The subject of smoking & PCa tends not to come up, but I imagine that many men my age (70) or older are ex- or current smokers.
I am using the appearance of a new study as an excuse to write about cadmium, zinc & selenium.
In 2015, an Italian-U.S. meta-analysis [1] led by Dr. Stephen Freedland reported that:
"Data from the peer-reviewed literature suggested an association of smoking and aggressive PCa. Although the pathophysiology underlying this association remains unclear, smokers presented higher PCa mortality and worse outcome after treatment."
The mortality statistics probably understate the problem, because smokers with PCa face a strong competing cause of mortality that acts somewhat faster.
"the pathophysiology ... remains unclear" means that they haven't figured out why smoke in the lungs would affect the prostate.
In March, a Swedish paper [2] asked:
"Cadmium in tobacco smokers: a neglected link to lung disease?"
Leafy crops tend to have a high water requirement which can result in a substantial accumulation of the heavy metals that may be in the soil. The tobacco leaf has long been recognized as having cadmium.
From a 1976 Swedish study [3]:
"Based on the more pronounced cadmium accumulation among smokers than nonsmokers, the respiratory absorption rate of cadmium from tobacco smoke is estimated to be approximately 50%."
A 1983 German paper [4] seems at pains to downplay the significance of cadmium in the modern cigarette:
"In the literature, cadmium concentrations in tobacco of between 0.5 and 5 ppm are reported. Modern German cigarette tobacco contains about 0.5-1.5 micrograms cadmium/cigarette. Of importance for the smoker is the amount of the metal in the mainstream smoke. The cadmium level in the mainstream smoke of modern cigarettes is reduced by means of filters and other construction features. The average Cd value of German filter cigarettes is less than 0.1 microgram/cigarette in mainstream smoke."
However: "An average daily intake of about 1 microgram cadmium by smoking 20 cigarettes can be calculated on the basis of an experimentally proved pulmonary retention rate of 50%."
Cadmium isn't cleared from the body to any great degree & 1 microgram every day might result in significant accumulation.
"Kipling and Waterhouse [5] (1967) reported that among 248 workers with a minimum of one year's exposure to cadmium oxide the expected number of prostatic cancers was 0.58, and 4 were observed."
"A similar type of study [6] was performed on 272 cadmium smelter workers in the USA (1976). The average cancer mortality rates for the whole of USA was used to calculate expected numbers. For all cancers the SMR was 154 ... The highest SMR was found for prostatic cancer (SMR = 347) (1.15 cases expected, 4 cases observed)."
Cadmium accumulates in the prostate. "Cadmium is considered a significant prostate cancer risk factor as it stimulates the growth of prostate epithelial cells and promotes their malignant transformation." [7]
Selenium appears to be protective of the prostate when cadmium is present. It appears that selenium & cadmium form a complex. This inactivates the selenium, so a greater intake of selenium might be required for optimum benefit. (Yes, we all remember the SELECT trial, but I'm not suggesting more than a minimal dose.)
"The excessive accumulation of Cd in the prostates of smokers along with sub-optimal Se intakes could explain why smokers develop more aggressive and lethal forms of prostate cancer than nonsmokers." [7]
Zinc is also protective against cadmium.
"Among men with zinc intake less than the median level of 12.67 mg/day, an increase in 1 microg/g creatinine cadmium exposure was associated with a 35% increase in PSA level. In contrast, among men with greater than median zinc intake, little evidence for an association between cadmium and PSA was found." [8]
One potential problem of cadmium exposure is that some of the changes that occur in prostate cells are epigenetic. "These heritable epigenetic changes include DNA methylation, post-translational modifications of histone tails (acetylation, methylation, phosphorylation, etc), and higher order packaging of DNA around nucleosomes." [9]
...
The new meta-analysis [10] that prompted this post ostensibly has nothing to do with cadmium:
"A total of 5157 reports were identified, of which 16 articles were selected for qualitative analysis and 11 articles were selected for quantitative analysis. All included studies were observational and nonrandomized and comprised a total of 22 549 patients. Overall, 4202 patients (18.6%) were current smokers. The overall median follow-up was 72 months. Current smokers had a statistically significantly higher risk of biochemical recurrence (HR, 1.40 ... [10 studies]), as did former smokers (HR, 1.19 ... [7 studies]). Current smokers were also at a higher risk of metastasis (HR, 2.51 ... [3 studies]) and cancer-specific mortality (HR, 1.89 ... [5 studies]), whereas former smokers were not (metastasis: HR, 1.61 ... [2 studies]; cancer-specific mortality: HR, 1.05 ... [4 studies])."
...
To sum up:
Smokers have increased exposure to cadmium, which can accumulate in the prostate. Cadmium is now recognized as being seriously carcingenic. Selenium & zinc offer some protection.
IMO sodium selenite is the preferred form of selenium:
swansonvitamins.com/nutrico...
& I favor zinc citrate at 50 mg:
swansonvitamins.com/nutrico...
Ironically, cadmium is often found with zinc. In the past, a number of zinc supplements were found to have unacceptable levels of cadmium. Be wary of the cheaper products.
-Patrick
[1] ncbi.nlm.nih.gov/pubmed/287...
[2] ncbi.nlm.nih.gov/pubmed/295...
[3] ncbi.nlm.nih.gov/pubmed/999342
[4] ncbi.nlm.nih.gov/pubmed/685...
[5] thelancet.com/journals/lanc...
[6] ncbi.nlm.nih.gov/pubmed/106...
[7] ncbi.nlm.nih.gov/pubmed/157...
[8] ncbi.nlm.nih.gov/pubmed/180...
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