The public health rationale for promoting plant protein as an important part of a sustainable and healthy diet

Lonnie M, Johnstone AM. The public health rationale for promoting plant protein as an important part of a sustainable and healthy diet. Nutrition Bulletin. 2020;45(3):281-93. 

Relevant to: 

All Dietitians-Nutritionists  

Question: 

This review examines sustainability, ethical and health considerations and challenges for consuming a more plant-based protein diet from a public health perspective, including whether plant-based diets supply enough and adequate quality protein. The article also discusses potential strategies to formulate messages to advance the shift toward an increase in plant-based protein diets.   

Bottom line for nutrition practice: 

The authors focus on the protein aspect of plant-based diets. They propose that the public needs a greater knowledge about protein requirements; this includes understanding that most people consume adequate protein if they are eating a healthy, balanced diet (whether or not they consume animal-based foods). They suggest that the term “protein package” be promoted to enhance understanding about protein needs; this term recognizes that protein occurs in foods that have a “package” of nutrients and compounds in addition to protein. 

The authors propose the need for researching and developing effective public health strategies to advance the consumption of plant-based diets and plant-based proteins. A variety of strategies must be developed, as research illustrates that diverse population groups respond to different messages, and also that messages must cut across the dimensions of environment, health, economics and culture. As seen in other studies, the authors cite studies showing that the public is more likely to respond to health-based rationale recommending shifts toward plant-based diets rather than environmental-based rationale. The authors recommend building on the interest of health-conscious consumers while also researching and removing barriers for those who are less health-conscious. 

Abstract:

Sustainable diets are proposed as a means to improve public health and food security and to reduce the impact of the food system on the environment. Guidance around sustainable diets include a reduction of animal products in order to move towards a more plant-based diet, meaning that plant-originated foods are a predominant, but not the sole component of a diet. The main principles of a sustainable diet (as provided by the Food and Agriculture Organization of the United Nations/World Health Organization) are to consume a variety of unprocessed or minimally processed foods, mainly as wholegrains, pulses, fruits and vegetables, with moderate amounts of eggs, dairy, poultry and fish and modest amounts of ruminant meat, which are consistent with the current UK healthy eating recommendations (e.g., Eatwell Guide). The aim of this review was twofold: (i) to discuss public health challenges associated with consumers’ knowledge regarding protein sustainability, healthier protein sources and protein requirements, and (ii) to review potential approaches to facilitate the shift towards a more sustainable diet. Consumers would benefit from receiving clear guidance around how much protein is needed to meet their daily requirements. The public health message directed to a consumer could highlight that desired health outcomes, such as muscle protein synthesis and weight control, can be achieved with both sources of protein (i.e., animal and plant-based), and that what is more important is the nature of the ‘protein package’. Health promotion and education around the benefits of plant-based protein could be one of the strategies encouraging the wider population to consider a shift towards a predominantly plant-based diet. 

Details of results: 

The authors present the case for a shift toward mostly plant based dietary patterns, with a focus on the protein aspect. They cite one study which estimates that about 83% of global farmland use and 56-58% of GHG emissions are generated by meat, aquaculture, egg and dairy production, while providing only 37% of the protein supply. They acknowledge, however, that environmental impact varies dependent on production practices – regardless of whether foods are animal or plant based.  

The authors cite studies illustrating that in the Netherlands and Britain, the key reasons for most people to reduce the intake of animal foods was health, with environment cited as the last reason in the British study. This suggests that persuading people to make dietary shifts for health reasons may be a more effective public health strategy than trying to convince them for environmental reasons.  

The authors note that results from modelling studies have led to varying recommendations about plant protein consumption due to differences in methodological approaches. For example, some studies recommend an increase in grams of legumes, while others focus on a percentage increase in the diet. As this can result in confusion for consumers, the authors recommend clearer guidance on protein requirements. They cite evidence noting that current nutrient recommendations for protein may not be adequate to prevent muscle loss in older adults. Nonetheless, the authors suggest that the population should be assured that protein requirements will likely be met if they are following a healthy, balanced diet – whether or not it is plant-based. This is in contrast to a current marketing trend promoting the intake of more protein. While protein quality is higher in animal than plant-based foods, adequate protein intake can be met with a plant-based diet; this is achieved by consuming more, and a variety of plant-based foods containing protein (the latter ensuring an optimal amino acid profile).  

The authors cite Harvard School of Public Health researchers in suggesting that the term “protein package” be promoted to consumers to enhance understanding about protein needs. This term recognizes that protein occurs in foods that have a “package” of nutrients and compounds in addition to protein. Animal protein packages include some nutrients which may not be included in plant proteins (e.g., vitamin B12, creatine) or may be available in higher quantities (e.g., iron, zinc). However, they often include saturated fats, and may be a source of carcinogenic heterocyclic amines (formed when cooking at high temperatures). Plant protein “packages” include nutrients which may not occur, or may be limited in animal foods (e.g., fibre, polyphenols, vitamin C, polyunsaturated fatty acids).  

The authors suggest that very little evidence exists regarding effective strategies to increase the population’s intake of plant-based foods. They note that diets need to be sustainable across the dimensions of environment, health, economics and culture, so facilitating this shift requires a wide range of actions. The authors review a number of studies which examine strategies. First, while modelling studies have shown that cost may not be increased in adopting environmentally sustainable diets, it can still be perceived to be a barrier. As such, the authors suggest that different strategies to promote dietary changes may be tailored for different income groups. Next, the study cites various studies where differences in age, gender, education, race and diet type (i.e., omnivores, vegetarians and vegans) have impacted protein consumption. They conclude that strategies need to be designed to target different groups, as no “one size fits all” strategy exists. And, as demonstrated by other research, the authors also suggest that effective recommendations are more achievable when dietary changes do not deviate substantially from typical diets. 

Evidence also illustrates that the strongest predictor of intentions to reduce meat consumption and incorporate a plant-based diet is attitudes. Social norms and perceived behavioural control were the next strongest predictors. Based on this evidence, the authors suggest that promoting healthy eating attitudes along with increasing consumers’ nutrition knowledge is important. The authors also cited a study illustrating that people who identified strongly as healthy eaters were more likely to consider moving toward a plant-based diet.  

Overall, the authors recommend building on the interest of health-conscious consumers while also researching and removing barriers for those who are less health-conscious. These may be important components in designing effective messages and communication channels to increase the consumption of plant-based foods.  

Finally, the authors suggest that the shift toward plant-based diets needs to be advanced within the context of avoiding trade-offs and unintended consequences. Additionally, there is a gap in understanding of the sustainability profiles of current alternative protein sources.  

Of additional interest: 

For more information from Harvard about protein, including “protein package”, see: 
https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/protein/ 

Editor’s comment:  

The idea of promoting “protein packages” (whether one eats meat or not) seems like it could be an effective way to shift people away from the idea that they need solely more protein, and could be especially important in situations where there is a need to focus on iron and micronutrients (e.g., specific populations or countries). 

Open access link to article: 

https://onlinelibrary.wiley.com/doi/epdf/10.1111/nbu.12453 

Conflict of interest/ Funding:  

This article was commissioned by the British Nutrition Foundation which received financial support from Tate & Lyle for this journal issue. The authors received financial support from the Scottish government.  

External relevant links:  

N/A

Corresponding author:

Alex.Johnstone@abdn.ac.uk

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