Current vitamin B12 intake guidelines may be too low to counter cognitive decline, experts flag

New research suggests that the current recommended levels of vitamin B12 may not be high enough to counter the cognitive decline that comes with aging.

The study authors looked at cognitive decline markers in older, healthy volunteers with levels of vitamin B12 considered normal by current standards.

They found that the volunteers with lower vitamin B12 concentrations, but still above the threshold for being defined as deficient, tended to show more signs of neurological damage and cognitive decline.

“The observed correlation with cognitive decline highlights the urgency of addressing vitamin B12 deficiency, potentially through food fortification,” says study lead and professor Martin Warren from the Quadram Institute.

“Beyond increasing vitamin B12 availability in foods, we must also enhance diagnostic methods to better identify those who require higher vitamin B12 intake,” he urges.

“It’s imperative that we get a handle on the biology of vitamin B12 deficiency and how it affects brain aging, as it could be a relatively simple way of preventing cognitive decline in a significant proportion of the population.”

Defining thresholds for deficiency

Researchers from the UK’s Quadram Institute contributed to the study, which was led by the University of California, San Francisco, US. They emphasize the need to revisit the threshold for B12 deficiency.

In the UK, a level below 180 ng/L of vitamin B12 in the blood is considered to be deficient. In the US, the level is 200 ng/L.

However, a significant number of older people reporting neurological symptoms but with vitamin B12 levels above that threshold have seen their symptoms improve with vitamin B12 supplementation.

The study enrolled 231 healthy volunteers, with an average age of 71. Each had their blood samples analyzed for the presence of variants of vitamin B12 by the Quadram Institute’s research team.

The Quadram Institute has advanced facilities that analyze different biomolecules at even the smallest concentrations. It provided its methods for quantifying various versions of vitamin B12 in the samples to get a full picture of the volunteers’ vitamin B12 levels.

In the UK, a level below 180 ng/L of vitamin B12 in the blood is considered to be deficient. In the US, the level is 200 ng/L.All participants in the study had levels above the threshold, indicating deficiency.

The participants took part in a series of tests designed to assess their neurological status, as well as having blood tests for known signs of neural injury.

The data analysis revealed that participants with lower vitamin B12 levels had impaired brain processing speed and a greater delay in responding to a visual stimulus. MRI scans also showed an association between lower vitamin B12 status and areas of damaged brain tissue.

This indicates that they could be experiencing cognitive decline, even though their vitamin B12 levels are above the current threshold, which would indicate a damaging deficiency. These effects were amplified among older participants.

Results of the study have been published in the journal Annals of Neurology.

Essential vitamin

Vitamin B12 is needed by the body for a range of functions, including making DNA and blood cells. It also plays a vital role in the production of the sheath that surrounds nerves, “like the insulation around an electrical wire,” the authors illustrate.

Humans can’t produce vitamin B12 and rely on dietary sources, which are limited mainly to animal-based foods as the nutrient is not found in plants. This can put vegan and vegetarian people at risk of being vitamin B12 deficient unless they take a supplement. 

However, the study authors see a lack of reliable data revealing how many people may be affected by vitamin B12 deficiency, making it part of the problem of “hidden hunger,” where parts of the population lack vital micronutrients.

A deficiency in vitamin B12 can produce a wide range of symptoms. Anaemia, caused by a lack of red blood cells, triggers tiredness and shortness of breath and can be picked up in blood tests.

Neurological symptoms, including confusion, memory loss, muscular coordination, and visual impairments, can be harder to diagnose and link back to a vitamin B12 deficiency. Previous studies have shown that vitamin B12 deficiency plays a role in mild cognitive impairment and Alzheimer’s disease.

Participants with lower vitamin B12 levels had impaired brain processing speed and a greater delay in responding to a visual stimulus.The implication of the threshold for deficiency being too low is that a much larger proportion of the population may be affected. The neurological effects and cognitive decline are subtle and may not be noticed until they have further progressed.

Providing vitamin B12 supplements to older people could help ward off some of these effects.

Efforts to increase the levels of vitamin B12 in the diet, for example, through fortification, could also prove beneficial.

“At Quadram, in collaboration with our partners at the John Innes Centre, we are actively exploring innovative ways to incorporate vitamin B12 into plant-based foods while also developing new gold-standard diagnostic approaches to improve detection and intervention,” says Warren.

In previous research, scientists identified a link between vitamin B12 supplementation and improved outcomes in multiple sclerosis treatment.

Meanwhile, an international research team developed a method of producing carbon-neutral spirulina containing biologically active vitamin B12 in levels “comparable to beef,” offering a viable plant-based source for the essential nutrient.