Research
Mixed
Daily supplementation with 2000 IU of vitamin D or 1 g of marine n-3 fatty acids does not reduce the risk of major cardiovascular events, invasive cancer, or secondary outcomes in adults.
Do not take Vitamin D or Fish Oil supplements expecting them to prevent heart disease or cancer. Large studies show they do not work for this purpose at standard doses.
StrongRefutesVERY_HIGH confidence
neither daily supplementation with 2000 IU of vitamin D nor 1 g of marine n-3 fatty acids had an effect on major cardiovascular events (vitamin D: HR, 0.97 [95% CI, 0.85–1.12]; marine n-3 fatty acids: HR, 0.92 [95% CI, 0.80–1.06]), invasive cancer, or any secondary outcomes.
Why this rating
Based on a large 2-by-2 factorial randomized clinical trial (VITAL trial implied) with 25,871 adults.
Source
Heart Disease and Stroke Statistics—2020 Update: A Report From the American Heart Association
Salim S. Virani et al. · Circulation · 2020
DOI 10.1161/cir.0000000000000757
narrative_reviewCited 9,341×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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