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Dietary Fat and Fatty Acids for Prostate Cancer
Dietary fat provides energy and essential fatty acids for the body. In addition, fat acts as a carrier for vitamins A, D, E and K. Fats are classified loosely as saturated, monounsaturated or polyunsaturated, depending upon which type of fatty acid is predominant in the fat. Polyunsaturated fats (found primarily in vegetable oils, such as oils of corn, safflower and sunflower) contain high amounts of linoleic acid, a fatty acid that stimulates prostate cancer cell growth. Olive oil consists predominantly of monounsaturated fat and does not pose a problem. Overall, high-fat diets are linked to an increased risk for prostate cancer.
During the metabolism of fat, a large number of damaging free radicals (which are discussed on the lycopene page) are produced. These damaging molecules can promote the growth of cancerous cells.
In prostate tumors, a specific group of fat receptors, the PPAR's (peroxisome proliferator activated receptors) are expressed at very high levels. These fat receptors act as fat sensors in the prostate cancer cells. When fat is put into the body, it binds to these PPARs. Once the fat has attached to the receptor, a signal is activated. This signal contains pre-programmed instructions, which may initiate cancer cell growth through an unknown mechanism. Therefore, when a high-fat diet is consumed, more PPARs are activated. When more receptors are activated, a greater number of signals that increase cancer growth are initiated. Scientists have found that one of these PPARs, the PPAR gamma, is a link between a high-fat diet and the development of colon cancer. Researchers are now studying this receptor to find out if it plays a similar role in prostate cancer.
Epidemiologic studies have shown that high-fat intake increases a man's risk for advanced prostate cancer. Giovannucci and colleagues of Harvard Medical School found that men who ate high-fat diets (including large amounts of red meat) had a significantly higher rate of advanced prostate cancer. An international study published in the Journal of the National Cancer Institute showed that the per capita fat consumption correlates directly with increased prostate cancer rates. An animal study by Wang and associates demonstrated that reduced fat intake inhibits androgen-dependent prostate cancer growth and decreases prostate tumor sizes in animals.
Many researchers have studied the relationship between fat and prostate cancer. Fatty acids are the building blocks of fats. Most fats are made up of a mixture of different fatty acids. However, few studies have looked at the effect of specific fatty acids on prostate cancer growth. Therefore, much controversy exists about their role in prostate cancer. Studies show that omega-3 fatty acids (including alpha-linolenic acid) have increased prostate cancer growth in vitro (in test tubes).
Yet, fish oils (which are also omega-3 fatty acids) have not demonstrated a role in increasing prostate cancer risk. Studies have shown that omega-3 fatty acids inhibit prostate cancer cell growth in a dose-dependent manner. In an animal study by Rose and Cohen, mice were fed a diet high in omega-3 fatty acids. The omega-3 fatty acids inhibited the growth of prostate cancer tumors in these mice.
Laboratory and animal studies have shown that another group of fatty acids, omega-6-polyunsaturated fatty acids, promotes the growth of human prostate cancer. Specifically, two omega-6 fatty acids, which are linoleic acid (safflower oil) and arachidonic acid (found in all meats and whole dairy), have been shown to increase prostate cancer risk. In one study, Ghosh and Myers showed that linoleic acid (omega-6 fatty acid) stimulated the growth of prostate cancer cells in culture.
In conclusion, many studies about fatty acids are contradicting. One study says that omega-3 fatty acids inhibit cancer growth. Another says that these fatty acids increase cancer growth! The bottom line is that more research must be done. In the meantime, it is recommended that you stay away from any type of extra fat.
Urology Center Recommendations
- 15 - 20% of your total daily calories should come from fat.
- Eliminate butter, cheese and salad dressings containing oil or mayonnaise, and use nuts sparingly.
- Read menus and food labels carefully.
- Avoid foods that are prepared au gratin, creamed or breaded.
- Look for foods that are roasted, broiled and grilled.
- Steam vegetables and roast, broil or grill fish and poultry, rather than frying.
- Eat one to two servings of fish per week, such as ocean-caught salmon, whitefish, halibut, shrimp, scallops, lobster, crab or even tuna fish (canned in water). These will give you the benefits of omega-3 fatty acids.
- Avoid foods especially high in saturated fats, such as animal fats, whole-dairy products, butter and coconut oil.
- Substitute high-fat snacks, like chocolate bars, with fresh fruits and vegetables.
- Do not overeat low-fat cookies, ice creams, etc. Cookies and ice cream are naturally high in fat. In the low-fat versions, the fat has been replaced with added sugar or salt.
- Use herbs, garlic, onion and spices instead of butter, salt and toppings rich in fats.
- Reduce or eliminate your intake of red meat.
- Reduce or eliminate your intake of farmed fish. These fish are fed fishmeal. Therefore, they do not feed on algae and other smaller fish in the ocean. Consequently, the flesh of farmed fish is much higher in total fat, yet lower in beneficial omega-3 fatty acids than ocean-caught fish.
- Limit cooking fats. Use pan sprays instead.
Click here to view information about dietary fiber.