Swapping even part of the milk, yogurt and cheese in your diet for unfortified plant-based alternatives could leave you short of key nutrients, especially iodine, according to a U.K. modelling study published in The Lancet Planetary Health.
Researchers at the University of Surrey and Queen’s University Belfast used food records from more than 3,500 people aged 18 months to 100 years in the U.K.’s National Diet and Nutrition Survey. They modelled what would happen if dairy were replaced, partly or fully, by an equal weight of plant-based alternatives currently sold in U.K. supermarkets. They looked at four nutrients that dairy supplies: iodine, calcium, riboflavin (vitamin B2) and vitamin B12.
Iodine falls fastest
Even modest substitution caused marked drops in all four nutrients. Iodine was the most sensitive. Replacing just 20 to 35 per cent of dairy raised the share of teenage girls with inadequate iodine intake from 54 to 65 per cent, and the share of women aged 19 to 49 from 32 to 42 per cent. With full replacement, 80 per cent of teenage girls and 72 per cent of teenage boys would fall short.
Iodine is needed to make thyroid hormones, which regulate metabolism and support growth and brain development. It’s especially important before and during pregnancy. In the U.K., dairy is a major source of iodine, and unfortified plant-based drinks contain very little.
“The UK is particularly vulnerable to iodine insufficiency due to a lack of an iodine fortification policy such as universal salt iodisation, which many other countries have,” said lead author Sarah Bath.
Fortification helps, but not completely
Requiring plant-based alternatives to be fortified prevented most of the drop in nutrients. But iodine intake still fell short for 59 per cent of teenage girls. Adding iodine to bread worked better, cutting the share to 37 per cent. The researchers say combining mandatory fortification of plant-based alternatives with iodine-fortified bread would be the most effective approach.
“Nutrition policy must evolve in tandem with environmental targets,” Bath said. Shifts to more sustainable diets shouldn’t come at the expense of public health, she added, and government policy is needed to make fortification happen.
The Canadian context
The study modelled the U.K. food supply, where salt isn’t routinely iodized. Canada has long required table salt to be iodized, so dietary patterns and risks here differ. Still, the findings are a reminder to check labels: plant-based drinks and yogurts vary widely in what’s added to them.
Source: “The impact of replacing dairy products with plant-based dairy alternatives on iodine and other micronutrients: a modelling study and evaluation of policy options to support population intake,” The Lancet Planetary Health, 2026. doi:10.1016/j.lanplh.2026.101515; University of Surrey news release, Nov. 4, 2026.
