Plant-based dairy swaps may lower iodine intake

UK researchers found in a Lancet Planetary Health study, reported by Healthline on Nov. 9, that only 12% of analyzed UK plant-based milk, yogurt and cheese products carried iodine fortification.

The finding matters because the same product set was more often fortified with calcium, at 61%, and vitamin B12, at 46%, while modeling suggested iodine inadequacy could rise after a 20% dairy replacement.

The study combined an analysis of UK plant-based milk, cheese and yogurt alternatives with dietary data from 3,500 people. Researchers used statistical modeling to estimate how replacing dairy with plant-based alternatives would affect iodine and other nutrients, rather than measuring iodine status directly.

In the model, replacing 20% to 35% of dairy with plant-based alternatives raised the estimated share of adolescent females with inadequate iodine intake to 65% from 54%. For females ages 19 to 49, the estimated share rose to 42% from 32%.

When researchers modeled full dairy replacement, the estimated inadequacy rate among adolescent females reached 80%. Among females ages 19 to 49, the share was reported as relatively stable as replacement increased.

“People often worry about a decline in calcium intake when they replace some of their dairy with plant-based alternatives. As a result, iodine is frequently overlooked. This study serves as a valuable reminder of iodine’s significance as a nutrient,” said Victoria Finn, a board-certified endocrinologist at Medical Offices of Manhattan who was not involved in the study.

Iodine is used by the thyroid to make thyroid hormones, which help regulate metabolism and support growth and development. Low intake over time can contribute to hypothyroidism, a condition in which the thyroid does not produce enough hormone; symptoms can include lethargy, sleepiness, weight gain and dry skin.

The pregnancy issue is more specific. Finn said hypothyroidism can be “particularly dangerous during pregnancy, as the baby’s brain, nervous system, and organs rely heavily on the mother’s thyroid hormone during the early stages of development.”

The study’s results apply most directly to UK foods and UK dietary patterns. In the United Kingdom, dairy is a major iodine source because cattle feed is supplemented, not because milk products are inherently high in iodine. The United States may differ because iodized salt is widely available, while iodine fortification of plant-based dairy alternatives remains voluntary under Food and Drug Administration guidance.

The study cannot show that people who switch to plant-based dairy alternatives will develop iodine deficiency or thyroid disease. It modeled dietary intake and product composition; it did not directly test blood, urine or thyroid outcomes after people changed diets.

For readers using plant-based dairy alternatives, the research supports checking labels for iodine fortification and considering overall dietary iodine sources such as seafood, eggs and iodized salt when those foods fit the diet. Finn said iodine supplements warrant caution, especially without thyroid testing, and added that kelp supplements can vary in iodine content.

Source: Healthline News article summarizing a Lancet Planetary Health study, Nov. 9, 2026.

Atlas360 reports health research and does not provide medical advice.