Vegan diets are unlikely to be widely adopted by the public, scientists have admitted, and eating only plant-based food may reduce intake of essential nutrients found only in meat and dairy.
The warning comes from the British Nutrition Foundation (BNF), which has published a report looking at the need to consider nutritional quality of diets, alongside environmental benefits, in order to achieve sustainable diets.
It says that evidence does not suggest the need to cut out meat or other animal-derived foods entirely in order to eat a healthier and more sustainable diet.
The BNF also explains it is 'important' to consider the essential nutrients that these foods can provide in the public's diet.
For milk and eggs, the report says that evidence does not consistently identify a need to reduce consumption due to 'trade-offs in the modelling studies between the important nutrients these foods provide and their intermediate environmental impact'.
Decisions about appropriate substitutes for animal-sourced products 'all too often just focus on protein', the paper says, adding that this is 'not enough'.
And while vegan diets can deliver environmental benefits in terms of lowering emissions and land use associated with food production, the report says they are unlikely to be widely adopted based on current adherence rates.
In fact, widespread adoption could reduce intakes of some essential nutrients found in foods such as meat, fish, milk and eggs, for example iron, zinc, calcium, iodine, and vitamin B12.
Animal-sourced products currently provide over a quarter of iron, a third of vitamin A and about half the calcium, zinc, iodine and riboflavin in UK adult diets.
Therefore, the BNF says there needs to be 'careful consideration' of how people will consume enough of these essential nutrients in a form that can be easily absorbed by the body if reducing their intakes of animal-derived foods.
Prof Judy Buttriss, director general of the BNF said: “While the evidence-base on sustainable food systems has grown significantly in recent years, all too often nutritional quality and delivery of essential nutrients is not considered in judgements about the environmental impact of foods and diets.
"It’s vital that nutrition is central in discussions about transformation of food systems so that we don’t risk encouraging dietary changes that might benefit the environment but could be detrimental to people’s health”.