University of Surrey study finds fortification could prevent nutrient losses from dairy swaps

Replacing dairy products with plant-based alternatives could reduce iodine and other micronutrient intakes under existing UK fortification practices, but adding nutrients to alternatives and bread could prevent those losses, according to research from the University of Surrey and Queen’s University Belfast.

• Researchers modeled dairy replacement using UK dietary records.
• Iodine intake was particularly sensitive to product substitution.
• Fortification could prevent declines and improve intake in vulnerable groups.

Published in The Lancet Planetary Health, the study examined partial and complete replacement of milk, yogurt and cheese, alongside policy options intended to maintain nutritional adequacy as consumers move toward more plant-based diets.

The researchers used National Diet and Nutrition Survey records from more than 3,500 people aged between 18 months and 100 years. They combined those dietary records with market information about plant-based alternatives and their fortification.

Dairy products were replaced with an equal weight of alternatives in a series of modeled scenarios. The analysis covered iodine, calcium, riboflavin and vitamin B12, examining both potential shortfalls and the possibility of excessive intake under different fortification approaches.

The results showed declines in all four micronutrients when dairy was replaced using products available under existing market fortification practices. Young children, adolescents and adult women were among the groups most affected, with iodine particularly sensitive to substitution.

At complete replacement, the modeled prevalence of inadequate iodine intake reached 80% among adolescent females and 72% among adolescent males. These were estimates of dietary inadequacy, rather than observations of clinical deficiency.

The researchers also tested whether mandatory fortification of alternatives could address the reductions. That approach prevented declines in micronutrient intake, although estimated iodine inadequacy remained high among adolescent females, at 59%.

Adding iodine-fortified bread offered another route to improving intake. In the bread-fortification scenario reported by the researchers, estimated iodine inadequacy among adolescent females fell to 37%. Combining fortification of alternatives and bread was the most effective strategy across population groups.

“Fortification of foods is one way that this could be achieved however government policy is needed to make this happen,” says Dr Katie Nicol of the University of Surrey.

The UK context is central to the findings. Dairy products are an important source of iodine in British diets, while the country lacks the universal salt iodization policies used elsewhere. The nutritional effect of replacing dairy therefore depends partly on what replaces that source of iodine.

The study also highlights the difference between preventing an additional shortfall and addressing inadequacy that already exists. Fortifying an alternative to match a dairy product can preserve its contribution, but does not necessarily resolve low intake across the rest of a person’s diet.

Independent experts responding through the Science Media Centre welcomed the examination of partial replacement, which reflects how consumers may change their diets, while emphasizing the limits of the modeling.

Professor Ian Givens, Emeritus Professor of Food Chain Nutrition at the University of Reading, says the findings show “a risk of inadequacy rather than confirming deficiency”.

He also noted that plant-based products differ in their fortification and change over time, meaning the estimated effect depends on the products consumers select.

Dr Pauline Scheelbeek, Associate Professor in Planetary Health and Nutritional Epidemiology at the London School of Hygiene & Tropical Medicine, highlighted the study’s assessment of available solutions. However, she cautioned that mandatory iodine fortification of bread would require a careful assessment of benefits and risks, including effects on people whose intake is already adequate.

The distinction is relevant to how the results are applied. This was a simulation of food replacement, rather than an intervention in which participants changed their diets and researchers measured subsequent health outcomes. Consumers might also adjust other foods when reducing dairy, something a direct substitution model cannot fully capture.

Product composition is another consideration. The analysis used dietary records from 2016-2019 and market information from 2020, so its estimates do not describe every alternative currently on sale.

A separate UK supermarket survey published in the British Journal of Nutrition in 2026 illustrates that changing market. It found that iodine fortification of non-organic milk alternatives rose from 28% in 2020 to 48% in 2024. Fortification remained much less common in yogurt and cheese alternatives, at 5% and 4%, respectively, in 2024.

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