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Head-to-head evidence comparison — which supplement is right for you?
Iodine and Vitamin K2 are closely matched across evidence, studies, and safety.
Verdict
Mixed evidence
4 of 12 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
12 of 15 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)
100-200mcg (MK-7)
With a meal containing fat
MK-7 (menaquinone-7)
4-12 weeks
4-8 weeks
6-12 months
1-3 years
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.
Vitamins K2 and D3 Improve Long COVID, Fungal Translocation, and Inflammation: Randomized Controlled Trial
Nutrients (2025) · Rct · n=151
The median age was 46 years; 71% were female and 29% were non-white.
The effect of vitamin K2 supplementation on bone turnover biochemical markers in postmenopausal osteoporosis patients: a systematic review and meta-analysis
Frontiers in endocrinology (2025) · Meta analysis · n=2570
Vitamin K2 (VK2) increased osteocalcin (OC; MD 1.86, 95% CI 1.17-2.56) and bone-specific alkaline phosphatase (BAP; MD 1.49, 95% CI 0.98-2.00).
Vitamin K2 in Managing Nocturnal Leg Cramps: A Randomized Clinical Trial
JAMA internal medicine (2024) · Rct · n=310
Of the 199 enrolled individuals, 108 (54.3%) were female, and the mean (SD) age was 72.3 (5.5) years.
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 meta-analyses showing 2.17% WMD improvement in lumbar BMD. Effects primarily demonstrated with MK-7 form in postmenopausal women. Combination with vitamin D3 may enhance effects.
AI-estimated from published studies. Interpret as directional guidance.
Both Iodine and Vitamin K2 are closely matched — the best choice depends on your specific health goals.
For prenatal support, Iodine has a higher relevance score (82 vs 80).
No known interactions between Iodine and Vitamin K2 have been documented in our database. However, always consult a healthcare provider before combining supplements.