Starch colorectal cancer

In addition to the walls of the parenchyma cells, the walls of the periderm (skin) cork cells form part of the total intake of dietary fiber and a waste product of potato processing for food as well as for starch. Although much is known about the suberin present in these cell walls (Bernards, 2002 Franke and Schreiber, 2007 Grafos and Santos, 2007), little is known about their polysaccharides (Harris et al., 1991). Nonetheless, because of the presence of suberin, these cell walls are able to adsorb hydrophobic dietary carcinogens and their intake may be important in the prevention of colorectal cancer (Harris et al., 1991 Ferguson and Harris, 1998, 2001). 

Ahmad MZ, Akhter S, Anwar M, Ahmad FJ. Assam Bora rice starch based biocompatible mucoadhesive micro sphere for targeted delivery of 5-fluorouracil in colorectal cancer. Molecular Pharmaceutics. November 5, 2012 9(ll) 2986-2994. PubMed PMID 22994847. 

Chemoembolization Chemoembolization with the combination of Ivalon and FUDR (800 mg), mitomycin C (10 mg), or cisplatin (150 mg) for colorectal hepatic metastases led to no significant improvement in response or survival. Yamashita et al. (1993), who treated 68 patients with various hepatic metastases using iodized oil and chemotherapeutic agents,noted a response rate of 22% and a median survival of 10 months. A similar result was observed by Inoue et al. (1989), i.e., a partial response rate of 16% and a median survival period of 11 months. We currently do not perform chemoembolization in patients with metastatic colorectal carcinoma because the survival rates have not improved compared to the less aggressive approach of intraarterial chemotherapy. However, Lang and Brown (1993) and Pentecost et al. (1992) are encouraged by their results for chemoembolization of hepatic metastases from colorectal cancer and they believe that the technique can be recommended as palliative treatment. More recently, Pajkos et al. (1998) treated 41 patients with metastatic colorectal carcinoma to the liver with chemoembolization consisting of Adriamycin (50 mg), mitomycin C (8 mg), cisplatin (50 mg), or carboplatin (150 mg), Lipiodol (10 ml), and starch microspheres every 6 weeks, as well as systemic 5FU (425 mg/m ) and leucovorin 20 mg/m for 5 days every 28 days. The response rate was 68% with a median survival time of 15 months. 

Mathers JC, Movahedi M, Macrae F, et al. Long-term effect of resistant starch on cancer risk in carriers of hereditary colorectal cancer an analysis from the CAPP2 randomised controlled trial. Lancet One. 2012 13 1242-1249. 

Much of the resistant and slowly hydrolysed starch is fermented by bacteria in the colon, and a proportion of the products of bacterial metabolism, including short-chain fatty acids, may be absorbed and metabolized. As discussed in section 7.3.3.2, butyrate produced by bacterial fermentation of resistant starch and non-starch polysaccharides has an antiproliferative action against tumour cells in culture, and may provide protection against the development of colorectal cancer. 

The main products of bacterial fermentation of non-starch polysaccharides and resistant starch are short-chain fatty acids such as propionate and butyrate. In addition to being absorbed, and hence used as metabolic fuels, they have an antiproliferative effect on tumour cells in culture, and there is some evidence that they provide protection against the development of colorectal cancer. 

Some types of non-starch polysaccharides bind a number of potentially undesirable compounds in the intestinal lumen, and so reduce their absorption. Again this may be protective against colorectal cancer. A number of compounds that are believed to be involved in causing or promoting cancer of the colon occur in the contents of the intestinal tract, both because they are present in foods and as a result of bacterial metabolism in the colon. They are adsorbed by non-starch polysaccharides, and so cannot interact with the cells of the gut wall but are eliminated in the faeces. 

An obvious factor for the inconsistent results of the effect of different intakes of dietary fiber on colorectal cancer is the variation in the analytical methodology used in different studies. There is also increasing evidence that total dietary complex carbohydrates may be as important as fiber. Analysis of stool weight from 20 populations in 12 countries showed that larger stools were correlated with a lower incidence of colon cancer. Intakes of starch and dietary fiber (rather than fiber alone) were the best dietary correlates with stool weight. A subsequent meta-analysis showed that greater consumption of starch (but not of NSPs) was associated with low risk of colorectal cancer in 12 populations. The examination also showed that fat and protein intakes correlated positively with risk. This meta-analysis is probably the first of its kind to... 

Table 1 Effects of dietary fiber and resistant starch that could impact on the etiology of colorectal cancer...

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