Nutrient Intake and Status in Adults Consuming Plant-Based Diets Compared to Meat-Eaters: A Systematic Review

Abstract

Health authorities increasingly recommend a more plant-based diet, rich in fruits, vegetables, pulses, whole grains and nuts, low in red meat and moderate in dairy, eggs, poultry and fish which will be beneficial for both health and the environment. A systematic review of observational and intervention studies published between 2000 and January 2020 was conducted to assess nutrient intake and status in adult populations consuming plant-based diets (mainly vegetarian and vegan) with that of meat-eaters. Mean intake of nutrients were calculated and benchmarked to dietary reference values. For micronutrient status, mean concentrations of biomarkers were calculated and compared across diet groups. A total of 141 studies were included, mostly from Europe, South/East Asia, and North America. Protein intake was lower in people following plant-based diets compared to meat-eaters, but well within recommended intake levels. While fiber, polyunsaturated fatty acids (PUFA), folate, vitamin C, E and magnesium intake was higher, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) intake was lower in vegetarians and vegans as compared to meat-eaters. Intake and status of vitamin B12, vitamin D, iron, zinc, iodine, calcium and bone turnover markers were generally lower in plant-based dietary patterns compared to meat-eaters. Vegans had the lowest vitamin B12, calcium and iodine intake, and also lower iodine status and lower bone mineral density. Meat-eaters were at risk of inadequate intakes of fiber, PUFA, α-linolenic acid (ALA), folate, vitamin D, E, calcium and magnesium. There were nutrient inadequacies across all dietary patterns, including vegan, vegetarian and meat-based diets. As plant-based diets are generally better for health and the environment, public health strategies should facilitate the transition to a balanced diet with more diverse nutrient-dense plant foods through consumer education, food fortification and possibly supplementation.

Keywords: dietary intake; micronutrients; nutritional status; plant-based diet; vegan; vegetarian.

Figure 1

Flow diagram.

Figure 2

Boxplots represent 25, 50 and 75 percentiles of intake with whiskers at <1.5 interquartile range (IQR) per diet group; black dots represent mean intake and red dots outliers >1.5 IQR: (a) protein—dotted lines represent the lower limit of the acceptable macronutrient distribution range; (b) fiber—blue and pink dotted lines represent adequate intakes for men and women respectively; (c) polyunsaturated fatty acids (PUFA)—dotted line represents lower acceptable macronutrient distribution range; (d) α-linolenic acid (ALA)—blue and pink dotted lines represent adequate intakes for men and women respectively; (e) eicosapentaenoic acid (EPA); (f) docosahexaenoic acid (DHA).

Figure 2

Boxplots represent 25, 50 and 75 percentiles of intake with whiskers at <1.5 interquartile range (IQR) per diet group; black dots represent mean intake and red dots outliers >1.5 IQR: (a) protein—dotted lines represent the lower limit of the acceptable macronutrient distribution range; (b) fiber—blue and pink dotted lines represent adequate intakes for men and women respectively; (c) polyunsaturated fatty acids (PUFA)—dotted line represents lower acceptable macronutrient distribution range; (d) α-linolenic acid (ALA)—blue and pink dotted lines represent adequate intakes for men and women respectively; (e) eicosapentaenoic acid (EPA); (f) docosahexaenoic acid (DHA).

Figure 3

Vitamin intake per diet group in all studies. Boxplots show 25, 50 and 75 percentiles of intakes with whiskers at <1.5 interquartile range (IQR); black dots represent mean intake and red dots outliers >1.5 IQR; dotted lines represent the estimated average requirement (EAR) for adults (green), women (pink) and men (blue): (a) vitamin A; (b) vitamin B1; (c) vitamin B2; (d) niacin; (e) vitamin B6; (f) folate; (g) vitamin B12; (h) vitamin C; (i) vitamin D; (j) vitamin E.

Figure 3

Vitamin intake per diet group in all studies. Boxplots show 25, 50 and 75 percentiles of intakes with whiskers at <1.5 interquartile range (IQR); black dots represent mean intake and red dots outliers >1.5 IQR; dotted lines represent the estimated average requirement (EAR) for adults (green), women (pink) and men (blue): (a) vitamin A; (b) vitamin B1; (c) vitamin B2; (d) niacin; (e) vitamin B6; (f) folate; (g) vitamin B12; (h) vitamin C; (i) vitamin D; (j) vitamin E.

Figure 4

Mineral intake per diet group. Boxplots show 25, 50 and 75 percentiles of intakes with whiskers at <1.5 interquartile range (IQR); black dots represent mean intake and red dots outliers >1.5 IQR; dotted lines represent the estimated average requirement (EAR) for adults (green), women (pink) and men (blue): (a) calcium; (b) iron, EAR for vegans and vegetarians is adjusted for lower iron bioavailability; (c) iodine; (d) magnesium; (e) phosphorus; (f) zinc, EAR for vegans and vegetarians is adjusted for lower zinc bioavailability.