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Salt of the Earth: Why Iodine Matters

  • Writer: Timothy P. Smith MS, RD, LDN
    Timothy P. Smith MS, RD, LDN
  • Aug 17
  • 3 min read
Seaweed is a great source of iodine.
Seaweed is a great source of iodine.

What is Iodine?

Iodine is a trace mineral your body needs in small amounts—but its impact on your health is anything but small.


It plays a critical role in thyroid function, the health of your metabolism, and your overall well-being. Unfortunately, many Americans don’t get nearly enough iodine, especially if they avoid iodized salt, or live in regions with iodine-poor soil.


Iodine and the Thyroid

Your thyroid gland—located at the base of your neck—uses iodine to produce two key hormones: thyroxine (T4) and triiodothyronine (T3). These hormones regulate many aspects of metabolism, energy production, and even body temperature. Without enough iodine, the thyroid can’t make adequate hormone levels, which may lead to hypothyroidism. Symptoms of hypothyroidism include fatigue, weight gain, dry skin, and slowed heart rate. In severe cases, iodine deficiency can cause goiter, an enlargement of the thyroid gland.


For pregnant and breastfeeding women, iodine is especially critical. Thyroid hormones are essential for fetal brain and nervous system development, and deficiency during pregnancy can increase the risk of developmental delays.


How Much Iodine Do You Need?

The Recommended Dietary Allowance (RDA) for adults is 150 micrograms (mcg) per day, with higher needs during pregnancy (220 mcg) and lactation (290 mcg) (National Institutes of Health [NIH], 2022). Because iodine is not stored in large amounts in the body, it’s important to get it regularly through diet.


Food Sources of Iodine

  • Iodized salt – Just ¼ teaspoon can provide nearly the full daily requirement.


  • Seafood – Fish, seaweed, and shellfish are naturally rich in iodine due to the ocean’s mineral content.


  • Dairy products – Milk, yogurt, and cheese often contain iodine from cow feed and sanitizing solutions used in dairy processing.


  • Eggs – Particularly the yolks, which contain iodine from the hen’s diet.


It’s worth noting that “gourmet” salts such as sea salt or Himalayan pink salt are typically not fortified with iodine unless labeled as such.


Risks of Too Little—or Too Much—Iodine

Too little iodine can cause hypothyroidism, goiter, and—in children—impaired growth and cognitive development. Globally, iodine deficiency remains a leading cause of preventable intellectual disability (World Health Organization [WHO], 2014).


Too much iodine can also disrupt thyroid function, potentially leading to hyperthyroidism or hypothyroidism, especially in individuals with pre-existing thyroid conditions. The tolerable upper intake level for adults is 1,100 mcg per day (NIH, 2022).


Practical Tips for Maintaining Healthy Iodine Levels

  1. Use iodized salt in moderation—remember, you don’t need much.

  2. Incorporate seafood into your diet 1–2 times per week.

  3. Check labels on specialty salts or plant-based milks to see if they are fortified.

  4. Be mindful with supplements—too much iodine can be just as problematic as too little.

  5. Discuss your needs with a healthcare provider, especially if you have a thyroid condition or are pregnant.


The Bottom Line

Iodine might not get as much attention as other nutrients, but it’s a cornerstone of healthy thyroid function and metabolic health. By including iodine-rich foods in your diet—and being aware of your individual needs—you can help protect your energy, hormonal balance, and long-term well-being.


Thank you for reading,


Tim Smith MS, RD, LDN




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References

  1. National Institutes of Health. (2022). Iodine: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional

  2. World Health Organization. (2014). Iodine deficiency. https://www.who.int/news-room/fact-sheets/detail/iodine

  3. Zimmermann, M.B., & Boelaert, K. (2015). Iodine deficiency and thyroid disorders. The Lancet Diabetes & Endocrinology, 3(4), 286–295. https://doi.org/10.1016/S2213-8587(14)70225-6

  4. Pearce, E.N., et al. (2016). Consequences of iodine deficiency and excess in pregnant women: An overview of current knowns and unknowns. The American Journal of Clinical Nutrition, 104(suppl_3), 918S–923S. https://doi.org/10.3945/ajcn.115.110429

 
 
 

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