The study’s outcome is that those who eat a regular quantity of dried plums have a greater chance of retaining bacteria beneficial to the intestines. Higher quantities of these types of bacteria correlate with lower incidents of colon cancer. While there are several possibilities at play here, these various linkages are backed by empirical data.
Plums are a diverse fruit, with the taste ranging from sweet to tart. In the dried form plums are often called prunes. Dried plums contain antioxidants and have a laxative effect. However, some dried plums contain high amounts of acrylamide (a neurotoxin) which is formed during the drying process (which takes place at a high temperature).
Using an animal model, rats were fed a diet rich in dried plums or a diet without the fruit. Both diets were of the same calorific value and contained similar levels and types of nutrients. After a period of time, tissue extracts were taken from the colons of the rats and the microbial composition compared.
The bacteria were divided into common phyla (large groupings of different species of bacteria). The rats that consumed the plum rich diets had increased levels of bacteria grouped into the Bacteroidetes and lower number of bacteria grouped as Firmicutes. With the rats that did not eat the dried plum rich diet these proportions were reversed (so that Firmicutes dominated.)
Bacteroidetes is composed of classes of Gram-negative anaerobic and aerobic, rod-shaped bacteria. The Firmicutes are made up of Gram-positive bacteria, many of which are spore forming. “Gram” refers to a common staining method in bacteriology where bacteria are morphologically differentiated based on the composition of their cell wall, which affects how they take up various dyes.
It was also observed that the rats which eat the dried plum rich diet had fewer aberrant crypts, aberrant crypt foci and high-multiplicity aberrant crypt foci. Crypt foci are early sign of precancerous lesions and they a strong indicator for cancer development.
Based on the crypt observations and different bacterial composition, the researchers make a speculative case in favour of dried plums having properties that lower the risk of cancer. However, it is important to point out that the studies conducted were in rats and the effects may not be directly reproducible with people. Moreover, further research would be needed to rule out other dietary and environmental factors, as well as to see if the study results are reproducible.
The research is a joint effort between scientists based at Texas A&M University and the University of North Carolina. The findings have yet to be reported to a peer reviewed journal; however, interim findings were presented to the 2015 Experimental Biology conference in Boston, U.S. earlier this year.
