Nitrates from tap and bottled water may play a role in prostate cancer, says a new study in Environmental Health Perspectives.
Spanish researchers studied men with and without prostate cancer to determine the connection between waterborne nitrates and prostate cancer odds. Nitrates contaminate certain water supplies via agricultural fertilizers and manure. “Nitrate is a compound that is a part of nature, but we have altered its natural cycle,” explained Cristina Villanueva, an ISGlobal researcher specializing in water pollution.
One of the key areas of focus was how nitrates impacted prostate cancer risk over the course of someone’s lifetime. For the study, 697 cases of prostate cancer were studied (including 97 aggressive tumors) against a control group of 927 men between 38 and 85 without the disease. The participants’ nitrate intake — going back to the age of 18 — was based on multiple factors, including available data from water municipalities and testing of popular bottled water brands.
Higher intake of nitrates correlated with an increased risk of prostate cancer. Subjects with greater nitrate consumption — an average of 14 mg per day or more over a lifetime — were 1.6 times more likely to get low-grade or medium-grade prostate cancer. And these men were almost 3 times more likely to be diagnosed with an aggressive prostate tumor compared with subjects who ingested fewer nitrates (6 mg or less per day over a lifetime).
“It has been suggested that aggressive prostate cancers, which are associated with a worse prognosis, have different underlying etiological causes than slow-growing tumors with an indolent course, and our findings confirm this possibility,” explained ISGlobal researcher Carolina Donat-Vargas, lead author of the study. “The risks associated with waterborne nitrate ingestion are already observed in people who consume water with nitrate levels below the maximum level allowed by European directives, which is 50 mg of nitrate per liter of water.”
On a positive note, the researchers also discovered that food may help offset the damaging effects of waterborne nitrates. In particular, high intakes of fiber, fruits, vegetables, and vitamin C were singled out as potential antidotes to nitrates in drinking water.
Findings suggest long-term waterborne ingested nitrate could be a risk factor of prostate cancer, particularly for aggressive tumors and in men <66 y old. A high dietary intake of fiber, fruits and vegetables, or vitamin C may reduce this negative effect of drinking-water nitrate. Association with residential levels but not ingested chloroform/Br-THM may suggest inhalation and dermal routes could be relevant for prostate cancer. Further studies are warranted to draw firm conclusions.