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Head-to-head evidence comparison — which supplement is right for you?
Multivitamin wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Probably helps
8 of 12 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
27 of 34 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (1)
Outcomes where both Multivitamin and Selenium have evidence — compare verdict strength side-by-side.
1 serving daily (as directed on label, typically 1-2 tablets/capsules)
With breakfast, With lunch (if GI sensitive)
Capsule or softgel
100-200mcg
With food
Selenomethionine (best absorbed)
Combined selenium intake from multivitamin plus standalone selenium supplement can approach or exceed the 400 mcg/day UL, risking selenosis symptoms. The SELECT trial documented increased T2DM risk at 200 mcg/day in selenium-adequate men.
Do not add standalone selenium supplementation to a multivitamin unless selenium deficiency is confirmed via serum selenium testing. Total selenium from all supplement sources should remain below 400 mcg/day. Most individuals in developed nations with adequate dietary intake do not benefit from supplemental selenium above 55–100 mcg/day.
3-6 months
4-8 weeks
2-6 weeks
6-12 weeks
4-8 weeks
4-8 weeks
Effect of multivitamin-mineral supplementation versus placebo on cognitive function: results from the clinic subcohort of the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized clinical trial and meta-analysis of 3 cognitive studies within COSMOS
The American Journal of Clinical Nutrition (2024) · Meta analysis · n=5765
Multivitamin-mineral supplementation significantly improved global cognition vs placebo (pooled meta-analysis)
Multivitamin Supplementation Improves Memory in Older Adults: A Randomized Clinical Trial
The American Journal of Clinical Nutrition (2023) · Rct · n=3562
Daily multivitamin supplementation for 3 years significantly improved immediate and delayed recall memory
Effects of cocoa extract and a multivitamin on cognitive function: A randomized clinical trial
Alzheimer's & Dementia (2023) · Rct · n=2262
Multivitamin-mineral supplementation (not cocoa extract) drove significant cognitive improvements in COSMOS-Mind
Selenium, antioxidants, cardiovascular disease, and all-cause mortality: a systematic review and meta-analysis of randomized controlled trials
The American journal of clinical nutrition (2020) · Meta analysis · n=9423
However, a decreased risk with antioxidant mixtures was seen for CVD mortality when selenium was part of the mix (RR: 0.77; 95% CI: 0.62, 0.97; P = 0.02), with no association when selenium was absent.
Selenium for preventing cancer
The Cochrane database of systematic reviews (2018) · Meta analysis · n=27232
For analyses of RCTs with low risk of bias, the summary risk ratio (RR) for any cancer incidence was 1.01 (95% confidence interval (CI) 0.93 to 1.10; 3 studies, 19,475 participants; high-certainty evidence).
Selenium and prostate cancer: systematic review and meta-analysis
The American journal of clinical nutrition (2012) · Meta analysis · n=13254
Three high-quality studies included in the meta-analysis of toenail selenium and cancer risk indicated a reduction in prostate cancer risk (estimated RR: 0.29; 95% CI: 0.14, 0.61) with a toenail selenium concentration between 0.85 and 0.94 μg/g.
Based on COSMOS trials (n=5765) showing equivalent of 2.0 years cognitive decline prevention. Effects most pronounced in those with cardiovascular disease. Study duration was 3 years. Effectiveness reflects conservative interpretation of memory and global cognition improvements.
Based on Cochrane systematic review showing moderate-certainty evidence for TPO antibody reduction. Effects on thyroid hormone levels (TSH, T4, T3) were inconsistent across studies.
AI-estimated from published studies. Interpret as directional guidance.
Multivitamin has a higher evidence score (6/10 vs 6.5/10) and wins in 2 of 3 categories.
For support immune system, Multivitamin has a higher relevance score (82 vs 70).
Caution: Combined selenium intake from multivitamin plus standalone selenium supplement can approach or exceed the 400 mcg/day UL, risking selenosis symptoms. The SELECT trial documented increased T2DM risk at 200 mcg/day in selenium-adequate men. Do not add standalone selenium supplementation to a multivitamin unless selenium deficiency is confirmed via serum selenium testing. Total selenium from all supplement sources should remain below 400 mcg/day. Most individuals in developed nations with adequate dietary intake do not benefit from supplemental selenium above 55–100 mcg/day. Always consult a healthcare provider before combining these supplements.