A major meta-analysis finds people with low vitamin D levels face a 59% greater risk of Alzheimer’s disease

Alzheimer’s disease, which causes up to 80% of all dementia cases, is expected to affect nearly 150 million people globally within the next 30 years. As its prevalence rises, scientists are racing to understand modifiable risk factors that could help slow the tide. One nutrient is emerging as a key player: vitamin D.

Researchers have long known that vitamin D receptors are present in the brain and that the nutrient plays a neuroprotective role. However, a comprehensive 2023 meta-analysis has now revealed a compelling link between low vitamin D levels and increased Alzheimer’s risk.

The study pooled data from six separate investigations involving almost 11,000 participants. It found that individuals with serum 25(OH)D levels below 25 ng/mL had a 59% greater likelihood of developing Alzheimer’s than those with higher vitamin D levels. Though it stops short of confirming causation, the research strengthens the case that vitamin D status is a significant factor in brain health.

Current medical guidelines define vitamin D deficiency as less than 20 ng/mL and insufficiency as 20–30 ng/mL. However, researchers and health experts increasingly suggest aiming for levels of 50 ng/mL or higher for comprehensive benefits, particularly for cognition, immunity, and hormone regulation.

The exact mechanisms behind vitamin D’s influence on the brain are still being explored, but the nutrient is known to regulate inflammation, support neurotransmitter production, and protect neurons from oxidative stress—all factors that may be involved in Alzheimer’s development.

Unfortunately, vitamin D deficiency is widespread, with an estimated 41% of people having insufficient levels. While fatty fish and fortified dairy offer some vitamin D, dietary options are limited. Sunlight also stimulates vitamin D production, but skin cancer concerns and limited sun exposure in many regions complicate that route.

That’s why health professionals often recommend supplementation. Experts suggest 2,000 to 3,000 IU of vitamin D3 per day to lift blood levels above 30 ng/mL—and as much as 5,000 IU daily to reach optimal status. Testing blood levels of 25(OH)D is the most accurate way to determine whether supplementation is needed.

Though more research is necessary to establish precise protective thresholds, this latest study reinforces vitamin D’s role in maintaining cognitive health. The takeaway: if you’re looking to reduce your risk of Alzheimer’s, checking and optimising your vitamin D levels could be a simple, proactive step.