Now that science is telling us that gut microbes are important to our health, what foods should we eat to encourage healthy gut bacteria to flourish?

Probably not chicken nuggets: too many foods that are fried, baked or toasted may reduce the numbers of friendly bacteria in our gut.

Gut indicator: AGE foods research suggests fried chicken is not the way to go. Credit:Koukichi Takahashi / EyeEm

It could be one more black mark against foods high in advanced glycation​ end products (AGEs) – compounds produced when food, especially animal food high in protein and fat, is cooked at high temperatures. Baked, crunchy or sugary processed foods also tend to be high in AGEs. Although our bodies produce some AGEs naturally there are concerns that accumulating too many of them through our diet over the long term can damage organs and accelerate ageing by increasing inflammation and oxidative stress. The list of problems linked to AGEs includes hardened arteries, complications of diabetes – including kidney disease – and Alzheimer's disease.

Some clues to the potential impact of AGEs on gut microbes comes from a study of adolescent boys in Spain who were fed two different diets. One was a "brown" diet big on browned, fried, crumbed​ and toasted foods rich in AGEs and the other was a diet based on similar foods but cooked in a different way – instead of fried chicken and chips, for instance, potatoes were boiled and chicken was poached.