Differences in diet and lifestyle may account for the variability of prostate cancer rates in different countries. Good nutrition may reduce the incidence of prostate cancer and help reduce the risk of prostate cancer progression. There are many studies currently being conducted to further understand how diet and prostate cancer are related.
We do know that improved nutrition reduces risk of heart disease, diabetes and obesity, and usually improves overall quality of life. It's estimated that a third of cancer deaths in the United States can be attributed to diet in adults, including diet's effect on obesity. Additionally, a healthy diet helps to increase energy levels, facilitate recovery and enhance the immune system.
Researchers conducted an 11-day study where men followed the Pritikin program. The Pritikin program includes a diet that is high in vegetables, fruits and whole grains and very low in fat. This diet is used in combination with 60 minutes of daily exercise. Serum IGF-I (insulin-like growth factor) decreased by 20 percent after following the program for 11 days. Higher IGF-I values previously have been associated with higher risk for various cancers, including prostate cancer. This reduction in IGF-I may be related to the lower serum insulin levels observed with a healthy, low-fat, plant-based diet and regular exercise.
Guidelines for a Healthy Diet
Your diet should be:
- Primarily plant-based
- Include plenty of fruits and vegetables
- High in fiber
- Low in fat
- Limited in the amount of simple sugars
In addition, drink adequate fluids and be physically active to help achieve and maintain a healthy weight.
A diet that is primarily plant-based includes the following:
- Fruits and vegetables
- Whole grains
- Beans and legumes
- Other plant protein sources
Fruits and Vegetables
It is important to eat plenty of fruits and vegetables. Here are a few reasons why:
- They contain vitamins, minerals and fiber as well as various cancer-fighting phytochemicals, such as carotenoids, lycopene, indoles and flavonols.
- There is consistent evidence that diets high in fruits and vegetables are associated with decreased risks of many cancers. While results for prostate cancer risk are not yet conclusive, they are promising.
- Men who consumed at least 28 servings of vegetables per week had a reduced risk of prostate cancer compared with those who ate fewer than 14 servings per week.
- There is some evidence that vegetables — particularly cruciferous vegetables like broccoli, cauliflower, cabbage, kale, Brussels sprouts and bok choy — may be associated with a reduced risk of prostate cancer.
- Men who ate three or more servings of cruciferous vegetables per week had a 41 percent decreased risk of prostate cancer compared with men who ate less than one serving per week.
- The benefit of fruits and vegetables in regards to cancer protection may be related to high amounts of carotenoids in certain fruits and vegetables, according to some key population studies.
- One study indicated that fructose, or fruit sugar, resulted in a lower risk of prostate cancer.
What to Do: Consume at least five, preferably eight to 10, servings of fruits and vegetables daily for their cancer protective effects. One serving equates to:
- 1/2 cup fruit or vegetable
- 1 cup raw leafy greens
- 1/4 cup dried fruit or vegetable
- 6 fluid ounces of fruit or vegetable juice
A plant-based diet is naturally high in fiber, which has a number of benefits:
- Fiber may bind to toxic compounds and carcinogens, which are then later eliminated from the body.
- A high-fiber diet works to reduce hormone levels that may be involved in the progression of prostate cancer.
- One study indicated that a high-fiber, low-fat diet followed only for 10 days resulted in serum changes that reduced the growth of prostate cancer.
- Prostate cancer mortality is inversely associated with consumption of cereals and nuts or seeds, according to a study in the Journal of the National Cancer Institute.
- A diet rich in natural fiber obtained from fruits, vegetables, legumes and whole grains such as whole-grain cereals and breads may reduce cancer risk and reduce the risk of prostate cancer progression.
What to Do: Aim for 25 to 35 grams of fiber daily. To get more fiber, choose breads with three or more grams of fiber per slice. The first ingredient on the label should be whole or sprouted grain flour, not white flour or unbleached white flour. Also, include whole grains — such as oats, barley, quinoa, amaranth, bulgur and millet — in your diet.
For more ideas on how to get more fiber, see Increasing Fiber Intake.
Eating a low-fat diet has many benefits. Here are some points to keep in mind.
- The increased cancer risk observed in developed countries may be, in part, due to the fact that a high-fat diet stimulates increased testosterone levels, which is known to be associated with prostate cancer growth.
- A comprehensive review reported that 24 of 32 studies found positive, although not all statistically significant, associations between dietary fat intake and prostate cancer risk.
- Prospective studies to date, however, have failed to find a consistent association between prostate cancer and overall fat intake.
What to Do: Most researchers agree to aim for 20 percent of your total calories from fat, with less than 10 percent of total calories from saturated fat.
The type of fat is significant.
Several studies indicate a positive association between saturated fat intake from meat and dairy products and prostate cancer. Intakes of red meat and dairy products appear also to be related to increased risk of metastatic prostate cancer. Therefore, it is wise to reduce or eliminate consumption of red meat, milk and other dairy products.
What to Do: Reduce or eliminate consumption of red meat, milk and other dairy products. Limit use of butter, mayonnaise, baked goods and regular salad dressing due to their high saturated fat and total fat content. Consider rice vinegar, balsamic vinegar, lemon juice or salsa as alternative salad dressings. Limit cheese consumption. Cheese is typically between 60 to 80 percent fat, much of which is saturated fat.
Trans fatty acids are known to be atherogenic, or heart disease causing. They also may cause an imbalance in hormonal systems that regulate healing, lead to the construction of defective membranes and encourage the development of cancer.
What to Do: Limit use of hydrogenated fats found in products such as margarine, fried foods and processed foods, which are high in harmful trans fatty acids. When you read that a product contains "hydrogenated" or "partially-hydrogenated" oils, you may want to consider putting it back on the shelf. Trans fatty acid labeling went into effect in 2006, so nutritional labels should spell out the amount of trans fatty acids in the product.
Omega-6 Fatty Acids
Omega-6 fatty acids, which is linoleic acid that can be converted to arachidonic acid, may stimulate growth of prostate cancer cells. These fatty acids are found in corn oil, safflower oil, sunflower oil, cottonseed oil, soybean oil and other polyunsaturated oils.
What to Do: Substitute olive oil for your current cooking oil, but remember to use in moderation. These oils are rich in monounsaturated fats, which have not been shown to increase cancer risk.
Omega-3 Fatty Acids
Omega-3 fatty acids may reduce your risks for prostate cancer and cancer progression. They induce apoptosis (cell death), suppress cancer cell initiation and compete with arachidonic acid, which limits harm from arachidonic acid. One study indicated that men who consumed cold-water fish three to four times per week had a reduced risk of prostate cancer. A more recent study found similar results. Men who consumed fish three or more times per week also had a lower risk of prostate cancer, especially for metastatic prostate cancer where the effect was even greater.
Researchers in New Zealand reported that men with high levels of EPA and DHA, the omega-3 fats found in fish, had a 40 percent lower risk of prostate cancer than those with low blood levels. A 30-year follow-up study found that men who ate no fish had a two to three times higher frequency of prostate cancer than those who ate moderate or high amounts of fish. The mechanism of cancer reduction may occur through the inhibition of arachidonic acid-derived eicosanoid biosynthesis.
Dietary sources of omega-3 fatty acids include cold-water fish — such as salmon, trout, herring and sardines — flaxseeds, walnuts, soybeans and canola oil.
What to Do: It may be wise to consume fish at least twice weekly to obtain an adequate amount of omega-3 fatty acids.
Fish and plant-based foods contain different types of omega-3 fatty acids. Fish contains EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), two specific fatty acids that have shown promising results in research. The plant-based omega-3 fatty acid sources, such as flaxseed and others listed above, contain ALA (alpha-linolenic acid).
In an ideal environment, ALA is converted to EPA and DHA, however, in 10 percent to 20 percent of the population, this conversion process is dysfunctional. On the positive side, the conversion process is enhanced by following a diet that is low in saturated fats and low in omega-6 fatty acids.
Nuts are highly concentrated in monounsaturated fatty acids, which are neutral in terms of stimulating cancer growth and may be beneficial for heart disease. They are, however, high in fat.
What to Do: Minimize consumption of nuts due to their high fat content. This includes peanuts, macadamia nuts and pistachios.
Key Points About Fat
- Less fat is better
- Olive oil is preferred
- Avoid hydrogenated fats
- Increase dietary omega-3 fatty acids
Limit the amount of simple sugar in your diet. High-sugar foods are usually:
- Highly processed and refined
- Low in nutrient value
- Low in fiber
Furthermore, these foods appear to increase serum insulin and serum IGF-I levels, which may stimulate cancer cell growth.
What to Do: Simple sugars should be consumed in limited amounts. Avoid sweets such as candy, cookies, cakes and pies. Limit your intake of products made with refined flours.
Your body needs an adequate amount of fluid. Water in the body:
- Carries nutrients and waste products
- Participates in chemical reactions
- Acts as a lubricant and cushion around joints
- Acts as a shock absorber in the eyes and spinal cord
- Aids in the body's temperature regulation
- Maintains blood volume
In addition, the body needs more fluid when eating a high-fiber diet.
What to Do: Drink plenty of water daily to help meet fluid needs. Note that caffeine acts as a diuretic, increasing water loss. Your fluid needs increase with high consumption of caffeinated beverages.
Modest Caloric Restriction
Some evidence indicates that a high caloric intake increases one's risk of various cancers, including prostate cancer. A case-control study reported a 115 percent increase risk in local prostate cancer and a 96 percent increase risk in regional/distant prostate cancer for those consuming higher calorie diets (2,439 or more calories a day) compared with individuals consuming a lower calorie diet (less than 1,322 calories a day).
In a separate study, researchers reported a nearly four-fold increase in prostate cancer risk in men who consumed the most calories (more than 2,624 calories a day) compared with men who consumed the least calories (1,064 calories a day).
An earlier study found that caloric intake was positively associated with preclinical prostate cancer risk; as caloric intake increased, cancer risk rose significantly. The greatest risk was for subjects who consumed more than 3,475 calories a day. All of this suggests that the mechanism involved may be related to the decrease in IGF-I observed when caloric intake is restricted.
UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.
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