Vitamin B12 is essential for producing DNA, red blood cells, and nerve tissue. While current guidelines define “normal” B12 levels, new research suggests that these levels might not be high enough—especially for older adults.
A recent study from the University of California, San Francisco (UCSF) found that even people with B12 levels considered normal could still experience brain changes and cognitive decline if their levels were on the lower end of the spectrum.
Lower B12 Levels Linked to Brain Changes and Cognitive Slowing
The study, published in Annals of Neurology, analyzed 231 healthy adults with an average age of 71. None of the participants had dementia or mild cognitive impairment.
Researchers measured their active B12 levels, which show how much of the vitamin the body can actually use. The participants had an average B12 level of 414.8 pmol/L, which is well above the U.S. minimum of 148 pmol/L.
Despite being within the normal range, those with lower active B12 levels showed clear signs of neurological and cognitive impairment.
- Slower thinking and reaction times: Participants with lower B12 levels performed worse on tests measuring processing speed, meaning they took longer to think through and respond to questions.
- Delayed visual processing: They were slower to react to visual stimuli, suggesting that the brain’s ability to process what the eyes see was also affected.
- Brain lesions on MRI scans: MRI scans revealed more damage to the brain’s white matter in those with lower B12 levels. White matter is responsible for transmitting signals between different parts of the brain, and damage to it has been linked to dementia, stroke, and cognitive decline.
These effects were more pronounced in older participants, suggesting that aging makes the brain more vulnerable to lower B12 levels.
Are Current B12 Guidelines Outdated?
The study raises concerns about how B12 deficiency is currently defined. Traditionally, doctors have only diagnosed B12 deficiency when a person shows severe symptoms, such as anemia or nerve damage. However, lead researcher Dr. Ari J. Green believes this approach misses more subtle signs of deficiency, particularly those affecting brain function.
“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,” Green said.
Should More Older Adults Take B12 Supplements?
The study’s co-first author, Alexandra Beaudry-Richard, emphasized that low-normal B12 levels might be more harmful than previously thought, possibly affecting a much larger portion of the population. She believes that doctors should consider B12 supplementation for older adults showing neurological symptoms, even if their levels fall within the current normal range.
“Ultimately, we need to invest in more research into the underlying biology of B12 insufficiency, since it may be a preventable cause of cognitive decline,” Beaudry-Richard said.
What This Means for You
This study suggests that meeting the minimum B12 requirement may not be enough to protect brain health, particularly as people age. It may be time to reconsider B12 guidelines and expand screening for B12 insufficiency in older adults.
While more research is needed, increasing awareness about the role of B12 in cognitive function could help prevent unnecessary cognitive decline—a crucial step in maintaining brain health as we grow older.
If you care about nutrition, please read studies that vitamin D can help reduce inflammation, and vitamin K may lower your heart disease risk by a third.
For more information about nutrition, please see recent studies about foods that could sharp your brain, and results showing cooking food in this way may raise your risk of blindness.
The research findings can be found in the Annals of Neurology.
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