Higher living standards in the developing world - especially eating more protein and fat - are leading to a "standard global food supply" consisting of a comparatively short list of crops, meat and dairy products, according to an international study.
The researchers warn that this threatens future food security by leaving producers more at the mercy of major threats such as drought, insect pests and diseases, which are likely to worsen because of climate change.
It also suggests this changing diet could accelerate a global increase in obesity, heart disease and diabetes.
They have called for action to be taken to encourage the growth of a wider range of crops and varieties of crops, as well as steps to make staple foods more nutritious and better teaching about a healthy diet.
Luigi Guarino, of the Germany-based Global Crop Diversity Trust (GCDT), who co-authored the report, said: "As the global population rises and the pressure increases on our global food system, so does our dependence on the global crops and production systems that feed us. The price of failure of any of these crops will become very high."
The research, published in the Proceedings of the National Academy of Sciences (PNAS) journal found that human diets had become 36% more similar over the past 50 years. The study claims wheat is now a staple in 97.4% of countries.