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Selenium is another supplement that was commonly suggested to men with a history of prostate cancer that has been questioned by prospective human trials. Recall the 2003 van den Brandt study that associated low toenail selenium levels with higher risk of prostate cancer.58 Even Hurst's 2012 meta-analysis furthered this belief.59 Yet this notion was countered by the results reported in the SELECT cohort that found supplementation with selenium had no significant impact on disease risk.60
Van Blarigan and colleagues reported in 2014 after following 4,459 men diagnosed with prostate cancer for 22 years that those who took selenium supplements had a higher risk of dying from prostate cancer. During 7.8 years of follow up, recurrence rates were 5.6/1000 person-years for those not taking selenium supplements and 10.5/1000 person-years for those who took 140 μg/day or more. Rates of biochemical recurrence were 28.4 vs. 29.3/1000 person-years comparing non-selenium users with users. Risk of dying from prostate cancer increased with selenium doses. Men consuming low-dose selenium (1 to 24 μg/day of selenium) had an 18% higher risk than non-users. Those consuming 25 to 139 μg/day had a 33% increased risk and those taking 140 or more had a 2.60-fold greater risk of prostate cancer mortality. This clearly contradicted the general belief that every man who had prostate cancer should take 200 mcg or more of selenium per day.61
In a 2015 Van Blarigan was part of a team that identified specific polymorphisms in selenoprotein coding genes that were associated with higher-grade disease that might affect prostate cancer recurrence.62
In 2014 Richman had an important paper on folate published. She prospectively examined the association between post-diagnostic folate consumption and the risk of prostate cancer recurrence after radical prostatectomy, external beam radiation therapy, and brachytherapy. Prior to starting this study, a randomized, placebo controlled clinical trial of folic acid supplementation for the chemoprevention of colorectal adenoma had revealed an increased incidence of prostate cancer in the treatment group. Erin's study was done with 1,153 men who had been treated with radical prostatectomy, external beam radiation therapy and brachytherapy and participated in the CaPSURE Diet and Lifestyle study.
Prostate cancer progressed in 101 men (8.76%) during a mean 34-month follow-up. Though initially no evidence of folate intake and recurrence was seen, on secondary analysis by treatment type, after radical prostatectomy, patients in the lowest decile of dietary folate intake had a 2.6-fold increase in the risk of recurrence (HR 2.56, 95% CI 1.23-5.29, p = 0.01). In patients treated with external beam radiation and brachytherapy, no evidence of an association between prostate cancer progression and increased folate intake was seen.
Though it is rare to see low folate levels in patients, this paper would suggest we should not worry about folate supplementation in men who have had prostate cancer, in fact we should consider supplementation if a man's levels are low post initial treatment with surgery.63
Taking a multivitamin is safe and probably useful. The Physicians Health Study randomized trial of a regular multivitamin reported a modest but significant (8%) reduction in total cancer incidence in men (HR, 0.92; 95% CI, 0.86-0.998; P=.04). The men with a history of prior cancer had a 27% reduction in total cancer during the study (HR, 0.73; 95% CI, 0.56-0.96; p=0.02). There was no significant affect on risk of prostate cancer.64 There is still no strong evidence that any single supplement offers protection against prostate cancer (neither development nor progression).
In a 2016 paper, Nordström, Van Blarigan, Ngo, et al reported that circulating carotenoids, "were inversely associated with the risk of high-grade prostate cancer…odds ratios (OR)… highest versus lowest quartiles were: 0.34 (95% CI: 0.18-0.66) for α-carotene, 0.31 (95% CI: 0.15-0.63) for β-carotene, 0.55 (0.28-1.08) for lycopene and 0.37 (0.18-0.75) for total carotenoids." Once again, these effects were modified by various SNPs. Thus, the argument that we should be doing genetic testing in prostate cancer patients continues to strengthen.65
So, what is the current bottom line for men diagnosed with prostate cancer?
- No smoking;
- If BMI is 27 or higher, lose weight;
- Exercise rigorously, do something to sweat;
- Eat lots of vegetables (particularly tomato sauce and cruciferous vegetables);
- Eat more vegetable fats (i.e. fish, nuts, vegetable oils, soybeans, avocados, and flaxseed) and fewer saturated fats. Eat less carbohydrates;
- Drink coffee – regular or de-cafe doesn't seem to matter;
- Limit eggs and poultry with skin on;
- Limit whole milk if your BMI is high, probably should even if it isn't; and
- Limit refined grains, sugars, processed meat, and high-fat dairy.66,67
We should probably be testing SNPs before making suggestions for vitamin E, selenium or lycopene.
Granted at this point we do not have the sort of randomized human clinical trials implementing these recommendations that we would prefer. Still this is a great deal more information than we had just a few years ago. A good bit of it is the result of Erin Van Blarigan's research. Hopefully at some future date she will be able to link the earlier research published under her maiden name to her current list. We'll keep our fingers crossed that she keeps this married name for a long, long time and does so with much happiness. Congratulations Erin!
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Dr Jacob Schor, ND, FABNO has practiced as a naturopathic doctor in Denver, Colorado since 1991. He is past president of the Colorado's professional association for naturopathic doctors (CoAND) and the Oncology Association of Naturopathic Doctors. He is a frequent contributor to the Townsend Letter.