by Dr. C.H. Weaver M.D. 8/2019
Overall, results from studies have indicated that eating more fruits and vegetables and fewer processed foods and meats appears to decrease the risk of developing cancer and/or improve outcomes of patients with cancer. However, specific food and nutrient associations are still being evaluated to define which food types may affect risks or prognoses of prostate and other cancers.
Diet has long been hypothesized to play a role in the development or prevention of cancer. Antioxidant micronutrients such as vitamin E, beta-carotene, and vitamin C could potentially decrease cancer risk by protecting cells from reactive substances known as free radicals. Food sources of vitamin E include vegetable oils, nuts, and whole grains. Beta-carotene is found in orange and yellow fruits and vegetables, as well as dark green leafy vegetables such as spinach. Vitamin C is found in citrus fruits, strawberries, melons, tomatoes, broccoli, and peppers. (1-19)
The Role of Diet in the Prevention of Prostate Cancer
There is increasing evidence that diet does play a role in the development and perhaps the prevention of prostate cancer. Interestingly, when people from areas with low prostate cancer rates move to areas with higher prostate cancer rates, they assume the rates of their new environment, although their genetic make-up clearly has not changed. This suggests that environmental factors may play a role in the development of prostate cancer.
Several clinical studies have suggested that low-fat diets, lycopoenes, vitamin E, and selenium may play a role in preventing, or at least slowing the development of prostate cancer.
High Fat Diet Increases Risk
According to results from 15 out of 22 clinical studies, a higher dietary fat intake is related to a higher risk for prostate cancer. One study showed that men with a high fat intake had a 40% higher risk of developing prostate cancer.(1)
High Intake of Dairy Products Modestly Increases in Prostate Cancer Risk
In a combined analysis of 10 published studies, men with the highest intake of dairy products and calcium were more likely to develop prostate cancer than men with the lowest intakes.(17)
Calcium is a nutrient that has been linked with a decreased risk of osteoporosis, hypertension, and colorectal cancer. Some studies, however, have suggested that high calcium intake may increase the risk of prostate cancer.
The reason for a link between high calcium intake and prostate cancer is unclear, but could potentially involve suppression of plasma 1,25-dihydroxyvitamin D3 (the active form of vitamin D; thought to play role in the control of prostate cell growth and differentiation) or elevation of plasma levels of insulin-like growth factor-I (a hormone associated with an increased risk of prostate cancer).
To evaluate the link between dairy products, calcium, and risk of prostate cancer, researchers combined information from 10 published studies that addressed this question conducted in the U.S. or Europe and were published between 1984 and 2005. Information about consumption of dairy products and calcium was collected by questionnaires completed by the study subjects.
Data from the 10 studies suggest a modestly increased risk of prostate cancer among men with the highest intake of dairy products or calcium:
- Men with the highest intake of dairy products were 11% more likely to develop prostate cancer than men with the lowest intake.
- Men with the highest intake of calcium were 39% more likely to develop prostate cancer than men with the lowest intake.
- A trend between increasing intake and increasing risk of prostate cancer was observed for both dairy products and calcium.
The researchers conclude that “High intake of dairy products and calcium may be associated with an increased risk of prostate cancer, although the increase appears to be small.”
Diets High in Fish Appear to Lower the Incidence of Prostate Cancer - Particularly Metastatic Prostate Cancer
Men who eat fish regularly appear less likely to develop prostate cancer, especially metastatic cancer. Researchers from the US and Sweden investigated whether marine fatty acids may have an effect on the incidence of prostate cancer. They evaluated fish and marine fatty acid consumption using a dietary questionnaire in 47,882 men participating in the Health Professionals Follow-up Study. This group of men was assessed during 12 years of follow-up.
By the end of the study, 2,482 men had developed prostate cancer. There were 617 cases of advanced cancer, 278 involving metastasis (spread of cancer to distant sites in the body, often invading vital organs). The researchers found that eating fish more than three times per week was associated with a reduced risk of prostate cancer, particularly metastatic cancer. Men consuming that amount of fish were approximately half as likely to develop metastatic prostate cancer as men who ate fish less than twice a month. Marine fatty acids also appeared to lower the risk of developing prostate cancer, but not as significantly.
The authors reported that “each additional daily intake of 0.5 g of marine fatty acids from food was associated with a 24% decreased risk of metastatic cancer”. This study suggests that high fish consumption appears to protect against the development of prostate cancer, particularly metastatic cancer. The effects are most strongly linked with fish consumption, although foods containing marine fatty acids also appear to confer some risk reduction.(18)
Omega-3 Fatty Acids Linked to Increased Risk of Prostate Cancer
Omega-3 fatty acids may be linked to an increased risk of prostate cancer, according to the results of a study published in the Journal of the National Cancer Institute. Omega-3s, are essential fatty acids made up of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) and can be found in salmon, sardines, tuna, mackerel, and walnuts.
The Selenium and Vitamin E Cancer Prevention Trial (SELECT) included more than 35,000 men over the age of 50 in the U.S., Puerto Rico, and Canada. A case-cohort study examined associations between blood levels of omega-3 fatty acids and prostate cancer risk. The analysis included 834 men from the trial who had been diagnosed with prostate cancer and a control group of 1,393 men selected randomly from all 35,000 participants.
The analysis found that men with the highest levels of omega-3 fatty acids had a 43 percent higher risk of developing prostate cancer and a 71 percent higher risk of developing high-grade prostate cancer, which is more likely to be fatal. Because the study did not collect information on the men’s diets—only on supplements—it is not clear whether blood levels of omega-3 fatty acids came from food or supplements.
The researchers included that high blood levels of omega-3 fatty acids were associated with an increased risk of prostate cancer. More research is needed to confirm the link. In the meantime, men need not avoid fish—but instead should consume a healthy, balanced diet rich in a variety of nutrients.(19)
Researchers affiliated with the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial conducted a study to evaluate the relationship between fruit and vegetable intake and the risk of prostate cancer. The study included 1,388 men with prostate cancer and 29,361 men who were enrolled in the screening group.
- Overall, vegetable and fruit consumption did not affect the risk of developing prostate cancer.
- High vegetable intake significantly decreased the risk of developing prostate cancer that had spread outside of the prostate (advanced prostate cancer).
- Higher intake of broccoli and cauliflower in particular provided significant protection against advanced prostate cancer.
The researchers concluded: “High intake of cruciferous vegetables, including broccoli and cauliflower, may be associated with reduced risk of aggressive prostate cancer”— however, such a diet did not reduce the overall risk of developing prostate cancer.(5)
Lycopene is an organic micronutrient abundant in tomatoes and tomato-based products, such as sauces and soups. Epidemiological studies have reported that dietary intake of lycopene appears linked to lower rates of prostate cancer.
In 57 out of 72 studies, lycopene has been associated with a lower risk of prostate cancer. In one study, subjects received either lycopene supplements or no supplement prior to surgery. Only 33% of the lycopene-supplemented group experienced a spread of cancer, compared with 75% of the control group. In addition, the PSA levels of the lycopene-supplemented group fell 20%, while the PSA levels of the control group remained unchanged. (2,4)
In response to claims about the cancer benefits of lycopene or tomatoes, the US Food and Drug Administration conducted a review of the available scientific evidence. (6) The main conclusions of the review were the following:
- There is currently no credible evidence that lycopene or tomato consumption reduces the risk of prostate, lung, colorectal, gastric, breast, ovarian, endometrial, or pancreatic cancer.
- There is very limited evidence that tomato consumption reduces the risk of prostate, ovarian, gastric, and pancreatic cancer.
Noting that lycopene or tomatoes may reduce the risk of cancer progression (rather than cancer initiation), an accompanying editorial explains that studies conducted recently—after the widespread adoption of PSA testing—may not be able to detect the effect of lycopene because prostate cancers detected by PSA testing tend to be very early-stage, and some of the cancers detected by PSA testing are likely to be indolent, slow-growing cancers; so if lycopene acts later in the process of prostate cancer development, when a cancer is progressing to a more aggressive or advanced stage, a study that includes mainly PSA-detected cancers may fail to detect this effect. This theory remains unconfirmed, however. (7)
Several studies have indicated an association between increased selenium intake and a reduced risk of prostate cancer. Two small studies comparing selenium-supplemented groups with control groups have demonstrated an approximately 60% reduction in prostate cancer risk.(16) In response to these promising results, the National Cancer Institute (NCI) initiated the 32,000 participant SELECT clinical trail to evaluate the effects of selenium on prostate cancer, as well as colorectal cancer and cardiovascular disease. Results of SELECT did not confirm the initial observations that selenium can reduce the risk of prostate cancer. (14)
Multivitamins and Supplements
Results from clinical studies have found that the use of multivitamins or supplements with micronutrients does not appear to reduce the risk of developing cancer or affect the prognosis of patients diagnosed with cancer. In fact results from a clinical study indicated that men who used multivitamins more than seven times per week were almost twice as likely as nonusers to develop fatal prostate cancer.
To assess the relationship between multivitamin use and risk of prostate cancer, researchers evaluated information from the National Institutes of Health (NIH)-AARP Diet and Health Study. (8) The study enrolled 295,344 men who were free of cancer at the start of the study.
During five years of follow-up, prostate cancer was diagnosed in 10,241 of the study participants. The prostate cancer was localized in 8,765 cases and advanced in 1,476. There were 179 prostate cancer deaths.
- There was no link between multivitamin use and risk of localized prostate cancer.
- High levels of multivitamin use were linked with an increased risk of advanced or fatal prostate cancer. Compared with nonusers of multivitamins, men who used multivitamins more than seven times per week had a 32% increased risk of advanced prostate cancer and an almost twofold increased risk of fatal prostate cancer.
- The links between high levels of multivitamin use and advanced or fatal prostate cancer were strongest among men with a family history of prostate cancer, and also among men who took individual micronutrient supplements (such as selenium, beta-carotene, or zinc) in addition to multivitamins. (9)
An accompanying editorial notes that these results “add to the growing evidence that questions the beneficial value of antioxidant vitamin pills in generally well-nourished populations and underscore the possibility that antioxidant supplements could have unintended consequences for our health.” (9) “The possibility that men taking high levels of multivitamins along with other supplements have increased risk of advanced and fatal prostate cancers is of concern and merits further evaluation.”
A second population based study found no evidence that higher intake of vitamin E, beta-carotene, or vitamin C reduced the risk of prostate cancer.
To evaluate the relationship between prostate cancer and intake of vitamin E, beta-carotene, and vitamin C, researchers analyzed close to 30,000 men assigned to the screening arm of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. The men were between the ages of 55 and 74 at the start of the study.
Information about intake of vitamin E, beta-carotene, and vitamin C was collected from a dietary questionnaire completed by the men at the start of the study. The questionnaire asked about specific foods, multivitamins, and single-nutrient supplements (such as vitamin E or vitamin C taken alone).
Dietary supplements (either multivitamins or single-nutrient supplements) were reported by 16,548 (56%) of the men. Use of supplemental vitamin E was reported by 52% of men, use of supplemental beta-carotene was reported by 42% of men, and use of supplemental vitamin C was reported by 51% of men.
During an average of four years of follow-up, 1338 men (4.6%) were diagnosed with prostate cancer. Advanced disease (stage III, stage IV, or a Gleason score of 7 or higher) was diagnosed in 520 of these men.
- Overall, there was no link between prostate cancer risk and either dietary intake or supplemental intake of vitamin E, beta-carotene, or vitamin C.
- Among current and recent smokers, use of high-dose or long-term supplemental vitamin E reduced the risk of advanced prostate cancer by roughly 70%. There was a suggestion, however, of an increased risk of non-advanced prostate cancer in smokers who were high-dose or long-term vitamin E users.
- Among men with the lowest intake of beta-carotene from food, high supplemental beta-carotene intake reduced the risk of prostate cancer by about half.
The researchers conclude that these findings “do not provide strong support for population-wide implementation of high-dose antioxidant supplementation for the prevention of prostate cancer.” It’s possible, however, that vitamin E supplementation could reduce the risk of advanced prostate cancer among smokers, and that beta-carotene supplementation could reduce the risk of prostate cancer among men with low intake of beta-carotene from food. (3)
Taken together, results from these studies underscore the confusion surrounding diet and nutrient supplementation and the risk or outcomes of cancer. In general, it appears that fruits and vegetables have a protective effect against the development or aggressiveness of some cancers. Conversely, multivitamin use has not demonstrated a benefit in regards to cancer prevention or survival. It is important for patients to discuss their use of vitamins or other dietary supplements with their physician.
In an initial small trial focused on lung cancer doctors reported that a 50mg/daily vitamin E supplementation over the course of 5 to 8 years correlated with a 32% reduction in the incidence of prostate cancer. (3)
When further evaluated in a large, randomized clinical trial researchers determined that taking daily vitamin E supplements may actually increase a man’s risk of prostate cancer.
To explore the relationship between selenium and vitamin E supplementation and risk of prostate cancer, researchers conducted a randomized trial known as SELECT (the Selenium and Vitamin E Cancer Prevention Trial). The study enrolled more than 35,000 men from the United States, Canada, and Puerto Rico. At the start of the study, all the men had normal prostate-specific antigen (PSA) levels and a normal digital rectal examination. Study participants were assigned to one of four groups:
- Selenium supplementation (200 micrograms per day)
- Vitamin E supplementation (400 IU per day)
- Selenium and vitamin E supplementation
- Placebo (sugar pill)
An initial report from this study (based on roughly five years of follow-up) found that the risk of prostate cancer was higher in the vitamin E group than in the placebo group; this result did not meet the criteria for statistical significance, however, suggesting that it could have occurred by chance alone. Nevertheless, because the results indicated that it was very unlikely that either vitamin E or selenium would provide a benefit, study participants were told to stop taking the supplements.(14)
Although study participants stopped using the supplements in 2008, researchers continue to collect information from them. At the time of the current analysis, men had been followed for a minimum of 7 years.
- Men in the placebo group had the fewest prostate cancers. Prostate cancer was diagnosed in 529 men in the placebo group, 620 men in the vitamin E group, 575 men in the selenium group, and 555 men in the selenium plus vitamin D group.
- Men in the vitamin E group were 17% more likely than men in the placebo group to be diagnosed with prostate cancer. This result was statistically significant (unlikely to be due to chance alone). The differences between the other study groups and the placebo group were not statistically significant.
The Physicians’ Health Study II (PHS II), enrolled more than 14,000 U.S. male physicians to assess vitamin E and vitamin C supplementation, as well as supplementation with a multivitamin and beta-carotene. Neither vitamin E nor vitamin C influenced the risk of prostate cancer. (15)
The results of these studies indicate that supplementation with selenium, vitamin E, or vitamin C is not effective for prostate cancer prevention and that daily vitamin E supplements may actually increase the risk of prostate cancer among healthy men.
Consumers need to be skeptical of health claims for unregulated over-the-counter products unless there’s strong evidence of a benefit from clinical trials.
Fruit - Veggies Cancer-fighting Phytochemicals
Naturally occurring plant chemicals, called phytochemicals, are being increasingly studied for their potential role as anticancer agents. Evaluations of phytochemical sources such as apples, onions, garlic, cranberries, and tomatoes have found that these foods all have anticancer capabilities:
Quercetin is a type of phytochemical called a flavonoid. A study on the effect of quercetin on prostate cancer cells found that this natural flavonoid inhibited the expression of the androgen receptor protein, which is involved in the development and progression of prostate cancer. When expression of these proteins is reduced, the cancer is less stimulated to grow. Quercetin, already a popular natural treatment for allergies, is found in whole foods such as cabbage, cranberries, kale, pears, grapes, apples, onions, and garlic, and is also available as a supplement. (10)
- Garlic, long known for its beneficial sulfur compounds, has also been the focus of some recent prostate cancer research. Garlic supports the immune system by killing viruses, bacteria, and fungus, and its sulfur compounds may also possess anti-prostate cancer properties. One study demonstrated that a natural component of garlic, called S-allylmercaptocysteine (SAMC), produces changes in biomarkers (including PSA) and testosterone activity—alterations that are similar to those produced by another proven approach to prostate cancer treatment, androgen deprivation.(11)
- Cranberries are another commonly available whole food with potential anticancer benefits. The phytochemicals contained in cranberries include flavonol glycosides, anthocyanins, proanthocyanidins (condensed tannins), and polyphenols. A 2004 study reported that these naturally occurring chemicals work together (synergistically) to stop the progression of prostate cancer cells.(12)
- The 2004 study was followed by another study that found that the flavonoids in cranberry extract inhibited cancer cell growth by 50 percent. (13)
While more research is needed to confirm the results of these studies, the possibility that nutritional factors could help prevent prostate cancer remains appealing. People who are at a high risk for developing prostate cancer may wish to speak with their physicians about the risks and benefits of participating in clinical trials designed to evaluate the effects of nutrition and diet on cancer.
Penne Pasta with Tomatoes and Sausage
1 T extra virgin olive oil
1 medium onion, diced
5 cloves garlic, minced
4 chicken apple sausages*, chopped
1 28 oz can organic diced tomatoes
1 16 oz package whole wheat penne pasta
8 oz crumbled feta
Cook penne according to the directions on the package. While the pasta is cooking, sauté the onion for 5 minutes, then add the garlic and sausage and sauté another five minutes. Add the diced tomatoes and cook until heated. Add the cooked penne and sprinkle in the feta or serve it on the side.
*If possible, choose a sausage made from organic chemical and hormone-free chicken meat.
4 large apples, peeled and sliced
1 t cinnamon
½ C whole wheat flour
½ C brown sugar
1 C rolled oats
½ C butter*
Preheat oven to 350 degrees F and grease an 8-inch-round pan. Peel and slice the apples and toss with cinnamon. Mix flour, sugar, oats, and butter until crumbly. Put the apples in the 8-inch pan and cover them with the oat mixture. Bake for 45 minutes at 350 degrees Fahrenheit.
* Butter can be reduced to ¼ cup for less fat and fewer calories if desired.
Mix equal parts carbonated water with cranberry extract. If you can’t find liquid cranberry extract at your local market, there are many online sources*. If you prefer a sweeter drink, add ½ cup white grape juice or other naturally sweet fruit juice. A slice of lemon is also makes a refreshing addition.
- 5th Annual NOAT Congress, September 7-9, 2000, Philadelphia, PA, Cancer Control: The Journal of the Moffitt Cancer Center, Vol 6, No 6, pp 580-586, 1999.
- Kirsh VA, Hayes RB, Mayne ST et al. Supplemental and Dietary Vitamin E, b-Carotene, and Vitamin C Intakes and Prostate Cancer Risk. Journal of the National Cancer Institute. 2006;98:245-54.
- Journal of the National Cancer Institute, Vol 93, No 24, pp 1872-1879, 2001.
- Kucuk O, Sarkar FH, Djuric Z, et al. Effects of lycopene supplementation in patients with localized prostate cancer. Experimental Biology and Medicine. 2002; 227:881-5.
- Kirsh V, Peters U, Mayne S, et al. Prospective study of fruit and vegetable intake and risk of prostate cancer. Journal of the National Cancer Institute. 2007;99:1200-1209.
- Kavanaugh CJ, Trumbo PR, Ellwood KC. The U.S. Food and Drug Administration’s evidence-based review for qualified health claims: tomatoes, lycopene, and cancer. Journal of the National Cancer Institute. 2007;99:1074-85.
- Giovannucci E. Does prostate-specific antigen screening influence the results of studies of tomatoes, lycopene, and prostate cancer risk? Journal of the National Cancer Institute. 2007.99:1060-1062.
- Lawson KA, Wright ME, Subar A et al. Multivitamin use and risk of prostate cancer in the National Institutes of Health-AARP Diet and Health Study. Journal of the National Cancer Institute. 2007;99:754-64
- Bjelakovic G, Gluud C. Surviving antioxidant supplements. Journal of the National Cancer Institute. 2007;99:742-43.
- Xing N, Chen Y, Mitchell SH, Young CY. Quercetin inhibits the expression and function of the androgen receptor in LNCaP prostate cancer cells. Carcinogenesis. 2001 Mar;22(3):409-14.
- Pinto JT, Qiao C, Xing J, Suffoletto BP, Schubert KB, Rivlin RS, Huryk RF, Bacich DJ, and Heston WD . Alterations of prostate biomarker expression and testosterone utilization in human LNCaP prostatic carcinoma cells by garlic-derived S-allylmercaptocysteine. Prostate. 2000 Dec 1;45(4):304-14.
- Seeram NP, Adams LS, Hardy ML, and Heber D . Total cranberry extract versus its phytochemical constituents: antiproliferative and synergistic effects against human tumor cell lines. J Agric Food Chem. 2004 May 5;52(9):2512-7.
- Ferguson PJ, Kurowska E, Freeman DJ, Chambers AF, and Koropatnick DJ . A flavonoid fraction from cranberry extract inhibits proliferation of human tumor cell lines. J Nutr. 2004 Jun;134(6):1529-35.
- Lippman SM, Klein EA, Goodman PJ et al. Effect of selenium and vitamin E on risk of prostate cancer and other cancers. The Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2009; 301:39-51.
- Gaziano JM, Glynn RJ, Christen WG et al. Vitamins E and C in the prevention of prostate and total cancer in men. The Physician’s Health Study II Randomized Controlled Trial. Journal of the American [early online publication]. December 9, 2008.
- Meir HL, Stampfer J, Giovannucci EL, et al. A Prospective Study of Plasma Selenium Levels and Prostate Cancer Risk. Journal of the National Cancer Institute. 2004;96:696-703.
- Gao X, LaValley MP, Tucker KL. Prospective Studies of Dairy Product and Calcium Intakes and Prostate Cancer Risk: A Meta-Analysis. Journal of the National Cancer Institute. 2005;97:1768-77.
- Augustsson K, Michaud D, Rimm E, et al. A prospective study of intake of fish and marine fatty acids and prostate cancer.
- Brasky TM, Darke AK, Song X, et al. Plasma phospholipid fatty acids and prostate cancer risk in the SELECT trial. Journal of the National Cancer Institute. 2013; 105(15): 1132-1141.
Cancer Epidemiology Biomarkers & Prevention. 2003;12:64-67.