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Paul Behrens

By adopting national dietary guidelines, people would improve not only their personal health status but, in most countries, also planetary health, as Paul Behrens and colleagues show. Their PNAS publication happened to appear around New Year’s Eve last year, when people were making new resolutions. ‘That may have been one of the reasons for the extensive media coverage of our paper’, Behrens says.

We can reduce the emission of greenhouse gases by cutting down meat consumption

Food production is one of the main causes of man-caused environmental problems, such as climate change, pollution, loss of habitat and soil degradation, threatening both human culture and nature. The production of red meat and dairy is particularly associated with severe impacts, and a reduction in consumption would be beneficial from an environmental point of view.

It is a lucky coincidence that adoption of a more vegetarian diet has health benefits too, potentially reducing the incidence of obesity, diabetes, cancer and cardiovascular disease. That is why most nations recommend eating less meat and dairy, and more vegetables and fruits instead. ‘National dietary recommendations are an important policy tool to promote health’, Paul Behrens says. ‘But only a few countries mention environmental issues in their guidelines.’ Together with colleagues, he set out to evaluate the potential for reducing environmental impacts through adoption of national dietary recommendations.

He first collected dietary recommendations of 28 high-income nations and 9 middle-income nations, representing 64 per cent of the global human population. He then retrieved data on average diets in those countries from a Food and Agriculture Organization database. He also used EXIOBASE, a database on global economy and its environmental impacts. By harmonising all data and feeding it into a model, he managed to quantify how a shift from average to recommended diets would affect emission of greenhouse gases, eutrophication of ecosystems and land use, the most acute environmental problems worldwide.

The results were striking. In high-income nations, caloric intake is high and consumption of meat and dairy is out of proportion. Environmental impacts are accordingly large. Governments increasingly stress the importance of eating less sugars, oils, meat and dairy, and to eat more vegetables, fruits and nuts. ‘For example, the recommendations presented in the simplified ‘My Plate’ US guidelines no longer directly recommend a certain amount of meat’, Behrens says. ‘Instead, a proportion of proteins is advised, which could include either meat, dairy, chicken, fish, eggs, or beans. This is a result of fierce lobbying by various stakeholders.’

If people in high-income countries adopt the guidelines, the emission of greenhouse gases would be reduced by a surprisingly large quantity, attenuating climate change. Also, the impacts of too much fertilisation would be reduced, and less land would be needed for food production.

In most middle-income countries, current consumption of meat and dairy is lower than in high-income countries, as are the corresponding environmental impacts. Only India and Indonesia recommend an increase of meat consumption to combat malnutrition, which would result in higher environmental impacts. In the other middle-income countries, guidelines are to eat less meat and dairy and more vegetables, fruits and nuts. When people would follow these guidelines, the environment would profit slightly.

In general, nations recommend reducing meat consumption, which will have environmental benefits in addition to the health benefits. Behrens perceives a huge potential: ‘A change in food choice is feasible, and could be realised much faster than technological solutions to environmental problems. We could cut down meat consumption even more than is currently recommended. Many people already are convinced: the number of vegetarians and flexitarians is increasing in many high-income nations.’


When studying Physics and Astronomy, Paul Behrens (UK, 1983) observed the sky with large telescopes on the Canary Islands. Although this was exciting, he decided to come down to earth. He joined a wind energy project in New Zealand for his PhD and became a scientific advisor at the Royal Society of New Zealand. Four years ago, he grasped the opportunity to return to academia when Leiden University offered a tenure track position. He started investigating how society can transform food and energy systems not only to survive, but also to thrive within environmental limits and climate change.

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