Shifting to plant-based diets by replacing dairy products with alternatives like oat milk and coconut yogurt could lead to significant nutrient deficiencies, according to a study published in The Lancet Planetary Health journal. Researchers found that these dietary changes, especially among women and adolescent girls, could increase the risk of inadequate intake of iodine, calcium, vitamin B12, and riboflavin.
Iodine is crucial for thyroid hormone production, which regulates metabolism and supports growth and brain development. Insufficient iodine can slow metabolism, potentially leading to weight gain, memory problems, and chronic fatigue. Mild iodine deficiency during pregnancy can also have long-term cognitive impacts on children. The study indicated that around a third of women of childbearing age already have low iodine levels, and this figure rose significantly with reduced dairy consumption.
Researchers from the University of Surrey and Queen's University Belfast analyzed the diets of 3,500 people and the nutritional content of various plant-based alternatives. They found that only 12% of non-dairy milks, yogurts, and cheese alternatives were fortified with iodine, while calcium fortification was more common but still insufficient for many. Riboflavin fortification was found in only 20% of products, and vitamin B12 in 46%.
The study highlighted that even replacing 20% to 35% of dairy products with plant-based options substantially increased the number of women and teenage girls failing to meet iodine requirements. For teenage girls, this switch increased the proportion with inadequate iodine intake from over half to nearly two-thirds. Among women of childbearing age, the percentage increased from 32% to 42%.
Calcium intake is also a concern. The study found that nearly half of teenage boys and 70% of teenage girls would be classified as calcium deficient if they replaced dairy products with plant-based alternatives, placing them at risk of osteoporosis later in life. Riboflavin, essential for healthy skin, eyes, and nervous systems, and vitamin B12, crucial for nerve function and red blood cell formation, were also found to be lacking in many plant-based options unless specifically fortified.
The researchers suggest that mandatory fortification of plant-based alternatives with essential nutrients could protect public health. They also proposed adding iodine to bread as a cost-effective method to increase population intake. While many countries fortify salt with iodine, UK health officials have been hesitant due to efforts to reduce salt consumption.
Experts noted that symptoms of iodine deficiency can include fatigue, weight gain, dry skin, constipation, difficulty concentrating, and hair loss. For individuals avoiding animal products, supplements may be necessary. Some plant-based drinks are fortified, but organic alternatives cannot be legally fortified. The study also cautioned against excessive iodine intake, particularly from supplements, which can also disrupt thyroid function.