Consumption of bottled or tap water containing nitrates over the course of a person’s lifetime could end up becoming a risk factor for prostate cancer, a Spanish study has found.
The study, published in Environmental Health Perspectives on Wednesday, was led by the Barcelona Institute for Global Health (ISGlobal). It looked at the link between waterborne nitrate and trihalomethanes (THMs) and prostate cancer risk. Both nitrate and THMs are some of the most common contaminants in drinking water. Nitrate in drinking water is the result of fertilizers and manure from livestock farming washed by rainfall into rivers and aquifers while THMs are byproducts of water disinfection.
The research team studied 697 cases of prostate cancer between 2008 and 2013, including 97 aggressive tumors, ISGlobal said. The control group was composed of 927 men between the ages of 38 and 85 who at the time had not been diagnosed with cancer.
The team then estimated the average nitrate and THM exposure of all individuals from the age of 18. The analysis found that a higher intake of nitrate was associated with prostate cancer.
Individuals classified as having higher waterborne nitrate ingestion were found to be 1.6 times more likely to develop medium-grade or low-grade prostate cancer. They were also three times more likely to develop an aggressive prostate tumor when compared to individuals with lower nitrate intakes.
“It has been suggested that aggressive prostate cancers, which are associated with a worse prognosis, have different underlying aetiological causes than slow-growing tumors with an indolent course, and our findings confirm this possibility,” ISGlobal researcher Carolina Donat-Vargas said in a news release.
The study also found that the association between nitrate ingestion and prostate cancer was only among men who had a low intake of fiber, vitamin C, fruits, and vegetables in their diet.
Among participants who consumed less than 11 grams of fiber per day, higher nitrate intake was found to have raised the likelihood of prostate cancer by 2.3 times.
In contrast, among individuals who consumed more than 11 grams of fiber, higher nitrate intake was not associated with a greater likelihood of prostate cancer.
“Antioxidants, vitamins, and polyphenols in fruits and vegetables may inhibit the formation of nitrosamines—compounds with carcinogenic potential—in the stomach,” Donat-Vargas said.
“Moreover, vitamin C has shown significant anti-tumor activity. And fiber, for its part, benefits the intestinal bacteria, which protect against food-derived toxicants, including nitrosamines.”
Prostate cancer is the most common cancer among men in Spain, accounting for 22 percent of all tumors diagnosed in this demographic.
The American Cancer Society (ACS) estimates that there will be about 288,300 new cases of prostate cancer in the United States this year, with 34,700 deaths. About 1 in 8 men are estimated to be diagnosed with prostate cancer during their lifetime.
Older men and non-Hispanic black men are more likely to develop prostate cancer, according to the ACS. About 6 in 10 cases are identified among men aged 65 or older, while the cancer is more rare in men under the age of 40.
A 2017 study found a link between low vitamin D and prostate cancer. Men who were deficient in vitamin D were found to have more aggressive prostate cancer during surgery.
“Men with dark skin, low vitamin D intake, or low sun exposure should be tested for vitamin D deficiency when they are diagnosed with an elevated PSA or prostate cancer. Then a deficiency should be corrected with supplements,” said Adam Murphy, an assistant professor of urology at Northwestern University and lead investigator in that study.
Earlier research by Murphy and colleagues found that black men who live in areas with low sunlight are likely to have up to 1.5 times more vitamin D deficiency compared to white men.