Healthier Macronutrient Profiles but Higher Risk of Specific Micronutrient Deficiencies: A Cross-Sectional Study of Vegans, Lacto-Ovo-Vegetarians and Omnivores in Northeast China

Background: Data on the nutritional adequacy of unsupplemented vegetarians in Northeast China are limited. Methods: We compared dietary intake, body composition, and serum biomarkers among vegans, lacto-ovo-vegetarians, and omnivores. This cross-sectional study included 356 adults (all diet ≥ 2 years, no supplements). Dietary intake was assessed using a validated semi-quantitative FFQ, body composition by BIA, and serum biomarkers. Kruskal–Wallis tests with Bonferroni correction were used. Results: Vegans had lower BMI (22.0 vs. 24.6 kg/m2), body fat (24.5% vs. 28.0%), and visceral fat (0.65 vs. 1.05 L) than omnivores (all p < 0.002). Vegans consumed more fiber (38.5 vs. 18.0 g/d) and vitamin C (180 vs. 85 mg/d), but less vitamin B12 (0.3 vs. 4.2 μg/d), vitamin D (0.5 vs. 3.2 μg/d), calcium (520 vs. 720 mg/d), iodine (65 vs. 130 μg/d), and selenium (45 vs. 85 μg/d). Serum vitamin B12, 25-(OH)D, ferritin, and selenium were significantly lower in vegans, while homocysteine was higher. The proportion of vegans with dietary intake below the recommendation reached 100% for vitamin B12 and 97% for vitamin D, whereas omnivores showed excessive sodium (75%) and SFA (70%) intake. Conclusions: In this Northeast China cohort, unsupplemented vegetarian diets offered favorable macronutrient profiles and body composition but were associated with a high prevalence of dietary intakes below recommendations for vitamin B12, vitamin D, iodine, selenium, zinc, and calcium. These findings underscore the need for targeted supplementation and food fortification strategies for individuals adhering to plant-based diets without supplement use in this region.