Intake and adequacy of the vegan diet. A systematic review of the evidence

Background: Vegan diets, where animal-and all their by-products are excluded from the diet, have gained popularity, especially in the last decade. However, the evaluation of this type of diet has not been well addressed in the scientific literature. This study aimed to investigate the adequacy of vegan diets in European populations and of their macro-and micronutrient intakes compared to World Health Organization recommendations. Methods: A systematic search in PubMed, Web of Science, IBSS, Cochrane library and Google Scholar was conducted and 48 studies (12 cohorts and 36 cross-sectional) were included. Results: Regarding macronutrients, vegan diets are lower in protein intake compared with all other diet types. Veganism is also associated with low intake of vitamins B-2, Niacin (B-3), B-12, D, iodine, zinc, calcium, potassium, selenium. Vitamin B-12 intake among vegans is significantly lower (0.24-0.49 mg, recommendations are 2.4 mu g) and calcium intake in the majority of vegans was below recommendations (750 mg/d). No significant differences in fat intake were observed. Vegan diets are not related to deficiencies in vitamins A, B-1, B-6, C, E, iron, phosphorus, magnesium, copper and folate and have a low glycemic load. Conclusions: Following a vegan diet may result in deficiencies in micronutrients (vitamin B-12, zinc, calcium and selenium) which should not be disregarded. However, low micro-and macronutrient intakes are not always associated with health impairments. Individuals who consume a vegan diet should be aware of the risk of potential dietary deficiencies. (C) 2021 The Authors. Published by Elsevier Ltd.