**1. Introduction**

206 Cancer Prevention – From Mechanisms to Translational Benefits

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It has been reported that the cause of 30% of cancer is associated with eating habits (Anand et al., 2008). Colorectal cancer is one of the most common causes of death all over the world, and there is a strong association between this type of cancer and food intake. Despite this statement, the preventive effects of foods and nutrients on colorectal cancer have not completely elucidated yet.

It has been proposed that some biologically active nutrients suppress colon carcinogenesis through the mechanisms of cytostatic properties, inhibition of cell growth, induction of apoptosis, an anti-inflammation effect or modification of DNA in *in vitro* studies.

Although the positive effects of these nutrients have been shown in *in vitro* studies, it is still difficult to apply the effects of these nutrients in *in vivo* studies, due to modifications to foods during the process of absorption and delivery within the body. There might be two possible active sites, where foods and their components affect colon epithelium cells, where nutrients are distributed hematogenously after absorption, or retained in the lumen without absorption. Absorbed foods and nutrients might show the effects of anti-inflammation, antioxidant, and anti-proliferative par hematogenously in cancer epithelial cells and stromal cells, while on the other hand, the regulation of enterobacteria might be provided by the component in a poorly-absorbed form. Recent studies have focused on resistant carbohydrates functioning as prebiotics that prevent colorectal cancer (Davis & Milner, 2009).

The normal human intake of food has a great advantage for oral administration and safety, compared with the administration of medicine, because safety has been proven by long food experience. Thus, the prevention of colorectal cancer through the intake of specific foods and nutrients might have a great potential, however further studies are required, especially in regard to absorption and disposition. In this paper, we focused on foods, and their components, with cancer preventive aspects.

### **2. The preventive effects of food components against colorectal cancer**

Colorectal cancer is one of the most common cancers in the world and it has been proposed that it is strongly associated with dietary habits (Anand et al., 2008; Jemal et al., 2011). Red and processed meat may convincingly increase the risk, and physical activity is only the

Colorectal Cancer and the Preventive Effects of Food Components 209

Abbreviations: COX, cyclooxygenase; AA, arachidonic acid; VEGF vascular endothelial growth factor;

Fig. 1. Proposed anticarcinogenetic effects of nutrients on colorectal cancer. Selenium, folate, vitamin A and CoQ10 have been reported to repair damaged DNA. Vitamin D and n-3 fatty acid may suppress the COX-2 mediated carcinogenesis. Ca plays a diverse role, including the inhibition of *APC* mutation, suppression of β-catenin and binding to bile acid. Probiotics and/or prebiotics reduce colorectal cancer to modify the proportion of gut microflora.

role in DNA damage (Kryston et al., 2011). Reactive oxygen spices (ROS) and DNA interactions induce DNA damage, which causes mutation via either double-strand break (DSB) or non-DSB lesions (Sedelnikova et al., 2010). Carcinogenesis of oxidative stress also involve immune cell activation via CCL2/MCP-1, pro-inflammatory factor (Martin et al.,

The methods of accurate measurement of oxidative stress have been brought by HPLC, tandem mass spectrometry (MS/MS) electrochemical detector (Cadet et al., 2010). There are also biomarkers to assess the level of oxidative stress, such as 8-oxo-2'deoxyguanosine (8 oxo-dG) (Ziech et al., 2010). These can allow us precise studies of anti-oxidative property by

Cyclooxygenase (COX) also plays an important role in carcinogenesis, e.g. to induce prostaglandin E2 (PGE2). PGE2 has diverse functions to promote cell proliferation, migration,

Ca, calcium; CoQ10, coenzyme Q10

2011).

food.

proven method of prevention. Avoiding body fatness, especially abdominal fatness, and the consumption of an excessive amount of alcohol are also important for colorectal cancer prevention (World Cancer Research Fund, 2007b). Despite the confirmation of cancer inducing foods, foods or nutritional elements that have protective qualities against colorectal cancer have not yet been fully confirmed.
