Vitamin B12 Levels Linked to Brain Damage in Older Adults, Study Finds

According to a study led by UC San Francisco (UCSF), researchers found that older adults with normal levels of vitamin B12 have shown cognitive decline and brain damage. These individuals seem to have slower thinking and reaction times. Vitamin B12, called cobalamin, is crucial for red blood cell formation, nervous system health and function, DNA synthesis, brain health, and energy production. It is normally obtained from meat, poultry, fish and shellfish, dairy products, and eggs. Vegans and vegetarians can obtain vitamin B12 from foods fortified with the vitamin.

This study, published in the Annals of Neurology on February 10, put forward the fact that older individuals had more damage to the brain’s white matter with lower B12 levels. White matter, the nerve fibers that enable different parts of the brain to communicate, performed worse on tests measuring both cognitive and visual processing speeds compared to those with higher B12 levels.

“A lot of previous studies might have missed fine functional manifestations of high or low levels of vitamin B12 that can affect people without observable symptoms,” says Dr. Ari Green of the University’s Weill Institute for Neurosciences and the Department of Ophthalmology. “Reconsidering the description of B12 insufficiency to incorporate functional biomarkers could lead to earlier intervention and prevention of cognitive decline.”

Once cobalamin, or vitamin B12, is absorbed into the bloodstream, two transporter proteins help it reach the areas where it is needed in the body. One, haptocorrin (HC), binds to most of the B12 in the blood, but the body cannot use it directly, so it largely ends up in the liver, where it is ultimately broken down and excreted. This form of vitamin B12 is considered biologically inactive because it is not immediately available to the tissues. The other protein, transcobalamin (TC), binds to a receptor called CD320, which allows cells to absorb it. This form is considered biologically active.

When blood levels of vitamin B12 are measured, both forms are included. The active B12 (Holo-TC) is what matters for the body’s cells. If active B12 is at lower levels, it could cause neurological symptoms. Meanwhile, inactive B12 (Holo-HC) is mostly stored in the liver and does not directly help with body functions.

In the United States, the UK, and Australia, vitamin B12 levels in the blood are measured in different units. To provide a consistent comparison, the reference ranges for each country have been converted to picomoles per liter (pmol/L). In the present study, which was conducted in the U.S., B12 “deficiency” was defined as a value less than 148 pmol/L, and “normal” was any concentration within the above reference range.

For this study, researchers enlisted 231 healthy participants with a median age of 71 years and a median B12 blood concentration of 414.8 pmol/L, well above the recommended lower level.

The participants were recruited through the Brain Aging Network for Cognitive Health (BrANCH) study at UCSF. The researchers estimated participants’ total blood B12 and Holo-TC levels.

Holo-HC values were deduced by subtracting Holo-TC from the total measured B12.

The researchers assessed the association of B12 concentrations with cognitive performance and myelin integrity. Myelin is the protective coating around nerve fibers and is essential for proper nerve function. Vitamin B12 plays a pivotal role in maintaining it. When B12 is insufficient, the body struggles to repair and maintain myelin’s integrity. The health of brain tissue was assessed using Magnetic Resonance Imaging (MRI).

The researchers could not determine from this study whether the white matter hyperintensities (small areas of injury in the brain’s white matter associated with aging, poor circulation, or neurological diseases like dementia or stroke) observed on MRI were a direct result of lower B12. They found it surprising that high levels of the inactive form of B12 were linked to high serum tau levels (a protein associated with brain cell degeneration and conditions like Alzheimer’s disease).

"Clinicians should rethink the process of supplementation in elderly patients with neurological symptoms, even if vitamin B12 levels are within normal limits,” said Alexandra Beaudry-Richard, the study’s co-lead author, who is completing her doctorate in research and medicine at UCSF’s Department of Neurology.

References:

1. Beaudry-Richard, Alexandra, Ahmed Abdelhak, Rowan Saloner, Simone Sacco, Shivany C. Montes, Frederike C. Oertel, Christian Cordano et al. "Vitamin B12 Levels Association with Functional and Structural Biomarkers of Central Nervous System Injury in Older Adults." Annals of Neurology. Accessed February 27, 2025. https://doi.org/10.1002/ana.27200. 

(Input from various sources)

(Rehash/Dr. Lakshmisahithi Tanneru/MSM)