older adults with vitamin B12 levels considered “normal” by current laboratory standards may still show signs of brain changes linked to slower thinking and memory problems.
The findings are raising important questions about whether current vitamin B12 deficiency cut-off values should be re-examined, especially for older adults.
Vitamin B12 is essential for a healthy brain
Vitamin B12 plays a vital role in the body. It helps produce red blood cells, supports healthy nerves, and is needed for DNA production. It is also important for maintaining the protective covering around nerve cells, allowing the brain and nervous system to function normally.
Severe vitamin B12 deficiency has long been known to cause nerve damage, numbness, balance problems, memory loss and cognitive decline.
The new research suggests that brain changes may begin even before blood test results fall below the current deficiency threshold. The study looked at healthy older adults.
The UCSF-led study included 231 healthy adults with an average age of 71 years. Importantly, none of the participants had vitamin B12 levels that would normally be classified as deficient.
However, researchers found that participants whose vitamin B12 levels were lower within the normal range performed worse on several brain-related tests than those with higher levels.
The researchers also found evidence of greater damage to the brain’s white matter, which contains the nerve fibres that allow different parts of the brain to communicate with one another.
Download a copy of this study – Annals of Neurology – 2025 – Beaudry‐Richard – Vitamin B12 Levels Association with Functional and Structural Biomarkers of
Slower thinking despite “normal” vitamin B12 levels
The researchers observed that participants with lower—but still normal—vitamin B12 levels had:
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Slower thinking speed
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Slower visual processing
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More changes in the brain’s white matter seen on MRI scans
These findings suggest that the current definition of “normal” vitamin B12 may not identify everyone at risk of neurological changes.
Does this mean normal vitamin B12 causes brain damage?
No. This is an important point. The study does not prove that normal vitamin B12 levels cause brain damage.
Instead, it found an association between relatively lower vitamin B12 levels within the normal range and markers linked to poorer brain health. Association does not prove cause and effect.
More long-term clinical studies are needed before doctors can conclude that raising vitamin B12 levels in these individuals will prevent cognitive decline.
Why standard vitamin B12 blood tests may not tell the full story
Most routine laboratory tests measure total vitamin B12 circulating in the blood. These blood tests do not always show how much vitamin B12 is actually reaching and being used by the body’s cells.
Researchers say additional markers, including holotranscobalamin, methylmalonic acid (MMA) and homocysteine, may sometimes provide a better picture of vitamin B12 status, particularly in people who continue to have symptoms despite apparently normal blood results.
Older adults are at higher risk of vitamin B12 deficiency
Vitamin B12 deficiency becomes more common with age. As people grow older, the stomach may produce less acid, making it harder to absorb vitamin B12 from food. Risk is also higher in people who:
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Follow strict vegetarian and vegan diets without supplementation
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Have stomach or intestinal disorders
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Have had stomach surgery
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Take medicines such as metformin or have history of long-term usage of proton pump inhibitors (PPIs) such as Pantoperazole and Omeperazole
These groups may benefit from closer monitoring of vitamin B12 status. Other studies support the importance of good vitamin B12 status. The UCSF findings are not the only research linking vitamin B12 with brain health.
A large study from the Framingham Heart Study, involving 1,994 adults, found that people with higher long-term vitamin B12 status experienced slower rates of cognitive decline over time than those with lower vitamin B12 status.
However, another large genetic study published in Communications Medicine found no evidence that simply increasing vitamin B12 levels in the general population prevents cognitive impairment or psychiatric disorders.
Taken together, these studies suggest that maintaining adequate vitamin B12 is important, but routine supplementation above normal levels has not been proven to protect everyone against memory loss or dementia.
What should people do?
Experts are not recommending that everyone start taking high-dose vitamin B12 supplements. Instead, the research highlights the importance of looking beyond a single blood test when symptoms persist.
Anyone experiencing:
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Memory problems
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Brain fog
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Tingling or numbness
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Poor balance
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Difficulty concentrating
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Unexplained fatigue