Long-Term Nitrate Exposure in Drinking Water Linked to Potential Prostate Cancer Risk
According to a recent study conducted in Spain by the Barcelona Institute for Global Health (ISGlobal), a person's consumption of nitrate through tap and bottled water over their adult lifespan may pose a potential risk for prostate cancer, particularly in younger men, and aggressive tumors. These findings, published in Environmental Health Perspectives, highlight the need for careful consideration of nitrate intake. The study also indicates that a diet rich in fiber, fruits and vegetables, and vitamin C may help mitigate the adverse effects of nitrate in drinking water.
ISGlobal researchers sought to determine whether drinking nitrate and trihalomethanes (THMs) found in water is associated with the risk of developing prostate cancer.
Nitrate, one of the most common pollutants in water globally, originates from the application of agricultural fertilizers and the discharge of manure from concentrated livestock production and is carried into rivers and aquifers by rain. “Nitrate is a compound that is a part of nature, but we have altered its natural cycle,” said Cristina Villanueva, an ISGlobal researcher specializing in water pollution.
THMs are compounds that can be found in drinking water because of water disinfection processes, typically involving chlorine. Unlike nitrate, which is only ingested through contaminated water, THMs can also be absorbed through the skin or inhaled while showering, washing dishes, or swimming in pools. Long-term exposure to THMs has been linked to an elevated risk of bladder cancer, although research into their potential impact on other types of cancer remains limited at this time.
The research team examined 697 cases of prostate cancer (including 97 aggressive tumors) at Spanish hospitals between 2008 and 2013, along with a control group of 927 men aged 38-85 who had not been diagnosed with cancer at the time of the study. To estimate each participant's average exposure to nitrate and trihalomethanes since the age of 18, the researchers analyzed the type of water they consumed (tap water, bottled water, or well water), the amount consumed throughout their lifetime, and where they lived. The team used available data from drinking water controls carried out by municipalities or concessionary companies (private companies contracted by the public sector), as well as analyses of bottled water from widely distributed brands and measurements taken from various Spanish locations supplied by groundwater.
According to the study's findings, there is a strong correlation between the consumption of nitrate and the likelihood of developing prostate cancer. Those who had a lifetime average of more than 14 milligrams (mg) per day of nitrate through water intake were found to have a one point six times increased risk of developing low or medium-grade prostate cancer, and almost a three times greater risk of developing an aggressive prostate tumor, compared to those who had a lifetime average of less than six mg per day.
“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 study authors acknowledged that causality cannot be established from a single study, and additional research is needed to confirm any causal relationship between nitrate exposure and prostate cancer risk.
Study participants also completed a food frequency questionnaire with personal dietary information. The researchers observed a significant association between nitrate consumption and prostate cancer only in men who had lower intakes of fiber, fruits, and vegetables, and vitamin C. Fruits and vegetables' antioxidants, vitamins, and polyphenols may inhibit carcinogenic nitrosamine formation in the stomach, while vitamin C has anti-tumor activity, and fiber supports intestinal bacteria that protect against nitrosamines, the authors said. Higher nitrate consumption led to a two-point three times increase in the likelihood of prostate cancer in participants with low fiber intake, but no such association was observed in those with high fiber intake. Therefore, it's important to interpret the study findings with caution and to consider the potential role of other factors in prostate cancer development.