The time it takes for ingested food to travel through the human gut – called transit time – affects the amount of harmful breakdown products produced along the way. This means that transit time is a key factor in a healthy digestive system.
Recent research has focused mainly on the influence of the bacterial composition of the gut on the health of people’s digestive system.
Taking this a step further, Danish researchers studied how food’s transit time through the colon affects gut bacteria’s role in the activity and health of the digestive system by measuring the products of bacterial activity, which end up in urine.
The effect of food’s transit time
Intestinal bacteria like to digest carbohydrates, but when these are depleted, the bacteria break down other nutrients such as proteins. Researchers have previously found links between some bacterial protein degradation products produced in the colon and the development of various diseases including colorectal cancer, chronic renal disease and autism.
The study found that the longer food takes to pass through the colon, the more harmful bacterial degradation products are produced. However, when the transit time is shorter, the researchers found a higher amount of substances produced when the colon renews its inner surface, which may be a sign of a healthier intestinal wall.
It’s thought that a very diverse bacterial population in the gut is most healthy, however studies now show that bacterial diversity in stool is often associated with a long (slow) transit time.
The researchers believe that a rich bacterial composition in the gut is not necessarily synonymous with a healthy digestive system, if it’s an indication that food takes a long time to travel through the colon.
Constipation, a risk factor
If transit time is a key factor in the activity of the intestinal bacteria, this emphasizes the importance of preventing constipation, which may impact on health, whether it is a risk factor for disease or a side effect of illness.
Influencing food’s transit time
Your diet can influence transit time. To help food pass through the colon eat a high fibre diet and drink plenty of water. Limit your meat intake, which slows down transit time and provides the gut bacteria with lots of protein to digest. Physical activity also helps to reduce the time it takes for food to travel through the colon.
Source: Nature Microbiology, June 2016.
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