In the news: Higher B12 May Slow Cognitive Decline; Is the MIND Diet Better for Obese?

Vitamin B12 Linked to Slower Cognitive Decline

Vitamin B12 plays an essential role in maintaining the central nervous system (CNS), including the brain. It’s needed to protect glial cells which support neurons in the CNS, for example, and to make myelin which insulates nerve fibers for efficient signal transmission.

B12 levels that are too low can cause neurological symptoms and cognitive problems too, such as memory loss, confusion and difficulty thinking. But can higher B12 levels lower the odds of developing dementia? Or help people keep mental sharpness as they age?

Observational studies provide mixed evidence on B12 and cognitive decline with age. Some controlled trials have reported that vitamin B12 is linked to slower decline in some areas of mental functioning, but not others.

Funded by the National Institutes of Health, researchers from Boston University teamed with other investigators to evaluate whether low vitamin B12 – starting in mid-life and continuing through older age – is associated with a faster decline in memory, language, or executive function (skills that help the brain manage itself)(1).

The team looked at over 1,900 dementia-free men and women who were part of the Framingham Heart Study and analyzed their B12 status and change in mental function over about 14 years. Participants were divided into 4 groups based on their cumulative average B12 status (measured by blood biomarkers) during follow-up.

People with a higher cumulative B12 status had a significant slower annual decline in all 3 domains examined: memory, language and executive function vs. those with a lower B12 status.

The link between B12 and memory was stronger when levels of folic acid, another B-vitamin, were elevated too.

Higher B12 was also linked with less cognitive decline over 10 years.

The results, though modest, are meaningful, and the take-home message is that ensuring healthy levels of vitamin B12 throughout life might help us retain mental function as we grow older.

Overweight? Mind Diet May Be Best for Brain

There are many healthy eating plans to choose from: the Mediterranean (Med) diet, DASH diet and the Healthy Eating Index to name a few. One plan that supports brain function is the MIND diet.

The MIND plan is similar to the Med diet. But it also emphasizes “brain-healthy” foods that have been linked to slower rates of age-related cognitive decline and Alzheimer’s prevention while limiting consumption of less healthy foods.

A previous 3-year long randomized trial evaluated the effects of the MIND diet on cognitive decline in older adults with no cognitive impairment, but at greater risk of Alzheimer’s due to family history of the disease.

In that study, participants either ate their usual diet or the MIND diet, and both groups cut their daily calories by 250 kcal to lose weight. Although the MIND plan didn’t affect cognitive decline, both groups did better in global measure of cognition over time, and they lost about 11 lbs.

Wanting to understand more, researchers analyzed the results of the earlier study to see whether other factors such as genetic risk (APOE4), CVD, lifestyle factors or demographics, might have influenced the MIND diet’s effects(2).

They found that body mass index (BMI) was the only influencing factor, with MIND improving cognition in those with a BMI of at least 35. BMI is a screening tool that measures the ratio of height to weight to estimate body fat. A BMI over 30 indicates obesity.

Obesity has been linked to greater risk of dementia and cognitive impairment, possibly due to inflammation and metabolic factors. It could be that the MIND diet’s positive cognitive effects are greater in obese individuals. More research is needed to confirm these findings.

References

1. Marino F, et al. Higher vitamin B12 from mid- to late life is related to slower rates of cognitive decline. Alzheimer’s Dement. 21:e70864, 2025.
2. Halloway S, et al. Effect modifiers of the MIND diet for cognition in older adults: The MIND diet trial. Alzheimer’s Dement. 21:e70731, 2025.