Your Editorial 'A fresh approach to water' (Nature 452, 253; 2008) points out that the world's looming water crisis is driven by climate change, population growth and economic development. In China, changing food-consumption patterns are the main cause of the worsening water scarcity. If other developing countries follow China's trend towards protein-rich Western diets, the global water shortage will become still more severe.

In China, it takes 2,400–12,600 litres of water to produce a kilogram of meat, whereas a kilogram of cereal needs only 800–1,300 litres (J. Liu and H. H. G. Savenije Hydrol. Earth Syst. Sci. 12, 887–898; 2008). The recent rise in meat consumption has pushed China's annual per capita water requirement for food production up by a factor of 3.4 from 255 cubic metres in 1961 to 860 cubic metres in 2003. Compared with China's population growth by a factor of 1.9 over the same period, this suggests that dietary change is making a high demand on water resources.

China's water requirement for food production is still well below that of many developed countries. The United States, for example, uses 1,820 cubic metres per capita per year. But the steady increase in the amount of meat in Chinese diets is worrying. Consumption already exceeds by 50% the optimal amount recommended by the Chinese Nutrition Society — although discrepancies between rural and urban areas and between eastern and western regions are significant. This diet shift may also have detrimental effects on the population's health, as in developed countries. In general, changes in food-consumption patterns are closely related to affluence, although they are influenced by food preferences as well. Raising public awareness about healthy eating habits could also help to mitigate water scarcity.