Diet and Prevention of Prostate Cancer
Professor Rune Blomhoff Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Norway
You can greatly reduce your risk of getting cancer Most types of cancers are not inevitable diseases that hit individuals due to some inherent risk. A wealth of studies has, during the last years, demonstrated that your risk of developing cancer can be greatly reduced if you take some precautionary steps related to your lifestyle. These conclusions have been drawn from different type of studies. For example, variations have been identified in patterns of cancer throughout the world. Studies consistently show that patterns of cancer change as countries become increasingly urbanised and industrialised. Furthermore, migrant studies which compare cancer rates for migrants, and for their offspring, in their current country of residence, with rates in their country of origin, shows that cancer incidence rates acquire the rates characteristic of their new location. This demonstrates that environmental, rather than inherited factors are primarily responsible for the large differences in cancer rates in different regions of the world. The same conclusion is drawn from correlation studies which prove that an unhealthy diet, physical inactivity and smoking are the main risk factors for developing cancer. Thus, you have more control over your risk for cancer than you might think. Roughly onethird of all cancer cases could be prevented through sensible dietary choices, maintaining a healthy body weight and keeping physically active every day. If we also could eliminate smoking, more than 50% of all cancers could have been eliminated. These encouraging observations are supported by evidence from a landmark recent research report called “Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective” that was published by the World Cancer Research Fund (WCRF) in November 2007. The WCRF report (can be downloaded from www.wcrf.org) that was written by a panel of 21 international experts summarised the state-of-the-art within this field of research and provides the most current, reliable and authoritative advice on the best ways to prevent cancer through diet and lifestyle choices. The report’s recommendations can be summarized in the following simple action steps: Choose mostly plant foods, limit red meat and avoid processed meat. Be physically active every day in any way for 30 minutes or more. Aim to be a healthy weight throughout life. Do not smoke or chew tobacco. A major conclusion of the report is that you do not need to give up your favourite foods or dramatically change to a specialized type of diet in order to reduce your risk of getting cancer. The major advice is simply to choose to eat more of the foods that offer cancer protection, like vegetables, fruits, whole grains and beans, and less of the foods that do not, like red meat, processed meats and salt. Studied shows that it is wise to make changes to your diet slowly,
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over time, rather than trying to change everything overnight. This will help you keeping your new dietary habits. The second important way you can reduce your cancer risk is by getting regular physical activity every day. It could either be through a sport, exercise machines at the gym or by doing household or work-related activities. WCRF recommends being physically active for at least 30 minutes every day with intensity similar to a brisk walk. As your fitness improves, you should aim for a goal of 60 minutes daily. The general recommendations for reducing your risk of developing cancer from the WCRF Expert Report: 1) Be as lean as possible without becoming underweight. 2) Be physically active for at least 30 minutes every day. 3) Avoid sugary drinks. Limit consumption of energy-dense foods (particularly processed foods high in added sugar or high in fat). 4) Eat more of a variety of vegetables, fruits, whole grains and legumes such as beans. 5) Limit consumption of red meats (such as beef, pork and lamb) and avoid processed meats. 6) If consumed at all, limit alcoholic drinks. 7) Limit consumption of salty foods and foods processed with salt. 8) Do not use supplements to protect against cancer. 9) Aim to breastfeed infants exclusively for up to six months. 10) If you have been treated for cancer, you should follow the general recommendations for cancer prevention. 11) Do not smoke or chew tobacco. The prostate gland and prostate cancer The prostate is the gland that produces semen – the fluid that carries sperm. About the size of a walnut, the prostate is located above the rectum, between the bladder and the penis. Most men first become aware of their prostate when it affects urination. In younger men, the prostate may become inflamed, a disease called prostatitis. Such prostatitis can lead to raised blood levels of prostate-specific antigen (PSA), a marker of prostate cancer. Increased levels of PSA in prostatitis is not, however, a sign of prostate cancer, and will decrease to normal levels after the prostatitis has been eliminated. As men enter middle age and then their later years, the prostate often enlarges. This condition is called benign prostatic hypertrophy. Some of the symptoms for benign prostatic hypertrophy may be the same as those for prostate cancer. In general, when cells grow too rapidly and without any order they produce tumours, which are classified as either benign or malignant. Benign tumours are not cancerous, can be removed by surgery and are not likely to return. Malignant tumours are cancerous and can spread to other parts of the body. Cancer that develops in the prostate gland is called prostate cancer. Prostate cancer, which is the third most common type of cancer in men in the world today, is one of these cancers that have a strong environmental link. Nearly 700 000 new cases are diagnosed every year, the majority of cases in men over 65 years of age. Prostate cancer is more common in high-income countries, but the incidence remains low in Japan. Incidence rates have been influenced by screening programmes, which increase diagnosis rates. This has
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resulted in an increase in the number of recorded cases in many countries, although the incidence in several high-income countries has declined since the 1990s. Prostate cancer incidence is increasing rapidly in low-income countries. This may partly be due to increased awareness and screening. Mortality from prostate cancer is approximately 10 times more common in the USA and Europe than in Asia. After reviewing the latest evidence, the WCRF expert panel has identified several compounds in foods that may modify a man’s risk of developing prostate cancer. It is important to keep in mind, however, that all components of a healthy diet may work together to help lower cancer risk. Tomatoes and lycopene may reduce risk of prostate cancer Lycopene is an antioxidant that protects against cell damage that may lead to cancer. It has attracted particular attention from prostate cancer researchers because lycopene and its related compounds tend to concentrate in tissues of the prostate. The WCRF 2007 report found substantial evidence that foods containing lycopene probably protect against prostate cancer. Lycopene is especially abundant in tomatoes and tomato products, but is also present in lower amounts in watermelon, apricots and pink grapefruit. These foods seem to provide the body with lycopene more effectively than lycopene supplements. According to researchers, lycopene is an antioxidant and is best absorbed from vegetables after they are cooked and pureed. So although fresh tomatoes appear to help prevent and slow the growth of prostate cancer, they are particularly potent when they are processed into products such as sauce, stewed tomatoes and tomato juice. Lycopene absorption is increased when its food source is eaten with a small amount of healthy fat, such as olive oil. WCRF therefore recommends eating tomatoes and tomato products as part of a diet that is generally high in a variety of vegetables and fruits. That is because different phytochemicals (i.e. biological active plant components) in these foods appears to work together to protect health. Thus, it seems to be a good idea to select the tomato products with most lycopene. In a recent survey we analysed a number of tomato products and observed that the content of lycopene varied a lot between apparently similar products. Below is a table with lycopene content in some common tomato products. PRODUCTS Canned tomatoes Passata di pomodoro con basilico, La bioIdea Polpa pomodori in finissimini pezzi, Mutti Chopped tomatoes, Biona Tomatoes, chopped, passed, Mutti Polpapezzi di pomodori italiani, Mutti Pelali mediterranei, Mutti Pomodorini di collini, Mutti Tomatoes, chopped, Landlord Chopped tomatoes, Del Monte Tomatoes, Landlord Tomatoes, chopped, italian, S&W Fine Foods Stewed tomatoes, mexican, S&W Fine Foods Tomatoes, Californian style, S&W Fine Foods Lycopene mg/100 g 17.8 14.8 13.4 12.0 11.8 11.1 11.0 7.6 7.6 6.8 5.7 5.3 5.2
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Stewed tomatoes, cajun, S&W Fine Foods Tomatoes with garlic, S&W Fine Foods tomat med balsamicoeddik, basilikum og olje, Hunt's Tomat with mushroom, Hunt's Pasta sauce Pomodoro al basilico, Andalini Pomodoro sauce, Barilla Pasta sauce with sundried tomatoes, Dolmio Tomato, oregano, onion and garlic pasta sauce, Knorr Pasta sauce classico, Dolmio Pasta sauce whith chilli and onion, Knorr Pasta sauce with basil, Dolmio Pasta sauce extra garlic, Dolmio Arrabbiata, Barilla Ricotta, Barilla Pasta sauce extra vegetables, Dolmio Spaghetti sauce, Sopps Al forno pasta sauce with parmesan and cream, Dolmio Spaghetti sauce, Toro Pasta sauce with sundried tomatoes and onion, Toro Spahetti sauce, Knorr Spahetti sauce, Toro Salsa Taco sauce, medium, Casa Fiesta Thick n` chunky salsa, medium, Old El Paso Habanero and tequila salsa, extra hot, Santa Maria Garlic salsa, Old El Paso Rio grande salsa, medium, Santa Maria Taco sauce, medium, Santa Maria Sweet red chili salsa, medium, Santa Maria Salsa dip, medium, Old El Paso Chunky salsa, medium, Santa Maria Taco sauce, medium, Old El Paso Tacosaus, Hot, Landlord Tropical salsa, medium, Santa Maria Tomato juice Tomato juice, Cadisco Tomato juice, ecological, Svanes Tomato juice, Maroc Tomato juice, Campbells Tomato juice, S&W Fine Foods Premium tomato juice, Del Monte Tomato juice, Cofrutos Tomato juice, Granini Tomato juice, Molinera
4.9 4.7 4.1 3.4 mg/100 g 22.7 17.2 17.1 15.6 14.8 13.6 11.6 11.6 11.3 10.9 5.6 4.6 4.8 3.1 3.1 2.0 1.2 mg/100 g 16.4 11.6 11.2 10.1 10.0 9.7 8.6 8.5 7.2 7.0 5.5 2.1 mg/100 g 11.8 11.5 9.6 9.4 8.6 7.7 6.8 6.6 5.1 4
Ketchup Ketchup classico, La BioIdea Tomato ketchup, Mutti Tomato ketchup, Idun Barbeque ketchup, Idun Red Hot Chili ketchup, Idun Tomato ketchup, Eldorado Tomato ketchup, ecological, Heinz Tomato ketchup, Heinz
mg/100 g 23.0 15.9 13.2 12.0 11.9 9.0 5.6 5.4
Selenium containing foods may also protect Selenium is a mineral that forms an essential part of some antioxidant enzymes produced by the cells in your body. These enzymes are an important part of your antioxidant defence that block cell damage that could lead to cancer. Similar proteins are also involved in testosterone production – an important regulator of both normal and abnormal prostate growth. According to the WCRF expert panel, there is strong evidence that selenium probably protects against prostate cancer. Selenium is found in many foods, including: Brazil nuts, whole grains, sunflower seeds, wheat germ, seafood, poultry and lean meats. Diet high in calcium may increase risk WCRF expert panel identified foods high in calcium as likely to increase risk for prostate cancer. The report suggests that a high calcium intake increases cell growth and cell division in the prostate, which may provoke the development of cancer cells. On the other hand, however, experts also caution that diets low in calcium can reduce bone health and may decrease risk of colon cancer. Because of these contradictory findings, WCRF experts offer no recommendation to alter calcium intake at this point. A preliminary advice may be that men should therefore meet their basic calcium needs through their regular diet, but try not to take in excessive amounts of calcium. Other dietary factors that may be linked to prostate cancer In addition to tomatoes and lycopene, selenium and calcium, some preliminary results may point to a relationship with other dietary factors and prostate cancer as well. The link in these associations are, however, much weaker and more studies are needed before firm conclusions and recommendations can be made. Soybeans Soy – a member of the legume or bean family – has shown cancer-fighting promise in some but not all studies. Researchers speculate that phytochemicals in soy known as isoflavones may offer prostate cancer protection. However, the evidence is limited and inconsistent and there is no consensus that soy protects against prostate cancer at this point. Soy foods such as tofu, tempeh, soy milk, miso can however be incorporated as part of a balanced diet, providing a good source of protein and other nutrients. Vitamin E The WCRF Expert Report found evidence supporting a protective effect of vitamin E is too limited and inconclusive to make a recommendation. Although more research in this area is necessary, results so far suggest an association between foods containing vitamin E and lower
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prostate cancer risk. Dietary sources of vitamin E include nuts, seeds and vegetable oils such as canola and olive oil. Processed Meat Limited, but suggestive, evidence is observed for increased prostate cancer risk from eating processed meats – usually red meat like beef, pork and lamb that is preserved by smoking, curing, salting or adding chemical preservatives. Examples include bacon, ham, sausage, hot dogs, pepperoni, salami and bologna. The WCRF Expert Report concluded that eating them regularly may lead to higher risk for prostate cancer and several other cancers. WCRF recommends avoiding processed meats except perhaps for a modest amount on special occasions.
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