Drawing upon evidence from multiple studies, Professor of genetic epidemiology at King’s College London and author of The Diet Myth, Tim Spector said the restrictive nature of highly processed diets which use just a few ingredients is responsible for reducing our microbe diversity - and is making us ill...
“That junk food is bad for you is not news – the combination of saturated fat, calories, sugar, chemicals and lack of fibre is an obvious signal. The lack of diversity in the diet, though, is an overlooked factor: 80% of processed food is made up of just four ingredients – corn, wheat, soy and meat,” he wrote.
“[In comparison] fifteen thousand years ago our ancestors regularly ingested around 150 ingredients in a week.”
In the manner of film-maker Morgan Spurlock’s Supersize Me experiment, Spector’s son volunteered to follow a junk food diet for ten days. Stool samples were taken before and after the diet.
In addition to feeling lethargic and sick, the samples showed that his son’s microbial gut richness had been decimated, with a loss of 40% of his detectable species after just three days.
Yet if junk food is so bad for us then why do our bodies crave more? Spector said it was the proliferation of certain ‘bad bacteria’ in the gut that was fuelling our cravings for more processed food:
“Each species of microbe has a preference for certain food sources, which allows them to feed and reproduce. They therefore have their own evolutionary drive to maintain their ecological niche and will do anything to ensure their survival. This includes sending signals to the hosting human that they want more of the same junk food that they thrive on.”
End this modern trend: Reformulate
Spector’s advice for consumers was to eat as varied a diet as possible, rich in fresh fruit and vegetables that provide essential vitamins and fibre – but he also said manufacturers should reformulate to boost the ingredient diversity of their products.
“This is an interesting area - increasing the use of nuts, seeds, and high fibre vegetables would be an improvement. I know milk powder companies are trialling adding prebiotics (e.g Inulin or GOS) to the mix,” he told FoodNavigator.
“[Manufacturers should] be aware of the consumer demand for foods that are more microbiome friendly and start changing the food labels to reflect this.”
Freelance dietitian Carrie Ruxton also called on food manufacturers to accept part of the responsibility for the obesity crisis, taking proactive steps to reverse it.
“Processed foods are part of our modern culture so companies can help consumers by reducing the energy density of products (fewer calories per 100 g), including vegetables, fruits or wholegrains where possible, and boosting the fibre content,” she told FoodNavigator.
Are probiotics the answer?
For Ruxton, although probiotics can boost gut bacteria, their efficacy is limited due to a short shelf-life. But she said that prebiotics, which have an EFSA-backed health claim for glycaemic control, can be easily added to food and beverages by companies.
Spector said that personalised probiotics could be the solution.
“Either they [the personalised yoghurts] could include 4 or 5 strains together or they contain one that we know would suit the rest of your gut microbes. To do that everyone would need to be tested for their gut microbes and put into groups. This may be relatively easy to do – as the test costs only around 70 euros and crowd funding projects like www.britishgut.org are allowing direct testing.”
A recent University of Pittsburgh study highlighted how quickly and radically sensitive gut microflora can change following changes in diet – for better and for worse.
For two weeks a group of African-Americans swapped their high-fat, low-fibre Western diet with that of rural Africans, rich in beans and vegetables. The researchers found that each group rapidly took on the biomarkers of the other, including bacterial activity, fibre fermentation and intestinal inflammation.
Lead researcher Stephen O’Keefe said: "These findings are really very good news. In just two weeks, a change in diet from a Westernized composition to a traditional African high-fibre, low-fat diet reduced these biomarkers of cancer risk.”