10.4 What are the possible unintended consequences of changing diets?

10.4.1 Multiple possible changes in diet may have unintended negative consequences.

Hypothetical example: Potential unintended consequences arising from measures to reduce people’s meat consumption

Adapted from Garnett T (2014). Changing consumption: How can we change the way we eat? A discussion paper. Food Climate Research Network, University of Oxford

There are many potential consequences of interventions, some intended, some unintended. These potential consequences and possible trade-offs need to be considered when planning interventions.

For example, the “doughnut effect”: when making changes in eating patterns people might substitute high impact foods such as meat for lower impact processed refined foods that have less nutritional quality and other environmental issues (e.g. grains or oils that drive land-use change). Similar substitution effects could occur between types of meat, or from unprocessed meat to unhealthy cheaper processed meats.

10.4.2 The substitution effect must be considered.

Substitution effects need to be understood and monitored

The substitution effect in this case refers to a change in consumption patterns in response to an interventions, such as a change in price . The substitution can be positive or negative.

Two potentially positive examples:

  • If the price of meat increased, people might eat less meat, and more legumes and diverse vegetables, providing good nutrition and lower environmental impacts.
  • If the price of fruit and vegetables was reduced, people might eat a greater proportion and diversity of these products in their diets, providing good nutrition and potentially lower environmental impacts.

Two potentially negative examples:

  • If the price of meat increased, people might in response maintain the same volume of meat consumption, but buy cheaper, less healthy meats. This might not reduce GHG emissions, and might worsen health problems.
  • If a carbon tax were applied to GHG emissions, people might in response eat more “high-sugar” processed foods because the price of such foods would be relatively low (sugar has a low GHG profile). This could have negative health consequences.