Close Send this page to a friend

Your link and message have been sent!

Close Send this page to a friend
* required
Oops! You forgot to fill in some required information.
Loading...

Back to Home

Sustainable Diets: What Are They and What Is Their Role in Nutrition and Health?

The concept of sustainable diets is not new, but it is complex. Changes to more sustainable dietary patterns are needed to reduce environmental burden. However, in doing so, nutritional, cultural, social and economic aspects also need to be considered.

Highlights

  • The environment is only one aspect of the concept of sustainability; social and economic aspects must also be considered;
  • An environmentally friendly diet is not necessarily healthy, and vice versa;
  • Eliminating animal-based foods such as meat and dairy in favour of only plant-based foods may not necessarily be the best option.

All food systems, from the primary production of the food to when it is consumed, rely in some way on natural resources such as water, fertile soil and biodiversity. Food systems currently account for about 30% of the world’s energy consumption and over 20% of total greenhouse gas emissions (GHGE).1

Sustainable diets are defined by the Food and Agriculture Organization (FAO) of the United Nations as “those diets with low environmental impacts that contribute to food and nutrition security and to healthy life for present and future generations. Sustainable diets are protective and respectful of biodiversity and ecosystems, culturally acceptable, accessible, economically fair and affordable, nutritionally adequate, safe, and healthy, while optimizing natural and human resources.”2

What makes a diet sustainable?

There is currently no consensus as to what constitutes a sustainable diet. While the concept of sustainable diet not new, it is complex.

Most studies support that there are environmental benefits to increasing the consumption of fruits and vegetables, while reducing the consumption of animal-based foods.3,4 However, the majority of studies have only looked at GHGE (a marker for climate change) as an indicator of environmental impact. Yet, in addition to climate change, the effects on various other aspects of the environment, such as land use, water footprint, energy or fossil use, also need to be considered. Furthermore, other aspects of sustainability also need to be taken into account, including social and economic factors, as well as nutrition and health. 

A 2015 systematic review evaluated the environmental impact of dietary change. Among the different scenarios examined, a vegan diet—followed by a vegetarian diet, a diet replacing ruminant meat with pork and poultry, and a “healthy” diet (according to dietary guidelines)—had the largest potential to reduce GHGE. Similarly, a vegan diet—followed by a vegetarian diet and a “healthy” diet—would result in the greatest improvement in land use demand.4

In another systematic review published in 2015, it was concluded that there is a “need for a far more complete assessment of the environmental, social, and economic impacts of foods and diets.”5

A study conducted in the UK showed that a model diet, without acceptability constraints, consisting of only 7 foods that met all energy and nutrient needs could reduce GHGE by 90%. Given that the amounts of the foods were large and atypical, the authors examined another model that accounted for acceptability constraints. In this more realistic scenario, which consisted of 52 food categories, GHGE were reduced by 36% without eliminating meat or dairy products, or increasing the cost to the consumer.6

Using data from the 1995 Australian National Nutrition Survey, Hendrie et al. conducted a modelling study to estimate GHGE from different dietary models.7

  • The typical average Australian diet had the highest GHGE, provided the greatest amount of energy, yet was not nutritionally adequate;
  • Non-core foods, such as cakes, biscuits, chips, desserts, soft drinks and processed meats, accounted for 27% of diet-related GHGE;
  • Both a dietary pattern consistent with the recommended guidelines and one meeting the minimum nutrient and energy requirements were nutrient-rich and had the lowest GHGE.

Is a healthy diet environmentally friendly?

An environmentally friendly diet is not necessarily healthy, and vice versa. There are data to suggest that increasing fruit and vegetable intake, while reducing animal-based foods, may not be the optimal environmental approach.

In a prospective cohort study of 40,011 subjects in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Netherlands cohort, GHGE and land use of a usual diet were not associated with all-cause or cause-specific mortality. The study also found that substituting meat—especially with the food categories of vegetables, fruits/nuts/seeds, fish, pasta/rice/couscous—was associated with a lower mortality risk and reduced environmental burden.8

A French national dietary survey of 1,918 adults found that:9            

  • When determined on the basis of food weight (i.e. per 100g), GHGE for dairy, mixed dishes, pork, poultry, eggs and fish were 2 to 5 times higher than for fruits and vegetables;
  • However, when determined on the basis of energy density (i.e. per 100 kcal), GHGE for fruits and vegetables were 25% higher than for dairy products, and similar to mixed dishes, pork, poultry and eggs;
  • Additionally, after adjustment for age, sex and energy intake, an increased intake of fruits and vegetables were also positively correlated to GHGE;
  • Regardless of assessing GHGE per food weight or energy density, ruminant meat was the food group with the highest GHGE value.

After adjustment for the energy intake of French dietary patterns, it was also found that:9

  • Higher-quality diets, with more fruits and vegetables but fewer sweets and salted snacks, were associated with significantly higher GHGE;
  • Conversely, lower-quality diets with high amounts of sweets and salted snacks were associated with lower GHGE.

There is also growing evidence that suggests that a diet low in meat and high in fruits and vegetables may not have a lower environmental impact because of the amount of vegetable substitutes that need to be consumed to replace animal proteins and calories.3,10  Vieux et al. found that when meat and deli meat were isocalorically replaced by fruits and vegetables there was a null effect, or even increased GHGE.10

There are also certain issues that need to be taken into account regarding plant-based diets:3,5,11

  • A strict plant-based diet may not be optimal as it would require a substantial shift in typical food choices and it poses nutritional risks;
  • Vegetables and grains require higher-quality land, but certain areas have more lower-quality land, which is suitable for forage crops not consumed by humans;
  • Most studies indicate that animal-based foods generate more GHGE than plant-based foods, but this does not apply to fruits and vegetables grown in greenhouses;
  • Sustainable and certified produce tends to be more expensive, which is a barrier to accessing a healthy, sustainable diet.

Other factors to consider regarding sustainable diets

Overconsumption of food has detrimental effects on both the environment and health. Overconsumption places an unnecessary increased demand on food production, resulting in higher GHGE.12

Moreover, food waste occurs across the entire food supply chain and has been estimated to be 10% to 40%.5 Particularly in developed countries, food waste at the retail and consumer levels is an important issue.13

Conclusion

While a lower consumption of foods from animal sources may be more environmentally friendly, the current available data are largely based on one indicator only, i.e., GHGE. Additionally, from a nutritional, cultural, social and economic perspective, reducing or eliminating animal-based foods from our diets may not be the optimal solution.

More research is needed to identify the dietary changes needed to achieve sustainable, healthy diets that are feasible and acceptable.

References

  1. Food and Agriculture Organization of the United Nations. Energy-smart food for people and climate. Rome, Italy. 2011.
  2. Food and Agriculture Organization of the United Nations. Sustainable diets and biodiversity: directions and solutions for policy, research and action. Rome, Italy: FAO and Bioversity International. 2012.
  3. Reynolds CJ et al. Are the dietary guidelines for meat, fat, fruit and vegetable consumption appropriate for environmental sustainability? A review of the literature. Nutrients 2014;6:2251-2265.
  4. Hallström E et al. Environmental impact of dietary change: a systematic review. J Clean Prod 2015;91:1-11.
  5. Auestad N and Fulgoni VL III. What current literature tells us about sustainable diets: emerging research linking dietary patterns, environmental sustainability, and economics. Adv Nutr 2015;6:19-36.
  6. Macdiarmid JI et al. Sustainable diets for the future: can we contribute to reducing greenhouse gas emissions by eating a healthy diet?  Am J Clin Nutr 2012;96:632-639.
  7. Hendrie GA et al. Greenhouse gas emissions and the Australian diet: comparing dietary recommendations with average intakes. Nutrients 2014;6:289-303.
  8. Biesbroek S et al. Reducing our environmental footprint and improving our health: greenhouse gas emission and land use of usual diet and mortality in EPIC-NL: a prospective cohort study. Environ Health 2014;13:27.
  9. Vieux F et al. High nutritional quality is not associated with low greenhouse gas emissions in self-selected diets of French adults. Am J Clin Nutr 2013;97:569-583.
  10. Vieux F et al. Greenhouse gas emissions of self-selected individual diets in France: changing the diet structure or consuming less?  Ecol Econ 2012;75:91-101.
  11. Clonan A and Holdsworth M. The challenges of eating a healthy and sustainable diet. Am J Clin Nutr 2012;96:459-460.
  12. Macdiarmid JI. Is a healthy diet an environmentally sustainable diet?  Proc Nutr Soc 2013;72:13-20.
  13. Reisch L et al. Sustainable food consumption: an overview of contemporary issues and policies. SSPP 2013;9:7-25.

Keywords: sustainability , environment , Mediterranean diet


  • Educational Material Educational Material Educational Material
    Educational Material

    Need educational resources for your practice? Download copies online, or order print versions free of charge.

    Make a request
  • /newsletter
    NutriNews®

    Every month, articles of interest are featured in our NutriNews Bulletin. Sign up today to stay up to date on the latest scientific evidence and research.

    Sign up