The proportion of plant-based foods in the diets of adolescent females in New Zealand

Abstract Background: There is a worldwide movement towards a plant-based diet, with the EAT-Lancet commission recommending consumption of largely plant-based foods to address both human and planetary health. Several plant-based dietary patterns are associated with a reduced risk of non-communicable diseases, including regular consumption of whole grains, fruits, vegetables, legumes, nuts and seeds. Adolescence is a critical stage of life as physical growth and development reach their peak during this time, and optimal nutrition is needed to ensure proper growth. Adopting a healthy dietary pattern, including more plant foods, in adolescence will have long-term health benefits. However, there are no data on the proportion of plant-based energy in the diets of adolescent females in NZ. Objective: To determine the proportion of energy that comes from plant-based sources in female adolescents aged 15 to 19 years. A comparison of the diets of adolescent females with the EAT-Lancet recommendations was a secondary objective. Design: A clustered, cross-sectional study of schoolgirls aged 15 to 19 years was carried out throughout New Zealand. A self-administered online questionnaire was used to collect sociodemographic and health information. Using the Multiple Source Method, adjusted dietary intakes were calculated from two non-consecutive 24-hour diet recalls obtaining participants’ usual intakes. Anthropometric measurements such as height and weight were measured to calculate the body mass index z-score. Based on the recipes provided by participants, all foods have been classified as either plant or animal. Foods that mixed animal and plant components were deconstructed. Results: Of the 256 participants included in this study, 15.2% were vegetarians. The mean daily energy intake of schoolgirls was 7946 kJ/d. The mean proportion of plant-based energy in the adolescent female cohort was 70.8%; omnivores and vegetarians consumed 70.2%, and 80.2%, respectively, of their energy from plant-based foods. The range of energy intake from plant-based foods was 43 to 92% for omnivores, 51 to 97% for vegetarians, and 89 to 100% for vegans. For nutrients of interest related to vegetarianism, protein intake was 1.2 g/kg/d for omnivores and 1.0 g/kg/d for vegetarians. There was no difference in the dietary intake of calcium, zinc, and iron between omnivores and vegetarians. However, a difference in vitamin B12 was found. In comparison with EAT-Lancet recommendations, the diets of vegetarian female adolescents were, on average, better aligned than the diets of omnivores. Participants ate fewer whole grains and more tubers daily than recommended by EAT-Lancet. Conclusion: This is the first study in which the energy intake from plant-based foods has been estimated in a sample of female adolescents in New Zealand. An important finding to emerge from this study is the considerable overlap in the energy that comes from plant sources of omnivores and vegetarians. This means that a person can be an omnivore and still have a predominantly plant-based diet, and, conversely, being a vegetarian does not necessarily equate to a high proportion of plant energy in the diet