Plant-based diets may lead to nutritional inadequacies

A plant-based diet (PBDs) is higher in nutrients and wholefood groups than a regular meat-eating (RME) diet, but it may result in nutritional inadequacies if not planned properly, suggests an Australian study.

“Nutrients of concern among PBDs and RMEs as well as suitability of supplementation should be carefully considered by individuals alongside tailored nutrition interventions with their healthcare professionals when adjusting dietary intakes to meet nutritional needs,” the researchers said.

“Moreover, nutrients found to be in deficit should be considered when designing plant-based alternatives,” they added.

A total of 240 adults aged 30‒75 years were enrolled in this cross-sectional study. Participants adhered to the following dietary patterns for ≥6 months: vegan (n=48), lacto-vegetarian (n=48), pesco-vegetarian (n=48), semi-vegetarian (n=48), or RME (n=48).

The researchers used validated food frequency questionnaires and dietitian-administered diet histories to assess dietary intakes. They also performed multivariable regression, adjusting for age, sex, BMI, race, energy intake, and physical activity.

Vegans and lacto-ovo vegetarians had significantly lower intakes of protein (4‒5 percentage energy intake [EN%]), saturated fat (2‒4 EN%), trans fat, cholesterol, vitamin B12, iodine, riboflavin, niacin, sodium, and long-chain omega-3 polyunsaturated fatty acids (LCn-3PUFA) than regular meat eaters. [Eur J Clin Nutr 2025;79:876-887]

Moreover, vegans and lacto-ovo vegetarians had higher intakes of carbohydrates (5‒7 EN%), fibre, vitamin E, folate, magnesium, iron, and n-6PUFA than those on RME diet, while pesco-vegetarians and semi-vegetarians showed intermediate intakes.

Compared with individuals on RME diet, those following PBDs consumed significantly more daily servings of vegetables (1‒1.5 servings), fruit (1 serving, vegan only), legumes/nuts (0.5‒1 serving), and had less discretionary choices (0.5‒1 serving).

Inadequacies

All dietary patterns demonstrated adequate intakes of protein, exceeded in fat, showed inadequacy in carbohydrate, and met the recommended servings of fruit and vegetables, but not grains.

Individuals following PBDs, except pesco-vegetarians, had inadequate servings of meat, poultry, eggs, beans, and nuts. Semi-vegetarians and those on RME also had inadequate intake of dairy.

Furthermore, vegans and lacto-vegetarians had inadequate nutrient intakes, particularly vitamin B12, LCn-3PUFA, and iodine. Calcium was also lacking among vegans, iodine among pesco-vegetarians, and LCn-3PUFA among semi-vegetarians and RMEs.

“Despite the healthful nature of PBDs, there is potential for nutrient inadequacies to occur given the restriction of key food groups such as dairy, eggs and animal meats,” the researchers said.

“Of most concern is iron, zinc, iodine, calcium, and vitamin B12 which are essential for human health including growth and development, immune health, production of hormones, bone health, and neurological functioning,” they added. [J Acad Nutr Diet 2016;116:1970-1980; Proc Nutr Soc 2022;81:190-198]

According to the researchers, the current study included vitamin and mineral-fortified food products, which likely explained the increased intake levels of calcium as well as vitamin B12 relative to previous studies.

“[These] findings may aid the development of national dietary strategies and guidelines to achieve nutritional adequacy for those following plant-based eating patterns, in congruence with the updated dietary guidelines around the globe,” the researchers said.

“Larger primary population-based longitudinal studies investigating nutrient intakes and objective biomarkers are warranted to substantiate nutritional status of various PBDs,” they added.