Prostate Cancer and Diet
My husband has prostate cancer. Are your (Diana Dyer's) nutrition guidelines appropriate for him, too?
Eating well during and after cancer care
The nutrition guidelines presented by Diana Dyer, MS, RD, in her book, A Dietitian's Cancer Story: Information & Inspiration for Recovery & Healing from a Three-Time Cancer Survivor are appropriate for most men with prostate cancer, and for most people affected by other types of cancer as well. In particular, for people who are feeling well, and who are able to eat well, moving toward a plant-based diet based around vegetables, legumes, fruit, nuts, seeds, and whole grains can improve health. This type of diet may help reduce the risk of cancer recurrence as well.
If you or a loved one is undergoing cancer treatment and is having difficulty eating enough to maintain a healthy body weight, a plant-based diet may not be appropriate. During active cancer treatment, unintentional weight loss—losing weight when you are not trying to do so—can be harmful.
Unintentional weight loss can make it harder to tolerate treatment and to recover and heal. People who lose a lot of weight often have poorer immune function, more fatigue and weakness, and lose lean body mass. None of these things are good. And plant foods, such as vegetables and fruit, may not contain enough calories for someone who is experiencing unintentional weight loss.
However, if you are able to eat well, you're maintaining a healthy weight, you feel good, and you aren't experiencing side effects that make it difficult to eat, the nutrition guidelines offered in A Dietitian's Cancer Story are a great place to start when planning your cancer care plan. It's never too late to benefit from healthful food choices; even after a cancer diagnosis, nutrition matters!
Overview: nutrition and prostate cancer
Health experts have noted that prostate cancer rates vary greatly from country to country, and from region to region, across the globe. There are many reasons for these differences, such as how much exercise people get, differences in obesity rates, and genetics. However, one of the biggest differences between countries with low vs. high rates of prostate cancer is diet.
Many prostate cancer specialists believe these differences in diet are one of the biggest reasons why prostate cancer rates vary so much among the different areas of the world. In other words, some ways of eating seem to protect against prostate cancer, while other dietary patterns may increase prostate cancer risk.
In general, following a plant-based diet is associated with lower risk of prostate cancer. A plant-based diet does not have to be completely vegetarian or vegan. Plant-based simply means that the majority of the foods you eat are minimally processed, whole plant foods. This includes vegetables, fruit, legumes, nuts, seeds, and whole grains. Lean protein from healthful sources, such as fatty fish (salmon, sardines, and others), also can be part of a diet plan designed to reduce prostate cancer risk, or risk of recurrence.
According to the American Institute for Cancer Research (AICR), a plant-based, cancer prevention diet should start with your plate:
- Approximately ½ of the surface should be covered with vegetables, fruits and/or legumes (beans).
- Approximately ¼ of the surface should be covered by starches, such as whole grains or potatoes.
- The remaining ¼ of the surface is covered by lean protein sources, such as fish, chicken, or other lean meats. If you want to follow a vegetarian or vegan diet, lean protein can come from legumes, and soy products, such as tofu or tempeh.
Research supports that this type of eating pattern reduces prostate cancer risk. As well, plant-based diets may reduce the risk of recurrence and progression of disease in men who already have prostate cancer. Dr. Dean Ornish, who has been studying the positive benefits of plant-based or vegetarian/vegan diets to reverse heart disease, also has used this approach with men with prostate cancer.
Dr. Ornish's studies suggest that following a low-fat, plant-based diet, as part of a comprehensive lifestyle program that includes exercise and stress reduction, may improve outcomes in men with prostate cancer. This approach may slow the increase of prostate specific antigen (PSA)—an increasing level suggests the tumor is growing and possibly spreading—and decrease the need for more aggressive treatment in men with low-risk prostate cancer.
Some men opt to "watch and wait," meaning they don't get treatment for prostate cancer right away, because their particular type of cancer is slow growing and less likely to spread. Dr. Ornish's program was tested in a group of men who were following the "watch and wait" approach for managing lower risk prostate cancers.
As well, the healthy lifestyle intervention increased relative telomere length after five years of follow-up, compared with men not following the program (controls). This is a good thing, because longer telomeres protect DNA, our genetic material, from damage. This, in turn, may be protective against chronic diseases, including cancer.
According to the Prostate Cancer Foundation, poor diet is the major risk factor for prostate cancer, and the group offers the following nutritional guidelines to prevent or delay the onset of prostate cancer. These guidelines also stress a healthy, plant-based diet as an important part of a prostate cancer risk reduction plan.
- Eat fewer calories or exercise more so that you maintain a healthy weight.
- Try to keep the amount of fat you get from red meat and dairy products to a minimum.
- Watch your calcium intake. Do not take supplemental doses far above the recommended daily allowance. Some calcium is OK, but avoid taking more than 1,500 mg of calcium a day.
- Eat more fish – evidence from several studies suggest that fish can help protect against prostate cancer because they have "good fat" particularly omega-3 fatty acids.
- Avoid trans fatty acids (found in margarine).
- Try to incorporate cooked tomatoes that are cooked with olive oil, which has also been shown to be beneficial, and cruciferous vegetables (like broccoli and cauliflower) into many of your weekly meals. Soy and green tea are also potential dietary components that may be helpful.
- Avoid smoking for many reasons. Drink alcohol in moderation, if at all.
- Seek medical treatment for stress, high blood pressure, high cholesterol, and depression. Treating these conditions may save your life and will improve your survivorship with prostate cancer.
- What about supplements? Avoid over-supplementation with megavitamins. Too many vitamins, especially folate, may "fuel the cancer", and while a multivitamin is not likely to be harmful, if you follow a healthy diet with lots of fruits, vegetables, whole grains, fish, and healthy oils you likely do not even need a multivitamin.
In addition to focusing on a healthy, plant-based diet, specific foods and nutrients may help men reduce risk of prostate cancer or its recurrence.
Isoflavones: Compounds called isoflavones are found mainly in soybeans, and these nutrients seem to protect against prostate cancer. Good sources of isoflavones include tofu, soymilk, soy nuts, tempeh, and edamame (steamed soybeans in the pod).
Green tea: Green tea contains compounds called flavonoids, which act as antioxidant and may have anticancer activities. Studies suggest several cups of green tea per day are needed to maximize the potential cancer-preventive effects of the beverage. And early trials have found that green tea extract may prevent pre-cancerous prostate growths from becoming cancerous tumors.
Steep for about 4 minutes, because this maximizes the flavonoid content. According to Dr. Douglas Balentine of the Lipton Tea company, if green tea is steeped for only one minute, the average flavonoid content is 208 mg. If it is steeped for four minutes, the flavonoid content increases to 300 mg. If a bitter taste bothers you, try using water that is just slightly less than boiling when you brew up a cup.
Red fruits and vegetables: Lycopene is one of a group of compounds called carotenes, which are known for their antioxidant properties, and which may have cancer preventive properties as well. Cooked tomato products, such as tomato juice and soup, and tomato sauce have the most lycopene. Watermelon and pink grapefruit also contain some lycopene, though not as much as cooked tomatoes.
Some studies suggest lycopene may decrease prostate cancer risk. Other research doesn't show a large cancer preventive effect of lycopene. However, given that eating lycopene-rich foods is unlikely to cause harm, it makes sense to include these foods in a healthy diet.
Cruciferous vegetables: Cruciferous vegetables include broccoli, cauliflower, cabbage, and Brussels sprouts, kale, collard greens, and several other pungent and bitter vegetables. These foods seem to be particularly good at protecting against cancer, and this includes prostate cancer. Eating these foods raw or lightly cooked—steam, sauté, or stir fry—seems to maximize the body's ability to absorb important nutrients.
Dairy and calcium
Dozens of research studies have looked at potential connections between calcium, dairy foods, and prostate cancer risk. These studies present a mixed picture, but some do suggest that high intakes of calcium and/or dairy foods may increase prostate cancer risk.
When studies have found an increased risk of prostate cancer associated with dairy foods or dietary calcium (food sources), the results suggest that more than three to five servings of dairy per day may be a problem. This suggests that moderate dairy intake—up to three servings per day, but no more—is not associated with increased prostate cancer risk.
But remember that calcium is important to health. Not getting enough calcium can increase the risk of osteoporosis, even among men. Further, for men with prostate cancer, some treatments can increase the risk of bone loss and fractures, so trying to completely avoid calcium is not a good idea.
Talk to a registered dietitian for advice on how best to meet your calcium needs.
Look at the big picture
No one food or supplement can protect against prostate cancer. However, a diet that is lower in fat, contains at least five servings of fruits and vegetables per day (more is better), and whole soy foods, will go a long way in protecting your prostate.
The original question and answer were generously donated by Diana Dyer, MS, RD a cancer survivor, registered dietitian, organic garlic farmer, and the author of "A Dietitian's Cancer Story: Information & Inspiration for Recovery & Healing from a 3-time Cancer Survivor.
Question and Answer updated by Suzanne Dixon, MPH, MS, RD on behalf of the ON DPG
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Page updated: January 2014