2013-12-18 16:13:57 UTC

Diet and Colon Cancer in Western and Eastern Countries

Dec. 20, 2013


Luigi Ricciardiello, MD

Department of Medical and Surgical Sciences, University of Bologna, Italy



Vincenzo Fogliano, PhD

Food Quality Design, Wageningen University & Research Centre, Wageningen, The Netherlands


Before the industrial revolution, human dietary intake was extremely rich in natural compounds obtained from plants and fruits. In particular, the Mediterranean diet has been traditionally characterized by unsaturated fats and a variety of phytochemicals coming from fruits, vegetables, whole grains and virgin olive oil. However, each geographical area has its favorite phytochemicals: in Asia, many phytochemicals present in spices, such as curcumin, and polyphenols in fruits and teas have constituted a central role in the dietary patterns of hundreds of millions of people over the centuries.

The 20th century has been characterized by an incredibly fast-growing change in dietary habits, coming from industrialized world and rapidly expanding throughout the planet. The abrupt switch toward the so-called Western diet (refined grain, animal proteins, low amount of fruits and vegetables, saturated fats) has led to a dramatic modification of the digestion by-products reaching the colon. This dietary modification has significantly contributed to the increase of colon cancer incidence. In fact, it is strongly believed that a westernized dietary pattern is a key contributor to colorectal cancer, which is one of the leading causes of cancer incidence and death worldwide.

In recent years, increased incidence rates have also been observed in countries where dietary habits have protected toward colon cancer development thus far, in particular those rapidly moving toward a Western lifestyle and dietary pattern, including Southern Europe and Japan. To corroborate this hypothesis, recent epidemiological data have confirmed that subjects following a strict Mediterranean diet are protected from distal colon cancer, indicating that phytochemicals present in plants, fruits, virgin olive oil and fish could have led to strong chemopreventive effects over years of consumption.

To understand the reasons for this beneficial effect it should be remembered that there has been a continuous co-evolution process between the microflora and the human gut which have adapted to the type of phytochemicals ingested, in particular non-digestible phytochemicals which are metabolized into final products with undisputed anti-inflammatory capabilities. The gut microflora have learned how to employ phytochemicals and used them to establish the most favorable host-bacterial relationship. The adoption of the Western diet has rapidly led to the replacement of saprophytes with pathogens, which we are now understanding as being critically involved in the development of obesity, metabolic syndrome and ultimately cancer.

Given the difficulties in the development of new synthetic agents suitable for cancer prevention, researchers are now focusing more and more on the use of natural compounds. However, in the search of possible chemopreventive agents, researchers have consistently tried to narrow the epidemiological data to single candidates in order to develop some sort of “magic pill” with disappointing results when applying the molecules in human trials. In the attempt of switching from pharmacological to dietary approach, it is critical to understand that food chemoprevention is a matter of whole diet and not of single molecules or even a single food. To favor the health-promoting equilibrium of the gut microbiota, it is necessary to provide manifold of phytochemicals and non-digestible polysaccharides. Importantly, one key issue is that this process takes a long time to be achieved.

From a molecular standpoint, it is known that colorectal cancer is characterized by a constellation of molecular events leading to at least three different pathways. In the same way, while multiple phytochemicals have redundant activities, it is highly improbable that one of them could have effects on all the pathways involved in colon cancer pathogenesis. On the other hand, the combination of multiple phytochemicals can lead to previously undisplayed molecular effects. Scientists are looking for new ways to demonstrate chemopreventive effects on colon cancer development. Preclinical models are designed to demonstrate positive effects in a very short time, using phytochemical concentrations that cannot be adopted by humans. Promising results have been obtained using the combination of multiple phytochemicals in order to reduce toxicity and enhancing synergisms, thus resembling a more “natural” approach to prevention. In fact, our experience has shown that whole plant and fruit extracts or combination of bioactives exert strong preventive effects toward colon cancer in animal models at concentrations much lower than those obtained using single compounds.

It is time to give up the idea of finding a single compound with anticancer effect; we should focus on more natural ways of preventing colorectal cancer that should be very well received by consumers. Also, food industries must contribute to this effort by designing food rich of phytochemicals and non-digestible polysaccharides tailored to modulate gut microbiota.

Dr. Ricciardiello has an unrestricted research grant from S.L.A. Pharma AG.

Dr. Fogliano has no conflicts to disclose.

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