Harvard Health Blog
Complementary therapies for prostate disease: What works and what doesn’t
Harvard experts discuss issues that patients may want to consider
If you have been diagnosed with prostate disease, chances are that you’ve thought about trying some type of complementary therapy in addition to conventional medical treatment from a physician. If you have, you are not alone. Various studies have found that anywhere from 27% to 43% of American men with prostate cancer use at least one form of complementary therapy. Similar findings have been reported in Canada and Europe. Although statistics are harder to find for how many men use complementary therapies for benign prostatic hyperplasia (BPH), erectile dysfunction, or prostatitis, it is likely that the practice is common.
Unfortunately, the issue of complementary therapies doesn’t often come up during a visit to the physician. Patients tend not to mention the complementary therapies they are using, while doctors may not ask about them. Often this is a function of time: A man and his doctor may have only 10 or 15 minutes together in a typical office visit.
To learn more about what physicians think about various complementary therapies — and about specific lifestyle changes — the Harvard editors invited three experts to participate in a roundtable discussion on this important topic. The panel consisted of these people:
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Dr. Edward Giovannucci, a professor of nutrition and epidemiology at the Harvard School of Public Health whose research has focused on how lifestyle factors such as diet and physical activity contribute to the development of cancer, particularly colon cancer and prostate cancer. Dr. Giovannucci is considered one of the nation’s pre-eminent experts on nutrition and prostate cancer.
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Dr. David S. Rosenthal, a professor of medicine at Harvard Medical School, director and chief executive officer of Harvard University Health Service, and medical director of the Leonard P. Zakim Center for Integrative Therapies at Dana-Farber Cancer Institute. In addition to serving on the editorial board of Perspectives, he is the author of numerous scientific articles and several publications for laypeople.
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Dr. Harvey B. Simon, an associate professor of medicine at Harvard Medical School, a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology, and a primary care physician at Massachusetts General Hospital. A member of the editorial board of Perspectives on Prostate Disease, he has authored numerous scientific articles and textbook chapters and is the founding editor of the monthly newsletter Harvard Men’s Health Watch.
Here you will learn what these experts had to say about the issue of complementary therapies in general, as well as their interpretation of what the published evidence shows about the effectiveness of specific foods, herbs, and other complementary remedies.
But first, a brief explanation of the terminology that will be used. The panel agreed to use the language as defined by the National Center for Complementary and Alternative Medicine (NCCAM), a division of the National Institutes of Health. NCCAM defines alternative medicine as therapies used in place of conventional medicine, while complementary medicine consists of therapies used together with conventional medicine. Although an even newer term, integrative medicine, is becoming popular with physicians and patients who want to fully integrate both conventional and complementary practices, for the sake of simplicity this article will use “complementary” to underscore a point our experts all agreed on: Any unconventional therapy patients choose is best used along with — rather than as a substitute for — conventional medical therapy.
How do you advise your patients when they ask about complementary therapies?
ROSENTHAL: The major role of a physician is to provide advice about two areas, efficacy and safety. I tend to divide these therapies into three categories based on safety and efficacy: the first category consists of those that are both safe and have evidence of effectiveness; the second includes those that are safe but lack evidence of efficacy; and the third consists of those that are unsafe and have been proven ineffective. The middle category is by far the largest. It includes herbs such as saw palmetto, which some men take for BPH. These herbs and botanicals are probably safe when used alone. But in many cases there is no evidence that they actually have any effect, or the only evidence has come from small pilot studies rather than from randomized clinical trials. So the evidence is suggestive, not conclusive.
SIMON: I think it’s also important that a patient have a frank conversation with his physician about any complementary therapies the patient is taking. Of course, how to do all that in the allotted 10-minute office visit is another matter.
ROSENTHAL: (Laughs.) That’s exactly why I started doing integrative medicine consultations, which take up to 45 minutes to an hour.
SIMON: Another issue that both patients and physicians need to be aware of is that herbs can interact with other herbs, and with drugs that we prescribe.
ROSENTHAL: One of the most common interactions involves herbs and botanicals that affect the liver, by acting on cytochrome P450 enzymes [see below]. Many herbs, such as St. John’s wort, affect this system. So it’s important that patients understand that some herbs can enhance the effects of medications, or sometimes negate any beneficial effect.
When I do integrative medicine consultations, I advise people not to try too many supplements at one time. Try one herb or botanical first, and see if you tolerate it without any side effects before adding anything else. That’s exactly the same thing we do when we prescribe any medication.
Cytochrome P450 enzymesCytochrome P450 enzymes, most often found in the liver, help people metabolize drugs and herbs. But health problems may occur when you are taking a drug metabolized by cytochrome P450 and then take another drug or herb that interferes with this process. Some drugs and herbs inhibit the function of cytochrome P450 enzymes, which can lead to increased effect of a drug and possibly toxic side effects. Other drugs and herbs stimulate cytochrome P450, so that any other drugs you are taking may be metabolized so quickly that they have little or no beneficial effect. A partial list of drugs, herbs, and foods that affect cytochrome P450 follows, but you should check with your own doctor to avoid problems. Antidepressants Fluoxetine (Prozac) Antifungals Ketoconazole (Nizoral) Other medications Cimetidine (Tagamet)\ Foods and herbs Garlic |
When it comes to vitamins and antioxidants, is it better for people to get these in food or take them as supplements?
SIMON: In studies done in adults, a finding that high blood levels of antioxidants correlate with a good health outcome doesn’t mean at all that people will get the same good effect by taking a pill or a vitamin.
GIOVANNUCCI: That’s generally correct. Blood levels of particular carotenoids usually reflect a diet consistently high in fruits and vegetables, rather than any benefit from taking a supplement.
ROSENTHAL: And I always warn patients that nothing is standardized with respect to over-the-counter substances. The PC SPES story is a glaring example of what can happen because there is no standardization [see “PC SPES: A cautionary tale”]. Patients lost faith. And clinical researchers lost a great deal of time and energy.
SIMON: Exactly! PC SPES was heavily promoted as a treatment for prostate cancer. But it turns out that the product contained not only the eight Chinese herbs listed on the bottle, but also a little estrogen and some other contaminants. And the real problem is that there’s no federal oversight over the quality of these products. We can’t verify what ingredients are in a particular bottle. So unless there’s a pretty good reason to think that something may be useful, I tell my patients, “Caveat emptor: Buyer beware.”
Assessing the evidence: ProstatitisFor more information, see Table 4 Capodice JL, Bemis DL, Buttyan R, et al. Complementary and Alternative Medicine for Chronic Prostatitis/Chronic Pelvic Pain Syndrome. Evidence-based Complementary and Alternative Medicine 2005;2:495–501. PMID: 16322807. Shoskes DA, Manickam K. Herbal and Complementary Medicine in Chronic Prostatitis. World Journal of Urology 2003;21:109–13. PMID: 12720037. Shoskes DA, Zeitlin SI, Shahed A, Rajfer J. Quercetin in Men with Category III Chronic Prostatitis: A Preliminary Prospective, Double-Blind, Placebo-Controlled Trial. Urology 1999;54:960–3. PMID: 10604689. |
Let’s look at particular prostate diseases. What does the research show in terms of what men can do to help themselves?
GIOVANNUCCI: My research focuses on lifestyle factors, which include nutrition, physical activity, and body weight. The studies show that these basic lifestyle factors actually have a lot of impact on the risk of developing various types of prostate disease. For example, there’s more and more evidence that cardiovascular disease contributes to erectile dysfunction. To lower risk for developing erectile dysfunction, or even to alleviate it, the best advice is to start exercising more, maintain a normal body weight, and avoid smoking. And some of this advice is probably also important for prostate cancer and BPH.
SIMON: We also need to educate physicians about the importance of lifestyle issues for prevention. Erectile dysfunction is the best example, since it’s basically a manifestation of atherosclerosis, which is a highly preventable disease.
GIOVANNUCCI: There is also some evidence that metabolic syndrome might be a factor in prostate cancer progression [see “Metabolic syndrome”]. And you can prevent or ameliorate metabolic syndrome by following the same basic advice: more exercise, a better diet. I know that’s going to sound like the same old boring message, but following this advice can have a huge benefit on overall health and on prostate diseases in particular. So patients don’t have to go searching for exotic herbs, especially when there is essentially no evidence that they are beneficial.
Metabolic syndromeAnyone with three or more of the following attributes meets the diagnostic criteria for metabolic syndrome, which increases the risk of diabetes or heart disease:
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What do the studies say about the impact of lifestyle factors on prostate cancer? Is there any way for a man to adjust his diet to reduce the risk of prostate cancer or slow its progression?
GIOVANNUCCI: Unfortunately, not all of the answers are in for preventing prostate cancer, and there’s even less evidence about how to stop its progression. Again, what seems to be most important is reducing body weight or keeping body weight normal. There’s a little bit of evidence that physical activity may be helpful, but probably only at a fairly high level. Walking is probably not sufficient to reduce risk.
In terms of specific foods, there is reason to believe that fish, selenium, and tomatoes might all be important in reducing risk of developing prostate cancer [see Table 3]. But there’s almost no evidence that changing your diet after diagnosis will have any impact on prostate cancer progression. Of course, eating a healthy diet, and including some of these specific foods, won’t do harm and would improve overall health, which would help men going through treatment for prostate cancer.
SIMON: The studies done to date on this issue are preliminary, and they don’t produce solid evidence that something really will slow the progression of prostate cancer. But I’m all for giving patients a ray of hope. An example is that I now advise my patients to consider selenium and possibly pomegranate juice. They’re not going to hurt you, and a small study suggests pomegranate juice might slow progression. But I also advise them not to expect too much from it.
PC SPES: A cautionary talePC SPES is now off the market, but in the 1990s this herbal product was promoted as being good for “prostate health.” After anecdotal reports and preliminary laboratory studies indicated that PC SPES might help men with advanced prostate cancer, the National Center for Complementary and Alternative Medicine (NCCAM) funded four research studies — including one in patients — to determine its efficacy, safety, and mechanism of action. The research ended abruptly in 2002, however, when the FDA issued a warning about PC SPES, based on reports that men taking the supplement developed blood clots; some patients died. Shortly after the FDA warning, NCCAM halted all four studies (although it eventually restarted the laboratory trials). The U.S. distributor issued a voluntary recall and eventually went out of business. Researchers analyzed samples of PC SPES to determine what went wrong and discovered that some batches were contaminated with DES, an estrogen. This helped explain a puzzling side effect many patients had experienced while taking PC SPES — breast enlargement and soreness that could result from taking female hormones. Scientists discovered that other batches of PC SPES contained indomethacin, a pain reliever, and warfarin, a blood thinner. Harvard’s Osher Institute, which conducts research into complementary therapies, is currently trying to develop a research “bank” of purified, standardized herbs so that future studies can avoid these problems. |
GIOVANNUCCI: I agree. And just one further point is that for prostate cancer, especially in men who may have a relatively good prognosis, such as localized cancer, it’s much more likely that a man will die of something else, possibly heart disease, before he dies of prostate cancer. So I think that it’s probably worth putting more energy into the basics, such as diet and lifestyle, to prevent conditions like heart disease.
What is the current thinking about lycopene, which has certainly received a lot of attention in the press?
GIOVANNUCCI: The evidence is still mainly from epidemiological studies, so it’s suggestive, not definitive. But the important point is that even if you go by the epidemiologic evidence, the benefits are really based on tomato consumption, and tomatoes contain many nutrients besides lycopene. So I would probably recommend slightly or somewhat increasing consumption of tomatoes or tomato products, such as tomato sauce.
What may work for BPHFor more information, see Table 1 Bent S, Kane C, Shinohara K, et al. Saw Palmetto for Benign Prostatic Hyperplasia. New England Journal of Medicine 2006;354:557–66. PMID: 16467543. Wilt TJ, Ishani A, Stark G, et al. Saw Palmetto Extracts for Treatment of Benign Prostatic Hyperplasia: A Systematic Review. Journal of the American Medical Association 1998;280:1604–9. PMID: 9820264. Wilt TJ, MacDonald R, Ishani A. Beta-Sitosterol for the Treatment of Benign Prostatic Hyperplasia: A Systematic Review. BJU International 1999;83:976–83. PMID: 10368239. |
What about the issue of cooked versus uncooked tomatoes?
GIOVANNUCCI: The epidemiologic data provide good evidence that cooked tomatoes enhance absorption of lycopene. There’s also evidence that oil enhances absorption of lycopene — but that doesn’t mean people should eat fatty pizza. You just need a little bit of oil.
SIMON: I’ve found that when I tell patients to eat more tomatoes, they’re not impressed. But if someone else tells them to go to the health food store and buy some lycopene pills, they dash right over. And the data suggest that eating tomatoes can help reduce risk of prostate cancer, but the evidence is not there for lycopene supplements.
GIOVANNUCCI: Another problem is that we have no idea how much of the lycopene contained in a supplement is absorbed by the body.
ROSENTHAL: We advise patients that, because of the unknown nature of over-the-counter supplements, the best way to get all of the vitamins and antioxidants you need is to eat healthy foods.
GIOVANNUCCI: I think that definitely makes sense because lycopene is not the only dietary factor to think about. Studies show that you may also be able to reduce your risk of prostate cancer by eating more fatty fish, which are full of omega-3 fatty acids and also contain vitamin D. There’s also some evidence that cruciferous vegetables, such as broccoli, may have a modest benefit.
SIMON: Whole grains have also shown some potential benefit for preventing prostate cancer, perhaps because they contain selenium. But we don’t know for sure.
GIOVANNUCCI: Right. And if patients want to take selenium supplements, it’s important not to overdo it.
SIMON: Taking a daily multivitamin is probably good insurance for all men. For the most part, it’s a way to ensure that you get adequate daily requirements of vitamins without overdoing it. But there are three possible exceptions to be aware of. The first is selenium, since most multivitamins contain less than the 200 mcg that appears protective in the Nutritional Prevention of Cancer Trial [see “What may work for prostate cancer”]. Second, most multivitamins contain 400 IU of vitamin D, but many experts now recommend 600–800 IU a day. Finally, multivitamins don’t contain any fish oil, but men with coronary artery disease, or with major risk factors for heart disease, may benefit from 1,000 mg of omega-3 fatty acids a day, and would be wise to take a supplement if they don’t get that amount in their diet.
What may work for prostate cancerFor more information, see Table 3 Chan JM, Gann PH, Giovannucci EL. Role of Diet in Prostate Cancer Development and Progression. Journal of Clinical Oncology 2005;23:8152–60. PMID: 16278466. Chan JM, Holick CN, Leitzmann MF, et al. Diet after Diagnosis and the Risk of Prostate Cancer Progression, Recurrence, and Death (United States). Cancer Causes and Control 2006;17:199–208. PMID: 16425098. Clark LC, Combs GF, Turnbull BW, et al. Effects of Selenium Supplementation for Cancer Prevention in Patients with Carcinoma of the Skin. Journal of the American Medical Association 1996;276:1957–63. PMID: 8971064. Duffield-Lillico AJ, Dalkin BL, Reid ME, et al. Selenium Supplementation, Baseline Plasma Selenium Status and Incidence of Prostate Cancer: An Analysis of the Complete Treatment Period of the Nutritional Prevention of Cancer Trial. BJU International 2003;91:608–12. PMID: 12699469. Giovannucci E, Rimm EB, Liu Y, et al. A Prospective Study of Tomato Products, Lycopene, and Prostate Cancer Risk. Journal of the National Cancer Institute 2002;94:391–8. PMID: 11880478. Pantuck AJ, Leppert JT, Zomorodian N, et al. Phase II Study of Pomegranate Juice for Men with Rising Prostate-Specific Antigen Following Surgery or Radiation for Prostate Cancer. Clinical Cancer Research 2006;12:4018–26. PMID: 16818701. |
ROSENTHAL: I think another important piece of advice for patients is that they should not go on a diet while undergoing treatment for cancer. It’s not healthy to lose significant amounts of weight, which a lot of fad diets will cause.
SIMON: Although if someone is obese and has prostate cancer, it might be a good idea to shed some body weight.
ROSENTHAL: That’s true, but once you’ve been diagnosed with prostate cancer it’s important not to go on a crash diet, but instead adopt a healthy one.
Assessing the evidence: Erectile dysfunctionFor more information, see Table 2 Moyad MA, Barada JH, Lue TF, et al. Prevention and Treatment of Erectile Dysfunction Using Lifestyle Changes and Dietary Supplements: What Works and What is Worthless, Part 2. Urologic Clinics of North America 2004;31:259–73. PMID: 15123406. |
How should people react when they read about something new in the paper, whether it’s about pomegranate juice or some new herb or botanical?
SIMON: The answer is simple: React with caution. As physicians, I think we first have to point out that medicine is science, that therapies can be evaluated, and that there are big bucks involved in the selling of herbs and other unregulated remedies, where people are making extravagant claims. If something sounds too good to be true, it is.
ROSENTHAL: I think that we should obviously also advise people to be skeptical of anything touted as a cure for cancer. And yet there are still some people out there who are going to prey on patients’ hope that something is going to work, and encourage them to use an alternative therapy instead of proven medical therapy.
GIOVANNUCCI: Maybe people get tired of hearing the same old message, but the fact is, we do know a lot about prevention of various diseases, and I think people get distracted. They are confronted every day with news about something that’s different, and may, in fact, have promise down the road. But even if it does, its effect may be relatively modest compared to what we know is effective — diet and physical activity.
Reliable online resourcesMore and more men with prostate disease are going online to find information about health topics, including complementary therapies. Our Harvard experts recommend the following Web sites: FREE ACCESSNational Cancer Institute Offers information about particular types of cancer as well as clinical trials and research evaluating complementary therapies. Features information from the Best Case Series Program, an independent review of medical records of patients treated with complementary therapies for cancer, to determine which ones hold promise. National Institutes of Health Provides general information about complementary therapies, as well as a list of clinical studies that are recruiting patients. Posts fact sheets about particular herbs and supplements and diseases — although not yet on prostate disease or prostate cancer. SUBSCRIPTION REQUIREDConsumerLab.com, LLC Reviews herbs and supplements a bit like Consumer Reports reviews cars and other consumer products — with rankings and grades. Provides in-depth information about products, recalls and warnings, and summaries by particular medical condition. Web access costs $27 per year. Natural Medicines Comprehensive Database Posts information that is medically reviewed and contains references to particular studies. Search by product name or medical condition and see drug/herb interactions. Web access costs $9.97 per month, or $92 per year. |
What large studies on complementary therapies for prostate disease should men be aware of?
ROSENTHAL: The SELECT study is the big one, which everyone is waiting for, because it will help determine whether taking selenium and vitamin E might reduce the risk of prostate cancer [see “SELECT study”]. But the results aren’t going to be known for years.
SELECT studySELECT (Selenium and Vitamin E Cancer Prevention Trial) is the largest prostate cancer prevention study ever undertaken, with more than 35,000 men participating. Participants have been randomly assigned to take 200 mcg of selenium or 400 IU of vitamin E — or the two in combination, or a placebo — and will be followed for a minimum of seven years and a maximum of 12 years. By that time it should become clear whether taking selenium or vitamin E, or both together, will reduce the risk of prostate cancer. |
Table 1: Complementary therapies for benign prostatic hyperplasia (BPH)To read more about the studies cited in this table, see “What may work for BPH.” |
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Substances that may work |
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Substance and possible mechanism of action |
Assessment |
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Beta-sitosterol Mixture of several extracts of plants containing substances that mimic cholesterol; not clear how it alleviates BPH symptoms. |
One review of four randomized trials involving a total of 519 men, published in 1999 in BJU International, concluded that beta-sitosterol improves urinary symptoms, but cautioned that long-term safety and effectiveness were unknown. |
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Pygeum Derived from the bark of an African evergreen tree; not clear how it works, but some researchers have proposed that it reduces inflammation or slows prostate growth. |
One study, involving 263 men recruited at eight sites in Europe, found that participants who took pygeum experienced improvement in urinary symptoms. (The study is available only in German, so a citation is not provided here.) |
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Saw palmetto Derived from the berry of the saw palmetto tree; not clear how it works, although a leading theory is that it affects male hormones. Safety considerations: May increase the risk of bleeding when taken with herbs and drugs that also have this effect (such as garlic, aspirin, anticoagulants, antiplatelet medications, NSAIDs); should not be taken with drugs that affect levels of male hormones. |
Probably the best studied herb for BPH treatment, but studies are conflicting. A review of 18 studies involving 2,939 men, published in 1998 in the Journal of the American Medical Association, concluded that saw palmetto supplements improved urinary symptoms about as much as the medication finasteride (Proscar). But a randomized trial involving 225 men who took saw palmetto for a year, published in 2006 in the New England Journal of Medicine, found no evidence that saw palmetto was any better at improving urinary symptoms than placebo. |
Table 2: Complementary therapies for erectile dysfunctionTo read more about the substances discussed in this table, see “Assessing the evidence: Erectile dysfunction.” |
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Substances that may work |
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Substance and possible mechanism of action |
Assessment |
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Korean red ginseng Derived from a plant root; not clear how it may help alleviate erectile dysfunction, but one theory is that it increases levels of nitric oxide, a chemical that occurs naturally in the body and contributes to erections. Safety considerations: Some formulations may lower blood sugar levels and alter the effects of blood pressure or heart medications; may affect the cytochrome P450 system. |
Three small studies suggest that this herb may improve ability to have an erection, but further study is necessary. |
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L-arginine A precursor to nitric oxide; may help erectile function by increasing blood levels of this substance. Safety considerations: May increase risk of bleeding when used with anticoagulants or antiplatelet drugs, or with herbs such as ginkgo biloba, garlic, or saw palmetto; when used with nitroglycerin or erectile dysfunction drugs, may cause blood pressure to drop; may increase blood sugar levels. |
Three small preliminary studies indicate that this substance may benefit men with low levels of nitric oxide, but larger studies are needed. Men at risk for heart disease should avoid taking this substance, as a study of possible benefits of taking L-arginine to treat heart attack survivors was stopped early when six volunteers taking this substance died. |
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Vitamin supplements May have a synergistic effect when used with erectile dysfunction medication. |
A small study of men who did not respond to medication alone found that erectile function and patient satisfaction improved in many who took daily folic acid and vitamin E supplements in addition to sildenafil (Viagra). |
Table 3: Complementary therapies for prostate cancerMany complementary therapies used for prostate cancer, such as vitamins and particular nutrients, are found naturally in food. Our panel of Harvard experts agreed that men seeking to reduce their risk of developing prostate cancer — or of having it progress, if it’s already been diagnosed — should eat a healthy diet and engage in regular physical activity. These “lifestyle” habits offer the best all-around protection because they reduce the risk of the number 1 threat to men — heart disease. Nevertheless, epidemiologic studies (which follow large groups over time) have identified a number of specific dietary factors that appear to affect risk of prostate cancer development. Data are limited, however, about whether dietary changes made after diagnosis will have any impact on cancer progression. To learn more about the studies cited in this table, see “What may work for prostate cancer.” |
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Substances that may reduce risk |
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Substance and possible mechanism of action |
Impact on prostate cancer risk |
Impact on prostate cancer progression |
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Fish Not clear why fish may be protective; one theory is that omega-3 fatty acids contained in fatty fish may inhibit a particular molecular pathway involved in cancer development. |
Fair to good evidence exists that eating fish may reduce risk of prostate cancer. Two large prospective studies, for example, found that men who ate fish were less likely to develop prostate cancer or die from it. |
May reduce progression, but less data are available. A 2006 study found that men with the highest intake of fish after diagnosis were 27% less likely to have their cancer progress than men with the lowest consumption. |
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Selenium May inhibit several biological pathways that encourage cancer growth, such as cell proliferation and angiogenesis. Safety considerations: Taking too much can cause nausea and vomiting; consult with your doctor if you are undergoing radiation treatment, as this supplement (and any antioxidant) may interfere with treatment. |
Strong evidence exists that selenium reduces risk. A 2003 randomized controlled study found that men who took selenium supplements were 50% less likely to develop prostate cancer than those who took placebo pills. Several other studies reported similar findings. |
Insufficient evidence exists regarding impact on progression. |
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Tomatoes Contain a number of nutrients; it remains unclear whether the antioxidant lycopene, some other nutrient, or combinations of nutrients underlie protective effect. |
Good evidence that consumption of cooked tomatoes may reduce risk. A 2002 study found that men who regularly consumed two or more servings of tomato sauce per week could reduce their risk of developing prostate cancer by 35% compared with men who ate tomato sauce less than once a month. A review of 21 studies found anywhere from a 10% to 20% reduction in risk among men with the highest intake of tomatoes, with cooked tomatoes offering the most protection. |
Increasing consumption after diagnosis may reduce progression but data are more limited. A 2006 study found that increased intake of tomato sauce after diagnosis might reduce risk of prostate cancer progression by 30% to 40%. Other studies reporting a protective effect from increased tomato consumption after treatment have been small or poorly designed. |
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Vitamin E Has antioxidant effects that may be helpful; supplements contain alpha-tocopherol, a form of vitamin E. Safety considerations: May increase risk of bleeding if you are taking anticoagulants or antiplatelet medications; may interfere with treatment if you are undergoing radiation therapy (ask your doctor). |
Good evidence that this may reduce risk, but the benefit is seen only in men who smoke. The Alpha-Tocopherol Beta-Carotene study, for example, reported that men who smoked and took 50-IU vitamin E supplements a day reduced risk of prostate cancer by 30% to 40%. Other studies have confirmed a protective effect for smokers. |
Limited data exist regarding impact on progression. |
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Substances that may be protective, but evidence is limited |
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Substance and possible mechanism of action |
Impact on prostate cancer risk |
Impact on prostate cancer progression |
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Carotenoids (Other than lycopene; see “Tomatoes,” above) Occur naturally in plants; may have antioxidant properties. |
Some evidence of reduced risk, but data are limited and findings have been mixed. One study reported that men with higher blood levels of particular antioxidants — lutein, beta-cryptoxanthin, and zeaxanthin — had a 70% to 80% reduced risk of prostate cancer. But a randomized clinical trial found that men who took beta carotene supplements had an increased risk of prostate cancer if they already had high blood levels of this antioxidant. |
Limited data exist regarding impact on progression. |
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Melatonin Inhibits prostate cancer cell growth in test tubes. Safety considerations: Avoid if you are taking anticoagulants or antiplatelet medications; may increase or decrease blood pressure, and may increase blood sugar levels in people with diabetes. |
Insufficient evidence, although some studies have suggested that men with prostate cancer have lower levels of melatonin than other men. |
A small study involving 14 men with advanced prostate cancer who were not responding to hormone therapy alone found that taking melatonin supplements in addition to hormone therapy improved response. PSA levels decreased by more than half in eight men, and nine lived longer than one year. |
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Pomegranate juice Contains a variety of antioxidants and flavonoids, which may inhibit cancer growth. |
Insufficient evidence regarding impact on developing prostate cancer. |
A small 2006 study suggests that men whose PSA is rising after cancer treatment may be able to slow the rate at which PSA increases by drinking 8 ounces of pomegranate juice every day. The study involved 50 men who were followed until their PSA doubled. Investigators found that average PSA doubling time slowed from an average of 15 months before the study began to an average of 54 months afterward. |
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Soy Contains isoflavones, nutrients that can inhibit cell growth and affect hormones that may fuel the growth of prostate cancer. Safety considerations: May interact with warfarin (Coumadin); check with your doctor for advice. |
Limited data exist, but suggest that higher soy intake may reduce risk. |
No evidence exists regarding impact on progression. |
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Vitamin D May inhibit growth of prostate cancer cells. |
Epidemiologic studies have produced mixed results. |
Limited evidence regarding impact on progression. |
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Substances that may increase risk |
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Substance |
Impact on prostate cancer risk |
Impact on prostate cancer progression |
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Calcium and dairy products |
Good evidence that higher intake increases risk. One study found that men who consumed more than 2,000 mg of calcium daily were five times as likely to develop metastatic prostate cancer as those who consumed less than 500 mg of calcium per day. A large epidemiologic study found that intake of more than 1,500 mg of calcium per day might increase the risk of aggressive and fatal prostate cancer, but not the risk of less aggressive, localized cancer. |
Studies suggest that high calcium intake may increase the likelihood of progression. One theory is that calcium has different effects, depending on the stage of cancer development or progression. |
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Meat consumption |
A number of studies have found that increased consumption of meat, especially red meat, increases risk of developing prostate cancer, possibly because of high fat content or the way the meat is cooked. |
Insufficient evidence regarding impact on progression. |
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Zinc Because zinc contributes to many bodily functions, including healthy immune functioning and wound healing, zinc supplements have sometimes been touted as a cure for various prostate diseases. However, there is no evidence that zinc supplements help — and in prostate cancer, such supplements may cause harm. |
Limited evidence that zinc supplements may increase risk. One study found that men who took 100-mg zinc supplements daily were more than twice as likely to develop advanced prostate cancer as men who did not take the supplements. |
No data are available regarding impact on progression. |
Table 4: Complementary therapies for prostatitisTo learn more about complementary therapies for prostatitis, see “Assessing the evidence: Prostatitis.” |
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Substance that may work |
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Substance and possible mechanism of action |
Assessment |
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Quercetin A bioflavonoid, a chemical that contributes to color in plants; its antioxidant and anti-inflammatory effects may explain how it works. |
One small randomized controlled study has evaluated quercetin for the treatment of chronic nonbacterial prostatitis (chronic pelvic pain syndrome). The study involved 30 men who took quercetin for a month. Investigators reported in 1999 in Urology that 67% of men taking quercetin reported improvement of symptoms, compared with 20% of men taking placebo. |
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