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Head-to-head evidence comparison — which supplement is right for you?
Iodine 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
2 of 3 studies with measurable effects showed benefit.
Top outcomes
150-300mcg for maintenance; higher only if deficient under supervision
Any time with food
Potassium iodide (most common and studied)
500mg twice daily
Morning and evening with meals
Niacinamide tablets (500mg)
4-12 weeks
4-8 weeks
3-12 months
8 weeks
Days
First days
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.
A Phase 3 Randomized Trial of Nicotinamide for Skin-Cancer Chemoprevention.
The New England journal of medicine (2015) · Rct · n=386
ONTRAC: phase-3, double-blind RCT randomizing 386 patients with ≥2 prior non-melanoma skin cancers to 500 mg nicotinamide twice daily or placebo for 12 months
Skin Cancer Prevention and Antiaging: Role of Nicotinamide.
International journal of molecular sciences (2026) · Review
Review of the biological rationale and clinical evidence for nicotinamide and NAD+ precursors in photoaging and cutaneous carcinogenesis
Topical nicotinamide compared with clindamycin gel in the treatment of inflammatory acne vulgaris.
International journal of dermatology (1995) · Rct · n=76
Double-blind RCT of 76 patients randomized to 4% nicotinamide gel or 1% clindamycin gel twice daily for 8 weeks for moderate inflammatory acne
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.
The ONTRAC RCT used 500 mg twice daily (1000 mg/day total) and reduced new non-melanoma skin cancers by 23%. Effect requires continuous use; it disappeared after discontinuation. Curve is indicative — only the 1000 mg/day regimen is directly RCT-supported.
AI-estimated from published studies. Interpret as directional guidance.
Iodine has a higher evidence score (8.5/10 vs 5.5/10) and wins in 2 of 3 categories.
No known interactions between Iodine and Nicotinamide have been documented in our database. However, always consult a healthcare provider before combining supplements.