Swapping dairy for plant-based milk could leave teenagers short of iodine and calcium, study warns

Swapping dairy for plant-based milk, yoghurt and cheese could leave many people short of key nutrients, especially teenagers and young women, a new UK study suggests.

Researchers from the University of Surrey and Queen’s University Belfast found that many plant-based products are not fortified with iodine, calcium or B vitamins, which dairy naturally provides. The study is published in The Lancet Planetary Health.

What did the study find?

The team used food data from more than 3,500 people in the National Diet and Nutrition Survey and modelled what would happen if people swapped some or all of their dairy for plant-based alternatives.

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If teenagers swapped all their dairy, the share of girls aged 14 to 18 not getting enough iodine would rise to 80%, and to 72% for boys of the same age. Calcium shortfalls among teenage girls would rise from 54% to 70%, and among teenage boys from 30% to 47%.

Even swapping just 20 to 35% of dairy raised iodine shortfalls in teenage girls from 54% to 65%, and in women aged 19 to 49 from 32% to 42%. Shortfalls in riboflavin, or vitamin B2, among women would rise from 29% to 50% with a full swap.

Why does iodine matter?

Iodine is needed to make thyroid hormones and is especially important before and during pregnancy for a baby’s brain development. Lead author Dr Sarah Bath said the UK is particularly vulnerable because, unlike many countries, it has no policy of adding iodine to table salt.

What do the researchers want?

They are calling for mandatory fortification of plant-based dairy alternatives. Their modelling suggests this would help, though iodine would still be too low for 59% of teenage girls, and adding iodine to bread would help further. Co-author Dr Katie Nicol said nutrition policy must keep pace with environmental goals without harming public health.

Not everyone agrees

Professor Tom Sanders of King’s College London said iodine deficiency cannot be reliably predicted from diet records, and that seafood is the best natural source. The Vegan Society said most UK plant milks are already fortified and advises people to choose fortified versions.

What should you do?

If you use plant-based milk, check the label for added calcium, iodine, vitamin B12 and riboflavin, and choose fortified versions where you can, especially for teenagers and anyone planning a pregnancy. If you are worried about your diet, speak to your GP or a dietitian.

Sources: University of Surrey and Queen’s University Belfast study in The Lancet Planetary Health, LBC, Irish Examiner. This is general information, not medical advice.