Practical Dietary Advice to Reduce Colon Cancer Risk

Introduction

Diet and Cancer

Overall, the statistics are sobering: Cancer, the second leading cause of death, will strike half of all men and one-third of all women. Cancers arise from a combination of genetic susceptibility and exposure to environmental factors, including toxins. The good news is that adopting a healthy diet and lifestyle may prevent as many as 60% to 70% of cancer cases. Increasing fruits and vegetables alone may decrease cancer risk by 20%. Colorectal cancer, one of the four most common cancers, may be particularly diet- and lifestyle-related: an estimated 66% to 75% of colorectal cancer cases might be prevented by dietary and lifestyle changes.

Western Diet Woes

Colon cancer arises from a series of genetic or environmental "hits." Evidence suggests that dietary factors play an important role (Please see article "Diet, Drugs and Colon Cancer: Is There A Connection?"). The typical Western diet is high in total and saturated fat (especially from red meat and processed meats), high in sugar and refined grains, and low in fruits, vegetables and whole grains, a diet associated with high rates of colorectal cancer. This diet commonly contains:

• Too much fat -- comprising 38% of calories instead of the recommended 25% or less.
• Too little fiber -- averaging 10 grams a day instead of the recommended 20 to 35 grams.
• Too few fruits and vegetables -- less than the recommended five or more servings a day.

Offending Foods

The following dietary and lifestyle factors have been linked to colon cancer. Preventive strategies are listed for each.

Total Fat

Ingesting large amounts of fat typically results in incomplete digestion by the small bowel. Undigested fat appears to be unhealthy for the colon: bacteria present in the colon act upon the fat, producing cancer-causing substances that may damage the colon lining. Most experts recommend that you receive between 20 to 25% of your calories from fat. Recommended calorie levels and corresponding fat intake for this type of diet are:

For a moderately active woman:

• To maintain weight: 1600 to 2000 calories, 35 to 55 fat grams
• To lose weight: 1200 to 1500 calories, 25 to 40 fat grams

A moderately active man

• To maintain weight: 1900 – 2500 calories, 40 to 70 fat grams
• To lose weight: 1600 – 1900 calories, 35 to 50 fat grams

Table One lists the fat content of some common foods.

Table 1

FAT CONTENT OF FOODS

Food	Total Fat (grams)	Saturated Fat (grams)
1 T oil	14	1.7 *
1 T butter	14	7.1
1 T mayonnaise	11	1.6
2 T regular salad dressing	16	varies
3 oz. high fat meat (salami, prime rib, etc.)	30	12
3 oz. lean meat (flank, round, pork tenderloin, etc.)	6 - 9	2 – 3.5
8 oz. whole milk, 1 oz. Cheese	10	5 – 6
3 oz. Skinless poultry or fish	3 – 4	1 – 2
1 slice pizza	17	10

* varies depending on type of oil

Saturated fat and animal fat

Controversy continues regarding the relationship between different types of fat and risk of cancer. Research has linked diets high in red meat and saturated fat to an increased risk of colon and rectal cancer. Saturated fat is found mainly in foods of animal origin, including beef and other meats, poultry skin, whole milk and whole milk products (i.e., cheese, ice cream, butter), eggs, etc. These foods, therefore, should be consumed in moderation.

Other fats

Studies also suggest that omega-6, a type of polyunsaturated fat found in many vegetable oils (i.e. corn and safflower) and margarine, may increase the risk of cancer. However, omega-3, another type of polyunsaturated fat found in flaxseed and fatty cold-water fish like salmon, may help reduce risk of cancer. Studies have found monounsaturated fats, found in olive and canola oil, do not increase the risk of cancer, and may actually be protective. But keep in mind, that all oils and fats must be used in moderation and within your total daily fat gram goal. All oils, whether saturated or unsaturated, have 14 grams of fat per tablespoon. The majority of your fat intake should be in the form of omega-3 fats and/or monounsaturated fats.

Alcohol

Alcohol use contributes to development of cancers of the mouth, larynx, liver and esophagus, and may play a role in colon and rectal cancers. The combination of alcohol and smoking presents an even greater risk. If you drink alcohol at all, keep to a limit of two drinks a day for men, and one drink a day for women.

The Good Stuff

Fruits and Vegetables
High intakes of fruits and vegetables are associated with a decreased risk of colon cancer. These foods contain an abundance of vitamins, minerals, and fiber, all of which may aid in preventing cancer. In addition, researchers have been identifying chemicals in plants called phytochemicals, which have even stronger cancer fighting effects. To get the most benefit, it is recommended that you eat a variety of fruits and vegetables, as they all contain different cancer fighting elements.

Tips for Adding Fruits/Vegetables:

• Add fruit to breakfast cereal,
• Eat fresh or dried fruits for snacks.
• Snack on baby carrots.
• Add veggies (fresh or frozen) to pasta, rice and other grain dishes.
• Drink vegetable juice (lacking in fiber, but packed with nutrients).
• Add more vegetables to lettuce-based salads – broccoli, carrots, peppers, cabbage, etc.
• Make vegetables and grains the base of your meals.
• For sweet cravings, try frozen grapes or frozen bananas.

Fiber
Historically, cultures with diets high in fiber, such as African groups, have had very low rates of colon cancer. Numerous studies have demonstrated that high fiber intake reduces the risk of colon cancer.

Not all the data, however, are in agreement. In a review of studies examining fiber intake and cancer risk, only 26 of 39 studies found a protective effect. Recently, a well-publicized study in the New England Journal of Medicine demonstrated an apparent increase (albeit a small one) in colon cancer risk associated with fiber intake in a group of nurses followed by Harvard researchers. This apparent incongruity has challenged prevailing beliefs. In studies that show fiber to be protective, insoluble fiber (found in whole grain breads and cereals, vegetables, some fruits, and seeds) appears to be more effective than soluble fiber (found in oats, legumes, and some fruits).

The bottom line? Even if fiber is found to have no protective role against colon cancer (and this has by no means been proven definitively), the foods that contain fiber -- fruits, vegetables and whole grains -- are healthy sources of vitamins and minerals as well as phytochemicals. The general recommendation remains to increase fiber intake to 20 to 35 grams a day.

Table 2

High Fiber Foods (grams)

Food	Total fiber
1/2 cup All Bran cereal	14 g
3/4 cup Raisin Bran	5 g
2/3 cup oatmeal	3 g
1/5 cup beans	8 g
2 slices whole grain bread	6 g
1 apple	5 g
1 cup whole wheat pasta	6 g
1 baked potato w/skin	4 g
1 pear	4 g
1/5 cup broccoli	2 g

Tips to increase fiber intake (goal = 20 – 35 grams a day)

• Select 100% whole wheat foods instead of white or refined wheat foods.
• Select high fiber cereals (with at least 4 grams of fiber per serving) instead of refined cereals.
• Select brown rice and whole wheat pasta.
• Try other grains such as bulgar, couscous, quinoa, etc.
• Add more vegetables to salads.
• Eat fiber rich fruits and vegetables as snacks.
• Snack on air popped popcorn or baked tortilla chips.
• Increase intake of legumes by adding to grain dishes, soups, and salads.
• Read food labels for fiber.
• Plan more vegetarian meals, incorporating grain, legumes and vegetables.

Calcium
Calcium may play a role in cancer prevention. The exact mechanism is not known, but it appears that calcium may bind to cancer-causing substances, thereby preventing abnormal cell growth. If you are not getting 1000 – 1200 mg of calcium from foods, consider taking a calcium supplement.

Table 3

Calcium Content of Common Foods

High Calcium Foods *	Milligram of Calcium
8 oz. milk	350
8 oz. fruit yogurt	375
1 oz. cheese	200
Canned salmon with bones	150
8 oz. plain yogurt	450
8 oz. calcium fortified orange juice	330
4 oz. frozen yogurt	100 - 200
1 cup ricotta cheese	165

* Remember to select low fat/non fat sources of dairy products

Selenium
Selenium is a powerful antioxidant that can block cell DNA damage, which may lead to cancer. Diets high in selenium appear to reduce the risk of colorectal and many other cancers. The recommended daily allowance for selenium is a small amount, 55 micrograms for women and 70 micrograms for men. Most Americans consume diets adequate in selenium, averaging about 110 micrograms a day. Good food sources of selenium include fish, seafood, poultry, meat, milk, eggs, Brazil nuts, and grains and soybeans grown in selenium rich soils. Supplements are probably unnecessary and may pose health risks, as excess selenium can be toxic.

Exercise
Be physically active. People who exercise even moderately have a reduced risk of colon cancer. Exercise can help control body weight and help prevent constipation. People who exercise regularly also tend to eat a more healthy diet. The American Institute for Cancer Institute recommends a long-term goal of 60 minutes, beginning gradually and increasing as tolerated. The exercise does not have to be vigorous. Incorporating more walking into your day is a great way to increase activity for many people. For example, try walking part of the way to and from work and take a brief walk on your lunch hour.

Practical Advice

There is no guarantee that you can avoid cancer by diet, but overall, data suggest that you may greatly reduce your risk. Most people know they should eat more fruits and vegetables and less fat. However, this knowledge often does not translate into behavior change. As a nutritionist in private practice, I see two major trends with regards to the typical American diet.

The first trend is our increasing dependence on convenience foods. Increased consumption of fast foods and snack foods are no doubt linked to the fact that the average person works longer hours, and more households have two working spouses. These foods tend to be higher in fat and lower in fiber.

The second trend is the increasing popularity of low carbohydrate, high protein, high fat diets. Many people are under the false impression that carbohydrates promote weight gain. In reality, excess calories promote weight gain. Foods high in fat have 9 calories per gram, and are more likely to contribute to weight gain than proteins and carbohydrates, which have only 4 calories per gram. In addition, fat in food is much more efficiently converted to body fat than protein and carbohydrate. Such diets are low in fiber, nutrient rich whole grains, fruits and vegetables, and are overly high in total fat and animal fat -- the kind of diets linked to many cancers, including colorectal cancer, as well as heart disease.

The first step towards improving your diet is identifying your problem areas. I usually recommend that my clients keep food records for several days, then compare your diet to the "ideal" cancer prevention diet:

• 2 to 3 servings of fruit.
• 3 to 5 servings of vegetables.
• 2 to 3 servings of nonfat / lowfat dairy or 1000 – 1200 mg of calcium.
• 2 to 3 servings of lean protein, preferably fish, skinless poultry, tofu, legumes.
• 20 to 35 grams of fiber (see Fiber, above, for tips to increase fiber and for fiber content of common foods).
• Red meat should be lean and consumed in moderation, if at all.
• Fat should be eaten sparingly, mainly omega-3 fats and monounsaturated fats (see Total Fat, above, for fat gram goals)

Once you identify your problem areas, set one or two small goals towards improving your diet. For example, if your diet lacks fruit, try having a piece of fruit for an afternoon snack. Or if your diet is low in fiber, try substituting a higher fiber breakfast cereal such as raisin bran or bran flakes for low fiber corn flakes. Remember, it is difficult to make permanent behavior changes, so start small, adding a change or two every week. Each improvement that you can make in your diet will help decrease your risk of cancer.