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# Why Vitamin D supplements may harm aging brains than actually help, study suggests
- URL: https://tsrv2.apphq.dev/world/why-vitamin-d-supplements-may-harm-aging-brains-than-actually-help-study-suggests/
- Published: 2026-09-11T02:13:27.000Z
- Updated: 2026-10-23T04:54:57.000Z
- Description: Vitamin D supplements may not be as beneficial as commonly believed, particularly among older adults, according to a landmark study published in BMJ Open. The study, led by researchers Rong Hua, Chun Siang Lam, Vincent Chung Tong Mok, and Yin Ting Cheung, challenges the widely held view that…
- Author: Liam Demafelix
- Tags: World, News, Explainers

Vitamin D supplements may not be as beneficial as commonly believed, particularly among older adults, according to a landmark study published in *BMJ Open*.

The study, led by researchers Rong Hua, Chun Siang Lam, Vincent Chung Tong Mok, and Yin Ting Cheung, challenges the widely held view that routine vitamin D supplementation helps protect against age-related cognitive decline.

Researchers analyzed longitudinal data from 5,065 dementia-free participants aged 67 and older from the U.S. Health and Retirement Study. Findings showed that older adults who took vitamin D supplements experienced a faster decline in overall cognitive performance and executive function compared to those who did not take supplements.

While earlier observational studies suggested that low vitamin D levels are linked to a higher risk of dementia, the researchers said real-world supplementation does not appear to provide cognitive protection.

The analysis also found an unexpected association between supplementation and faster cognitive decline among individuals who already had sufficient vitamin D levels prior to taking supplements.

For participants with vitamin D deficiency or insufficiency at baseline, supplementation showed no statistically significant positive or negative effect on cognitive outcomes, the study noted.

The study further revealed that vitamin D supplement users had a significantly steeper annual decline in global cognitive function scores compared to non-users.

Rather than offering benefits, supplementation was linked to a more rapid decline in executive function, which includes working memory, processing speed, and attention.

Even among participants with lower baseline vitamin D levels, researchers found no clear cognitive benefit from supplementation.

“The findings from real-world data do not support the use of vitamin D supplements to prevent cognitive decline in older people with adequate vitamin D status,” the study said.

Researchers noted that vitamin D remains one of the most widely used dietary supplements among older adults worldwide, with usage likely increasing during the COVID-19 pandemic due to its perceived role in immune health. However, it is often taken without proper clinical diagnosis or testing for deficiency.

They emphasized that while adequate vitamin D intake through a balanced diet and safe sun exposure should still be encouraged, healthcare providers should exercise caution in recommending over-the-counter vitamin D supplements to older adults without clear evidence of deficiency.