We know what we eat affects our health as well as the health of our planet. Sustainable diets are promoted as one of the ways we can reduce our environmental footprint, but less is known about their impact on our health. In the first of its speaker series, the Vancouver Acute/Vancouver Community Medical Staff Planetary Health Committee enlisted University of Oxford Senior Nutritional Epidemiologist Keren Papier to discuss sustainability and sustainable diets, sustainable diets and health, and current and ongoing research into such diets. Dr. Papier’s interests include examining the diet- and lifestyle-related causes of morbidity and mortality; she is the principal investigator for the Feeding the Future Study being conducted in collaboration with the World Health Organization.

“Food systems account for 30 per cent of all greenhouse gas (GHG) emissions,” began Dr. Papier. “And red meat production accounts for about half of food-related GHG emissions. In the coming decades, as the world’s population increases from 7 to 10 billion people, we expect to see a continued rise in the consumption of red meat, particularly in countries with large populations such as China.”

Dr. Papier shared graphs demonstrating the modelled environmental impact of various foods on several environmental indicators including acidification potential, eutrophication potential, GHG emissions, land use, and water use. The modelled health impact of these different foods was also reviewed including their effect on mortality, coronary heart disease, colorectal cancer, diabetes, and stroke. In all instances, red meat had a negative impact.

The UN Food and Agriculture Organization defines sustainable diets as ones with low environmental impacts that contribute to food and nutrition security and to healthy life for present and future generations. They are protective and respectful of biodiversity and ecosystems, are culturally acceptable, accessible, economically fair and affordable, nutritionally adequate, safe and healthy.

Dr. Papier went on to discuss the 2019 EAT-Lancet Commission’s universal healthy reference diet. Modelled health impacts stemming from this suggest that adopting the EAT-Lancet diet would lead to avoiding anywhere from 10.8 million to 11.6 million deaths per year by 2030. The publication of the universal diet has led to additional research into its purported benefits including from the Cancer Epidemiology Unit where Dr. Papier works. She points out that modelling a diet does not consider actual dietary patterns of eating.

There are also challenges in turning the EAT-Lancet universal reference diet into a diet score in different populations, which EPIC-Oxford has tried to address through food frequency questionnaires. According to data from this cohort, 90 per cent of participants achieved the EAT-Lancet recommendations for poultry, eggs, fish, legumes, and fats; 60 per cent achieved the recommendations for tubers, fruit, vegetables, and dairy, whole grains, red and processed meat, nuts, and sugar.

When comparing high versus low adherence to the EAT-Lancet diet score for the incidence of selected outcomes in the EPIC-Oxford study, Dr. Papier and her colleagues concluded that the diet shows beneficial associations for coronary artery disease and diabetes, but no association with stroke and no clear association with mortality.

Dr. Papier also discussed the environmental impacts of vegetarian and vegan diets.

“There have been many studies of vegetarian and vegan dietary intakes and nutritional status, but most of these have been small. There are few prospective studies with follow-up for disease risks, and small numbers for vegans,” said Dr. Papier, who provided data from the EPIC-Oxford study.

Published work from this cohort suggests that that dietary GHG emissions and other environmental indicators in self-selected meat eaters are approximately twice as high as those in vegans. Further, vegetarians in the EPIC-Oxford study have a relatively low risk of for coronary artery disease, diabetes, diverticular disease, kidney stones, cataracts, and some cancers, but a relatively high risk of stroke (primarily haemorrhagic stroke) and bone fractures in comparison to meat eaters. She cautioned that there is a potential over-representation of severe outcomes for some conditions (e.g., diabetes) since outcomes were assessed using hospital admissions.

Dr. Papier addressed differing preconceptions: there are those who believe meat and dairy products are essential and healthy while others believe 100 per cent plant-based diets are optimal and that meat is unhealthy. She emphasized that vegetarian diets vary and are not necessarily healthy. Interpretation needs to be cautious as the diet and lifestyle of the comparison groups affects the results.

Finally, Dr. Papier also talked about her current work on the Feeding the Future study, which has recruited over 6,000 participants in the UK. She reviewed their characteristics and dietary motivations.

“Sustainability is increasingly important, and diet plays an important role in climate change and environmental health,” concluded Dr. Papier. “Research mainly uses economic modelling to estimate impacts but increasingly cohort studies are being used to estimate both climate and health impacts of sustainable diets. The available data suggest sustainable diets could have lower environmental impacts, and beneficial health effects but also some risks.”

Post-event survey findings

Comments from survey respondents included:

• 12 of the 26 people attending this presentation took part in the survey.
• They gave the talk a net promoter score of 75%.
• Seven respondents strongly agreed and two somewhat agreed they would apply content from this session in conversations with their patients.

Comments from survey respondents included:

• Excellent speaker; important, timely topic. I want to read more research on this topic and Dr. Papier’s presentation will help me read more critically and consider the practical implications of research findings and recommendations, as well as broader policy statements.
• I really appreciated hearing about the different methodologies and the challenges and limitations that exist to draw conclusions. I was surprised about the link between higher meat consumption and diabetes.
• [What resonated the most was] that just by cutting out meat I can make an impact (didn’t realize that red meat was responsible for almost 50% of food-based greenhouse gas emissions).