Normal Vitamin B12 Levels May Still Be Too Low for Brain Health, Study Finds

A UCSF study finds lower but still ‘normal’ B12 levels linked to slower cognitive processing and brain damage in older adults.

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Older adults with vitamin B12 levels currently considered normal may still face cognitive decline and brain damage, according to a new study.

Participants with lower—yet technically acceptable—B12 levels showed measurable brain white matter damage and slower cognitive processing, prompting researchers to call for a reevaluation of what constitutes “healthy” B12 levels in aging populations.

“[Lower levels could] impact cognition to a greater extent than what we previously thought, and may affect a much larger proportion of the population than we realize,” Alexandra Beaudry-Richard, co-first author, said in a statement.

Rethinking B12 Levels

Recent research published in Annals of Neurology found that older, healthy people with concentrations of B12 in their blood on the lower side of normal showed signs of neurological and cognitive deficiency. The study found that lower B12 was linked to damage to the brain’s white matter, which helps brain regions communicate.

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Researchers enrolled 231 healthy participants without dementia or mild cognitive impairment, with an average age of 71. Their average blood B12 level was 414.8 pmol/L, which exceeds the U.S. minimum threshold of 148 pmol/L, indicating that, on average, they do not exhibit B12 deficiency. Normal values for B12 are often cited as being roughly between 118 to 701 pmol/L.

Assessments of cognitive performance indicated that lower active B12 levels were associated with slower processing speeds, suggesting a potential for subtle cognitive decline. This effect was more pronounced in older participants.

The results raise questions about current B12 requirements and suggest the recommendations need updating, according to Dr. Ari J. Green, chief of the division of neuroimmunology and glial biology in the Department of Neurology at the University of California–San Francisco and senior author of the study.

Older people are more prone to lower vitamin B12 levels because their stomach acid production, which is crucial for properly absorbing B12 from food, decreases as they age. This malabsorption, combined with potential dietary inadequacies, can lead to deficiency.

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Low B12 levels are linked to brain lesions because B12 is vital for the health of nerve cells in the brain. As a result, a deficiency can cause damage to the white matter, leading to lesions that can affect cognitive 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 stated.

“Revisiting the definition of B12 deficiency to incorporate functional biomarkers could lead to earlier intervention and prevention of cognitive decline.”

Brain Lesions Linked to ‘Normal’ B12

Participants with lower yet still normal B12 also experienced significant delays when responding to visual stimuli. This was tested by flashing patterns across their field of vision.

Participants looked at a flashing pattern on a screen while electrodes on their head measured their brain’s response. This showed how quickly their brain processed what they saw and which parts of their vision were affected.

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The results were indicative of slower visual processing speeds and a general decline in brain conductivity—an important measure of how well electrical currents travel through brain tissue.

Participants with lower, yet still normal, B12 levels showed increased white matter lesions on MRI scans. These lesions, which disrupt brain communication, may contribute to cognitive decline, dementia, or stroke.

The findings suggest that the current “healthy” B12 range might be too broad, overlooking subtle health issues caused by B12 levels that are just outside that range, even if people don’t have obvious symptoms, according to the researchers.

“In addition to redefining B12 deficiency, clinicians should consider supplementation in older patients with neurological symptoms even if their levels are within normal limits,” Beaudry-Richard stated.

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“Ultimately, we need to invest in more research about the underlying biology of B12 insufficiency, since it may be a preventable cause of cognitive decline.”

Best Sources of B12

The official recommendation for how much vitamin B12 people should consume daily might not be enough for everyone, especially because of absorption issues related to age, pregnancy, or gut health, Aderet Dana Hoch—registered dietitian, founder and owner of Dining with Nature by Aderet, a nutrition private practice, and not associated with the study—told The Epoch Times. In these cases, she said, increased intake may be necessary.

Lori Carrell, a registered dietitian affiliated with Persona Nutrition, emphasized the importance of animal-based foods for maintaining proper B12 levels. To ensure adequate B12 intake, include a variety of meats such as beef, pork, and lamb in your diet, Carrell said. She also recommended poultry options such as chicken and turkey, along with fish and seafood including salmon, tuna, sardines, and clams. Carrell noted that dairy products—milk, cheese, and yogurt—as well as eggs are excellent sources of this essential vitamin.

“For those following a vegetarian or vegan diet,” she said, “B12-fortified foods such as plant-based milks, nutritional yeast, and breakfast cereals or a high-quality supplement is necessary, as plant-based sources alone do not provide enough B12.”