Swapping dairy for plant-based milk could cut iodine intake, study finds

What the study found

A Lancet Planetary Health paper argues that switching from dairy to plant-based foods could leave people short of vitamins and minerals, and that even a partial switch carries the risk. The analysis came from researchers at the University of Surrey and at Queen's University Belfast, with Dr Sarah Bath as lead author. The team reviewed 146 plant-based milks, 76 yoghurts and 67 cheese products, and tracked iodine, calcium and vitamins B2 and B12. Iodine showed the sharpest decline of the four nutrients. Fortification was patchy: 12% of the products had added iodine, 61% had added calcium, 46% had added vitamin B12 and 19% had added riboflavin (vitamin B2).

Calcium61%

Vitamin B1246%

Riboflavin (B2)19%

Iodine12%

Calcium

61 %

Vitamin B12

46 %

Riboflavin (B2)

19 %

Iodine

12 %

Data from the article text

Iodine and the young women most exposed

The thyroid gland needs iodine to make hormones, and a shortfall can bring tiredness, weight gain and poorer brain function. The UK does not add iodine to table salt, so dairy has long been a major source, since cattle feed is supplemented with the mineral. The modelling found that swapping 20-35% of dairy products for plant-based ones lifted the share of girls aged 14-18 with inadequate iodine intake from 54% to 65%, and the share of women aged 19-49 from 32% to 42%. Under a full swap the figure reached 80% for teenage girls and 72% for boys of the same age. Children get about half their iodine from dairy and adults about a third, and more than half of UK teenage girls already fall short, the researchers said.

Usual diet54%

20-35% of dairy swapped65%

All dairy swapped80%

Usual diet

54 %

20-35% of dairy swapped

65 %

All dairy swapped

80 %

Data from the article text

Bath linked the risk to the UK's lack of salt iodisation.

“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.”

Calcium, riboflavin and vitamin B12

Calcium supports bone and tooth health and muscle contraction, including the heartbeat. Under a full swap, inadequate calcium intake climbed from 30% to 47% among boys aged 14-18 and from 54% to 70% among girls of the same age. Riboflavin followed a similar pattern, with inadequacy in men aged 19-49 rising from 14% to 26% after a full swap, and in women from 29% to 50%. Half-swapping still lifted the women's figure to 39%. B12 supports nerve function and blood cell health, and there is no formal requirement in the UK for plant-based alternatives to be fortified with micronutrients.

Official guidance and the climate push

The NHS describes cheese and butter as high in saturated fat, which is bad for the heart, and advises people to choose low-fat milk or plant substitutes. Oat milk is generally the most popular plant-based choice. The UK Climate Change Committee, which advises the government, has net zero goals that include a one-fifth cut in meat and dairy consumption by 2030 and a one-third drop by 2050. Ty Beal, a food researcher at the Swiss Global Alliance for Improved Nutrition who was not involved in the study, took a firm view of strict dairy removal. Beal said:

“Strictly cutting out [dairy] is extreme. Even reducing it is a risk.”

What researchers want next

The researchers want vegan dairy alternatives fortified, with iodine a priority. Bath said that young women and women of childbearing age had the lowest intakes, and that this life stage matters because iodine plays a particularly important role in it. Katie Nicol, a research fellow at the University of Surrey, co-authored the paper, and the UCC Cork Centre for Vitamin D and Nutrition Research also contributed. Iodine-fortified products made up only 12% of the items studied. Children, teenagers and pregnant or breastfeeding women need more iodine to support brain development, which is why the risk is considered especially high for them.