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Head-to-head evidence comparison — which supplement is right for you?
Folic Acid vs Iodine: Iodine has the stronger overall evidence (8.5 vs 8/10); they're alternatives for prenatal support — the best pick depends on your goals. Take the 60-second quiz for a pick tailored to your goals.
Iodine wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
400 mcg/day for anyone planning or capable of pregnancy (USPSTF: 400-800 mcg); adult RDA 400 mcg DFE/day, 600 mcg DFE in pregnancy, 500 mcg DFE in lactation (IOM)
any
Folic acid (pteroylmonoglutamic acid)
150-300mcg for maintenance; higher only if deficient under supervision
Any time with food
Potassium iodide (most common and studied)
and 2 more not shown
Periconceptional
Weeks
Weeks to months
4-12 weeks
4-8 weeks
Prevention of the first occurrence of neural-tube defects by periconceptional vitamin supplementation.
N Engl J Med (1992) · Rct
Randomised trial of periconceptional vitamin supplementation for prevention of a FIRST neural tube defect (PubMed publication types: Randomized Controlled Trial, Clinical Trial)
Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. MRC Vitamin Study Research Group.
Lancet (1991) · Rct
Randomised, multicentre trial of periconceptional folic acid for prevention of RECURRENT neural tube defects (PubMed publication types: Randomized Controlled Trial, Multicenter Study, Comparative Study)
Effects and safety of periconceptional oral folate supplementation for preventing birth defects.
Cochrane Database Syst Rev (2015) · Meta analysis
Cochrane Database of Systematic Reviews CD007950, third edition (PubMed publication types: Meta-Analysis, Systematic Review)
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.
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.
AI-estimated from published studies. Interpret as directional guidance.
Iodine has a higher evidence score (8.5/10 vs 8/10) and wins in 2 of 3 categories.
For prenatal support, Folic Acid has a higher relevance score (95 vs 82).
No known interactions between Folic Acid and Iodine have been documented in our database. However, always consult a healthcare provider before combining supplements.
Selenium helps; iodine can WORSEN Hashimoto’s. The honest take on "thyroid support".
What’s safe while nursing, the truth about milk-supply herbs, and what to avoid (it passes into milk).
Commonly recommended vs ask-your-clinician vs avoid — a general, safety-first overview.
The right pick depends on your goals. Answer a few quick questions for a personalised recommendation — or dig into the full evidence on each.