April 3, 2019

expert reaction to systematic analysis on health effects of diet by country

Research conducted by The Lancet provides evidence of the potential impact of sub-optimal diet on non-communicable diseases mortality and morbidity and highlights the need for improving diet across nations.

Dr Oyinlola Oyebode, Associate Professor at Warwick Medical School, said:

“This high-quality research examines dietary patterns across the globe and linking these to data on death and illness to determine what might be the most important dietary factors in the development of disease in the countries studied. It is important to note that the authors linked the dietary factors to death and disease based on data from observational studies, which they mention as a limitation in the paper and the press release. This confounding is possible in the underlying observational studies (people with healthy diets are healthier in other ways too- so the link between the dietary factor and subsequent disease may be overstated). Regardless, this study gives us good evidence of what to target to improve diets and therefore health at the global and national level.

“The lack of fruit, vegetables and whole grains in diets across the world are very important- but the other dietary factor highlighted by this study is the high intake of sodium. Actually, high intake of sodium is ranked first, above all other factors in terms of its importance for deaths due to poor diet. This high intake of sodium is likely to be due to consumption of salt in processed food including junk food in settings such as the UK.”

Prof Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London (KCL), said:

“Most deaths from cardiovascular disease and cancer occur after the fifth decade of life and immortality is not an alternative – you have to die of something. As death rates from infectious diseases fall, more survive to an age where they die from CVD or cancer.

“This analysis puts too much emphasis on individual components rather than the overall diet. The data on salt intake in relation to risk of high blood pressure is strong.  But alcohol, which is another factor that causes high blood pressure as well as cancer, is ignored. The weaknesses are that fruit and vegetable intake are associated with other health related behaviour.  Trans fatty acids from industrially processed fats are probably not relevant as they are no longer consumed in any significant amounts in Western Europe, North America, Australasia and most of Asia. People who eat whole grains are a small minority and the global per capita availability of nuts is very small about 1-2g/d whereas the target for nuts and seeds is 21g/d. The level used for polyunsaturated fatty acids used is the upper limit recommended by WHO/FAO. The target for milk is 435 g/d. Generally, the targets set do not represent the amounts that are consumed in actual diets.

“In the U.K., deaths from CVD rates under the age of 75 years have fallen by more than 75% since the 1960s and life expectancy in men, in particular, has increased substantially from around 68 to 79 years now; some of this change can be attributed to fewer people smoking. However, over 1 in 5 in the U.K. are obese now compared with fewer than 1 in 20 in the 1960’s and prevalence of type 2 diabetes is greater (now 6-8% of adults). 

“This analysis ignores the impact of the effect of diet on foetal growth and post-natal growth, which are major determinants of risk of cardiovascular disease (CVD), diabetes and probably some cancers. Improved pregnancy outcomes may in part explain the decline on CVD in the U.K. However, accelerated growth in infancy and adolescence may increase risk of breast and colorectal cancer.

“Obesity is a major driver for risk of type 2 diabetes as well as cancer and the health evidence for this relationship is strong. Obesity is caused by eating more food energy than required rather than specific dietary components such as sugar. The trend for populations to become increasingly sedentary is a major reason why there is an imbalance between energy intake and expenditure but increased availability of foods with a high energy density (more calories/gram) makes it too easy to overeat. Overall, I find the analysis in this paper hard to swallow.”

‘Health effects of dietary risks in 195 countries, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017’ by GBD 2017 Diet Collaborators was published in The Lancet at 23:30 UK time on Wednesday 4th April.

Declared interests

Dr Oyinlola Oyebode: No declarations of interest

Prof Tom Sanders: Honorary Nutritional Director of HEART UK and scientific governor of the British Nutrition Foundation.

None others received.