Study highlights risks in plant-based and meat-based diets

Health authorities, such as the World Health Organization (WHO), are increasingly advocating for sustainable and nutritious diets that emphasize the consumption of plant-based foods and incorporate moderate amounts of animal-based foods.

Nevertheless, there are apprehensions regarding the ability of purely plant-based diets to adequately fulfill all essential nutrient requirements, particularly among children and adolescents, who have heightened nutritional demands for growth and development. 

Empirical evidence suggests that while plant foods provide adequate energy and fulfill several nutritional prerequisites, they typically exhibit deficiencies in one or more essential amino acids.

Conversely, meat and dairy represent protein-dense sources encompassing the full spectrum of requisite amino acids essential for sustaining growth, development, and various associated physiological functions.

Despite this, plant-derived oils are recognized as valuable reservoirs ofessential fatty acids, namely α-linolenic acid (ALA) and linoleic acid (LA), as well as fiber, and vitamins C and E. However, it is noteworthy that they exhibit limitations in the provision of key minerals such as calcium, zinc, iron, selenium, riboflavin, and vital vitamins A and B12 like animal foods. 

Furthermore, omega-3 fatty acids, eicosapentanoic acid (EPA) and docosahexanoic acid (DHA), recognized for their essential roles in neuronal, retinal, and immune function, especially in growing years, are abundantly present in fish and seafood, which happens to be great natural sources of vitamin D and iodine, too.

About the study

For the present systematic review, researchers first searched relevant English articles in the PubMed database from 2000 onwards.

The study identified observational and intervention studies conducted among healthy children and adolescents aged two to 18 who consumed a predominantly plant-based or a conventional diet with meat.

This database search  retrieved 30 studies for analysis, of which 15, 24, and 11 included children and adolescents aged two to five, six to 12, and 13 to 18 (sub-groups). The researchers also noted the age, gender, and country of the study population and the dietary patterns and supplement use of sub-groups.

All the studies incorporated in the analysis documented diets that were voluntarily self-selected by the participants and included comprehensive data on dietary energy intake, as well as detailed nutritional components, with a particular focus on protein, polyunsaturated and saturated fatty acids (PUFA and SAFA), alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).

Applying uniform definitions to all dietary patterns observed in the included studies ensured consistent data interpretation, which resulted in five categories: vegan, vegetarian, pesco-vegetarian, semi-vegetarian, and meat eating.

Vegans did not consume meat or dairy, while vegetarians consumed dairy products but no meat and fish. On the other hand, semi-vegetarians consumed meat and fish less than or once per week but more than once per month.

Participants in the pesco-vegetarian category either self-defined their dietary pattern or did not consume meat during the days of dietary assessment or less than or just once per month. As expected, some studies reported combined data for vegetarians, pesco-vegetarians, and vegans.

During data analysis, the team computed average nutrient intakes and status for the different dietary patterns and reported this data as means and standard deviations (SDs).

They conducted separate analyses of studies that assessed nutrient intake from foods alone and both foods and supplements, which helped the researchers evaluate participant’s micronutrient intake.

For every included study, the researchers also compared the average nutrient intakes of the different dietary patterns with the dietary reference values (DRVs) to report the number of studies where average intakes were above or below the reference values.

Notably, DRVs differ for different age groups, as well as for girls and boys. Finally, the team assessed the risk of bias based on the Observational Study Quality Evaluation (OSQE) checklist.

Results

The authors noted that studies comparing plant- and animal-based diets showed no marked difference in energy intake from both diets. 

Further analysis revealed that children consuming plant-based diets, especially vegans, fell short of meeting protein intake recommendations. For all other diet groups, mean protein intake was within the recommended threshold.

However, intake of fiber, SAFA, and PUFA were highest in vegan children and lowest in meat-eating children. Intriguingly, while children fed a plant-based diet were at risk of getting inadequate fiber, SAFA, and possibly PUFA, their intakes were more favorable than those of meat-eating children. 

Regarding other macronutrients, i.e., omega-3 fatty acids, EPA, and DHA, only two studies found that their intake was suboptimal in all five diet groups. Similarly, average intakes of vitamin D and calcium were low in all diet groups, and two studies reported a risk of iodine deficiency in all diet groups.

Children fed meat-based diets were likely at risk of inadequate folate and vitamin E intakes, and children consuming plant-based diets were at a higher risk of deficiency of vitamin B12, zinc, and iron intakes.

Interestingly, average intakes of vitamin A, B1/B2/B6, niacin, vitamin C, and magnesium, i.e., other micronutrients, were lower than the WHO or IOM recommendations in all the diet groups.

Conclusions

This systematic review reveals that children adhering to plant-based diets and those consuming meat-based diets face the potential risk of inadequate nutrient intake. Across various dietary groups, vitamin D, calcium, iodine, EPA, and DHA deficiencies appear to be prevalent.

Moreover, findings suggest that children following plant-based diets may be susceptible to iron, zinc, and vitamin B12 insufficiencies. At the same time, their meat-consuming counterparts might face shortfalls in vitamin E and folate.

Conversely, vegan children generally exhibited intakes of saturated fatty acids (SAFA), polyunsaturated fatty acids (PUFA), and dietary fiber that did not align with recommended guidelines compared to vegetarian and meat-eating children.

Enhancing the dietary diversity with nutrient-rich plant foods, alongside potential food fortification and supplementation strategies, can contribute to developing more sustainable and nutritionally balanced diets for children and adolescents.

However, it’s important to acknowledge the limited extent of research involving children, underscoring the need for future well-designed observational studies.

These studies should focus on monitoring the effects of diverse plant-based diets on nutrient intake and status, leveraging appropriate biomarkers, and exploring functional outcomes such as growth, development, and the prevention of non-communicable diseases (NCDs).

Moreover, there is a notable need for data from regions beyond Europe, facilitating the examination of cultural and geographical variations in the adequacy of plant-based and meat-containing diets.