Food system inequality between nations has generally declined since 1970, but greater access to food and nutrients presents new health problems such as hypertension and diabetes in more countries, according to a new study. 

The research, published in Nature Food, measured food system inequality by focusing on resource inputs, food and nutrient outputs and nutrition and health outcomes across countries from 1970 to 2010. These were the years with the most comprehensive data for all areas of focus. Previous research on inequality has looked at some aspects of food systems such as dietary patterns, but this is the first research to quantify how nutrient availability and health outcomes have been impacted by economic, environmental and population-related changes to our food system. 

The researchers quantified inequality using the Gini coefficient, a measure of the distribution of income across a population. The coefficient uses a scale of 0 to 1, with 0 equaling perfect equality and 1 equaling perfect inequality. This method was initially developed to study income and wealth inequality but has also been applied to other aspects of well-being and social epidemiology such as inequality of water use, industrial goods, carbon emissions and energy use, and subjective well-being, according to the research. 

The study is also one of the first to create data visualizations of food system inequality.

"I'm an economist and I could draw on the ways that income inequality is visualized to think about health, nutritional and agricultural inequality," said William A. Masters, a professor of economics at Tufts University. "One of the things we hope to do with this research is to dramatize through visualization how important the data infrastructure of the world is."

Over the study period, there have been modest improvements to inequality of gross domestic product, land and livestock. GDP distribution has improved in the past 40 years for the bottom 80% of the global population, but the largest and most enduring inequalities relate to the agricultural resources used by each country's rural population, according to the research. The most land-abundant countries, which represent 20% of the global rural population, account for almost 60% of the world's harvested area. The Gini coefficient rose only slightly from 0.42 to 0.43 from 1970 to 2010. 

One notable change has been the shift in the sub-Saharan region. In 1970, sub-Saharan African countries were in the middle of the global distribution of GDP, but by 2010, they had moved to the bottom of the distribution and been displaced by China. China's rise as a global power in the last several decades has moved it toward the middle of the distribution in all areas examined by the research. 

"All inequality arises because some people get better off first or faster than others," Masters said. "With overall income, there's no top to it. The rich can just keep getting richer, but in contrast with nutrition, people max out somewhere, and so there's a race for lower-income people to catch up to that appropriate level and others can overshoot it, get more than enough."

The research found that all foods were more equally distributed in 2010 compared to 1970; availability of nutrients such as vitamin A, zinc and dietary iron have all also increased globally. However, despite the improvements in equal distribution, poorer countries are still less likely to be consuming the proper amount of fruits, vegetables and animal-sourced foods. The worldwide Gini coefficient for animal-sourced foods per capita plummeted from 0.55 to 0.36 as China and other nations rose in the global ranking and left about one-fifth of the world population with consumption below 10% of dietary energy.

The mean dietary energy from fruits and vegetables has increased in the last several decades from 108 to 205 kilocalories per capita, again with steep increases in China; the worldwide Gini coefficient decreased from 0.35 to 0.27. Still, many countries in sub-Saharan Africa remain below the mean consumption, and some, such as Nigeria, have even seen declines in the last 40 years. 

This has important implications to global health, Masters said; more nations having greater access to the food and nutrients provided by a more equal food system is a benefit to reducing the rates of health concerns such as malnourishment and stunting. The latter, once a very prevalent problem in developing nations, is when a child's height falls more than two standard deviations below the mean height for age. Stunting has improved as global food systems have equalized, according to Masters, but new problems are now arising. 

Rates of diabetes and hypertension are on the rise, particularly in low-income countries in South Asia, East Asia and the Pacific, the Middle East and North Africa, and Latin America and the Caribbean. Wealthier countries have been able to mitigate the rise because they have better resources for detection and treatment, according to the study. 

The research is a reminder that important progress has been made in improving global food system inequality, but that more needs to be done to properly manage the massive changes that have taken place in a relatively short amount of time.

"Global inequity and equality are a 'chasing the next thing' problem," Masters said. "What I hope this paper does is to help people visualize the process of catching up in one domain and then needing to catch up in the next and the next." 

Policymakers should prioritize more research and funding to ensure that the equality gains in the system are reflected in the outcomes, said Masters. He and his fellow researchers plan to continue this research by looking further at changes within countries.

"We went from 10,000 years of agriculture to about 50 years of food as a manufactured good," he said. "So for about 10,000 years we ate mainly food that came from the ground or an animal in close proximity to us, and now we eat food that mainly comes from a factory or lab. So we need to start thinking about ways to regulate food and understand where it's coming from."

The study "Global dietary convergence from 1970 to 2010 altered inequality in agriculture, nutrition and health," published March 19 in Nature Food, was authored by William A. Masters, Winnie Bell and Keith Lividini, Tufts University.