Replacing dairy with plant-based milk, cheese and yoghurt in the dairy vs vegan milk nutrition study was linked to lower iodine intake and a rise in deficiency, especially for adolescent girls and women aged 19 to 49. The study, published in Lancet Planetary Health, modeled the effect of partial and full swaps in the UK.
Sarah Bath, an associate professor in public health nutrition at the University of Surrey, said the groups at risk and with the lowest intakes were young women and women of childbearing age. She said: "There are known health effects of iodine deficiency and that’s why we want to raise awareness of this".
Bath and the UK model
The researchers looked at 146 non-dairy milks, 76 yoghurts and 67 cheeses on the UK market. They found that replacing a fifth to a third of dairy intake with plant-based alternatives would push iodine deficiency from 54% to 65% in adolescent girls, and from 32% to 42% in women aged 19 to 49.
Bath said: "The population groups that seem to be at risk and have the lowest intakes were the young women and women of childbearing age, and that’s the key life stage where iodine is particularly important." The same modeling found that swapping a third of dairy intake for vegan alternatives could cut iodine intake by 9% to 21%.
Plant-based products and fortification
The study also found falls in calcium, riboflavin and vitamin B12 if the substitutes were not fortified. Of the plant-based products reviewed, 61% had added calcium, 46% had added vitamin B12, 19% were fortified with riboflavin and 12% with iodine.
That split matters because the UK does not have a formal requirement for vegan alternatives to be fortified with micronutrients, even though children get about half of their iodine from dairy products and adults get about a third. Some products already make up the gap: Danone said its core range of Alpro products was fortified for calcium, iodine and vitamins B2 and B12, and Oatly said all its unflavoured, non-organic oat drinks were fortified with nutrients including iodine, calcium, riboflavin and vitamins B12 and D.
Danone and Oatly
Caroline Orfila Jenkins, vice-president for science and technology at Oatly, said: "This research underlines the importance of appropriate fortification as diets become more plant-based". The study’s findings suggest that if consumers replace dairy without checking the label, the nutritional trade-off is not the same across brands or product types.
The clearest pressure point is iodine. The study found inadequate iodine levels could reach 80% in teenage girls and 72% in teenage boys with a full switch to non-dairy alternatives, so the practical choice for families is not simply whether to buy plant-based products, but whether those products carry iodine fortification. The remaining question is how much fortification across non-dairy alternatives would be needed to eliminate the modeled deficit.
