How can we eat healthily and sustainably?

22 August 2017

Interview with

Dr Peter Scarborough, University of Oxford

People often think about eating for their own health, but what about the health of the planet? What changes could we make to our diets that will also have an impact on our carbon footprint, particularly as the world population continues to grow? Georgia Mills put these questions to Peter Scarborough from Oxford University’s Nuffield Department of Population Health, asking first how much of an impact do our food choices actually have on the environment?

Peter - Diet is a good place to start if you’re looking to reduce your global carbon footprint. Not many people realise that the food that they eat has a massive implication on greenhouse gas emissions. In fact, in total 30% of the world’s greenhouse gas emissions that are produced are from the global food systems.

Georgia - Can we juggle these ideas of being healthy and being sustainable at the same time?

Peter - We can, but there are some tensions. The classic one is fish, so the healthy advice for healthy eating is for everyone to eat two portions of fish a week, one of which is oily fish. If everyone in Britain actually met those guidelines, there’d probably be no fish left in the sea; that clearly works against sustainability.

There are ones that are the other way round as well. In sustainability terms it’s best off if we eat all of the food that we produce. So things like sausages and other kinds of processed meat is very good for sustainability because you get cuts of meat that otherwise wouldn't be eaten and you wrap them up with salt and saturated fat to make them palatable, and they’re not good for health. But the general message of being able to eat a healthy sustainable diet largely can boil down to one area and that is meat consumption. So if are eating a diet that is lower in meat, higher in plant based foods, then you’re probably hitting something which is both healthier and better for the environment.

Georgia - I know it’s an age old debate isn’t it - should we be vegan, vegetarian, or continue to eat meat? What do the numbers say I guess?

Peter - In terms of the sustainability, we’ve known for a long time that greenhouse gas emissions related with plant based foods compared to meat based foods are far, far lower - orders of magnitude lower. That’s particularly the case for ruminant meats, so that’s for cows and for sheep because that’s basically about the kind of processes that are involved in the way that meat is raised. When you’re talking about animal based products you’ve got inefficiencies in the system of raising livestock, which is about the fact that you have to feed animals with food that otherwise could have gone to human consumption.

Then you’ve also got natural systems with ruminants like methane production when cows burp and they fart. Essentially methane is about 25% times as high a greenhouse gas emission as carbon. So they all add up to a much higher greenhouse gas emissions for meat based foods than plant based foods.

The work that we’ve been looking at is to say let’s take a vegetarian diet and a vegan diet and compare it to a meat based diet, measure the greenhouse gas emissions from those diets and compare across them. What we found was that in the UK, a meat eating diet has about double the greenhouse gas emissions of a vegan diet and about 50% more greenhouse gas emissions than a vegetarian diet.

Georgia - I know some people say veganism definitely wins in terms of carbon emission, but can you be fully healthy cutting all of this out of your diet?

Peter - Well, the results there in the dietary epidemiology is a little bit more disputed. In non-randomised studies we see that vegetarians and vegans tend to have better health outcomes than meat eaters, but that might be due to confounding. There might be other elements there that vegetarians and vegans are fundamentally different types of people than meat eaters.

We know from the Cohort studies, which are studies which look at people with different diet groups and follow them up over a long time and see how there’s differences in health outcomes.  We know that there’s lower cardiovascular disease outcomes related with a lower meat diet. We also know there’s now very good evidence that a lower meat diet, particularly red and processed meat diet, is related with lower colorectal cancer outcomes. We also know from randomised control trials of short term changes in meat consumption, so moving to small lower meat diets, that’s also associated with reduction in body weight, and reductions in blood cholesterol levels.

Georgia - What should we be doing on an individual and national level to try and reduce our carbon footprint?

Peter - If you’re living in a family and two meat eaters in that family decided to go vegetarian, then that’s roughly the same sort of carbon footprint as a small family car running for a year. Similarly, if you’re a meat eater and you move to be a vegan, that’s the same as an economy trip from London to New York on a plane. It’s those sort of levels of carbon footprint you’re talking about removing from these dietary choices.

The important thing is it isn’t just about changing from being a meat eater to being a vegan, that’s a big switch, it’s a big lifestyle change that not many people would be willing to make. But we know that dietary greenhouse gas emissions are very well correlated with the amount of meat that you eat. So if you just reduce the amount of meat that you consume; start cutting it back on a few days a week, you’ll make a big impact on your dietary carbon footprint.

On a global scale you’re seeing that we’re actually making some progress towards reducing greenhouse gas emissions in a lot of sectors. We’re moving toward cleaner energy, solar power is getting cheaper and we can see a future where we can potentially have clean energy. Similarly there with transport, if you’re moving towards more cleaner energy, you can see a world where we get clean transport.

With food, it’s going in completely the opposite direction. The reason being there is because we’ve got more and more people on the planet that we need to feed. Because the developing world are getting richer, as time goes by they’re moving towards more western diets, and that’s a higher greenhouse gas emission footprint there.

Yet with all the global agreements on climate change, food never comes into it. It’s just too complicated to be within those discussions. If that came into those discussions and if food started to get included and things like cap and trade schemes, then we could start seeing price and greenhouse gas emissions within the food system. But people are very worried about that because the don’t want to see any kind of impact on food prices because that can a lot of very negative knock on effects to the world’s poorest people.

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