Due to a growing world population and increasing prosperity, the demand for good nutrition that provides an optimal intake of nutrients with a low impact on the environment is growing (1). The science behind food sustainability is a developing area and it is important to consider both the nutritional and environmental impact of dietary advice.
Food production has an impact on the environment, including greenhouse gas emissions, land use and loss of biodiversity. A more sustainable food chain from production to consumption is therefore becoming increasingly important. A key part of this is a more sustainable diet.
Scientists, policy makers and politicians agree that a more sustainable diet needs to be healthy and contain all essential nutrients for optimal functioning of the body. In addition, it is important that a more sustainable dietary pattern is culturally appropriate, is affordable, safe and traded fairly. (2) Composing a healthy diet with a lower environmental impact is complex, especially if all factors that are mentioned above are taken into account. For example, the most healthy dietary patterns (high in nutrients, low in energy) are associated with higher greenhouse gas emissions per calorie. On the other hand, the most sustainable diet is not necessarily the healthiest choice when looking at the nutrients supplied (3). With the omission of certain products or product groups often the intake of nutrients also changes, because each food contributes to a greater or lesser extent to the nutrient intake (4).
What are the first steps towards a more sustainable diet? Considering the total dietary intake is a starting point. A ‘simple’ step is to consume as little processed food, extras such as confectionary, biscuits and snacks, and drinks such as alcohol, soft drinks and fruit juice. These products provide relatively less nutrients and more energy, and are not necessarily needed from a health perspective. A diet with less of these foods is therefore in general healthier and more sustainable. Preventing waste, both in the production chain and by the consumer, is one of the steps. (5)
Establishing what a more sustainable diet might look like is regularly assessed via linear programming research. This research uses calculation models to adjust the diet step by step. Indicators such as health (amount of nutrients), sustainability (greenhouse gas emissions, land and energy use) and consumer behavior (food must contain acceptable portion sizes and be not too distant from the current diet) are taken into account. This research area is in full development and there are several ongoing studies. (4)
A recent study by Kramer et al. (2017) used linear programming to optimise the diets of 3819 Dutch men and women in terms of nutrient composition, environmental impact and dietary preferences. (6) Calculations were performed using the Optimeal® programme (Blonk Consultants, Gouda, the Netherlands) which illustrated the effect of changes in the dietary pattern on nutrient sources, in relation to overall environmental impact. Environmental impact of food products was based on Life Cycle Assessment (LCA) research.
As a first step in remodelling a more healthy and sustainable diet, Kramer et al. (2017) optimized the nutrient intake of the current diet in accordance with nutritional recommendations. Thereafter, adjustments in the diet were made by reducing the environmental impact of the diet step by step. The aim was to make minimal changes to the participant’s current diet as the researchers reasoned that consumers do not like to change their diet.
Figure adapted from Kramer et al (2017)
Reducing meat, especially beef, was found to be the most effective way to lower the environmental impact of diets across all the age and gender groups. Removing fish and dairy products did not appear to be as effective as their nutrients must be replaced by other food sources which can also impact on the environment. However consumers can substantially reduce the environmental impact of their diet by drinking less soft drinks, fruit juices and alcoholic beverages. These steps that are not at the expense of the nutritional composition of a diet, ensure a reduction of the environmental impact by 21-30% and only require the slightest change in relation to the current dietary pattern.
The model showed that simply replacing products with more sustainable variants is not always the solution. Practice shows that replacement of one product (group) often changes the nutrient intake. The challenge lies in keeping food valuable from a dietary point of view with minimum environmental impact.
The production of meat, dairy and eggs has a higher environmental impact than the production of, for example, grains, vegetables and fruit. Vegetable material is converted into animal production and ‘energy’ is lost. As a result, animal products score worse on the depletion of fossil and natural resources (including land use) and greenhouse gas emissions. (7) However, food consumption data from the National Diet and Nutrition Survey (NDNS) shows that milk and milk products are the major provider of calcium (35-45% of daily intake), iodine (33%), vitamin B2 (28-34%) and vitamin B12 (33-35%) within the daily diet of adults in the United Kingdom (UK) (8). As a result of this contribution to essential nutrients, lowering of dairy products has no or hardly any effect on the environmental impact of food. This is because in order to preserve nutrient intakes the consumption of other products must be increased to compensate for the nutrients in dairy. Cheese is an exception. Cheese has a higher impact on CO2 emissions per 100 grams than for example 100 milliliters of milk, because about 10 liters of milk is needed to make 1 kilo of cheese. However, when considered per portion consumed, for example a glass of milk (150 ml) or a portion of cheese (20 g) the difference in impact becomes smaller. (9).
Putting sustainable diets into practice
- The science behind food sustainability is still a developing area. There are different ways to achieve a more sustainable diet that provides sufficient nutrients.
- Composing a more sustainable and healthy diet is complex. Simply replacing food product groups can lower the environmental impact, but it also affects the nutrient intake. Less processed foods and less food waste are sustainable choices, as is the reduction of meat intake, alcohol and beverages. This also requires the least change for the consumer.
- Milk provides essential nutrients and the environmental impact of dairy farming should be weighed against the high nutrient density of milk, yogurt and cheese (10)
This article has also been published in the magazine of the British Dietetic Association (November 2018).
Infographic sustainable and healthy nutritionAn infographic on sustainable and healthy nutrition; feeding a growing world population.
Measures and metrics of sustainable dietsDesigning food patterns that are more sustainable and healthy is more challenging than it first appears. Especially when aspects such as availability, affordability and food culture are also taken into account. How do you determine a more sustainable and healthy diet? Drewnowski (2018) is using linear programming models in his research.
Ensuring healthy nutrients in sustainable food requires insightThe world's population is growing rapidly, but our natural resources are finite. So we have to be more careful with them. But what should we do? Simply eat fewer animal and more vegetable products? Well, it would seem that it's a bit more complicated than that and this became clear at FrieslandCampina Institutes's conference on sustainable food held in Utrecht on 19 June 2018.
- FAO (2009). High Level Expert Form, How to feed the world 2050, Rome 12-13 October 2009.
- FAO (2012). Sustainable Diets and Biodiversity, directions and solutions for policy, research and action, 2012
- Drewnowski (2014). Healthy diets for a healthy planet AJCN. First published ahead of print April 30, 2014 as doi: 10.3945/ajcn.114.088542.
- Mertens et al (2016). Operationalising the health aspects of sustainable diets: a review. Public Health Nutrition. doi:10.1017/S1368980016002664
- Kazer, John. (2016). The Eatwell Guide: A more sustainable diet. https://www.carbontrust.com/media/672635/phe-sustainable-diets.pdf
- Kramer et al (2017). Decreasing the overall environmental impact of the Dutch diet: how to find healthy and sustainable diets with limited changes. Public Health Nutrition: 20(9), 1699-1709.
- De Bosatlas van het voedsel, Hoofdstuk: Effect op klimaat en ecosysteem, 2014.
- Public Health England and Food Standards Agency (2017) National Diet and Nutrition Survey. Results from Years 1-4 (combined) of the Rolling Programme (2008/2009 – 2011/12) REVISED FEBRUARY 2017.
- Broekema, G. Kramer, LCA of Dutch semi- skimmed milk and semi- mature cheese, October 2014
- Drewnowski A. (2018). Measures and metrics of sustainable diets with a focus on milk, yogurt, and dairy products. Nutr Rev. 2018;76(1):21-8.