Are you wondering what to prepare for dinner tonight? Data analyses reveal that certain food choices greatly benefit both your health and the environment. But what to do with this evidence remains a challenge to society.
Food production has a strong effect on the environment — it is responsible for about 25% of global greenhouse-gas emissions1, and biodiversity is greatly affected by agricultural land and water use, nutrient loss and fisheries. Within the agricultural sector, livestock farming has the largest environmental footprint2, and this impact is increasing as traditional diets around the world are being rapidly replaced by diets that are higher in meat, refined sugar and fat. As the scientific basis for the link between diet and the environment grows stronger, the idea has emerged that global dietary changes may contribute to climate-change mitigation3. In response, campaigns to promote meat-free days have been launched, such as 'Meatless Monday' in the United States and United Kingdom and 'Veggie Thursday' in Germany and Belgium. In a paper published onNature's website today, Tilman and Clark4 show that dietary adjustments would not only reduce greenhouse-gas emissions and agricultural land use, but also greatly reduce individual health risks.
The main novelty of Tilman and Clark's study is that it summarizes strong empirical evidence for the effect of diet on both health and the environment in one publication. For the link between diet and health, the authors compiled data from 18 papers, comprising 8 study cohorts and 10 million person-years of observations, to compare reference diets (including all food groups) to three alternatives: a Mediterranean diet (rich in vegetables, fruit and seafood, but including other foods); a pescetarian diet (including fish and almost no meat); and a vegetarian diet (including dairy products and eggs but almost no meat or fish).
Their review finds a substantial reduction in several negative health indicators for each of these alternative diets compared with the reference diet, including type II diabetes incidence (16–41%, depending on the diet), cancer incidence (7–13%), mortality due to heart disease (20–26%) and overall mortality (0–18%). These effects relate to the fact that the alternative diets contain higher amounts of fruits, vegetables and nuts, and fewer 'empty' calories (energy-containing products that have little other nutritional value, such as alcohol and added sugars) and less meat.
The data are based on an analysis of 555 food production systems: a, per kilocalorie; b, per United States Department of Agriculture (USDA)-defined serving;c, per gram of protein. The mean and s.e.m. are shown for each case. Extended Data Tables 1, 2, 3 list data sources, items included in each of the 22 food types and show the mean, s.e.m. and number of data points for each bar, respectively. NA, not applicable
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