Sustainable eating: which diet is best?

By planetm | May 10, 2021

Avoiding meat, dairy and fish might be a great start if you want to eat a sustainable diet, but local, seasonal eating is important too, says Laura Silverman.

In an episode of Horizon entitled ‘Feast to save the Planet’, MasterChef presenter Gregg Wallace served dinner to five celebrities. He scored dishes on their environmental impact.

He used a measure devised by Professor Mike Berners-Lee, at Lancaster University. It calculated the carbon footprint of each ingredient by considering the carbon emissions of fertilisers, agricultural machinery, transport, processing and packaging.

On average, we each create the equivalent of 8.2kg of carbon from food every day, said mathematician Hannah Fry, his co-host. This needs to fall to 3-4kg a day to meet the government commitment of net-zero carbon by 2050 and slow the speed of global warming.

But how can we ensure that our diet has a low impact on the environment?

Is plant-based best?

It may come as little surprise that the dishes that fared worst were sirloin steak and a cheese plate.

By every measure, a plant-based diet is best. A 2018 study, led by a researcher at Oxford University and published in the journal Science, found that the biggest thing we can do to help the environment is avoid meat and dairy.

Eating plants is a much more efficient use of resources than feeding plants to animals, which we then eat. 

The following year saw another big study by the EAT-Lancet Commission. This looked at ‘planetary boundaries’ that affect the Earth, such as greenhouse gas, freshwater use, land-system change, biodiversity loss and fertilisers.

The resulting ‘planetary health diet’ is similarly plant-based. It consists of half fruit and vegetables, a third wholegrain cereals, some plant proteins (beans, lentils, pulses, nuts) and unsaturated plant oils. And, if you like, small amounts of meat and dairy. 

But the issue is complicated. Is cutting out or dramatically reducing dairy, meat and fish enough?

Locally- grown produce

Helena Norberg-Hodge, founder and director of NGO Local Futures, claimed recently at the Oxford Real Farming Conference that eating local food could ‘save the world’.

The global food economy is responsible for half of global greenhouse gas emissions and small-scale, biodiverse farms are the only way to increase productivity and make the best use of the soil.

And eating locally produced food, in season, seems to make sense as it comes with a lower carbon footprint from transport. It just might not be everything.

Dr Cassandra Coburn, who advocates the planetary health diet in her new book, Enough, warns that “carbon emissions from transport in the food system make up just six per cent of greenhouse gases”.

You also need to consider the impact of farming methods on the environment.

The benefit of buying locally, from a farm shop or market, is that you can find out about the farmer’s approach to sustainability from the source.

Go for organic or LEAF (Linking Environment and Farming), which shows that a farm adheres to good environmental practices (the latter, unlike the former, allows fertilisers where essential).

This means you will be staying away from intensive farming, where the farmer doesn’t rotate what they grow, leading to pollution and soil erosion.

Synthetic fertilisers contain chemicals such as ammonium and nitrogen, which contribute to global CO2 emissions.

Riverford delivers a 100 per cent UK organic veg box, with a changing seasonal selection, as does Abel & Cole.

You could also shop through Farmdrop, or look for a community scheme near you. 

Root vegetables, like celeriac and parsnips, are in season in the UK for eight months and store well. You can preserve fresh produce, too, by making jam and pickles, or freezing it (berries, green beans, spinach and peas freeze well).

But if you’re strict about eating locally and seasonally, your diet could, at times, be narrow. Even Riverford stops its UK veg box in May and June, when there is little to harvest.

Is is that simple?

It might then come as a relief to hear that local produce is not always best. While food may have lower transport emissions, the cost of growing produce in unsuitable climates can eclipse the benefits.

“If you’re buying something grown in the UK,” says Dr Coburn, “you have to think about what grows well here. We have lots of water, but little sunlight. Do farmers use artificial light? Do they have to protect their crop from getting over-saturated with water?”

Tomatoes grown in a hothouse in the UK, for example, often have several times the climate impact of those imported from sunnier countries such as Spain.

If you do buy produce from abroad, shipping is much better than air travel: cargo planes can emit ten times more carbon than freight ships.

But how do you know? Labels rarely show the mode of transport. As a guide, highly perishable vegetables like asparagus tend to be flown in and are therefore best eaten in June, when they’re in season in the UK. Bananas, however, tend to be shipped, making them relatively low impact.

Eating the most sustainable diet for you

The planetary health diet recommends we get protein from chickpeas, lentils and soyabeans, which have a much lower impact than that of meat or dairy.

Much of our soya comes from Brazil and Argentina, where forests are cleared to grow it. It’s a huge issue, but most of this soya is produced for animal feed.

Buy soya products from stores like Co-op and Tesco, which have signed up to Round Table on Responsible Soy schemes.

Berners-Lee, author of How Bad Are Bananas?, has called for traffic-light labels, based on the carbon footprint of each food.

“If we’re constantly having to think about what we should eat, it becomes exhausting and we want to give up,” says Dr Coburn.

“If you look at the impact globally, it’s enough to move towards a ‘veganish’ diet, wherever produce comes from.”

And yet, if you do know where – because it’s a local, organic farm who grow produce sustainably, then surely that’s all the better. To find out what’s in season now, visit Eat The Seasons.

This article first appeared in issue 16 of Planet Mindful magazine. Join our community and make a pact to prioritise your self care – try an issue here for just 99p!

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