It is known that dietary alterations can cause rapid shifts in weight, but few studies have examined how quickly diet can impact other physiological parameters, especially those related to cancer. A recent study in Nature Communications has identified that diet can have profound health effects in as little as two weeks. The researchers investigated the impact of dietary change on markers of colon health and correlated these changes with shifts in gut microbiome composition.
Two populations with common ancestry eating vastly different diets were compared- African Americans eating a Western diet and rural South Africans eating a native diet. After taking baseline measurements, the participants swapped diets for two weeks. Colon cancer risk factors including rate of proliferation and inflammation were examined.
At baseline, African Americans had higher rates of proliferation than rural Africans. After swapping diets, African Americans experienced a decrease in proliferation whereas rural Africans experienced an increase. In fact, the effects of the diet, either positive or negative, were greater than the baseline measures (i.e. rates of proliferation in African Americans switching to native diet were lower than native Africans continually eating the diet).
Similar results were observed when measuring inflammation. When African Americans switched to the native diet, colonic inflammation decreased. The opposite effect was observed in native Africans switching to a Western diet.
The high rates of proliferation and inflammation associated with the Western diet are key risk factors for colon cancer, so the researchers investigated gut microbiome-related effects of the diets that could impact these parameters. Specifically, they measured the amount of bacteria capable of producing butyrate, a fatty acid that linked to beneficial effects on colon health. They also quantified the abundance of bacteria capable of converting bile acids into carcinogenic compounds in the colon.
Consistent with the observed physiological effects of the Western diet, the researchers found that the diet caused a decrease in butyrate-producing bacterial species. They confirmed the result by showing a reduction in butyrate concentration in stool samples. Secondly, they showed the Western diet increased the abundance of bacterial species capable of converting bile acid to secondary carcinogen compounds. They then showed an actual increase in these compounds in stool samples.
An important consideration in the study is that individuals shared a common ancestry. There is a growing body of evidence that the effect of a diet is strongly dependent on an individual’s genetics. By comparing individuals of common ancestry, these genetic differences were minimized.
Together, these results indicate that colon health can rapidly change depending on what we eat. These changes that occur are likely to act, at least partially, through alterations of gut microbiome composition. Next, we need to identify whether these effects are reversible and to identify how genetically diverse individuals respond to dietary shifts.