A Systematic Analysis Attributes Eleven Million Deaths in 2017 to Dietary Risk Factors

A systematic analysis by Dr. Ashkan Afshin and the Global Burden of Disease (GBD) 2017 Diet Collaborators published in the Lancet showed that in 2017, 11 million deaths and 255 million disability-adjusted life years (DALYs) were attributable to dietary risk factors. The leading dietary risk factors were a high intake of sodium, low intake of whole grains, and low intake of fruits. The study provides a clear image of the potential impact of a sub-optimal diet on death and disability.

Although long-term randomized controlled trials to investigate the potential causal relationship between dietary habits and chronic non-communicable diseases have not been practical, there have been many long-term prospective cohort trials and short-term randomized trials that have supported this association. Additionally, due to the complexity of characterizing dietary habits across different nations, assessing the impact of a sub-optimal diet on a population level has not been done. As part of the Global Burden of Diseases, Injuries, and Risk Factors Study published in 2017, geographically representative dietary data that characterized the dietary habits of adults aged 25 or older across 195 countries were collected. The authors estimated the effect of a sub-optimal diet as well as individual dietary factors on non-communicable disease mortality. The authors also evaluated the relationship between diet and socioeconomic development as well as the trends in disease burden of diet over time. Socioeconomic development was assessed through the socio-economic index (SDI) which is a summary measure of a region’s socio-demographic development (This is based on average income per person, educational attainment and total fertility rates).

The authors found that globally in 2017, the consumption of all healthy foods and nutrients was suboptimal. This included nuts and seeds (12% of the optimal level consumed), milk (16% of optimal level), and whole grains (23% of optimal level). The consumption of unhealthy foods exceeded the optimal level. This included sugar-sweetened beverages (49g per day), processed meat (90% greater than the optimal amount), and sodium (86% greater than the optimal amount). The authors noted that men had a higher intake of both healthy and unhealthy food. Additionally, food intake was higher among middle-aged adults (50-69 years) and lowest in young adults (25-49 years). However, the highest intake of sugar-sweetened beverages and legumes was in young adults and decreased with age. Additionally, dietary risks were responsible for 11 million deaths and 255 million DALYs in 2017. Cardiovascular disease was the leading cause of diet attributable deaths (10 million deaths) and DALYs (207 million DALYs). This was followed by cancer (913,090 deaths and 20 million DALYs) and type 2 diabetes (338,714 deaths and 24 million DALYs). More than half of diet-related deaths and two-thirds of diet-related DALYs were attributable to a high intake of sodium (3 million deaths and 70 million DALYs), low intake of whole grains (3 million deaths and 82 million DALYs), and low intake of fruits (2 million deaths and 65 million DALYs). However, the leading cause of death and DALYs differed by region with a high intake of sodium being the leading dietary risk associated with death and DALYs in China, Japan, and Thailand. In the United States, India, Brazil, Pakistan, Russia, Egypt, Germany and Turkey, the leading dietary risk was a low intake of whole grains.

The authors also assessed the relationship between diet and socioeconomic development on the occurrence of deaths and DALYs. They found that the highest age-standardized rates of all diet-related DALYs and deaths occurred in low-middle and high-middle SDI countries. Cardiovascular disease and diabetes were the highest cause of diet-related deaths and DALYs in low-middle SDI countries. High-middle SDI countries had the highest age-standardized rates of diet-related mortality for cancer. High SDI countries had the lowest burden of dietary related deaths and DALYs. It is important to note that this study does have its limitations. Data were collected from a variety of sources and were not available for all countries. This would increase the degree of uncertainty of these findings.

Overall, this study showed that a sub-optimal diet was responsible for more deaths than any other global risk factor, including tobacco smoking. It highlighted the need to improve upon diet globally. When talking about the results of the study, Dr. Afshin stated, “We found that poor dietary habits are associated with a range of chronic diseases and can potentially be a major contributor to NCD mortality in all countries worldwide. This finding highlights the urgent need for coordinated global efforts to improve the quality of the human diet. Given the complexity of dietary behaviors and the wide range of influences on diet, improving diet requires active collaboration of a variety of actors throughout the food system, along with policies targeting multiple sectors of the food system.” In her editorial, Dr. Nita Forouhi wrote, “The current GBD findings provide evidence to shift the focus, as the authors argue, from an emphasis on dietary restriction to promoting healthy food components in a global context. This evidence largely endorses a case for moving from nutrient-based to food-based guidelines.”