A Plain Jane among supplements, iodine is easy to take for granted. After U.S. salt manufacturers began iodizing their salt in the 1920s, iodine deficiency practically disappeared. But a flurry of studies have brought iodine back into the nutritional spotlight.
A recent study, published this spring in the British Journal of Nutrition, monitored 100 pregnant women in England and found, surprisingly, that two-thirds of them were mildly to moderately iodine deficient, particularly if they were non-milk drinkers. “Our findings suggest that women should be given advice about iodine before and during pregnancy,” the researchers wrote.
Another study, cited in the BMJ, linked iodine deficiency in pregnancy with later poor cognitive outcomes in children. That study was longitudinal; it assessed children at age 8. The children whose mothers had been iodine deficient during their pregnancies had lower IQs and reading abilities than the children of women who had sufficient iodine.
This month, the American Academy of Pediatrics came out with its first statement on iodine. It noted that one-third of pregnant and breastfeeding mothers in the U.S. are iodine deficient. The group recommends that expectant and lactating women take a supplement that contains at least 150 micrograms of iodide and use iodized table salt. If the mother is vegan or does not consume dairy or fish, she may also need more intense monitoring of her iodine levels, which is done via a urine test.
Iodine is a micronutrient crucial not just to developing babies but also to adults as well, helping the thyroid gland function to regulate the body’s metabolism and hormones correctly. You might assume Americans get plenty of iodine these days, with our high sodium diets and tendency to pop multivitamins. But prenatal vitamins, for example, don’t necessarily have iodine in them, and while processed foods are certainly high in sodium, they don’t usually contain iodized salt. Home-cooked food with table salt provides more iodine than a processed frozen meal. Sea salt, more popular than ever, isn’t always fortified with iodine, and another past source, bread, is no longer boosted with iodine.
Symptoms of iodine deficiency in adults can include fatigue, depression, a weakened immune system, and weight gain, as well as the most obvious symptom, an enlargement of the thyroid gland in the neck called goiter. The recommended daily dose of iodine is 150 micrograms for adults, 220 micrograms for pregnant and 290 micrograms for lactating women, according to the National Institutes of Health.
If you want to get iodine from food, rather than supplements or iodized salt, eat sea vegetables such as kelp and nori. Intriguingly, in Pen Tsao, the herbal of the Chinese pharmacopoeia published in 1596, seaweed is mentioned as useful in the treatment of goiter. Other good sources include dairy products such as milk, yogurt, eggs and cheese, and saltwater seafood, though the concentration can vary quite a bit from fish to fish. Cod, for example, has more iodine than canned tuna or shrimp. Strawberries are another good source of iodine.
Iodine has also been cited as a way to keep breasts healthy: Iodine supplementation can reduce some painful symptoms of fibrocystic breast disease, and a study published in the International Journal of Medical Sciences suggested that iodine may protect against breast cancer, via its anti-estrogen effects.
Lastly, iodine can also help protect against toxins. In its statement this June, the American Academy of Pediatrics noted that sufficient iodine levels can protect babies against some environmental pollutants, such as thiocyanate and nitrates in cigarette smoke, and perchlorate in drinking water. Please pass the salt!
Kathryn Drury Wagner is a freelance editor and writer based in Los Angeles. Her book for young readers, Hawaii’s Strangest, Ickiest, Wildest Book Ever! came out last fall.