Replacing dairy products with plant-based alternatives such as oat and almond milks could lead to people missing out on vitamins and minerals, even with a partial swap, according to a study published in the Lancet Planetary Health journal. The research found that children, teenagers and women appeared to be worst affected by any switch to plant-based milks, yoghurt and cheese.
Study scope and findings
The researchers examined the risks of dropping dairy in favour of plant-based items, looking at 146 plant-based milks, 76 yoghurts and 67 cheese products. They assessed the effect on micronutrient intake for iodine, calcium and vitamins B2 and B12, and found variations in the extent to which plant-based foods are fortified with added vitamins. Some 12% of the plant-based items contained added iodine, 61% had added calcium, 46% had vitamin B12 and 19% had riboflavin (vitamin B2).
The team, from the University of Surrey and Queen's University Belfast, found that even modest replacements of dairy intake with plant-based alternatives, including fortified ones, led to declines in all four micronutrients, but particularly iodine. For example, replacing 20-35% of dairy products with plant-based ones increased the inadequate intake of iodine among girls aged 14-18 from 54% to 65%, and from 32% to 42% in women aged 19-49.
Impact on specific groups
If all dairy was replaced, iodine inadequacy rose to 80% in teenage girls and 72% in boys of the same age. If all dairy was swapped for plant-based products, inadequate calcium intake rose from 30% in the usual diet to 47% among boys aged 14 to 18, and from 54% to 70% among girls the same age. For riboflavin (vitamin B2), if all products were swapped, inadequate intakes in men aged 19-49 rose from 14% to 26%, while the figure rose from 29% to 50% for women. There was also a meaningful increase to 39% in this group if only half of usual dairy was swapped for plant-based items.
According to the NHS, calcium is important for building healthy bones and teeth as well as regulating muscle contractions, including heartbeat. Vitamin B12 helps keep the nervous system and blood cells healthy, while B2 is important for skin, eyes and the nervous system.
Expert commentary and fortification
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 iodisation, 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."
Dr Katie Nicol, co-author of the study and research fellow at the University of Surrey, said: "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."
The research included data from more than 3,500 people in the National Diet and Nutrition Survey. The team also used modelling to look at the impact of fortification, including through introducing laws around it. The study suggested mandatory rules to fortify plant-based foods would help increase nutrient intake, although levels of iodine remained inadequate in 59% of teen girls. Fortifying bread with iodine would lead to a further cut in iodine deficiency.
Professor Mairead Kiely, from the Cork Centre for Vitamin D and Nutrition Research, said: "Vitamins and minerals that are supplied by animal source foods will need to be replaced in a transition to diets that substantially reduce intakes of these foods and replace them with plant-based alternatives. Plant-based dairy alternatives, unless fortified appropriately, do not contain equivalent amounts of calcium, iodine, riboflavin and vitamin B12 as milk, yoghurt and cheese."
Tom Sanders, Professor emeritus of nutrition and dietetics at King's College London, said a weakness in the study was that "iodine deficiency cannot be reliably predicted from dietary intake records because the iodine content is dependent on the amount in the soil in which plant foods are grown". He added: "Milk is not naturally high in iodine: the high levels found in milk are because dairy cattle are given 'salt licks' that contain supplemental iodine… Seafood is the best natural source of iodine."
Emily Angus, senior dietitian at The Vegan Society, said: "To say that 'replacing dairy in UK diets with the plant-based alternatives currently on sale could reduce the average intake of iodine' is misleading. The majority of plant-based milk alternatives available to UK consumers are fortified with calcium and vitamin D as a minimum."
Elisa Allen, vice-president of programmes and operations at People for the Ethical Treatment of Animals, said: "The NHS confirms that a well-planned vegan diet can provide the nutrients we need and even the researchers' own modelling points towards fortification as the solution."
