By Salma El-Sakka
A study published in The Lancet Planetary Health suggests that replacing dairy products with plant-based alternatives such as oat or almond milk could lead to lower intake of essential nutrients, particularly iodine, calcium, vitamin B2 and vitamin B12. Children, teenagers and women appear to be the most affected by such dietary changes.
Study details and findings
Researchers from the University of Surrey and Queen's University Belfast analysed 146 plant-based milks, 76 yoghurts and 67 cheese products. They found wide variation in fortification: only 12 per cent of products contained added iodine, 61 per cent had added calcium, 46 per cent had vitamin B12 and 19 per cent had riboflavin (vitamin B2). Even modest replacements of dairy with fortified plant-based alternatives led to declines in all four micronutrients, with iodine showing the sharpest drop.
Impact on specific groups
Modelling based on the National Diet and Nutrition Survey showed that replacing 20-35 per cent of dairy with plant-based options increased inadequate iodine intake among girls aged 14-18 from 54 per cent to 65 per cent, and among women aged 19-49 from 32 per cent to 42 per cent. A full swap raised iodine inadequacy to 80 per cent in teenage girls and 72 per cent in boys of the same age. Inadequate calcium intake rose from 30 per cent to 47 per cent in boys aged 14-18 and from 54 per cent to 70 per cent in girls. Riboflavin inadequacy in men aged 19-49 increased from 14 per cent to 26 per cent, and in women from 29 per cent to 50 per cent.
Expert commentary
Lead author Dr Sarah Bath, associate professor at the University of Surrey, said the UK is particularly vulnerable to iodine insufficiency because it lacks a universal salt iodisation policy. She noted that dairy is a major iodine source in the UK, while unfortified plant-based alternatives have very low iodine content. Co-author Dr Katie Nicol stressed that nutrition policy must evolve alongside environmental targets and that mandatory fortification could help. Professor Mairead Kiely from the Cork Centre for Vitamin D and Nutrition Research said plant-based alternatives do not contain equivalent amounts of calcium, iodine, riboflavin and vitamin B12 unless appropriately fortified.
Counterpoints
Professor Tom Sanders of King's College London cautioned that iodine deficiency cannot be reliably predicted from dietary records alone, as iodine content in plants depends on soil levels. He added that milk's iodine comes from supplemented cattle feed and that seafood is the best natural source. Emily Angus, senior dietitian at The Vegan Society, said most UK plant-based milks are fortified with calcium and vitamin D as a minimum, and that fortified alternatives are considered safe and acceptable from age one according to 2025 guidance.
Policy implications
The study suggested that mandatory fortification of plant-based foods would improve nutrient intake, though iodine inadequacy would remain high in teenage girls. Fortifying bread with iodine was shown to further reduce deficiency levels.
