The growth of the plant milk market is nothing short of amazing. Given the variety of options, it’s easier than ever to switch out cow’s milk for a more compassionate alternative.

But as these milks become more popular it’s natural (and important) to ask questions about how replacing cow’s milk with plant milks might affect nutrient intake.

In a study published this month in the British Journal of Nutrition, researchers looked at iodine content of plant milks in the United Kingdom. Iodine is a mineral needed for healthy thyroid function. Deficiency in pregnancy or early childhood can have lifelong effects on learning and development in children. In adults, chronic deficiency may affect mental function and it might raise risk for one type of thyroid cancer.

The researchers looked at 47 plant milks from 20 brands. They included milk made from soybeans, almonds, coconut, oats, rice, hazelnuts and hempseed. Except for the three samples that were fortified with iodine, all of the plant milks came up short compared to cow’s milk. It’s a legitimate concern because in both the UK and US, cow’s milk is a significant source of dietary iodine. This is largely due to farming practices since iodine is added to the diets of the cows and is also in the solutions used to clean the cows and milking equipment (which leach into the milk itself).

Aside from cow’s milk, the best sources of iodine are fish, sea vegetables, some commercial breads, and iodized salt. Although most plant foods contain some iodine, the amount varies depending on where the foods are grown, and it tends to be fairly low.


Iodine Recommendations for Vegans

Given the role that cow’s milk has traditionally played in iodine nutrition, it would be good for companies producing plant milks to fortify them with small amounts of iodine. Until that happens, vegan experts recommend either of two options for getting adequate iodine.

  • Include approximately ¼ teaspoon of iodized salt in your diet every day. Note that, although salt is iodized by law in Canada, it’s optional in the US and the UK (and it’s not commonly iodized in the UK) so you need to read labels. Sea salt may be iodized, but it usually isn’t. Kosher salt is not iodized. The salt used in production of processed foods is rarely iodized.
  • Or, take a small iodine supplement providing 75-150 micrograms of iodine every two to three days.

Some vegan advocates suggest regular consumption of sea vegetables as a source of iodine. This is probably not the best option, though, since iodine content of these foods varies widely. The British plant milk study included two samples that had added sea vegetables in their ingredients. Both were still low in iodine. In contrast, batches of soymilk fortified with the sea vegetable kombu were taken off the market in Australia and New Zealand several years ago because of dangerously high iodine contents. This doesn’t mean you shouldn’t consume sea vegetables, but it’s probably wise to limit them to a few servings per week and to not depend on them for iodine. Avoid iodine supplements that are made from kelp for the same reasons.

None of this is an indictment against plant milks or vegan diets and it’s certainly not some big cause for concern. A vegan diet simply represents a different way of meeting nutrient needs. It’s good to have the information that this study provides so that we can do what we need to do to ensure the health of vegans. I’m more than happy to sprinkle a little iodized salt on my beans if it helps the cows. (It also makes the beans taste better.)

For more on iodine in vegan diets see this article on Vegan Health.