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If we are serious about tackling climate change, most of us need to eat fewer animal products. But there are other benefits, too. By Andrea Graves.
It’s been a harsh summer in the northern hemisphere.
Almost everyone has got the message by now: combating climate change is not something we can put off until the future – it is already starting to bite. When it comes to putting some teeth behind your actions, however, what kind of diet might help? What is the most climate-friendly diet, and is the trade-off malnourishment?
According to the latest report by the Intergovernmental Panel on Climate Change (IPCC), a plant-based diet is the biggest behavioural shift a person can make to reduce their individual greenhouse-gas emissions. Food choice falls into the “shift” rather than “avoid” category, says the IPCC, because the global food system is responsible for about a quarter of human emissions.
But what exactly does “plant-based” mean? Merriam-Webster hasn’t yet added the term to its dictionary, stating that the definition is still unclear. To some people, it means cutting out all animal products, but to many, it encompasses low-meat diets. It can mean vegan, vegetarian or flexitarian.
Whatever rules you follow, there appears to be a growing number of such eaters in Aotearoa: according to an annual survey of more than 1500 Kiwis commissioned by Rabobank, vegetarians have increased from 7 per cent to 9 per cent of respondents over the past year, while those declaring themselves vegans are up from 2 per cent to 5 per cent. Nearly a third of those surveyed want to eat less meat, whereas 7 per cent plan to eat more.
Australasians are the world’s biggest red-meat and milk consumers, outpacing even high-income North Americans. People in South Asian countries eat, on average, about a 20th of our typical red-meat intake.
Red meat sits at the pinnacle of greenhouse-gas producing foods. Beef consistently leads the pack, followed by lamb, processed meats, pork and cheese. Milk in its unprocessed form falls far lower on the scale. But products’ emissions depend on how they are produced; New Zealand beef, lamb and milk lie at the lower end of the spectrum, but still well above plant proteins.
Local research shows that cutting out meat still significantly lowers diet-related emissions. A University of Otago study found that compared with a standard New Zealand diet, vegetarianism cut emissions by 30 per cent and veganism by 33 per cent. Another study showed that meatless but dairy-rich fare cut dietary emissions by nearly a quarter. That study’s authors, who were mostly from the Ministry for Primary Industries and Massey University’s Riddet Institute, emphasised that a century from now, when the eater will have died, the methane emissions associated with meat will have largely finished exerting their powerful warming effect and broken down. However, if younger generations keep eating meat, they’re likely to keep methane levels elevated.
One of the study’s authors, Carlos Gonzalez-Fischer, is now at Cornell University in New York, but was previously at the New Zealand Agricultural Greenhouse Gas Research Centre. Gonzalez-Fischer, whose speciality is food systems with an emphasis on livestock and climate change, says the important message is that all studies show that changing your diet to reduce your meat intake can significantly reduce dietary emissions.
As with all trends, individual changes may not make a huge difference on their own, but collectively they have a multiplier effect, he notes. And they can also have important ramifications for other issues, such as land use, health, and animal welfare.
Land use matters because if people can be fed from less land, there’s more space to restore or preserve native forests and wetlands. Those ecosystems sequester far more carbon than land comparatively denuded for agriculture or crops.
Because it takes a lot of land to feed cattle, beef production is considered particularly tough on the environment, regardless of whether the cattle graze pasture or are fed crops and crop residues. Such calculations also rate a food as more climate-friendly if its production is more intensive and therefore spares land. However, this assumes freed-up land is actually used for carbon-sequestering ecosystems.
“There are other consequences to eating less meat that are so positive it’s crazy not to consider it,” says Gonzalez-Fischer. “For most people in the developed world, eating less meat is a good idea.”
Could cutting back on meat harm our health? The weight of evidence falls heavily on the opposite effect. Most studies show vegetarian, vegan and low-meat diets reduce the risk of developing what most Westerners die of: cardiovascular disease, cancer and type 2 diabetes.
Professor Sheila Skeaff, of the University of Otago’s human nutrition department, says the evidence from numerous studies, published in reputable journals, is that a decrease in meat consumption in many countries would benefit both human and planetary health. “All the food and nutrition guidelines being redeveloped in countries around the world are shifting their emphasis towards a plant-based diet and reducing consumption of meat,” she says.
Boyd Swinburn, professor of population nutrition and global health at the University of Auckland, says diet is by far the biggest risk factor in the world for disease and early death. “Diets high in salt and sugar and low in fruit and vegetables account for about 18 per cent of disease in Aotearoa. That’s twice the impact of tobacco.”
He says the global food system is responsible for the human and environmental health “syndemic” (meaning problems caused by two of more epidemics interacting with each other). “Of the types of food that have health impacts, ultra-processed foods are the worst. Sugar, confectionery, french fries and chocolate biscuits are all plant-based, but definitely not wholefoods,” he says. “‘Plant-based’ needs to be qualified as wholefoods.”
To tease out what dietary factors move the health dial, Swinburn and all the experts the Listener spoke to pointed to the Global Burden of Disease (GBD) study. It crunches a massive amount of international data to show that although a diet high in red meat (which includes pork) is indeed a risk factor for disease and early death, processed meat is worse.
The riskiness of either is dwarfed by sodium (salt). After salt, and well above meat, comes a lack of certain foods. The deficits that have the greatest effects are, starting with the highest risk: wholegrains, fruit, nuts and seeds, vegetables, omega-3 fatty acids, fibre, legumes and polyunsaturated fatty acids.
When people reduce meat, they typically eat far more of these foods if they can choose healthy options. (A possible exception is omega-3 fatty acids, which come mostly from marine sources.) Their production comes at a much lower greenhouse-gas cost than does red meat, but sometimes uses more water.
The average downunder diet is far from ideal, according to the GBD study, and even falls below the suggested milk intake of 400g a day. For instance, Kiwis devour about three times too much red meat and processed meat. According to the study, the optimal red meat intake is about 23g a day – perhaps a sixth of an average steak.
Cristina Cleghorn, a public health nutrition researcher at the University of Otago’s department of public health, took part in the research that showed that vegetarianism, and especially veganism, cuts diet-related emissions.
“When you change the average diet towards a low-emissions one, you’re changing the intake of dietary risk factors,” says Cleghorn. “We looked at the potential savings to the health system associated with those reductions in chronic disease. Over the lifetime of the modelled cohort, the savings got up to about $20 billion if the whole population went vegan.”
Cleghorn also leads research into finding a Kiwi diet that meets nutrition needs and reduces greenhouse-gas emissions without increasing costs to individuals. The outcome is similar in several ways to the internationally formulated EAT-Lancet “planetary health” diet. That diet is designed to feed 10 billion people, reduce deaths caused by unhealthy and insufficient diets, and prevent the collapse of the natural world. It calls for plant-sourced protein and, optionally, modest animal-product consumption.
Modest” means just under 100g of red meat (a small steak) weekly and 200g each of poultry and fish at most. Potatoes are limited to the equivalent of a small spud daily and eggs to two a week. Wholegrains, vegetables, nuts and legumes are abundant. The diet includes up to two cups of dairy milk and two tablespoons of sugar a day.
According to the authors, this diet would improve almost everyone’s health, and reduce early death by an estimated 19 per cent. It would not free up much land, although it would prevent further wild areas being cleared, while feeding more people.
Not surprisingly, some of those associated with the agricultural industries are keen to put forward a different point of view. Warren McNabb, professor of nutritional science at the Riddet Institute, says mathematical modelling by the institute and Fonterra (with which it has a strategic relationship) has shown that if meat and seafood were removed from global food systems, it would not be possible to grow enough plant foods to provide sufficient micronutrients for the 2030 global population without further deforestation.
McNabb is also concerned that cutting meat will cause people to over-consume calories. The problem, he says, is that a plant-based diet has a much lower concentration of several nutrients. “When we model this, we see calories go up. If you control calorie intake in this kind of scenario, then you get less micronutrients because they tend to be lower in plant foods.”
His co-author, Nick Smith, notes that although people consuming a vegetarian diet tend to have a healthier body mass index than the average person, this may be because people who avoid meat have other healthy habits that lower body weight.
Sheila Skeaff is sceptical. Seven out of 10 adults in New Zealand are overweight or obese, she notes. “If eating meat helped with calories, surely we should see fewer people in New Zealand who are overweight than in other countries that have much lower meat intakes,” she says.
Skeaff also observes that substituting meat with vegetables, legumes and wholegrains is likely to increase some other nutrients. “Although the amount of nutrient in a diet can give an indication of a problem – or not – it is more important to look at the outcome of the poor diet such as anaemia, osteoporosis, growth in children, heart disease, etc.”
Boyd Swinburn insists that switching to wholefood, plant-based diets actually leads to lower calorie intake. “It increases the bulk considerably because plants are full of water and fibre. People tend to eat to a weight of food, so more whole plant foods at the same weight of food gives fewer calories.”
Swinburn also suggests the institute’s claims about potential deforestation are unrealistic because there is no serious proposal to end all meat-eating.
When the Riddet team modelled removing flesh production, it left dairying at current levels and evenly upscaled eggs, milk and existing plant crops.
“What this shows,” says Gonzalez-Fischer, “is that if we remove all meat from global diets, we need to restructure the whole food system. But it does not necessarily mean we can’t find a combination of eggs, dairy and crops that would satisfy global nutritional requirements.”
The mixture of crops would likely have to change significantly in a low-meat future, according to the EAT-Lancet report, featuring proportionately more legumes and nuts. These are low-yielding crops but it is believed they could benefit from the same efforts that have boosted yields from wheat, maize and rice, which contribute more than half the calories people eat.
None of the experts the Listener spoke to believe we all need to stop eating meat, but most say we can safely do so. “Adults in rich countries are perfectly fine without meat and dairy, or a small amount,” says Swinburn. “That’s compatible with being responsible environmental citizens and doing what we can to reduce climate change.”
Going vegan is too much for most people, he says. “People have busy lives and when their bandwidth gets taken up … they take the easy, cheap option. There are quick, cheap vegan meals, but they’re mostly not part of our national cuisine.”
One way to make changes to what’s “normal” would be free school lunches, he says. He has been calling for years for the government to pull levers to improve diets.
Skeaff agrees. “Moving towards more plant-based diets is a no-brainer. But it has to be a gradual shift. If you’ve had meat every day, shift to one day a week without it, then two, then three.”
Perhaps a literal carrot and figurative stick might work, says Cleghorn. “With food prices at the moment, people aren’t keen on taxes, but if you put a tax on some of the more emissions-intensive foods, with a subsidy on foods that are good for health and have low greenhouse-gas emissions, the impact on people’s weekly shop could be cost-neutral.”
Her team found that a greenhouse-gas tax plus a fruit and vegetable subsidy would save about $6 billion in health costs over the modelled cohort’s lifetime.
“If the average New Zealander could eat less meat – smaller portion sizes and less frequently – that could have a big impact on our dietary greenhouse-gas emissions, rather than relying on a smaller proportion of the population giving up meat.”
Swinburn is involved in the Aotearoa Circle, a voluntary collective that aims to reverse the decline of our natural resources. Its Mana Kai initiative is taking a mātauranga Māori approach to the future of food that considers how the wellbeing of people and the natural environment connect. “It’s a world view that’s far closer to what we need,” he says.
Andy Reisinger, one of New Zealand’s climate commissioners and vice-chair of the working group that produced the latest IPCC report, says one thing is clear: without targeted efforts to reduce food-related emissions, it will become impossible to restrain global heating within the “safe” limit — even if we rapidly reduce fossil-fuel use and achieve global net zero carbon dioxide emissions by the middle of the century. “We can only limit warming to anywhere near 1.5 degrees if we pull all levers, not one or the other,” he says.
A shift towards less meat cannot be universal. “It’s naive to think that not eating animal products can be a global prescription,” says Andy Reisinger. “Livestock provide a basic reliable income and nutrition for many people in developing countries. When crops won’t grow, people can rely on animals to carry them through a drought period. Dung is used for fertiliser and fuel. And there are about 900 million malnourished people, most of whom could really do with consuming more milk and meat for the nutrients they provide.” He says it would be unfair for rich countries, which have generated the vast majority of emissions to date and continue to have high emissions per capita, to tell poor countries what they can eat to save the climate.
Carlos Gonzalez-Fischer notes that more than a billion people globally have livelihoods supported by livestock systems. “Policies aimed to reduce demand for livestock systems will need to provide for a ‘just transition’ for those livelihoods,” he says.
Some climate-friendly food habits are simpler to cultivate than diet change.
Avoiding food waste is one. It matters because greenhouse gases are emitted when food is produced, processed, packaged, transported, chilled, and cooked – but it’s all for nothing if the food isn’t eaten. If it rots in landfill, it produces even more gases.
The problem is huge. It has been calculated that if global food waste were a country, it would be a bigger emitter than India.
The office of the prime minister’s science adviser estimates that New Zealanders waste 157,000 tonnes of food per year, and hundreds of thousands more tonnes may be wasted before reaching our homes or plates.
Eating more than you need is also unhelpful. A climate-friendly diet involves eating enough nourishing food to maintain a healthy body weight, but not more.
Eating locally is another common recommendation. However, that would only have a significant impact if transport generated a large share of food’s carbon footprint. “Transport tends to be a small part of a product’s total emissions, unless it’s air-freighted here – emissions from production are generally much bigger,” says climate commissioner Andy Reisinger.
Counterintuitively, imported foods that can be grown more efficiently elsewhere could have a lower footprint.
Eating seasonally can also be climate-friendly, particularly if it’s produce that’s grown outdoors. Natural gas or even coal is regularly used to heat glasshouses to grow summer vegetables over winter. And some indoor crops, like tomatoes, are grown with added carbon dioxide.
Vegan diets need more planning and dietary knowledge than vegetarian ones, and plant milk fortified with B12 and perhaps calcium is advisable. People are often concerned about getting enough calcium and iron, but Sheila Skeaff says calcium intake is low in many groups, regardless of whether they eat meat or dairy, and Kiwi women can have low iron regardless of how much meat they eat.
Although dietary changes in themselves don’t usually trigger an eating disorder, they may be a symptom of one, especially if accompanied by significant calorie reduction and over-exercise.
“For most young people it’s a good idea to be aware of the environment and eat more healthily,” says child and adolescent psychiatrist and paediatrician Hiran Thabrew of Starship Children’s Hospital. “Parents can support these young people to adjust their diet in a healthy way, making sure they get enough quantity and variety of food. But if they notice their children significantly restricting the amount and type of plant-based food they’re eating, they should seek advice from a health professional.”
Athletes’ bodies have high demands but seem to do well without meat. Studies have compared the performance of omnivorous athletes with vegetarians and/or vegans and come up with a consistent result: it makes no difference at all.
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