In October 2019 researchers from Qatar published their review of the association between a Western diet and chronic diseases. A Western diet is characterised by a high intake of energy-dense and processed food which is a risk factor for many chronic diseases including diabetes type 2, obesity and cardiovascular diseases. A lot of the scientific research has concentrated on the high intake of fat, sugar, and low intake of fibre and fruits and vegetables. However, one of the underlying mechanisms linking a Western diet and chronic diseases is inflammation.
An individual’s diet provides not only the nutrients the body needs to survive but also the material and medium for sustenance and growth of gut bacteria. It also determines the types of bacteria that grow in the gut. Since the role of the gut microbiota in determining an individual’s health has been discovered, there have been a growing number of studies on the role of diet on gut microbiota. Among the studied foods, ultra-processed food has attracted great attention. Ultra-processed foods (e.g., soft drinks, savoury snacks) are highly palatable, having a long shelf-life and being relatively cheap and can be consumed anywhere at any time. However, these foods are typically characterized by a poor nutritional profile. The consumption of ultra-processed food is high in many countries, eg the percentage of energy intake from ultra-processed food is 29% in France, 42% in Australia and 58% in the USA.
Research on the topic has shown that a high consumption of ultra-processed food can change the gut microbiota and lead to inflammation. One of the constituents in ultra-processed foods causing concern is food additives (e.g., emulsifiers and artificial sweeteners). There is no regulation that requires the testing of the effects of food additives on gut microbiota. Although some food additives can be beneficial for human health, others may alter the composition of the microbiota and lead to gut inflammation, which in turn may promote very many different forms of inflammatory disease.
Research consistently suggests a strong association between ultra-processed food and health outcomes in different countries. In France, for example, studies have suggested that the association between ultra-processed food and cardiovascular disease is independent of BMI, intake of energy, fat and fibre. In addition, consumption of ultra-processed food was found to be associated with an increased risk of mortality and depression. In Spain, studies suggest that for each additional serving of ultra-processed foods, all-cause mortality increases by 18%. The consumption of ultra-processed food has also been linked to urinary levels of phthalates and bisphenols in the USA.
However, current dietary guidelines in most countries concentrate on nutrients or food groups. The Mediterranean diet is recommended for better health outcomes but does not take into account to what extent the major food groups are processed. Even home processing of these food may unintentionally change the health effects, eg frying vegetables with olive oil at a high temperature is less likely to have the anticipated beneficial health effects. In fact a vegetable-rich dietary pattern in which vegetables were cooked with oil has been found to be associated with the risk of obesity in the Chinese population.
Making healthy foods from raw material which is both available and affordable is essential to reduce the consumption of ultra-processed food. To achieve this goal, the government and the food industry should work together. Monetary policy should be in place to foster a healthy food environment. This includes putting a tax on ultra-processed food. Using gut microbiota as indicators for the assessment of food safety could be an effective way to regulate the production and amount of ultra-processed food in the market. However, further research is required before gut microbiota can be used in the assessment of food safety.
Shi Z. Gut Microbiota: An Important Link between Western Diet and Chronic Diseases. Nutrients 2019, 11(10), 2287; pii: E2287.