Prostate cancer is a malignancy of the prostate. It is characterized by unregulated replication of cells creating tumors, with the possibility of some of the cells spreading to other sites (metastasis).
This article includes a discussion of studies that have assessed whether certain vitamins, minerals, herbs, or other dietary ingredients offered in dietary or herbal supplements may be beneficial in connection with the reduction of risk of developing prostate cancer, or of signs and symptoms in people who have this condition.
This information is provided solely to aid consumers in discussing supplements with their healthcare providers. It is not advised, nor is this information intended to advocate, promote, or encourage self use of these supplements for cancer risk reduction or treatment. Furthermore, none of this information should be misconstrued to suggest that dietary or herbal supplements can or should be used in place of conventional anticancer approaches or treatments.
It should be noted that certain studies referenced below, indicating the potential usefulness of a particular dietary ingredient or dietary or herbal supplement in connection with the reduction of risk of prostate cancer, are preliminary evidence only. Some studies suggest an association between high blood or dietary levels of a particular dietary ingredient with a reduced risk of developing prostate cancer. Even if such an association were established, this does not mean that dietary supplements containing large amounts of the dietary ingredient will necessarily have a cancer risk reduction effect.
Prostate cancer is the most common cancer among men in the United States. Although the cause is not known, most researchers believe that alterations in testosterone metabolism and/or bodily responses to testosterone are involved.
Throughout the world, autopsy reports show that evidence of microscopic prostate cancer is extremely common in older men. However, most men who have such microscopic disease are never diagnosed with, nor do they die from, prostate cancer. Unlike this dormant form of the disease, the incidence of potentially life-threatening prostate cancer varies greatly in different parts of the world. Researchers believe that some factors, possibly involving diet or lifestyle issues, determine the risk of having potentially life-threatening prostate cancer.
American men are at high risk of being diagnosed with such prostate cancer, and African-American men are at particularly high risk, for reasons that are not completely clear. A family history of prostate cancer increases the risk to a limited extent. Farmers, mechanics, workers in tire and rubber manufacturing, sheet metal workers, and workers exposed to cadmium have also been reported to be at increased risk.
What are the symptoms of prostate cancer?
Prostate cancer usually grows slowly, initially producing no symptoms. Later in the course of the disease, symptoms that overlap with symptoms of prostatic hyperplasia, a very common benign condition, may appear. Some of these symptoms include frequent urination (including having to urinate more frequently at night), pain on urination, a weak urinary stream, dribbling after urination, and a sensation of incomplete emptying. In addition, blood may appear in urine. None of these symptoms is specific to prostate cancer; the diagnosis of this disease requires the help of a doctor.
If prostate cancer spreads to a distant part of the body, it most often is found in bone, a condition that may cause bone pain. Late stages of the disease are associated with severe weight loss, untreatable fatigue-inducing anemia, and finally death.
Dietary changes that may be helpful for prostate cancer
Avoidance of alcohol
A review of published research found that higher intake of tomatoes or higher blood levels of lycopene correlated with a reduced risk of cancer in 57 of 72 studies. Findings in 35 of these studies were statistically significant.3 Evidence of a protective effect for tomato consumption was stronger for prostate cancer than for most other cancers.
Meat and how it is cooked
Low-fat diet and prevention
Avoidance of alpha-linolenic acid
Concentrations of alpha-linolenic acid are much higher in flaxseed oil, canola oil, soybean oil, and certain nuts compared to the concentrations found in meat. However, because so much meat is consumed as part of many western diets, a significant portion of dietary alpha-linolenic acid often does come from meat. Therefore, at least in theory, alpha-linolenic may merely be a marker for meat consumption. When researchers have adjusted for the intake of meat or saturated fat, however, a correlation between alpha-linolenic acid and prostate cancer risk has remained.25 26 On the other hand, in a preliminary study of men with prostate cancer, supplementation with 30 grams of ground flaxseed per day for approximately one month appeared to decrease the rate of tumor growth.27
How alpha-linolenic acid might increase the risk of prostate cancer remains unclear. Alpha-linolenic acid has promoted the growth of prostate cancer cells in one test tube study,28 but inhibited prostate cell growth in another.29
In preliminary research, men who consumed soy milk more than once per day were reported to have a significantly lower risk of prostate cancer compared with other men.32 Some researchers are now saying that genistein may eventually be shown to have the potential to treat prostate cancer,33 while others say only that enough evidence exists to recommend that future genistein research be devoted to the subject of prostate cancer prevention.34
Lifestyle changes that may be helpful for prostate cancer
Maintaining healthful body weight
Nutritional supplements that may be helpful for prostate cancer
The following nutritional supplements have been studied in connection with prostate cancer.
No trials have investigated the effect of natural beta-carotene supplements on the risk of prostate cancer.
The strongest evidence supporting the anti-cancer effects of selenium supplementation comes from a double-blind trial of 1,312 Americans with a history of skin cancer who were treated with 200 mcg of yeast-based selenium per day or placebo for 4.5 years and then followed for an additional two years.47 Although no decrease in skin cancers occurred, a dramatic 50% reduction in overall cancer deaths and a 37% reduction in total cancer incidence were observed. A statistically significant 63% decrease in prostate cancer incidence was reported.48
Increasing calcium intake from food, water, and supplements has been associated with an increased risk of prostate cancer in some preliminary studies51 52 but not in others.53 54 A few researchers now believe that increasing calcium intake may increase the risk of prostate cancer by reducing the amount of vitamin D activated in the kidneys.55 (Vitamin D may protect against prostate cancer. See the Vitamin D discussion below.) If the relationship between higher calcium intake and increased risk of prostate cancer were to be confirmed by future research, then the question would arise whether the negative effect of calcium from food and supplements could be overcome by taking vitamin D supplements.
In a preliminary trial, 7 of 16 men who had prostate cancer that had spread to bone and who had been unresponsive to conventional treatment were found to have evidence of vitamin D deficiency.63 All 16 were given 2,000 IU of vitamin D per day for 12 weeks, and levels of pain were recorded for 14 of these men. Vitamin D supplementation led to reduced pain in 4 of the 14 men, and 6 showed evidence of increased strength.64 Those with vitamin D deficiency were more likely to respond, compared with those who were not deficient.65 While anyone with vitamin D deficiency should be treated with vitamin D, taking 2,000 IU per day requires a doctor’s supervision.
In another preliminary trial, 14 men with prostate cancer unresponsive to conventional treatment were given activated vitamin D66 —the form of vitamin D believed to have anti-tumor action against prostate cancer.67 A reduction in prostate specific antigen (PSA) scores, a marker for prostate cancer progression, occurred in only two men, and in no case did the PSA score decline by as much as 50%. In a small preliminary trial, activated vitamin D slowed the rate at which PSA increased.68 Activated vitamin D is a prescription hormone with significant side effects requiring careful monitoring by a physician.
The ability of vitamin D or its activated form to prevent cancer or effectively treat people who have cancer remains unproven.
Patients with advanced prostate cancer who had previously not responded to drug therapy (triptorelin) were given melatonin plus triptorelin in a preliminary trial.82 PSA scores, a marker of disease progression, fell (i.e., improved) more than 50% in 8 of 14 patients.
Patients with advanced cancer have been reported to have improved survival and fewer side effects from taking chemotherapy when given melatonin plus chemotherapy vs. chemotherapy alone.83
In a preliminary report, high amounts of shark cartilage were administered by enemas or suppositories to eight late-stage cancer patients.87 After 7 to 11 weeks, 6 of the 8 were reported to show significant reductions in tumor size, though the long-term outcomes of these patients were not reported.88
In a telephone survey of cancer patients, 11 of 18 patients claimed a reduction in tumor size had resulted from the use of shark cartilage, 17 of 21 reported an improvement in their quality of life, and 7 of 7 prostate cancer patients reported a reduction in PSA scores—a marker of cancer progression.89 However, a report limited to patients capable of responding by phone necessarily omits patients who have died while taking shark cartilage and includes no objective medical information. The meaning of these findings, supported by a company selling shark cartilage, remains unclear.
In a preliminary trial, 60 late-stage cancer patients were given 1 gram of shark cartilage for every 2.2 pounds of body weight per day in three divided doses and followed for 12 weeks or longer.90 No evidence of a therapeutic effect was found.91
Because the evidence remains weak and mixed, shark cartilage remains unproven as a treatment for men with prostate cancer.
Are there any side effects or interactions with prostate cancer?
Refer to the individual supplement for information about any side effects or interactions.
Herbs that may be helpful for prostate cancer
The following herbs have been studied in connection with prostate cancer.
In several preliminary trials, this formula has been shown to reduce blood levels of prostate specific antigen (PSA, a marker for prostate cancer progression) in men with prostate cancer.94 95 96 97 98 While such a reduction suggests a therapeutic effect, trials have yet to explore whether PC-SPES increases survival in people with prostate cancer.
One trial distinguished prostate cancer patients with androgen-dependent (an earlier, milder form of the cancer) and androgen-independent (a later, more severe form of the cancer) disease.99 PSA scores began to decline in most people within two to six weeks after first receiving PC-SPES. Scores reached their lowest point in an average of 23 weeks in men with androgen-dependent prostate cancer and 16 weeks in men with androgen-independent prostate cancer. PSA scores declined an average of 80% and became undetectable in four out of every five men with androgen-dependent disease. In contrast, 54% of androgen-independent prostate cancer patients had a PSA decline of 50% or more. After an average of about one year, 31 of 32 androgen-dependent prostate cancer patients continued to have normal PSA scores. However, 28 of the 35 patients with androgen-independent prostate cancer ultimately developed PSA increases consistent with progression of their cancer, despite continued use of PC-SPES. Improvement or disappearance of cancer was seen in four patients who had previously had cancer spread to the bone, as well as in one patient who had previously had cancer spread to the bladder. Rarely, PSA levels have risen slightly (less than 20%) during PC-SPES use, according to other studies.100 Testosterone levels are almost always decreased by PC-SPES therapy, according to most studies, which presumably accounts, in part, for the therapeutic effect.101 102
Many men who take the formula have been reported to develop symptoms of estrogen excess, including breast tenderness, enlargement of the breasts, loss of libido, and the more serious problem of blood clots in the veins (venous thrombosis).103 104 105 At least one person who took PC-SPES developed a potentially life-threatening blood clot in the lung. For this reason, some doctors recommend that people taking PC-SPES also take blood-thinning medication, such as heparin or warfarin (Coumadin®).106 107 However, each of these drugs can cause excessive bleeding. Because of the potential side effects of PC-SPES and the complex medical issues involved with the use of blood-thinning drugs, people should never take PC-SPES without the close supervision of a doctor. The amount of PC-SPES used in most studies was 320 to 960 mg three times per day.108 109 110
In February 2002, the sole supplier of PC-SPES in the United States (BotanicLab) issued a recall of the product after the California Health Department reported it contained warfarin, a prescription drug that can cause severe bleeding. However, PC-SPES is known to contain compounds that, though distinct from warfarin, could potentially be mistakenly identified as warfarin using currently available laboratory methods.111 There has been one case report of excessive bleeding occurring in a man who was taking PC-SPES. 112 However, the warfarin concentration in this patient’s blood was not high enough to explain his abnormal bleeding. In addition, allegations have been made that PC-SPES contains small amounts of a synthetic estrogen (diethylstilbestrol; DES). That claim has been disputed by BotanicLab.
Although additional information is needed to determine whether PC-SPES has been adulterated with one or more prescription drugs, at the time of this writing (February 2003) the product is not available in the United States.
Warning:PC-SPES has been reported to cause serious side effects, including potentially life-threatening blood clots. PC-SPES should never be taken without the close supervision of a doctor. PC-SPES is not for sale is certain parts of the world.
Shiitake (Lentinus edodes)
Other herbal therapies
Are there any side effects or interactions with prostate cancer?
Refer to the individual herb for information about any side effects or interactions.