Can low vitamin D levels raise dementia risk? Yes, research shows that people with low vitamin D have a higher chance of developing dementia, with some studies linking deficiency to up to a 32 percent increased risk or more.
Vitamin D is a nutrient that helps your body in many ways, including keeping bones strong and supporting brain health. When levels drop too low, it is called vitamin D deficiency. A study in BMC Neurology looked at many reports and found that this deficiency raises dementia risk by 32 percent overall. Severe cases, where blood levels are at or below 10 ng/ml, can increase the risk by nearly 50 percent. Dementia is a group of symptoms that affect memory, thinking, and daily activities, often linked to diseases like Alzheimer’s.
Scientists think low vitamin D harms the brain through a few key paths. First, vitamin D helps control calcium in the body, which is vital for forming memories. Without enough vitamin D, calcium balance gets disrupted, speeding up brain cell aging. A review in Hormones journal from 2018 noted this connection. Second, vitamin D acts like an antioxidant in the brain. It protects against damage from too much glutamate, a brain chemical that can kill neurons if levels are high. Research in the Journal of Neurobiological Studies from 2018 supports this protective role.
Other studies add more evidence. One found that taking vitamin D supplements cut dementia risk by 40 percent compared to not taking them. Animal and cell studies show vitamin D helps clear harmful proteins like amyloid beta, which build up in Alzheimer’s brains. It also boosts brain cell growth and reduces inflammation. Low levels have been tied to mild cognitive impairment in older adults.
Not all results agree, though. Some clinical trials giving vitamin D to older people did not slow dementia progression or lower new cases. This might depend on whether someone starts deficient or other factors like diet and location. For example, rural areas with less sun may see bigger benefits from good nutrition. Observational studies, which track real-world patterns, often show stronger links between higher vitamin D and lower dementia risk than some supplement trials.
About 29 percent of U.S. adults lack enough vitamin D, partly due to less time outdoors and limited sun exposure. Getting enough can come from sunlight, foods like fatty fish or fortified milk, or supplements. One recent finding is that magnesium helps balance vitamin D levels. If you are deficient, magnesium can raise them; if too high, it lowers them. This might explain why supplements do not work the same for everyone.
Sources
https://www.mindbodygreen.com/articles/getting-ample-vitamin-d-reduces-your-dementia-risk-by-32-how-to-achieve-and-maintain-healthy-vitamin-d-levels
https://pmc.ncbi.nlm.nih.gov/articles/PMC12745284/
https://www.aol.com/taking-daily-vitamin-could-slash-165700364.html
https://www.sciencedaily.com/releases/2025/12/251228020010.htm
https://www.grassrootshealth.net/blog/vitamin-d-insights-why-observational-evidence-outperforms-clinical-trials-dr-grant-oct-2025/
