Following the diet slashes land use by 50 per cent, greenhouse gas emissions by 29 per cent, and fertiliser use by 21 per cent, but I just felt hungry, says Sophie Morris

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It’s breakfast time and I feel like I’ve failed already. I am supposed to be starting the family off on a new, so-called ‘eco-friendly’ diet, but my daughter is already shovelling down Brazilian mangoes, Moroccan blueberries, and peanut butter that has probably seen half the Sahara drained for irrigation.

I used to be quite sniffy about the vogue for “feeding” toddlers exotic fruit and hummus, when most of it was thrown at the wall, and have long bought seasonal British fruit and veg, avoided fish we’re told aren’t sustainable, and have several meat-free days each week. All the same, I’ve mostly defaulted to the easy life when I’m shopping for my daughter, as I’d rather she eat imported fruit than ultra-processed snacks. I squeeze an avocado in the fruit bowl and estimate it will be perfect by lunchtime. We’ll try again tomorrow.

When I first heard about the Planetary Health Diet, I wondered if I’d be required to eat under a pink moon, or only when Pisces is rising. In fact, it’s a far more prosaic approach to eating, which asks greedy consumers to think about the planet when they’re filling their plate.

Following the diet slashes land use by 50 per cent, greenhouse gas emissions by 29 per cent, and fertiliser use by 21 per cent, according to a new study from the American Journal of Clinical Nutrition. And along with its altruistic benefits, it’s good for you, reducing the risk of early death by almost a third.

“The findings show just how linked human and planetary health are,” says Professor Walter Willett, a Harvard academic of epidemiology and nutrition involved in the study. “Eating healthfully boosts environmental sustainability, which in turn is essential for the health and wellbeing of every person on earth.”

The irony of my own lazy attitude is unsettling. Why placate my daughter’s morning mood with a mango, when it’s her generation we need to preserve the planet for?

A vast proportion, around a quarter to a third, of the carbon emissions widely understood to cause climate change, come from food and drink. If we change the way we shop and eat, we should be able to impact these figures.

So what’s involved? No burgers, you won’t be surprised to learn, given that the United Nations estimates that livestock account for 12 per cent of all carbon emissions caused by humans. Instead, the planetary health menu is broadly flexitarian with a focus on wholegrains and an ‘eat the rainbow’ range of fruit and veg.

“The planetary health diet emphasises a plant-forward diet where whole grains, fruits, vegetables, nuts and legumes comprise a greater proportion of foods consumed,” explains the EAT-Lancet Commission. “Meat and dairy constitute important parts of the diet but in significantly smaller proportions than whole grains, fruits, nuts and legumes.”

It sounds very similar to the Mediterranean Diet. But to me, it feels much more restrictive. Although it is flush with fruit and veg, and features some unsaturated plant oils and little refined sugar, the protein is limited.

Alcohol should be consumed in limited amounts, or not at all – while the Med diet recommends moderate drinking, such as a glass of red wine with a meal a day.

There is an illustration of a plate as a guide to what your diet should be composed of, and my typical meal looks nothing like it. I support the idea that 50 per cent is made up of fruit and veg – I tend to put out three or four veg options at dinner so that everyone gets something they like, and eat the leftovers for lunch the next day. But the recommended amounts of dairy, fish, meat and sugar are tiny – under 50g each, which is a single egg, a thumb-sized portion of fish or a few bites of a burger. Suggestions to meet the tiny protein portions include: one skinless chicken thigh every other day, one strip of bacon every other day, and one egg every third day. This highlights the disparity between rich and poor diets, and makes me feel very hungry indeed.

Worse still, starchy veg like potatoes are even more limited than dairy. It feels like I’m being asked to survive on piles of brown rice. Overconsumption, the planetary health diet makes clear, is a huge contributor to climate change; it recommends 2,500 calories a day for the average adult. No doubt the reason I’m hungry on this diet is because I habitually eat too much. While I do eat meals packed with plant-based foods, I’ll add two eggs or a whole tin of tuna to fill me up. I love my morning coffee, but now a single latte blitzes the daily milk allowance.

When I try to overhaul our breakfasts, with porridge instead of peanut butter, I’m stumped when my daughter asks for coconut milk over dairy milk. Which is better for the planet, I wonder. Cow’s milk from down the road, but produced by a beast well known for its gassy habits, or milk from a far flung island struggling to meet the western world’s sudden voracious appetite for coconuts?

But the planetary health diet doesn’t ask us to worry about food miles or seasonality, instead suggesting that if you follow its flexitarian approach overall, the benefits to people and planet will follow. I don’t think that this is an excuse to avoid seasonal or local eating, but it is a good lesson to pay attention to the big picture, instead of feeling swamped by the details about what we should be eating when.

For dinner I make “pink fish” – not salmon, which is an environmental disaster, but trout – new potatoes, along with peas, sweetcorn, broccoli, green beans, pickles and tomatoes. When my daughter asks for more fish, I suggest she finish the broccoli she has taken first. She does, and reports that she is full. I feel like I’ve won the lottery.

Other mealtimes are less successful, because when we don’t eat meat or fish I tend to turn to eggs. I make a white bean soup with lemon, kale, parmesan and a single rasher of bacon and it’s delicious, but our guts can’t take beans every day. Vegetable curries are cheap and tasty, but I need some yoghurt or paneer to fill me up. I reflect on the wide choices available to me for every meal, how much protein I eat compared to what is available to most people around the world, and how little I want to give it up. I remember that insects are supposed to be a sustainable form of protein, but don’t feel like eating them.

The World Health Organisation (WHO) has withdrawn its support for the planetary health approach, saying that the one-size-fits-all regime will damage traditional diets and methods of food production, and lead to job losses in animal-based agriculture and food. Cost is complicated, too, and dependent on location. Critics say it is too expensive for many people, while for others focusing on plants over red meat would reduce food bills.

Shopping and eating with an informed conscience is one thing, but the rub here is that plenty of the problems with our food system come down to production, packaging and distribution. Individuals cannot improve the poor behaviour of Big Food, and given that 100 companies are responsible for 71 per cent of global emissions, there’s little point panicking too much about your own avocado habits.

The planetary health diet reminds me of the food activist Michael Pollan’s most famous quote: “Eat food. Not too much. Mostly plants.” But his recent film FOOD, INC. 2 shows how little power we have to make these good choices as individuals.