9.3 Do recommended healthier diets contribute to lower environmental impacts and vice versa?

9.3.1 Comparing GHG emissions and land use of idealised diets with ‘average’ diets: the Netherlands

‘Recommended’ diets have lower GHGs than ‘average’ Dutch diets, but higher GHGs than nutritionally balanced vegetarian, vegan or ‘Mediterranean’ diets


van Dooren et al. (2014).
 

Government-approved food based dietary guidelines may recommend that meat intakes are moderate rather than high (for example stipulating a maximum of 500g red and processed meat per person, per week), and that energy intakes are in line with energy requirements.

This study compared a range of idealised diets with the average Dutch diet – the official Dutch ‘recommended diet’, a Mediterranean diet and nutritionally balanced semi-vegetarian, vegetarian and vegan diets. (A Mediterranean diet is explained here: oldwayspt.org/programs/mediterranean-foods-alliance/what-mediterranean-diet).

These were based on modelled, rather than real-life diets. In reality, people may not always eat in a nutritionally balanced way, an important point to take into account.

The recommended Dutch diet did have a lower GHG than the average Dutch diet, but other diets had lower emissions still.

The GHGs of the nutritionally balanced vegan diet were 34% lower than that of the average nutritionally balanced Dutch diet.

The study did not take into account any possible carbon sequestering effects arising from ruminant production. The potential that well managed grazing can promote soil carbon sequestration is still an under researched area, would apply (if borne out by evidence) only to ruminant rearing systems, and is discussed briefly in Chapter 8.

The same pattern is found for land-use requirements from different diets


van Dooren et al. (2014).

The same trends are evident for land-use requirements.

 

9.3.2 Comparing GHG emissions, land use and biodiversity impacts of a variety of diets: Sweden

Recommended healthy diets can have lower GHG, land-use and biodiversity impacts than ‘average’ diets and Paleo diets: the example of Sweden


Röös, et al. (2015).
 

This study compared the impacts of the average Swedish diet with a diet following Swedish government recommendations and a popular fad eating pattern, the ‘Paleo’ (Palaeolithic) diet. (Followers of the Paleo diets consume a great deal of animal protein and avoid carbohydrates – an interpretation of the ‘Paleo’ diet is explained here: thepaleodiet.com/what-to-eat-on-the-paleo-diet).

The research showed that the Swedish recommended diet had 30% lower GHGs than the average Swedish diet, due to lower impacts from meat and certain beverages.

The recommended diet also had lower land-use requirements and lower impacts on biodiversity (Biodiversity Damage Potential or BDP, based on land occupied).

The Paleo diet had considerably higher impacts across all metrics.

The study did not take into account any possible carbon sequestering effects arising from ruminant production. The potential that well managed grazing can promote soil carbon sequestration is still an under researched area, would apply (if borne out by evidence) only to ruminant rearing systems, and is discussed briefly in Chapter 8.

9.3.3 Possible environmental impact increases resulting from average to recommended diet shift: USA

Models have not always shown environmental benefits from a shift from “average” diets towards recommended diets. This study modelled current USA diets compared to diets based on USDA recommendations under the following scenarios:

A shift from average to recommended diets might increase environmental impacts, depending on the recommendations: USA as an example


Tom, Fischbeck and Hendrickson (2015).
Modelled comparisons between current USA diets and diets based on USDA recommendations show increases in GHG, energy use and irrigation water use.

This is due to USDA recommendations for high fruit intake leading higher energy and water use, and high dairy intakes, leading to an increase in GHGs, as well as recommendations to eat more fish.
 

 

1.recommended calorie intake (the “average” diet in terms of nutrient balance, but with fewer calories consumed)

2.recommended food mix (shift to the recommended diet, but no reduction in calorie intake)

3.both (fewer calories and shift to the recommended diet).

Only scenario 1 resulted in lower environmental impacts (the same food, but fewer calories consumed), whereas the recommended diet was determined to have higher GHG, energy use and blue water footprint than current USA diets for both scenarios 2 and 3. In other words, a shift towards the USDA recommended diet might be considered healthier, but could result in increased environmental impacts even with reduced total calorie intake.

The reasons for this were considered to be the very high levels of dairy and fruit in the recommended diet (the USA has the highest recommended dairy intakes in the world), which tend towards high GHGs (especially dairy) and energy and water-use (especially fruits). This demonstrates two key points:

-The food that is substituted can critically influence the environmental outcome, especially where energy-dense sugary foods (which have relatively low GHGs) are replaced. This substitution effect is discussed in more detail below.

-Not all recommended diets align with sustainability. For more on interventions, government policy and transitions towards SHEPs, see Chapter 10.

9.3.4 GHG emissions of real-life healthier diets higher than average diets: France

Healthier diets do not always lead to lower environmental impacts for several reasons. The substitution effect is an important consideration – this is where swapping one food for another may be healthier, but can also have negative environmental impacts (in this case GHG). This study compared real life French diets and clustered them into a range of nutritional classes, ranging from high to low.

This French study on real-life diets shows that some healthier diets can have higher GHGs than unhealthy diets


Vieux, et al. (2013).
 

It found that the reported healthiest diets had a higher GHG impact than the unhealthiest diets. This was for several reasons:

  • The healthiest diets did contain lower quantities of ruminant meat, but quantities of pork, poultry and egg consumed did not differ much from less healthy diet.
  • The reported healthier diets were also higher in dairy products than the unhealthy diets – these are animal source foods of ruminant origin and so are associated with high GHG impacts.
  • The healthier diets were rich in fruit and vegetables and lower in sugary foods; the unhealthy diets had the reverse characteristics. Sugar has a relatively low GHG profile (which is why it is cultivated as a biofuel), so can be part of an unhealthy eating pattern that has a relatively low GHG impact. There are however other environmental concerns that arise from sugar cultivation.

So, in terms of the substitution effect, replacing sugary foods with fruits and vegetables (especially if grown unseasonally, in heated greenhouses) can result in an increase in GHGs. Interventions designed to encourage changes in eating patterns need to be aware of these effects (see Chapter 10  for more on interventions and potential substitution effects and trade-offs)

9.3.5 Substitution effect

Shifting consumption towards healthier diets does not always or necessarily result in lower environmental impact.

If a shift towards a healthier diet results in eating high levels of dairy and fruits (that are grown in greenhouses or airfreighted, see Chapter 3), this can result in higher GHGs and potentially increase other impacts such as water stress.

Potential substitution effects from changes in eating patterns can therefore have important consequences