VASECTOMY AND RISK OF PROSTATE CANCER
The weight of evidence shows no association between a vasectomy and the risk of prostate cancer. However, there has been concern that a risk might exist in subgroups such as men with a family history of prostate cancer, men who undergo the procedure at a younger age, or that risk might develop over a longer period than studied. A recent study addresses these issues. Approximately 1000 men diagnosed with prostate cancer were matched with over 900 controls. The prevalence of vasectomy was similar in the cases and controls (36.2% and 36.1%) and thus no association was found. In addition there was no association between prostate cancer and age at vasectomy, years elapsed since the procedure, or the calendar year of the vasectomy. It was concluded that prostate cancer is not an issue associated with having a vasectomy.
Holt SK, Salinas CA, Stanford JL. Vasectomy and the risk of prostate cancer. J Urol 2008 Dec;180(6):2565-7
GREEN TEA AND PROSTATE CANCER RISK
TRANS-FATTY ACIDS AND RISK OF PROSTATE CANCER
A recent study from Harvard Medical School and Brigham and Woman's Hospital has examined
the hypothesis that trans-fats are related to prostate cancer risk. This hypothesis was in part
based on studies indicating that the trans-fats increase systemic inflammation and insulin
resistance, both of which may play a role in prostate carcinogenesis. These fatty acids also
interfere with transcription genes that may be important in prostate cancer initiation and
progression. They conducted a prospective case-control study nested within the Physicians'
Health Study. A 13-year follow-up was involved. It was found that blood levels of two trans-fatty
acids were associated with an increased risk of non-aggressive prostate tumors. When the top
and bottom quintiles of intake were compared, the relative risk was more than double for total
trans-fatty acid intake and approximately double for each of the two acids that were implicated
(oleic and linoleic). The authors point out that this type of tumor represents a large proportion of
prostate cancer detected using PSA screening and that these finding may have implications for
prostate cancer prevention.
FRUIT AND VEGETABLE INTAKE AND RISK OF PROSTATE
Cruciferous vegetables in general and broccoli in particular seem to come up rather frequently in
studies of diet and disease. Neither are probably top choices in North America for the vegetable
portion of meals. However, this study found benefit for only on serving per week, which is not
really an overkill in broccoli consumption. There is another option, albeit unproven by proper
studies, and that is the cruciferous vegetable concentrate available in capsule form. But of
course, there is no assurance that this extract contains the ingredients that are actually active in
cancer prevention. Studies that will settle that question will probably never be conducted, given
that vegetable extracts are not patentable. A compromise is to eat that one serving of broccoli or
cauliflower or both per week and to play it safe take extract capsules as well. For those who do
not like broccoli or cauliflower, experimenting with sauces such as cheese sauces or a rich
Hollandaise sauce is suggested as a way of enhancing the palatability of these vegetables.
RISK FACTORS FOR PROSTATE CANCER. NEW RESULTS FROM THE
HEALTH PROFESSIONAL'S FOLLOW-UP STUDY
It is interesting that high intakes of calcium keep turning up in prostate risk studies. Men need to
worry about their total intake from supplements, diet and anti-acids containing calcium carbonate.
In this latest study, the threshold for increased risk from calcium intake occurred around 1200
mg/day. Calcium carbonate, the active ingredient in popular anti-acids, contains 40% elemental
calcium. Thus the extra-strength 750 mg tablet contains 300 mg of calcium.
ZINC INTAKE AND PROSTATE CANCER RISK
Many popular multivitamin preparations contain approximately 15 mg per tablet or capsule and it
is not uncommon for someone to take two a day. Thus in view of this recent study, there is the
potential for increasing the risk of prostate cancer from this source alone.
Prostate cancer risk may be raised by high cholesterol
Androgens - hormones that have a role in prostate tissue and cancer - are synthesized from cholesterol, suggesting a possible biological relationship between high cholesterol and prostate cancer. Gallstones are also related to high cholesterol levels and are often composed of cholesterol. So the direct relationship found between gallstones and prostate cancer, while it was not statistically significant, suggests that a similar biological mechanism is at work. The authors add that statins may potentially be protective against prostate cancer, but the studies so far have been limited and inconclusive.
Testosterone therapy may be linked to prostate cancer
The article appears alongside an editorial by a urologist from Cornell University who points out "serious flaws" in the study. For example, it does not show how common the risk of prostate cancer is in men on testosterone therapy. If results from a previous study are accurate, it may be no higher than in the general population. Moreover, in this study there is a lack of pre-treatment data for many of the patients on PSA or DRE (digital rectal examination). Nevertheless, doctors need to be extremely careful before beginning testosterone therapy, he writes, and PSA and DRE testing should be performed frequently during treatment.
Possible prostate cancer link to low-fat milk
PHILADELPHIA, PENNSYLVANIA. Several previous studies have linked dairy foods with risk of prostate cancer. The cause of the link was initially attributed to the fat content of these foods, but it may be that their calcium content suppresses the body's production of vitamin D, a potential protective factor against prostate cancer. As dairy products are widely promoted and have certain health benefits, researchers from the Fox Chase Cancer Center investigated the link to prostate cancer using a group of men from the first National Health and Nutrition Examination Epidemiologic Follow-up Study.
They followed 3,612 men from across the US for about eight years, during which time 131 were diagnosed with prostate cancer. Food questionnaires were given at the start of the study, when the participants were, on average, 58 years of age. The men consumed an average of 13 portions per week of dairy products, varying from three to 23 portions. Calcium intake was 730 mg on average and vitamin D intake was 172 IU on average (well below the recommended daily intake of 400 IU). Analysis showed that men in the highest third for dairy intake were 2.2 times more likely to develop prostate cancer than those in the lowest third. When each food was studied separately, risk was increased with low-fat milk but not whole milk or any other dairy food. Calcium intake also increased risk by the same amount, but in further analyses only calcium from milk was significant. Calcium supplements did not increase risk.
The authors suggest that their findings support the vitamin D suppression hypothesis. They explain that the
suppressive effects of the calcium from whole milk may be countered by fortification with vitamin D, but low-
fat milk has a lower vitamin-D content, as it is a fat-soluble vitamin. On the other hand, prostate cancer may
simply be diagnosed more in the higher social groups which tend to drink low-fat milk and are more likely to
attend screening. In conclusion, the authors state that the increased risk from dairy may occur through a
calcium-related pathway. They add that the link must be clarified, as both calcium and low-fat milk may be
important in avoiding osteoporosis and colon cancer.
Diabetes protects against prostate cancer
The researchers found that overall; diabetes reduced the risk of prostate cancer by 33 per cent once age, race, education and prostate-specific antigen testing were taken into account. However, risk was significantly increased (by 23 per cent) in the first three years after diabetes diagnosis, compared with non- diabetic men, and only began to be protective after four years. The protective effect remained consistent when stage or grade of prostate cancer at diagnosis was examined. These results are consistent with the hypothesis that diabetes is associated with reduced risk of prostate cancer but only several years after diagnosis of diabetes, say the authors. The protective effect may be due to the reduced insulin levels found in men who have been diabetic for some time, as prostate cancer has been linked to high circulating levels of insulin.
The findings in the present study are consistent with results from a Health Professionals Follow-up Study,
which also found an increased risk following diagnosis of diabetes and a protective effect after several
years. In this study, prostate cancer risk was lowest 10 years after diabetes diagnosis, a reduction of 46 per
cent. On the other hand, a recent case-control study within the US Physicians' Health Study found a
reduction in risk of 36 per cent, but with no link to the time since diabetes diagnosis.
Selenium and prostate cancer risk
After 13 years of follow-up the researchers concluded that study participants with a plasma selenium level
of 0.12-0.19 ppm had a 50% lower incidence of advanced prostate cancer than did men with a level of
0.06-0.09 ppm. The correlation was only apparent in men with a PSA level of more than 4 ng/mL and
was particularly strong for those with a baseline (1982) PSA level greater than 10 ng/mL. For these men
a high selenium level corresponded to a 70% decrease in the risk of advanced prostate cancer. The
researchers also observed a trend for a lower incidence of localized prostate cancer with high selenium
levels, but this trend was not statistically significant. They conclude that selenium is perhaps not too
effective in preventing the initiation of prostate cancer, but that it is highly effective in slowing down tumor
progression. They believe that selenium acts by selectively killing off cells whose DNA has been
extensively damaged, by inhibiting cellular proliferation, and by its role as a key component of glutathione
peroxidase, which protects cells from peroxide damage.
Editor's comment: The evidence is now indeed overwhelming that selenium helps protect against prostate cancer. While this study concluded that the protection mainly involves slowing down tumor progression, other studies have shown that selenium also helps prevent initiation of the cancer. Thus daily supplementation with 200 micrograms of selenium should be an integral part of all supplementation programs for men.
Prostate cancer: Risk factors and prevention
Several studies have found a clear association between the western lifestyle and an increased risk of prostate cancer. A high intake of fat, meat and dairy products has been found to be particularly detrimental. Consuming fried or charcoal-grilled red meat has been clearly associated with increased risk. A high intake of alpha-linolenic acid and calcium from dairy products has both been associated with higher risk. A Swedish study found that men who consumed 600 mg/day of calcium from dairy products had a 32% greater risk than those consuming 150 mg/day or less.
Smoking, degree of physical activity, and alcohol consumption have not been associated with an increased risk and neither has vasectomy.
Soybean products (soy milk or tofu) have been found to have a preventive effect as has a high intake of
tomato products, lycopene, selenium, and vitamin E. Supplementation with selenium reduced risk by
66% in one study while vitamin E supplementation lowered it by 40%. A large study involving 32,400 men
is currently underway to confirm the benefits of vitamin-E and selenium supplementation. Results are
expected by 2013.
IGF-1 and advanced prostate cancer
A team of researchers from Harvard Medical School and the University of California has just completed a major study aimed at determining if IGF-1 and IGFBP-3 levels can predict the risk of developing advanced stage prostate cancer. Their study involved 530 patients with prostate cancer and 534 controls matched for sex and smoking status. All participants were part of the Physicians' Health Study and were between the ages of 40 and 84 years at enrollment in 1982. Almost 15,000 of the men provided blood samples that were stored for future analysis. By the end of 1995, 786 cases of prostate cancer had been diagnosed among the 14,916 participants (5.2%). Sufficient blood plasma for IGF-1 and IGFBP-3 analysis was available for 530 of the cases and their matched 534 controls. The diagnosis of prostate cancer was made an average of 9 years after the drawing of the blood samples.
The researchers observed a strong association between IGF-1 and IGFBP-3 levels and the risk of
advanced prostate cancer, but found no association with early stage disease. They found that men with
IGF levels in the highest quartile had a 5.1 times higher risk of later developing advanced stage prostate
cancer than did men in the lowest quartile. Men with IGFBP-3 levels in the highest quartile, on the other
hand, had a 5 times lower risk of later advanced stage cancer (OR=0.2). Advanced stage prostate
cancer was defined as stage C (extraprostatic, but no evidence of distant metastases) or stage D (distant
metastatic or fatal). About 10% of the total 530 cases were stage D. The researchers speculate that IGF-
1 not only stimulates tumour initiation and growth, but may also facilitate invasion and metastases. They
conclude that measurement of IGF-1 and IGFBP-3 levels may predict the risk of advanced stage prostate
cancer years before the cancer is actually diagnosed and may thus be helpful in aiding decision making
Sun avoidance increases cancer risk
Testosterone replacement in men
Calcium and prostate cancer
Prostate cancer linked to omega-3 fatty acid deficiency
Researchers at the Korea Institute of Science and Technology now report that
men with prostate cancer and benign prostatic hyperplasia (BPH) have markedly
different ratios of omega-3 to omega-6 as compared to men with healthy
prostates. Their study involved 24 men with BPH, 19 men with prostate cancer
in various stages, and 21 age-matched men with normal prostates. All
participants provided blood samples that were analyzed for a total of 21
different fatty acids. The researchers found no significant differences in
the overall levels of saturated, monounsaturated, and polyunsaturated fatty
acids. However, there was a very marked decline in the levels of EPA
(eicosapentaenoic acid) and DHA (docosahexaenoic acid) from the normal men to
the men with BPH to the men with prostate cancer. The ratios of serum omega-3
to omega-6 polyunsaturated acids were also quite different for the three
groups ranging from 0.89 for normal subjects to 0.71 for men with BPH to 0.50
for men with prostate cancer. The men with prostate cancer also had
significantly higher levels of omega-6 acids than did the normal men and the
men with BPH. The researchers conclude that their work supports the
contention that omega-6 polyunsaturated fatty acids have a tumor-promoting
effect while omega-3 acids have a protective effect. They urge further work
to determine the association between the omega-3 to omega-6 ratio and prostate
Vasectomy does not increase cancer risk
COPENHAGEN, DENMARK. A major Danish study concludes that vasectomy does not cause testicular cancer. The study involved over 73,000 Danish men who had undergone a vasectomy during the period 1977-89. During the study period, 70 men developed testicular cancer. The researchers found that the incidence of testicular cancer was no higher among vasectomized men than among the general population and that vasectomy does not cause testicular cancer nor accelerate the growth of existing testicular tumors. The researchers also found no evidence that vasectomy increases the risk of prostate cancer in the time period covered by the study. However, they do caution that prostate cancer develops very slowly and that their results regarding this cancer are therefore inconclusive at this time.
Moller, Henrik, et al. Risk of testicular cancer after vasectomy: cohort study of over 73,000 men. British Medical Journal, Vol. 309, July 30, 1994, pp. 295-9
Vasectomy does not increase cancer risk
Fatty acid intake linked to prostate cancer
Fat intake and prostate cancer are linked
Insulin-like growth factor 1 implicated in prostate cancer
New early warning signal for prostate cancer
High calcium intake linked to prostate cancer
The researchers also found that fructose protects against the development of
prostate cancer. Men who consumed more than 70 grams/day had half the risk of
developing advanced prostate cancer than did men who consumed only 40
grams/day or less. The main sources of fructose in the study were fruits,
carbonated beverages, and sweet bakery products. A high fruit intake as such
was also found to be protective with men consuming five servings a day having
a 37 per cent lower risk of advanced prostate cancer than men who only
consumed one serving a day or less. The researchers speculate that calcium
interferes with the formation of 1,25-dihydroxycholecalciferol, the
biologically active form of vitamin D which has been found to suppress the
development of prostate tumors. Somewhat surprisingly, they did not find any
relationship between prostate cancer risk and vitamin D intake from foods or
supplements between the range of less than 150 IU/day to more than 800 IU/day.
They conclude that increased fruit consumption and avoidance of a high calcium
intake by middle-aged and older men may reduce the risk of prostate
Prostate cancer - Is it mainly because of the meat?
Surprising risk factors for prostate cancer
Diet and prostate cancer
Prostate cancer risk and diet
Testosterone levels and prostate cancer