Nutritional adequacy of plant-based diets for weight management: observations from the NHANES

Observational studies have shown that body mass indexes of vegetarians are lower than those of nonvegetarians and that caloric intake of vegetarians is typically lower than that of nonvegetarians, suggesting that a vegetarian diet could be an approach for weight management. However, vegetarians may be at risk of inadequate intakes of certain vitamins and minerals. Population-based studies indicate that vegetarians have lower mean intakes of vitamin B-12 and zinc and higher intakes of fiber, magnesium, and vitamins A, C, and E than do nonvegetarians. Usual intake data suggest a similar prevalence of inadequacy between vegetarians and nonvegetarians for magnesium and vitamins A, C, and E, with both groups at high risk of inadequate intakes of these nutrients. These same data report that vegetarians have a higher prevalence of inadequacy for iron, vitamin B-12, protein, and zinc than do nonvegetarians. Although mean intake data suggest that a vegetarian diet may be a useful approach for weight management, combined with energy restriction it may have a detrimental effect on diet quality. Mean intakes of fiber, vitamins A and C, magnesium, and iron were significantly lower for vegetarians with energy intakes ≥ 500 kcal below Estimated Energy Requirements than for vegetarians who did not restrict energy. Vegetarian diets should be recommended for weight management; however, care should be taken to optimize food intake to provide adequate intakes of nutrients of concern when energy restriction is used in conjunction with a vegetarian dietary pattern. At any caloric amount, vegetarians should optimize intakes of vitamin B-12, zinc, and protein; and both vegetarians and nonvegetarians need to increase intakes of calcium, magnesium, fiber, and vitamins A, C, and E.