A new study reveals that even partially replacing dairy products with plant-based alternatives could significantly reduce the intake of essential nutrients.
Replacing even a modest amount of dairy with plant-based alternatives could significantly reduce essential nutrient intake, according to a new study from the University of Surrey. Researchers found that substituting just 20% to 35% of dairy products increased the estimated prevalence of inadequate iodine intake among adolescent girls from 54% to 65%. Among women ages 19 to 49, the figure rose from 32% to 42%.
The study also identified reductions in calcium, riboflavin, and vitamin B12 intake. However, researchers found that fortifying plant-based alternatives and other foods could help prevent these nutritional shortfalls.
How Plant-Based Alternatives Affect Nutrient Intake
In the first UK study of its kind, researchers from the University of Surrey and Queen’s University Belfast analyzed dietary data from more than 3,500 people, ages 18 months to 100 years. Using the National Diet and Nutrition Survey, they modeled how replacing milk, yogurt, and cheese with commercially available plant-based alternatives would affect intake of four essential micronutrients.
Dr Katie Nicol, a research fellow at the University of Surrey and co-author of the study, explained:
“With the growing need to address environmental sustainability, many dietary recommendations are focused on plant-based diets and the reduced intake of animal products.”
“With the rise in plant-based alternative foods, we need to know whether they are like-for-like replacements for the micronutrients that are found in dairy products. This is particularly important for vulnerable groups, including young children and adolescent females, who are more likely to be deficient in certain micronutrients, which could affect their overall health.”
Why Iodine Deficiency Is a Major Concern
Iodine was the nutrient most affected by dairy replacement. When researchers modeled completely replacing dairy with plant-based alternatives under current fortification levels, the estimated prevalence of inadequate iodine intake reached 80% among adolescent girls and 72% among adolescent boys. These figures reflect modeled dietary inadequacy, not confirmed clinical deficiencies.
Iodine is essential for producing thyroid hormones, which regulate metabolism and support growth and brain development. It is particularly important before and during pregnancy, when iodine requirements increase.
Dr Sarah Bath, associate professor at the University of Surrey and lead author, said:
“The UK is particularly vulnerable to iodine insufficiency due to a lack of an iodine fortification policy such as universal salt iodization, which many other countries have.”
“People may also be unaware of the importance of iodine, which is needed to make thyroid hormones to regulate our metabolism, support healthy growth, and brain development. Iodine is particularly important during pregnancy, when the requirement increases, but it is also essential prior to pregnancy to ensure that stores are optimized. People are also unaware that dairy products are a major source of iodine, particularly in the UK, and that plant-based alternatives, unless fortified, have a very low iodine content.”
Fortified Foods Could Reduce Nutritional Risks
The researchers found that mandatory fortification of plant-based dairy alternatives could prevent declines in micronutrient intake. However, even with fortified alternatives, an estimated 59% of adolescent girls would still have inadequate iodine intake. Adding iodine to bread reduced that figure to 37%, suggesting that combining both fortification strategies could be more effective.
Dr Nicol emphasized the importance of aligning nutrition policies with environmental goals:
“Nutrition policy must evolve in tandem with environmental targets; however, it is important that shifts towards more sustainable diets do not compromise on public health. Fortification of foods is one way that this could be achieved; however, government policy is needed to make this happen.”
How Researchers Tested Dairy Replacement
Dr Anne Nugent, from Queen’s University Belfast, described how the team identified dairy-containing foods in the UK National Diet and Nutrition Survey and modeled replacing them with equal amounts of plant-based alternatives. The researchers accounted for differences in the nutritional content of available products and tested whether fortification could prevent deficiencies without causing excessive nutrient intake.
“During the analysis, we first identified all foods and recipes containing dairy produce (milk, cheese, and yogurt) in the national food survey for the UK, the National Diet and Nutrition Survey. Next, we conducted a series of replacement scenarios whereby we substituted the dairy present with an equal weight of plant-based dairy alternatives. As the nutrient composition of dairy alternatives available on our supermarket shelves can vary, we also applied a condition to make sure that every dairy alternative we had identified in our previous market survey had an equal chance of selection. The last step was to examine the impact on dietary intakes of key nutrients following either the reduction or removal of dairy from the diet, replacing it with the dairy alternatives as above, and asking whether a series of fortification options could mitigate against any shortfalls in intake while avoid situations of excess.”
Reference: “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” by Katie Nicol, Anne P Nugent, Jayne V Woodside, Kathryn H Hart and Sarah C Bath, , The Lancet Planetary Health.
DOI: 10.1016/j.lanplh.2026.101515
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