Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Adequate dietary iodine is required for normal thyroid function. In fact, the two thyroid hormones are named after how many iodine atoms they contain: T3 and T4. Given that iodine is extensively stored in the thyroid gland itself, it’s not something you have to get every day, but your overall diet needs to have some good source. Unfortunately, the common sources aren’t particularly health-promoting: iodized salt and dairy foods (because iodine-based cleansers like betadine are used to sanitize the udders, which results in some iodine leaching into the milk). They also add iodine to cattle feed, and some commercial breads have iodine-containing food additives.

So, if you put people on a paleo-type diet, and cut out dairy and table salt, they can develop an iodine deficiency, even though they double their seafood intake, which can also be a source. What about those switching to diets centered around whole plant foods? They’re also cutting down on ice cream and Wonder Bread, and if they’re not eating anything from the sea––seaweed; sea vegetables—they can run into the same problem.

Her parents reported striving to feed her only the healthiest foods. The three-year-old only got plant-based, unsalted, unprocessed foods with no vitamin supplementation. Now, that could be deadly. With no vitamin B12, those on strictly plant-based diets can develop irreversible nerve damage, but in this case, a goiter arose first due to inadequate iodine intake.

Here’s another case of “veganism as a cause of iodine deficient hypothyroidism” in a toddler after weaning. Before weaning, he was fine, because his mother kept taking her prenatal vitamins, which luckily contained iodine.

Most vegetarians and vegans are apparently unaware of the importance of iodine in pregnancy, just as clueless as their omnivorous counterparts. The American Thyroid Association and the American Academy of Pediatrics have recommended that women even just planning on getting pregnant should ingest a daily supplement that contains 150 micrograms (mcg) of iodine, yet only 60 percent of prenatal vitamins marketed in the U.S. contain this essential mineral. So, in spite of the recommendations, about 40 percent lack it. Therefore, it is extremely important that pregnant and breastfeeding women read the labels to ensure that they are receiving an adequate amount.

Women of reproductive age have an average iodine level of 110 mcg/liter, which is fine for nonpregnant individuals, but we’d really like to see at least 150 mcg/liter in pregnancy. (It’s basically a 24-hour urine test, in which iodine sufficiency is defined as 100 mcg/liter of pee in nonpregnant adults, which your average vegan fails to reach in the largest study done to date, out of Boston.)

The recommended average daily intake is 150 mcg/day for most people, which you can get in like a cup and a half of cow’s milk. Sadly, plant-based milks are typically not fortified with iodine, averaging only about 3 mcg/cup. In the largest systematic study to date, although many plant-based milks are fortified with calcium, they only found just three of 47 fortified with iodine. Those that were had as much as cow’s milk, but those that weren’t fell short.

Plant-based milk companies brag about enriching their milks with calcium, and often vitamin B12, vitamin D, and vitamin A, but only rarely are attempts made to match the iodine content. The only reason cow’s milk has so much is that they enrich the feed, or it comes dripping off the udders. So, why don’t plant-milk companies add iodine, too? I was told by a food scientist at Silk that my carrageenan video played a role in them switching to another thickener. Hopefully, they’ll see this video and consider adding iodine too, or some company will snatch at the market advantage opportunity.

The researchers conclude that individuals who consume plant-based milks not fortified with iodine may be at risk for iodine deficiency, unless they consume alternative dietary iodine sources, the healthiest of which is sea vegetables––which we’ll cover next.

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