Okwudiri Straightman Nwali

Don't wash your hands! A bit of dirt is good for you: Experts say cleaning less often would protect against allergies by allowing helpful bacteria into the body 

• Dr Justin Sonnenburg said modern diets lacking in fibre may cause irreversible damage to vital gut bacteria 
• He suggested not washing your hands after gardening or petting a dog
• Low-fibre diets that we now eat might not be enough for future generations 

Modern diets lacking in fibre may cause irreversible damage to vital gut bacteria for generations of the same family, suggests a new study.

Friendly bacteria in the gut thrive on roughage, the fibrous materials found in fruit and vegetables and bran.

But the low-fibre diets we now eat in industrialised nations mean that for future generations, simply ‘eating right’ might not be enough. 

Dr Justin Sonnenburg said that humans are able to pick up bacterial colonies from external sources. He suggested not washing your hands after tasks such as gardening and reducing our reliance on antibiotics (file image)

The study, conducted by researchers at Stanford School of Medicine in the US, showed that certain microbes living in the intestines of mice raised on diets comparable to those of people in first world countries were at risk of ‘extinction’. 

Study senior author Dr Justin Sonnenburg, who worked on the study with his wife Dr Erica Sonnenburg, said that fibre, which cannot be digested by the human gut, was the primary source of food for bacteria living in our gut.

He added: ‘We would have difficulty living without them. They fend off pathogens, train our immune systems and even guide the development of our tissues.

Humans are able to pick up bacterial colonies from external sources. However, one of the most significant sources of bacteria is from our immediate families, especially during birth and infancy.

Dr Sonnenburg added that when compared to hunter-gatherer and rural populations, the diversity of intestinal bacteria was far lower than that of those living in modern industrialised societies, where a low-fibre diet is often the norm.

Dr Erica Sonnenburg explained that widespread antibiotic use, caesarean sections and less-frequent breastfeeding in industrialised nations could account for the depletion of intestinal microbes.

Dr Sonnenburg also suggested that simple tweaks in our culture, such as not washing our hands after petting a dog could be a step in the right direction (file image)

But she added: ‘We asked ourselves whether the huge difference in dietary fibre intake between traditional and modern populations could, alone, account for it.’

Two sets of mice - one raised on a low-fibre diet and the other on a high-fibre diet - were analysed during the experiment.

The results showed that within a couple of weeks, a huge change in the microbes could be measured. There was a 75 per cent reduction in microbial diversity in those raised on a low-fibre diet, with many species disappearing from the intestines all together.

Researchers were stunned to find that by the fourth generation, some mice had a reduction of intestinal bacteria of up to three-quarters compared to that of their great-grandparents.

Dr Justin Sonnenburg said: ‘The extremely low-fibre intake in industrialised countries has occurred relatively recently.

‘Is it possible that over the next few generations we’ll lose even more species in our gut? And what will the ramifications be for our health?’

He also suggested that simple tweaks in our culture, such as not washing our hands after gardening or petting a dog and reducing our reliance on antibiotics, could be a step in the right direction.