Prostate cancer risk is a very complex and difficult thing to analyze. We are probably seeing an increase in diagnosis of prostate cancer because of the increasing utilization of the prostate specific antigen (PSA) screening being used in a large segment of the male population. This test uncovers many prostate cancers that may have lain dormant or undiagnosed clinically. The more aggressive cancers are also diagnosed early with the screening, so there are benefits to the screening—but it can cause a lot of anxiety.
The search for dietary causes has not been particularly rewarding, though heavy dairy consumption has been associated in some reports with a small increase in aggressive prostate cancer, but not the more indolent form. The study authors stated that the association was statistically weak but deserved further study. The interesting finding that this effect was
not seen with full-fat dairy, only the reduced-fat dairy, raises all kinds of questions.
Vitamin D intake is becoming a very prominently discussed topic as far as prostate cancer is concerned, but also for many other disorders. The long-standing recommendations of 400 international units (IUs) per day, while adequate for preventing rickets, appears to be insufficient for many other diseases. Researchers are fairly unanimous in proposing 1,000 IUs per day as being a more desirable level of intake, with up to 2,000 IUs being a possible optimal level. Vitamin D has anticancer properties, as well as antiinflammatory properties. Naturally secured through sunshine’s effect on the skin, many in northern climes, as well as those in sunny areas, do not get enough vitamin D.
The human genome has also been unraveled, and from this information scientists are discovering new gene activities. Prostate cancer has a very marked genetic component. Men are at increased risk for prostate cancer in proportion to the number of first-degree relatives they have with the disorder.
In a recently published study by Zheng et al. (The New England Journal of Medicine, Feb. 28, 2008; vol. 358, no. 9, pp. 910-919), the associations between prostate cancer and five genes were explored. The relative risk was shown to vary with the number of genes present reaching as high as 4.47, where four or five of these genetic predisposing genes were functioning. But this
is not the whole story. When family history was added to the mix, a group of men with a relative risk of 9.46 was identified. With a 400 to 900 percent increased risk, based on genetics, the relatively tiny increases of 20 percent increased risk based on dietary preferences begin to pale in significance.
Clearly, prostate cancer is of a very complex etiology and pathogenesis, and much more work will have to be done before we can crystallize our recommendations into easy, take-home messages. In the meantime, vigilance and a commonsense approach will stand us in good stead.
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Allan R. Handysides, M.B., Ch.B., FRCPC, FRCSC, FACOG, is director of the General Conference Health Ministries Department; Peter N. Landless, M.B., B.Ch., M.Med., F.C.P.(SA), F.A.C.C., is ICPA execu-
tive director and associate director of Health Ministries.
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