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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
Mixed evidence
4 of 12 studies with measurable effects showed benefit.
Top outcomes
Verdict
Probably helps
8 of 12 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (1)
Outcomes where both Iodine and Multivitamin have evidence — compare verdict strength side-by-side.
150-300mcg for maintenance; higher only if deficient under supervision
Any time with food
Potassium iodide (most common and studied)
1 serving daily (as directed on label, typically 1-2 tablets/capsules)
With breakfast, With lunch (if GI sensitive)
Capsule or softgel
Excess combined iodine above 1100 mcg/day disrupts thyroid homeostasis. In Hashimoto's disease, moderate iodine excess (above ~500 mcg/day) can exacerbate hypothyroidism and thyroid peroxidase antibody levels.
Audit total iodine from all supplement and dietary sources (seaweed, iodized salt). Individuals with autoimmune thyroid disease should restrict supplemental iodine to the RDA (150 mcg/day) and should not combine multivitamin iodine with additional iodine supplements. Total supplemental iodine should not chronically exceed 500–1100 mcg/day.
4-12 weeks
4-8 weeks
3-6 months
4-8 weeks
2-6 weeks
6-12 weeks
Maternal Iodine Status and Birth Outcomes: A Systematic Literature Review and Meta-Analysis
Nutrients (2023) · Meta analysis · n=42269
Birth weight was similar between UIC ≥ 150 μg/L and <150 μg/L (difference = 30 g, 95% CI −22 to 83, p = 0.3, n = 13, I2 = 89%) with no evidence of linear trend (4 g per 50 μg/L, −3 to 10, p = 0.2, n = 12, I2 = 80%).
Iodine fortification of foods and condiments, other than salt, for preventing iodine deficiency disorders
The Cochrane database of systematic reviews (2019) · Meta analysis · n=4317
This is equivalent to an increase of 38.32 µg/L (95% CI 24.03 to 52.61 µg/L).
Systematic review and meta-analysis of iodine nutrition in modern vegan and vegetarian diets
The British journal of nutrition (2023) · Meta analysis · n=4421
Vegan diets had the poorest iodine intake (17·3 µg/d) and were strongly associated with lower iodine intake (P = < 0·001) compared with omnivorous diets.
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
Based on meta-analyses showing urinary iodine concentration increases with supplementation. Effects only meaningful in iodine-deficient populations. Excessive intake (>300mcg) may increase thyroid cancer risk. Most studies used potassium iodide; kelp-derived forms have variable bioavailability.
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.
AI-estimated from published studies. Interpret as directional guidance.
Multivitamin has a higher evidence score (6/10 vs 8.5/10) and wins in 2 of 3 categories.
For boost daily energy, Iodine has a higher relevance score (95 vs 75).
Excess combined iodine above 1100 mcg/day disrupts thyroid homeostasis. In Hashimoto's disease, moderate iodine excess (above ~500 mcg/day) can exacerbate hypothyroidism and thyroid peroxidase antibody levels. Audit total iodine from all supplement and dietary sources (seaweed, iodized salt). Individuals with autoimmune thyroid disease should restrict supplemental iodine to the RDA (150 mcg/day) and should not combine multivitamin iodine with additional iodine supplements. Total supplemental iodine should not chronically exceed 500–1100 mcg/day. Consult a healthcare provider for personalized advice.