Anyone of a certain advanced age remembers iodine as the common medicine cabinet treatment for cuts and scrapes. Tincture of iodine is an effective topical antiseptic for wounds. It can sting at first, and may stain the skin or clothes.
Iodine, from food, is a nutrient. The recommended intake is small: 150 micrograms per day for an adult (that’s 0.15 mg). But unfortunately modern dietary habits are negatively impacting our intake from food.
I came across an article recently about the alarming decrease in iodine intake by pregnant women. Inadequate iodine intake can spell major trouble for a developing fetus, particularly for brain development, leading to cognitive impairment. While older people, such as myself, don’t need to worry about the negative impacts on fetal brain development, we definitely do need to worry about the negative impact of inadequate iodine on their own health. The iodine atom is critical for thyroid hormone structure. If iodine is lacking, less of this hormone is made. Negative effects on adults can include: cold intolerance, easy fatigue, constipation, apathy/low mood, sleepiness, weight gain. None of that sounds very attractive.
Diet vs. Iodine
What is it about 21st century diets that decreases iodine intake?
- People are eating fewer dairy foods. Milk, yogurt and cheese are good sources of iodine. When you replace cow’s milk with almond or oat milk, iodine intake is drastically reduced. You get the same negative effect If you switch to yogurt and cheese substitutes.
- Egg avoidance. We’ve been told to avoid eggs for decades thanks to the belief that eggs cause heart disease. Eggs are a very good source of iodine (see chart below).
- Salt avoidance. Cutting back on salt cuts out a key source of iodine — iodized salt. You can get a day’s worth of iodine from 1/2 tsp of iodized salt used on foods.
- Not choosing iodized salt. In the U.S. we do not have mandatory fortification of salt with iodine. When buying salt, you need to pay attention to the label, which clearly states whether the salt contains iodine.
- Switching to fashionable sea salt, kosher or other exotic salts. Most of these are not iodized at all, so they have zero iodine.
- Assuming food processors use iodized salt. They do not, unless the package specifically lists “iodized salt” in the ingredients. Your canned soup or chicken nugget lunch might be salted, but not with iodized salt.
What about seaweed?
Seaweed does contain higher levels of iodine than other foods.* The chemical form of iodine in seaweed varies from one species to another, and is generally less well absorbed than the iodine added to salt. If you’re a big seaweed fan, you might be consuming a sufficient amount. One popular dried seaweed snack claims that a 4 g serving provides almost 1/3 of the recommended daily iodine intake.
*NOTE: excess iodine is not a good idea either, and overeating seaweed products could contribute to that.
|food||serving size||micrograms iodine|
|table salt, iodized||1 tsp||310|
|table salt, not iodized||1 tsp||0|
|sea salt||1 tsp||0|
|kosher salt||1 tsp||0|
|milk, 2%||8 oz cup||97|
|milk, whole||8 oz cup||94|
|miso broth||8 oz cup||76|
|yogurt, plain whole milk||1/2 cup||35|
|almond milk||8 oz cup||0|
|soy milk||8 oz cup||0|
|shrimp, cooked||3 oz||13|
|cod, cooked||3 oz||146|
|tuna, canned in water||3 oz||8|
|seaweed snack||4 grams dried||60 – 48000**|
**Of seaweed tested in one study, Kombu had the highest iodine levels; Nori had the lowest.
Many multi vitamin/mineral supplements also contain iodine, frequently the entire days recommended intake. If you do take a multiple, check the label for iodine content.
What to do?
- Buy iodized salt for use in home cooking.
- Include dairy foods and eggs in your diet, unless you have a known allergy to those foods. Added benefit: plenty of other nutrients you might be lacking, like protein, calcium and B12.
- If you use a multiple vitamin/mineral, buy a brand that contains iodine.
- If you like seaweed snacks, enjoy! But don’t deliberately over do those thinking you’ll be better off with even more iodine.
- Eat fewer processed foods. That way you avoid the non-iodized added salt; you can add your own salt to foods.
Finally: Yes iodine is a critical component of thyroid hormone, but you can’t boost your metabolism by taking excess iodine. With iodine, as with other nutrients, over-consuming beyond your needs won’t improve your health.