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How much iodine is added to common table salt in the United States?
Executive Summary
The typical iodine content added to U.S. table salt is about 45–47 milligrams of iodine per kilogram of salt (roughly 45 micrograms per gram), aligning with the FDA-recommended target range of 46–76 mg I/kg, though many retail samples fall below the target (median ~44.1 mg/kg, mean ~47.5 mg/kg) [1] [2]. U.S. regulations permit addition of iodine as potassium iodide, potassium iodate, or cuprous iodide up to 0.01%, and labeling is required to indicate whether salt is iodized; but actual, measured iodine in commercial products varies by brand, container, and storage conditions [3] [2].
1. Why the numbers matter: what studies measured at the shelf say about iodine levels
A U.S.-based measurement study published in 2008 tested retail table salts and found a median iodine content of 44.1 mg/kg and a mean of 47.5 mg/kg, with 47 of 88 samples below the FDA-recommended 46–76 mg/kg range and six exceeding it, demonstrating substantial product-level variation [2]. The same analysis reported freshly opened container values near 45 mg I/kg, but also documented that humidity exposure and within-container heterogeneity drive iodine loss over time. These empirical measurements indicate that while the industry target and regulatory allowance center around about 45 mg/kg, consumers may encounter lower or higher levels depending on product and storage, making the “typical” value an approximate rather than absolute guarantee [1] [2].
2. What regulators allow and recommend: the FDA framework and its implications
The U.S. Food and Drug Administration permits manufacturers to add iodine to salt in the form of potassium iodide, potassium iodate, or cuprous iodide, with a regulatory allowance up to 0.01% for added iodine compounds and mandatory labeling when salt is iodized [3]. The FDA-recommended fortification target commonly cited is 46–76 mg iodine per kilogram of salt, a range designed to help populations meet a recommended daily iodine intake (150 µg for adults) while accounting for variable salt consumption. The regulatory framework therefore sets an upper legal boundary and a target range, but does not guarantee uniform iodine content across all retail products, leaving room for divergence between intended fortification levels and measured retail values [3] [2].
3. Practical translation: how much iodine per teaspoon and dietary context
Converting lab values to household measures, iodized salt at ~45 mg/kg supplies about 45 µg of iodine per gram of salt, so a half to three-quarters teaspoon of iodized salt can provide a substantial fraction of the 150 µg recommended daily iodine intake [4] [5]. Public-health messaging emphasizes that many Americans obtain iodine from other dietary sources—ocean-caught fish, dairy products, eggs, and certain breads—so iodized salt is one of several contributors to iodine status. Different salts sold at retail—regular iodized table salt, kosher salt, and many sea salts—vary in iodization status, with about half the retail market iodized according to available sales analyses, and consumers who use non-iodized specialty salts may not receive this source of iodine [6] [5].
4. Points of disagreement and data gaps: where sources diverge and what’s missing
Available sources agree that ~45 mg/kg is a practical central value but diverge on prevalence and consistency: the 2008 measurement study found many products outside the FDA target window, while regulatory texts emphasize allowable additives and labeling rather than routine enforcement testing [2] [3]. Published guidance and consumer-facing outlets round numbers differently—some state 0.01% KI or approximate 25–40 mg/kg—reflecting different assumptions about compound conversion and whether potassium iodide or iodate is used [7] [8]. Crucial gaps remain: up-to-date, large-scale retail surveys are limited, and temporal loss of iodine during storage is variably quantified, so current on-shelf iodine levels across brands and distribution channels are not uniformly documented [1] [2].
5. What to watch and how to interpret these figures as a consumer or policymaker
For consumers, the practical takeaway is that iodized table salt generally supplies about 45 µg iodine per gram, but actual intake depends on salt amount used, product iodization, and storage [1] [4]. Policymakers and public-health officials should note that while FDA rules permit fortification and require labeling, measured deviations in retail products and storage-related losses suggest a role for periodic, standardized monitoring of iodized salt in the marketplace. Researchers and advocates who emphasize micronutrient sufficiency may push for clearer labeling of iodine content and updated surveillance studies to ensure that population iodine needs are reliably met given changing dietary patterns and the growing use of non-iodized specialty salts [2] [3].