Does plant-based necessarily mean healthy and sustainable?

Are plant-based diets becoming unhealthy?

A healthy and sustainable diet, characterized by a predominantly plant-based diet with small amounts of meat, is recommended for its benefits in terms of human health and the environment, as stipulated in the joint report of the FAO and WHO on guiding principles for sustainable healthy diet (FAO and WHO, 2019).

However, consumers perceive plant-based diets as inconvenient in terms of cooking skills and time as well as affordability which challenges the changing food environment and industries.

Therefore, to overcome these barriers, a ‘modern’ plant-based diet that is very different from a more traditional diet, emerged, offering plant-based foods that are ultra-processed, high in energy, fats, sugar, and salt and thus, present a concern as regard to both public health and environmental impact.

Thus, this paper reports the challenges of the trend towards a plant-based diet based of the current evidence on human and planetary health. Those findings were presented during the conference on “Nutrition in a changing world” at the Nutrition Society Summer Conference 2021.

For environmental and/or health reasons, consumers are moving towards meat alternatives, particularly vegetarian options

In order to achieve global goals to reduce greenhouse gas (GHG) emission and to limit global warming (COP21, Paris, 2021), significant action is needed in all sectors, including food sector, with changes targeting the agriculture, the food chain but also the consumer. In high-income countries, guidelines targeting the consumer recommend mainly to change food consumption by eating less meat and dairy products, especially from ruminant animals, to decrease GHG emissions. Indeed, red meat and dairy products have higher GHG emissions than plant-based commodities (Poore J, 2018). Reducing red meat consumption could also have potential benefits for human health in line with national and international dietary guidelines for health to decrease risk of cancers, such as colorectal cancer (World Cancer Research Fund, 2018).

Currently, more and more consumers are turning to red meat alternatives, particularly plant-based food for environmental and/or health reasons. Healthy plant-based foods, such as fruits, vegetables, pulses, and nuts are low in fat and high in fiber and micronutrients as well as having lower GHG emissions. But these foods are perceived by some people as inconvenient, time consuming to prepare and expensive (Schösler H, 2012). Moreover, the use of legumes instead of meat (e.g., pulses or lentils) can change traditional meal formats and can be a significant challenge for consumers when meat is the core of the plate.

In the past few years, the food environment has changed dramatically, and the availability and accessibility of plant-based convenience foods has exploded to consider the barriers perceived by the consumers. The most popular plant-based foods are those that mimic meat products, such as burgers, sausages, or hash browns, which minimize changes to meals and do not require new cooking skills. These foods can also help overcome feelings of social inclusion, as people can eat the same meal as others, with a vegetarian alternative. Among these foods, many are classified as ultra-processed according to the NOVA score (Monteiro, 2019a). The appeal of ultra-processed foods (UPF) is not only their convenience, but they are also attractive, highly palatable and cheap, and typically energy dense and high in fat, added sugar or salt (Monteiro, 2019b).

Many studies have emerged in recent years on the association between UPF and chronic diseases. A recent systematic review including 43 studies shows that the majority found a negative association with at least one adverse health outcome (e.g. overweight, obesity, cardiovascular disease, cancers, type 2 diabetes) (Elizabeth, 2020). These studies are not specific to plant-based foods, but it is very likely that these energy-dense foods, high in sugar, fat, and salt also have these same negative effects. A cross-section study of a cohort of 21 212 adults in France found that 33, 32.5, 37 and 39.5% of energy intake came from UPF in diets of meat-eaters, pesco-vegetarians, vegetarians and vegans, respectively (Gehring, 2021).

The definition of plant-based diets is misunderstood by consumers

Traditionally, plant-based diets include minimally processed foods such as fruits, vegetables, legumes, nuts, and whole grains, but currently they changed with the increasing availability of industrially processed plant-based foods.

In fact, people who started recently to follow a vegetarian diet were more likely to consume plant-based processed foods. More particularly, young people (18-24 years) tended to consume plant-based processed meat and dairy alternatives (British Nutrition Foundation, 2020 ; Gehring, 2020).

This could be explained by the fact that consumers often perceive plant-based foods as “healthy” regardless of their nutritional profile. They also have difficulties to define this type of diet. A recent survey found that 41% of adults in the UK thought that a plant-based diet is a vegan diet, 20% a vegetarian diet, and 8% did not know what that meant (British Nutrition Foundation, 2020).

Therefore, it seems essential to point out that the emerging “modern” plant-based diet is very different from a more traditional diet. While convenient, desirable, and affordable plant-based foods have their place in encouraging dietary change towards a more sustainable diet, there is a need to ensure that they do not unconsciously lead to a shift that is ultimately neither healthy nor sustainable.

Based on: Macdiarmid JI. The food system and climate change: are plant-based diets becoming unhealthy and less environmentally sustainable? Proc Nutr Soc. 2022 May;81(2):162-167.

Key messages
  • Plant-based foods have a halo effect around human and planetary health, but many being produced are ultra-processed high in energy, fat, sugar, and salt with greater environmental impact than minimally processed plant-based foods.
  • The emerging “modern” plant-based diet is very different than a more traditional one comprising pulses, vegetables and wholegrain.
  • While there is a place for convenient, desirable, and affordable plant-based foods to encourage dietary change, care should be taken that this does not subconsciously set a path which may ultimately be neither healthy nor sustainable.
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