Can 'healthy' (but not high) Vitamin B12 levels still harm your brain? New study raises concern

Vitamin B12 is a crucial nutrient for your brain and is also required for optimal red blood cell production, and nerve health. A deficiency in this essential vitamin can lead to fatigue, memory problems, and even mood disturbances. It plays a key role in DNA synthesis and supports overall neurological function. However, new research has suggested that the current recommended levels may not be sufficient to prevent cognitive impairment, especially in older adults.

A study from UC San Francisco, published in Annals of Neurology, found that even older individuals with so-called healthy levels of B12, showed signs of cognitive decline and brain damage.

While Vitamin B12 is associated with maintaining cognitive health and preventing neurological issues as we get older, there is a need to revise the healthy range as it may not be enough to maintain older people's brain health.

In this study published in Annals of Neurology, older, healthy volunteers, with low levels of B12, but still in the normal range, displayed signs of neurological and cognitive deficiency. The levels are currently considered healthy but low enough to cause damage to the brain’s white matter – the nerve fibres that enable communication between areas of the brain. The older adults with these levels got test scores associated with slower cognitive and visual processing speeds, compared to those with higher B12.

“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 senior author Ari J. Green, MD, of the UCSF Departments of Neurology and Ophthalmology and the Weill Institute for Neurosciences, 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.”

For the study, 231 healthy participants without dementia or mild cognitive impairment with an average age of 71 were involved. Their Vitamin B12 levels averaged 414.8 pmol/L, which is well above the U.S. minimum of 148 pmol/L. Researchers considered the biologically active component of B12, which provides a clearer picture of how much vitamin the body can utilise.

During the cognitive test, participants with lower active B12 levels had slower processing speed, which indicated subtle cognitive decline. Its impact was amplified by older age. Such participants also showed significant delays in responding to visual stimuli, which pointed to slower visual processing speeds and sluggish brain conductivity.

Additionally, MRIs also showed a higher volume of lesions in the white matter of the participants which could be linked with cognitive decline, dementia or stroke.

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

Vitamin B12 also has an effect on fatigue and a lack of energy. If you always feel tired and your Vitamin B12 levels are now, supplementation can help give you more energy, studies show. But B12 supplements don't have any effect on people already at normal levels.

A deficiency in Vitamin B12 can also lead to neurological symptoms like tingling in the hands and feet or difficulty concentrating. Ensuring adequate intake through diet or supplements is essential for overall health and well-being.
Vitamin B12, also known as cobalamin, is one of the eight B vitamins. It is a water-soluble vitamin and is required by animals, which use it as a cofactor in DNA synthesis, and in both fatty acid and amino acid metabolism.
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