Abstract
Background: Worldwide, vegetarian-type diets are increasing in popularity for reasons including health, environmental and ethical. Appropriately planned vegetarian diets are nutritionally adequate, however some nutrients may be at risk of inadequacy due to the omission of nutrient rich animal source foods and a lack of nutrition knowledge. Given that energy and nutrient requirements are higher in relation to body weight during periods of growth, adolescents are especially at risk of nutrient inadequacies. Research evaluating the dietary intakes of vegetarian adolescents have received little attention. Therefore, the aim of this thesis was to compare the reported energy and select at risk micronutrient intake and adequacy of a group of New Zealand female adolescents consuming vegetarian and non-vegetarian diets. Design: A cross-sectional Survey of Nutrition, Dietary Assessment and Lifestyle variables (SuNDiAL project) was conducted among female adolescents aged 15 to 18 years, recruited from high schools (n=13) across New Zealand (Dunedin, Wellington, New Plymouth, Whangarei, Wanaka, Christchurch, Nelson, and Tauranga). Sociodemographic data were collected via an online questionnaire; and anthropometric measurements were taken to determine body mass index (BMI; kg/m2). Energy and dietary intake of calcium, iron, zinc, selenium, folate, vitamin A and vitamin B12 were determined using two 24-hour recalls, adjusted to reflect usual intake. Foods were categorised into 26 major food groups and ranked according to their median contribution to each nutrient.
Results: Of the total 291 eligible participants enrolled in the survey, 254 adolescents provided at least one day of dietary intake data. Of these, 38 (15%) were self-identified vegetarians and 216 (85%) were non-vegetarians. The majority of participants were New Zealand European and Other (NZEO) (78%), living in low to medium deprived neighborhoods (82%) and had a normal BMI (67%). Compared to non-vegetarians, usual dietary intakes among vegetarians were significantly lower for zinc [9.7 (3.0) vs 8.0 (2.2) mg/d, p = 0.003], selenium [46.8 (19.5) vs 36.5 (15.7) mg/d; p = 0.002] and vitamin B12 [3.06 (1.09) vs 2.32 (1.11) g/d; p < 0.001]. Morover, vegetarian participants were six times more likey to have an inadequate intake of selenium, three-times greater risk of zinc inadequacy and four times more likely not to meet the recommendations for B12 compared to their non-vegetarian counterparts. Among vegetarians, Grains, Pasta, and Bread provided the highest median intake of selenium, Milk and Milk-based beverages were ranked among the highest median intake of B12, and Meat alternatives and Breakfast cereals provied the highest median intake of zinc. Usual dietary intakes of the remaining nutrients (calcium, iron, folate, vitamin A) did not differ significantly between the two groups. Overall, usual dietary intakes of calcium, selenium and folate were concerningly low among both vegetarians and non-vegetarians with the prevalence of inadequacy of more than 80%, 71% and 58% for each nutrient, respectively.
Conclusion: To our knowledge, this is the first study in New Zealand to assess and compare the micronutrient intakes among adolescent females based on their vegetarian status. Vegetarian participants were at greater risk of inadequate intakes of zinc, selenium, and vitamin B12 than non-vegetarians, although both groups of female adolescents had very low intakes of calcium, folate, and selenium. These findings are important given the lack of data, the changing food landscape and trend towards vegetarianism.