Does Fiber Play A Role Preventing Colon Cancer

Several possible mechanisms may be considered by which the link between fiber and prevention of colorectal cancer can be explained.

Dietary fiber is considered to have a potential importance in the causation of colorectal cancer since early 1970s as it was observed that Africans who consumed a diet high in fiber had lower rates of colorectal cancer. Several possible mechanisms may be considered by which the link between fiber and prevention of colorectal cancer can be explained. Increased fiber intake leads to dilution of faecal carcinogens, reduces gastro-intestinal transit time, increases stool bulk and leads to some anti-carcinogenic effects by bacterial fermentation of fiber into short-chain fatty acids. The World Cancer Research Fund and American Institute of Cancer Research continuous update report on colorectal cancer in 2011 concluded that there is definite evidence that increased fiber intake is protective against the risk of colorectal cancer.

Colorectal cancer is the seventh most common cancer in India. The cause of colon cancer is multifactorial and complex. A low fiber diet is not the only reason colon cancer might develop. Risk factors include sedentary lifestyle, obesity, tobacco, increased consumption of red meat, low fiber diet, smoking and alcohol consumption. High-risk for colon cancer includes age above 60 years, a positive family history of colorectal cancer, chronic inflammation such as having inflammatory bowel disease and having familial polyposis syndrome. 

Colonic adenomas are formed initially, which may progress to become cancer in some individuals. This known as adenoma-carcinoma pathway. Individuals consuming the highest intakes of dietary fiber have reduced risks of developing colorectal adenoma and distal colon cancer and that this effect of dietary fiber, particularly from cereals and fruit, may begin early in colorectal carcinogenesis. Dietary fiber may act early in the adenoma-carcinoma sequence and reduce both the risk of adenoma and cancer. Colon cancer does not happen overnight. Usually it can take many years to develop. So, starting to eat whole grains in early age is important. Consumption of adequate fiber in the diet should be encouraged as early as possible. Individuals with the highest fiber intake had a 27% reduced risk of prevalent adenoma.

The European Prospective Investigation of Cancer and Nutrition (EPIC) Study evaluated diet and colon cancer in 519,978 people living in 10 countries with a broad range of dietary habits. The volunteers were tracked over six years, who ranged in age from 25 to 70. Compared with the people who ate the least fiber, those who ate the most enjoyed a 42% reduction in the risk of colon cancer. No source of fibre was more protective than others; the study did not evaluate fiber supplements. Another study of 2,157 residents of Utah and California linked high consumption of fiber to a 46% reduction in the risk of rectal cancer. Fiber is also found to reduce exposure of the colorectal passage to carcinogenic N-nitroso compounds produced on processed meat consumption.

Dietary fibers are non-starch complex carbohydrates which are found in plant foods. They are of 2 types: soluble and insoluble. There are not non vegetarian (animal) sources for fibre.

Soluble fiber dissolves in water to form a gel, which promotes delayed emptying and early satiety. Soluble fiber is easily digested in the colon, which also can cause bloating and gas. Soluble fiber is often associated with cardiovascular and diabetes prevention and colon health, as it reduces blood cholesterol and glucose levels. It does this in 2 ways. Firstly, the soluble fiber is fermented to short-chain fatty acids, these are absorbed and metabolized by the liver for bile synthesis. Second, fiber passes through the body undigested.

Soluble-fiber sources include apples, barley, citrus fruits, peas, avocado, husks, legumes, oats, rye, and many vegetables, such as broccoli and carrots. 

Insoluble fiber does not dissolve in water and is much less fermentable or gassy. It promotes bowel movements by adding bulk and water to stool, creating a stool softening action in the digestive system.

Insoluble-fiber sources include brown rice, fruits like apples, legumes, seeds, whole grains, vegetables such as Brussels sprouts and cabbage, and wheat bran.

Fiber supplements available include gums, inulins, lignins, pectins, and psyllium or isabgol husk.

Juice is not a good source of fiber. Even if juice is made from fresh fruits and vegetables, the fiber is often gets removed in the juicing process. Ideally, you should get fiber from whole food sources, not supplements or juices.

Researches showed that each 10-gram a day increase in total fiber and cereal fiber was linked with a 10% reduction in colorectal cancer risk. Aim for fiber intake amounts of 25 to 35 grams per day or a ratio of 14grams of fiber/1000kCal consumed. In regard with fiber, more is not necessarily better, so do not overdo it. Too much of high fiber can be disruptive, in turn affecting mineral absorption and GI distress.

Be sure to increase your fiber intake gradually. Adding large quantities of fiber into the diet too quickly can cause gas or discomfort. Instead, try to add a little more fiber to each of your meal by including a piece of fruit or by switching processed or refined grains with whole grains. Drink plenty of water, as staying hydrated will help ensure that the additional fiber doesn’t cause stomach problems.

Early lifestyle changes like regular exercise, consumption of a balanced diet with adequate fiber and avoiding risk habits can reduce your colon cancer risk.

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