Prostate Cancer: Can Men Reduce Risk without Drugs?
A new study published in today’s New England Journal of Medicine is re-opening discussions looking beyond screening, treating and using meds to prevent prostate cancer, as many ask what we know about reducing risk of prostate cancer through non-pharmaceutical means.
Many possible steps to reduce prostate cancer risk have been proposed based on preliminary evidence, only to find upon further research the link is not so clear. Prostate cancer is a complex disease, occurring in slow-growing forms that take many years to develop and do not threaten life — the most common by far — as well as more aggressive forms.
In today’s Smart Bytes®, we’ll look at the latest on three take-home messages for men about reducing risk of prostate cancer. Read on, share with the men in your life, and come back for Part Two on this topic to get the low-down on several more hot topics regarding diet and prostate cancer risk.
Foods containing lycopene are among the few choices with strong enough research support to qualify to be listed as probably reducing risk of prostate cancer by the American Institute for Cancer Research/World Cancer Research Fund analysis of research, Food, Nutrition, Physical Activity and the Prevention of Cancer: a Global Perspective. Lycopene is a natural plant compound from the family called carotenoids; sort-of a cousin to the more well-known beta-carotene.
Lycopene circulates throughout the body and accumulates in body tissues, with the prostate gland among those where it is most concentrated. Laboratory evidence is strong showing that lycopene and compounds that form as it’s metabolized in the body can serve as antioxidants. Lycopene also helps renew the ability of vitamins E and C to serve as antioxidants, and it increases the level of a system of body antioxidant enzymes (known collectively as ARE, the Antioxidant Response Element). In addition, lycopene-related compounds act directly to interrupt cancer development in laboratory studies, decreasing cell growth and reproduction, increasing self-destruction of abnormal cells and modifying the androgen hormones that drive development of prostate cancer.
In human studies, the waters get a bit murky. You could get whiplash trying to follow the ups and downs of each individual study on how lycopene and tomatoes (the source of more than 85 percent of Americans’ lycopene) impact prostate cancer risk.
♦ A major analysis in 2011 concluded the data in humans is insufficient to either support or refute lycopene as an aid to reducing risk of prostate cancer, and the link seen in a 2013 analysis shows a reduction in risk so small linked specifically to lycopene that it is “statistically non-significant” (which means it could have as well occurred by chance).
♦ Yet we don’t eat lycopene, we eat foods containing lycopene, and that may make a big difference. Studies in animals show that while lycopene alone shows cancer-protective effects, tomatoes provide greater effects, probably because of the other nutrients and compounds available to work with lycopene. And some animal studies suggest the protection from tomatoes plus another plant food, like soy or broccoli, are greater than from tomatoes alone.
♦ Randomized controlled trials allow researchers to make sure that every subject gets exactly the same amount of lycopene. Food is harder to study, because like any plant food, the amount of lycopene in any particular tomato or lycopene-containing fruit varies with the particular cultivar and growing conditions. So at best, we are getting rough estimates of how much lycopene people consume in most dietary studies. That can “blur the lines”, making it harder to detect an effect.
In a recent analysis summarizing studies on tomato consumption, men consuming raw tomatoes at least 3 to 5 times weekly were 19 percent less likely to develop prostate cancer than men consuming them only once or twice a month. Men consuming cooked tomatoes (including tomato sauce) twice a week or more were 15 percent less likely to develop prostate cancer than men consuming them less than once a month. However, neither of these results were “statistically significant”. Relatively wide variability in results could mean that individual genetic or hormonal differences made some men benefit from tomatoes more than others, the studies may have been too small to detect this relatively modest impact, or there might have been something else responsible for the lower risk of some men.
Here’s my take on today’s bottom line while we wait for clearer answers:
- Given the inconsistent findings on lycopene and the results of studies showing greater effect of lycopene in food than on its own, don’t bother with lycopene supplements.
- Considering the many nutrients in tomatoes, and the way they combine so well with other foods as part of a predominantly plant-based diet, they’re a smart choice to include regularly. Consuming foods rich in lycopene often is likely to be a small piece in the puzzle, but why ignore an opportunity for protection?
- Both raw and cooked tomatoes provide lycopene. Processing tomatoes – meaning chopping, cooking or puréeing – breaks down the matrix binding lycopene, making more of it available for us to absorb. So enjoy those gorgeous raw tomatoes now while they’re in season, but don’t hesitate to rely on jarred or canned tomatoes when winter comes.
- Fruits supply lycopene, too, but don’t assume that all red fruit signals lycopene, since that color can come from other compounds, too. Fruits that contribute significant lycopene are watermelon, papaya, pink guava and pink or red grapefruit.
Early studies suggested that the mineral selenium, was linked to reduced risk of prostate cancer. Indeed, in lab studies, selenium shows impact far beyond its antioxidant power, affecting carcinogen activation, cell growth rates and self-destruction of abnormal cells. Initially, human studies suggested potential protection from selenium, too. But a major controlled study, SELECT, surprised researchers and showed a very clear lack of protection in men taking supplements with 200 micrograms (mcg) selenium.
A closer look, including major analysis of available research as part of the American Institute for Cancer Research/World Cancer Research Fund Continuous Update Project, provides important insight. Analysis summarizing multiple studies shows that compared to men with low levels, men with higher blood levels of selenium – up to a point – show 15 to 25 percent lower risk of prostate cancer. And these higher blood levels linked to an even stronger 40 to 50 percent lower risk of advanced disease. Levels of selenium in toenails have long been recognized as a good marker of selenium status over a longer period than blood levels can represent, and toenail selenium levels that tend to match the low-risk blood levels showed a 71 percent decrease in prostate cancer risk.
Here’s my take on the bottom line regarding selenium:
- Getting enough selenium seems likely to reduce prostate cancer risk. There appears to be a point where more selenium stops being protective, and eventually where it may even increase risk, at least in some men.
- Studies compiled from around the world show benefit from selenium when comparing people with low blood levels (about 60 ng/ml) to people with higher blood levels (135-170 ng/ml). These studies do not address risk of prostate cancer at blood levels of selenium beyond that point.
- Looking back at a human controlled trial that showed benefit of selenium supplements, the protection was only seen in men who started the study with blood levels below 123 ng/ml – below the range associated with reduced risk in the AICR/WCRF continuous update project analysis. In the SELECT trial, which found no benefit, men started with selenium levels already at about 135 ng/ml. Supplementation raised levels to about 250 ng/ml, well beyond levels linked to reduced risk.
- Selenium is found in many foods, and overall selenium status varies widely around the world. Some areas of China, for example, have very low-selenium soil, and low blood selenium is common. Americans are among those worldwide with highest selenium levels. When you hear about a study conducted in another part of the world, such as low-selenium China, that shows benefits, don’t assume the same benefits apply to people much less likely to be deficient.
- How much is enough? The current Recommended Dietary Allowance for men is 55 micrograms (mcg) daily of selenium. This standard was established based on ideal levels for one of selenium’s functions in the body; some researchers suggest that for other functions it performs, optimal intake might be closer to 80 mcg/day. According to a major study of U.S. nutrient consumption, NHANES, average American adult selenium consumption averages 109 mcg from food alone (not counting any multivitamin or other supplements) — plenty.
We need more research to answer the question of how much selenium most effectively protects both prostate and overall health. Since higher blood and toenail levels of selenium stem from selenium-containing foods that also supply a variety of other nutrients, there is no basis for turning to selenium supplements unless you’ve been diagnosed with low selenium levels. That’s in agreement with the conclusion of the AICR/WCRF continuous update project analysis noted above.
- A wide range of foods supply selenium. Brazil nuts are widely known as super-concentrated sources. In fact, even if 80 mcg selenium a day becomes identified as optimal, just one ounce (6 to 8 nuts) would supply a whole week’s selenium on its own. Don’t overdo. Fish and poultry can be excellent sources of selenium; a three-ounce portion (the size of a deck of cards or checkbook) often supplies 50 to 100 mcg of selenium – nearly a day’s worth or more. Eggs, whole grains, and mushrooms are also among especially good sources of selenium. Small amounts are found in a wide range of foods, and it all adds up to meet our needs.
Is it Time for Tea?
Green tea contains natural compounds called polyphenols, including one called EGCG that has received a lot of attention for promoting antioxidant effects in the body, as well as potentially intervening directly in several steps in the process of cancer development. These compounds show benefit in cell cultures, and researchers do see green tea inhibiting prostate cancer development and progression in animal studies. Black tea, more commonly consumed in the U.S., is also high in polyphenol compounds, though they are a different type than those in green tea. These compounds, too, show anti-cancer potential in the lab.
Human studies are much less consistent. Studies in Asian men tend to show a stronger link between green tea and lower risk of prostate cancer than those in other populations. This could reflect genetic differences that make some people more affected than others by these compounds, or could reflect influence of other dietary differences that interact with tea’s compounds in providing protection….or could simply reflect that “high” consumption in Asia is quite different than “high” consumption (especially of green tea) in other parts of the world. In one analysis combining results of multiple studies, population studies that are less well-controlled for intervening influences (case-control studies) showed more than a 50 percent reduction in prostate cancer risk with more green tea; yet population studies regarded as the strongest (prospective cohort studies) showed no link at all to risk of the disease.
Here’s my take on the bottom line about tea:
- Tea, green or black, makes an excellent beverage choice with virtually no downside. Whether or not it helps reduce a man’s risk of prostate cancer remains to be seen.
- Since the results are so inconsistent, there’s no reason at this point to jump to supplements of EGCG in hopes of protection.
What’s next? Come back to Smart Bytes® soon! My next post will share a recipe for a delicious treat that fits with what we’ve discussed here about reducing risk of prostate cancer….along with input on how to make the “supreme” version from a variety of its fans.
And, come back for Part 2 on Prostate Cancer, when we’ll look at the evidence regarding other steps some have raised as potential ways to reduce prostate cancer, like vitamin E, omega-3 fats, soy and more. We’ll look at practical tips about how all the findings fit together, so you won’t want to miss it!
For Further Reading
Based on a reader’s suggestion (see below), I have come back to this post to share information about two of many research papers that may be helpful to readers who would like to go deeper in understanding the findings of lycopene and prostate cancer risk. There are many issues involved, and few can do as good a job addressing them as world-renowned Edward Giovannucci, MD, ScD, of Harvard.
Wei MY and Giovannucci EL. Lycopene, Tomato Products, and Prostate Cancer Incidence: A Review and Reassessment in the PSA Screening Era. Journal of Oncology. 2012. Article ID 271063, 7 pages. doi:10.1155/2012/271063
Giovannucci E. Commentary: Serum lycopene and prostate cancer progression: a re-consideration of findings from the prostate cancer prevention trial. Cancer Causes Control. 2011 Jul;22(7):1055-9.
Thompson, IM et al. Long-Term Survival of Participants in the Prostate Cancer Prevention Trial. The New England Journal of Medicine. 2013. 369(7):603-610.
Ford NA, Erdman JW Jr. Are lycopene metabolites metabolically active? Acta Biochim Pol. 2012;59(1):1-4.
Holzapfel NP, et al. The potential role of lycopene for the prevention and therapy of prostate cancer: from molecular mechanisms to clinical evidence. Int J Mol Sci. 2013 Jul 12;14(7):14620-46.
Ilic D, et al. Lycopene for the prevention of prostate cancer. Cochrane Database Syst Rev. 2011 Nov 9;(11):CD008007.
Chen J, et al. Lycopene/Tomato consumption and the risk of prostate cancer: a systematic review and meta-analysis of prospective studies. J Nutr Sci Vitaminol (Tokyo). 2013;59(3):213-23.
Hurst R, et al. Selenium and prostate cancer: systematic review and meta-analysis. Am J Clin Nutr. 2012 Jul;96(1):111-22.
Davalli P, et al. Anticancer activity of green tea polyphenols in prostate gland. Oxid Med Cell Longev. 2012;2012:984219.
Zheng J, et al. Green tea and black tea consumption and prostate cancer risk: an exploratory meta-analysis of observational studies. Nutr Cancer. 2011;63(5):663-72.