Key Takeaway:
- New studies link vitamin D, omega-3, and glucosamine supplements with faster cognitive decline in some older adults, raising questions about supplements and aging brain health.
- The findings show associations, not proof that supplements cause brain damage or dementia.
- Researchers urge caution and further study, rather than recommending that people stop supplements based on these findings alone.
New studies are linking vitamin D, omega-3 fish oil and glucosamine supplements with faster cognitive decline in some older adults, prompting scientists to investigate whether ageing changes how the brain responds to them.
New Studies Flag Potential Cognitive Risks
The findings do not show that the supplements cause dementia or other forms of cognitive decline. Researchers say the evidence is preliminary, and the studies are largely observational, meaning other differences between supplement users and nonusers could explain the results related to supplements and aging brain health.
A January study of 5,065 Americans with an average age of 67.5 found that vitamin D supplement users with normal vitamin D levels experienced slightly faster declines in overall cognition and executive function over six years. The association was not seen among participants with vitamin D deficiency or insufficiency.
In April, researchers reported another concerning association involving omega-3 supplements. An analysis of adults aged 55 to 90 found that the 273 omega-3 users experienced faster cognitive decline than 546 nonusers across three standardised measures during a median follow-up of five years.
Ageing May Change How Supplements Act
Scientists say ageing can alter the biological environment in which nutrients and medications work. Changes to brain metabolism and the blood-brain barrier may affect how substances enter brain tissue and how the brain responds to fats, calcium, glucose and inflammation, raising questions about supplements and aging brain.
The omega-3 findings are particularly notable because fish and omega-3 fats have long been associated with brain health. However, studies of omega-3 supplements have generally failed to establish the cognitive benefits many consumers expect from daily fish-oil capsules.
Onder Albayram, an associate professor of neuropathology and neuroscience at the Medical University of South Carolina, said the brain’s biological environment changes over a person’s lifetime. He said that means a supplement may not produce the same effects in an older or injured brain as it does under other conditions.
Marion Nestle, an emerita professor at New York University, said supplements can change biochemical markers in the blood without producing the same straightforward effects in the body. She said people can also obtain vitamin D through food and sunlight, raising questions about supplements and aging brain health.
Researchers Urge Caution, Not Alarm
Glucosamine has also drawn attention. A June study found that glucosamine use was associated with roughly a 25% greater likelihood of progressing from mild cognitive impairment to Alzheimer’s disease or a related dementia. Among people who already had Alzheimer’s or dementia, use was also associated with about a 25% higher rate of death.
Ramon Sun, a University of Florida professor and lead author of the glucosamine study, said the findings about supplements and aging brain surprised him. Researchers combined experiments involving mice, examinations of human brain tissue and analyses of electronic health records.
Still, the researchers do not recommend that older adults stop taking the supplements based on these studies alone. Differences in health, income, education, supplement doses and other behaviours could affect the findings, and some supplement use may go unreported.
Sun said supplements should be viewed as biologically active substances rather than automatically harmless additions to the diet. The emerging research, scientists say, raises a broader question: whether the benefits and risks of a supplement can change as the brain ages.
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