Evidence for Daily Multivitamin Supplementation

2-Year Multivitamin Trial on Cognitive Function (COSMOS Substudy)

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Here’s a summary of the 2-year randomized clinical evidence on daily multivitamin supplementation - specifically from large, well-designed trials comparing multivitamins to placebo:

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🧠 2-Year Multivitamin Trial on Cognitive Function (COSMOS Substudy)

Study design:

• Part of the COSMOS (COcoa Supplement and Multivitamin Outcomes Study) family of randomized, placebo-controlled trials.
• Participants were generally older adults (≥60 years).
• It tested daily multivitamin-mineral (MVM) supplementation versus placebo over ~2 years.
• Cognitive outcomes (especially episodic memory and global cognition) were assessed. (PubMed)

Key results after ~2 years:

✅ Improved episodic memory: Participants taking the multivitamin had significantly more favorable changes in memory compared with placebo. (PubMed)

✅ Better global cognition: When data were meta-analyzed across COSMOS cognitive substudies, daily multivitamin use was associated with modest benefits in overall cognitive performance. (PubMed)

🧠 Cognitive aging benefit: The effect size on global cognition was estimated to be roughly equivalent to slowing “cognitive aging” by ~2 years compared with placebo. (Mass General Brigham)

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📊 How Strong Is the Evidence?

• The COSMOS cognitive substudy reporting 2-year outcomes was randomized and placebo-controlled with formal neuropsychological assessments. (PubMed)
• A meta-analysis across multiple COSMOS cognitive studies (including this 2-year segment) strengthened the evidence of benefit. (Mass General Brigham)
• Other research (e.g., longer 3-year follow-ups) supports memory benefit over multiple years, but the clearest 2-year trial effects relate to memory and overall cognition. (PubMed)

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📌 What Didn’t Change Significantly?

• The benefit in executive function and attention was not statistically significant in this 2-year study. (PubMed)

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🧠 Summary

Feature	Result
Population	Older adults (≥60 years)
Intervention	Daily multivitamin-mineral supplement
Comparison	Placebo
Duration	~2 years
Main benefits	Episodic memory, global cognition improved
Interpretation	Effect ≈ ~2 years slower cognitive aging

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https://pubmed.ncbi.nlm.nih.gov/38244989/