Prostate cancer is now the most commonly diagnosed form of cancer in Canadian men. Since 1994, the incidence of prostate cancer has begun to decline after several decades of rapid increase. By the age of 50, as many as one in four men will have some cancerous cells in their prostate gland. That number increases to one in two by the time men reach the age of 70 and it is estimated that almost every male over the age of 90 has the disease.
The prostate is a male sex gland located below the bladder and in front of the rectum. It surrounds the urethra, which is the tube that carries both urine and semen out of the body. The prostate gland contributes to reproductive function by producing a milky fluid that helps to keep the sperm nourished, mobile and healthy. This fluid forms part of the semen, the sperm-carrying fluid released during ejaculation.
Cancer develops when abnormal or mutated cells go out of control, damaging the body's vital organs or tissues. As mutated cells accumulate, they form a mass or clump that is known as a tumour. In the case of prostate cancer, the tumour often remains inside the prostate gland, causing few symptoms until the cancer has reached an advanced stage. Sometimes, however, the cancer cells invade and destroy normal tissue, spreading to other organs and bones, where they can cause life-threatening problems. Very often, prostate cancer spreads to the lymph nodes, to the bones of the pelvis, ribs and spine or to the kidneys, where it causes kidney failure.
Scientists have not yet determined what causes abnormal cell growth in prostate tissues. Theories focus on genetics, hormones, environment and diet as key factors that influence prostate cancer risk.
Screening for prostate cancer
Considerable progress has been made in both the diagnosis and treatment of prostate cancer. If diagnosed at an early stage, prostate cancer can be cured. Unfortunately, more than 40 percent of all cases are not diagnosed until the cancer is advanced and has spread beyond the prostate gland.
To help improve the chances of early detection, doctors routinely screen for prostate cancer in men over the age of 40. A digital rectal exam is the most common and simplest diagnostic test for prostate cancer. Your doctor will manually check your prostate, using a gloved finger to feel for unusual bumps or hard spots on the gland wall. While the majority of tumours can be felt this way, approximately one-third of all prostate tumours develop deeper within the gland and cannot be detected using a digital rectal exam.
The prostate-specific antigen (PSA) test is rapidly becoming one of the most reliable indicators of prostate cancer. Normally, the prostate generates PSA as part of the fluid production process necessary for healthy semen. A small amount of this substance also circulates in the bloodstream. In approximately one-third of all cases elevated blood PSA levels indicate prostate cancer. High levels may also be the result of less serious conditions such as prostate enlargement, prostate infections and the use of certain drugs or herbal medications.
Symptoms, Risk Factors and Treatments
Often there are no symptoms in the early stages of the disease. The symptoms that do occur are very similar to those of benign prostatic hyperplasia (BPH), commonly known as prostate enlargement. These symptoms include:
- Chronic, dull pain in the lower pelvis, lower back or upper thighs
- Pain during urinationSudden need to urinate
- Frequent urination during the night
- Difficulty starting to urinate, dribbling, weak urine flow
- Blood or pus in the urine
- Painful ejaculation
- Loss of appetite and weight
Who's at risk?
- Older men; most cases are diagnosed in men over the age of 65
- Certain racial or ethnic groups; black men have a 60 percent higher incidence of prostate cancer than white men and Asian men have the lowest incidence
- Men with family history of the disease; having a father or brother with the disease, doubles the risk and is associated with developing the prostate cancer at an earlier age
- Men who eat a high fat diet
Prostate cancer is very slow growing and is not usually an aggressive type of cancer. Only three percent of the men diagnosed with prostate cancer actually die of the disease. Treatment for prostate cancer will vary depending on how far the cancer has spread, how fast the cancer is growing, your age and general health.
Older men with early-stage, slow-growing cancer may not need treatment because their risk of dying from the disease is not high. Watchful waiting for symptoms and a regular program of PSA tests and rectal exams may be sufficient. For younger men, the most effective treatment involves surgery to remove the prostate gland (radical prostatectomy) however research indicates that cancer recurs in 30 percent of all men who have this procedure.
Radiation therapy to kill cancerous cells may be used for older men in poor health who may have difficulty withstanding surgery. Cryotherapy may also be used to kill cancer cells. Liquid nitrogen is used to freeze and destroy cancerous cells. Impotence results from cryotherapy in 90 percent of cases. Hormone therapy may be used to prevent male sex hormones from speeding up the growth of cancer cells.
Prostate cancer and the treatments used to control the disease can cause a number of complications, including incontinence, impotence, reduced libido, breast enlargement and depression.
Preventing prostate cancer
A healthy diet
Studies comparing the diets of men with prostate cancer to those of men free of the disease have found a number of foods linked to development and progression of the cancer. Most notable is the link between animal (saturated) fat and prostate cancer. Many studies have found that men who have higher intakes total fat and animal fat increase the risk of the disease and are associated with more advanced forms of prostate cancer. When mice are injected with human prostate cancer cells and fed a high fat diet, the cancer grows faster. Dietary fat is believed to increase the level of circulating hormones that may cause prostate cancer.
Follow a low fat diet by choosing lean cuts of meat (flank steak, inside round, pork tenderloin), poultry breast without the skin, skim or 1% milk and yogurt, and skim milk cheese. Use butter sparingly. If you eat meat, consume no more than 3 ounces (90 grams) per day.
More often, substitute animal protein with vegetarian protein foods such as legumes and soy foods. Eating more legumes such as kidney beans, chickpeas and lentils has been associated with a lower risk of prostate cancer. Beans contain phyto (plant) estrogens called isoflavones that may slow the growth of prostate tumors.
Eating more fish will also help to reduce animal fat in the diet. Fish contains omega-3 fatty acids, compounds that have been shown in the laboratory to inhibit cancer growth. Some evidence suggests that men with higher levels of these fatty acids in their blood have a lower risk of prostate cancer. Aim to eat fish at least three times per week.
Consuming plenty of whole grain breads, cereals, brown rice, whole wheat pasta and other whole grains has also been linked with protection from prostate cancer. These foods offer fibre, phytoestrogens, vitamin E, selenium, flavonoids and antioxidants ' all of which may play a role in prostate cancer prevention.
When it comes to fruits and vegetables, cruciferous vegetables appear to offer the most protection from prostate cancer. One large study found that men with the highest intake of these vegetables had a 39 percent lower risk of the cancer. Broccoli, bok choy, cabbage, cauliflower, kale and turnip contain isothiocyanates, natural chemicals that have been shown to help the liver detoxify cancer causing substances. Orange/yellow vegetables and tomatoes are also protective (see lycopene below).
Some research suggests that drinking alcohol, regardless of the type, increases prostate cancer risk. If you drink, consume no more than nine drinks per week. Green tea may be beneficial. Studies have found populations that drink green tea regularly have lower rates of prostate cancer. Laboratory studies have determined that natural chemicals in green tea, called flavonoids, have anti-cancer properties.
Lycopene is an antioxidant compound found in red coloured vegetables and fruits but is especially abundant in tomatoes. A large study from Harvard University found that men who consumed 10 or more servings of tomato based foods per week had a 35 percent lower risk of prostate cancer compared to those who ate less than 1.5 servings per week. Eating tomatoes, tomato sauce, tomato juice, and pizza offered protection.
Lycopene taken in high supplemental doses is currently being studied for its potential role as a treatment for prostate cancer.
A daily intake of 5 to 7 milligrams of lycopene appears to offer protection. While the foods below are all good sources of lycopene, heat processed tomato products provide a source of lycopene that is much more available to the body. Lycopene is a fat-soluble compound, which means it is better absorbed in the presence of a little fat.
Food Lycopene (milligrams)
Tomato, raw, 1 small: 0.8-3.8
Tomatoes, cooked, 1 cup (250 ml) :9.25
Tomato sauce, 1/2 cup (125 ml): 3.1
Tomato paste, 2 Tbsp. (25 ml): 8.0
Tomato juice, 1 cup (250 ml): 23.0
Ketchup, 2 Tbsp. (25 ml): 3.1-4.2
Apricots, dried, 10 halves: 0.3
Grapefruit, pink, 1/2: 4.2
Papaya, 1 whole: 6.2-16.5
Watermelon, 1 slice (25 cm x 2 cm): 8.5-26.4
Asian men and vegetarian men have much lower rates of prostate cancer, an observation that has been linked to a higher intake of soy foods. A study of California Seventh-Day Adventist men found that drinking soymilk more than once a day was associated with a 70 percent lower risk of prostate cancer.
Soybeans contain isoflavones, phytoestrogens that have been shown to inhibit the growth of prostate tumors in animal and laboratory studies using human prostate cancer cells. So far, however, the evidence looks promising that soy foods may protect the prostate. To increase your intake, begin by replacing three animal based meals each week with soy. Tofu, soy meats, soy nuts, soymilk, canned soybeans, and tempeh are all good choices.
Vitamins and Minerals
Our requirements for this vitamin are met through food intake and exposure to sunlight. The sun's ultraviolet rays trigger the skin to produce vitamin D. The fact that populations who get little exposure to sunlight have higher rates of prostate cancer has led researchers to speculate that vitamin D is somehow involved. The recent finding that the prostate can also metabolize vitamin D has opened up investigations into vitamin D and cancer prevention. Laboratory studies have found that vitamin D inhibits the growth of human prostate cancer cells.
As we age, our skin becomes less efficient at producing vitamin D and this may contribute to prostate cancer risk. The RDA is 200 to 600 IU depending on your age. Food sources of vitamin D are limited to fluid milk, fortified soy and rice beverages, oily fish, egg yolks, butter, and margarine. Your multivitamin and mineral should provide 400 IU of vitamin D. High supplemental intakes of vitamin D have the potential for harm and should be used under the guidance of a doctor. The safe upper daily limit is 2000 IU.
Higher intakes of vitamin E are linked with a lower risk of prostate cancer. Researchers have also observed that men, especially those who smoke, with lower blood levels of this nutrient are at increased risk. A number of studies suggest that vitamin E supplements help to prevent prostate cancer.
Vitamin E is a potent antioxidant and may protect prostate cells from free radical damage that can lead to cancer. The vitamin may also prevent prostate cancer by altering the levels of sex hormones in the blood.
The recommended dietary intake for vitamin E is 15 IU (natural source) and 22 IU (synthetic). Vitamin E rich foods include wheat germ, nuts, seeds, vegetable oils, whole grains and kale. To supplement take 200 to 400 IU of natural source vitamin E. Buy a 'mixed' vitamin E supplement that contains gamma-tocopherol, a form of vitamin E that may offer added protection from prostate cancer. The safe daily upper limit is 1500 IU
The protective effects of this mineral were discovered by accident when researchers from Arizona investigated the effect of selenium supplement on skin cancer recurrence. Men with a history of skin cancer were given 200 micrograms of selenium or a placebo and followed for 4.5 years. While the risk of skin cancer was unaffected, there was a significant reduction in prostate cancer among men taking selenium supplements. In areas like the northeastern United States and Canada, where the selenium level in the soil is low, rates of prostate cancer are higher.
Selenium acts as an antioxidant in the body, protecting cells from the damaging effects of free radicals. The recommended dietary intake for selenium is 55 micrograms, an amount easy to get from the diet by consuming foods like fish, seafood, chicken, organ meats, whole grains, nuts, onions, garlic, and mushrooms.
To prevent prostate cancer, a dose of 200 micrograms is recommended. Buy a supplement made from selenium rich yeast. Do not exceed 400 micrograms per day.
Eating more garlic and taking garlic supplements may offer protection from prostate cancer. Researchers from the UK studied 328 men with prostate cancer and found that those who ate garlic at least twice weekly had a 44 percent lower risk of prostate cancer compared to those who never consumed it. Compared to men who never used garlic supplements, those who used supplements at least twice weekly had a 60 percent lower risk of the cancer.
Garlic contains natural sulfur compounds that have been shown to enhance the immune system and inhibit the growth of prostate cancer cells in the laboratory. Once study found that compounds in aged garlic extract suppress the growth of hormone-responsive prostate cancer cells.
Add more garlic to cooking. To supplement, buy a product made with aged garlic extract. Take two to six capsules a day in divided doses. Aged garlic extract is odourless and is less irritating to the gastrointestinal tract than other forms of garlic supplements. Garlic (both fresh and supplements) may enhance the effects of blood thinning medications like Coumadin' (warfarin). If you are taking this drug and garlic at the same time, be sure to inform your doctor.
The above an excerpt from "Leslie Beck's Nutrition Encyclopedia" (Penguin Canada, 2001/2003), available at bookstores across the country. The following is copyrighted and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or means - electronic, mechanical, photocopying, or likewise.
All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.