In the drinking water we drink, whether it comes from the tap or bottled, there are nitrates and trihalomethanes (THMs), two contaminants that may constitute a risk factor for prostate cancer, according to research carried out in Spain and led by the Barcelona Institute for Global Health (ISGlobal). Long-term exposure to these substances through ingesting water during adult life can contribute to the development of this type of cancer, especially in the case of aggressive tumors in young men.
The causes of prostate cancer are still not well known and the International Agency for Research on Cancer (IARC) has not identified a clear carcinogenic agent, but it is suspected that exposure to certain environmental factors may influence its appearance, especially in the more aggressive tumors with a worse prognosis.
The nitrate contained in the water usually comes from the fertilizers used in agriculture and from the excrement generated by intensive livestock farming and which is washed away by rain to the rivers and aquifers. The study also found that diet can play a key role in reducing its harmful effects, since a diet rich in fiber, fruits and vegetables, or vitamin C can counteract its negative impact on health. His findings have been published in Environmental Health Perspectives.
“It has been suggested that aggressive prostate cancers have different underlying etiologic causes than slow-growing tumors, and our findings confirm this possibility.”
Nitrate “is a compound that is part of nature, but we have altered its natural cycle,” explains Cristina Villanueva, an ISGlobal researcher specializing in water pollution. THMs are by-products that are generated after disinfecting water for consumption, generally with chlorine, and we can also inhale them or absorb them through the skin when we shower or bathe in swimming pools, or while washing dishes. Continued exposure to THMs had already been associated with increased risk of developing bladder cancer.
Prostate cancer associated with contaminants in drinking water
The authors of the study studied 697 prostate cancer patients in Spanish hospitals between 2008 and 2013 (97 of whom had aggressive tumors), and another 927 men between the ages of 38 and 85 who had not been diagnosed with cancer at the time of the study. study and who acted as a control group. Data such as where they had lived and how much water (tap, bottled, or even well) they had drunk allowed the researchers to estimate the average amount of nitrate and trihalomethanes each had been exposed to since they were 18 years old.
The results showed that the more amount of nitrate an older person had ingested was the association with prostate cancer. In men with a higher intake of nitrate through water (more than 14 mg/d on average throughout life) the probability of developing a low- or medium-grade prostate tumor was multiplied by 1.6, and nearly threefold the odds of developing an aggressive prostate tumor, compared with study participants with lower nitrate intakes (less than 6 mg/day on average over the lifetime).
“It has been suggested that aggressive prostate cancers and, therefore, with a worse prognosis, have different underlying etiological causes than slow-growing tumors with an indolent course, and our findings confirm this possibility,” explained Carolina Donat-Vargas, researcher of ISGlobal and first author of the study, who also highlights that “the risks associated with the ingestion of nitrate through water are already observed at water consumption with levels below the maximum allowed by European directives, 50 mg of nitrate per liter of water”.
Diet, an ally in the prevention of prostate cancer
These researchers have highlighted that it has not been possible to establish a causal relationship and that their findings must be confirmed with new studies. “Exposure to nitrates through drinking water does not imply that you will develop prostate cancer,” Carolina Donat-Vargas wanted to clarify, adding: “What we do hope is that this study, along with others, can contribute to the revision of the permitted levels of nitrate in the water in order to guarantee that they do not imply a risk to human health”.
THM ingestion was not associated with prostate cancer, but THM levels in residential tap water were, suggesting that inhalation and exposure through the skin could significantly influence total exposure.
Another of the findings of the study is that a good diet can help prevent prostate cancer, since the participants reported on the frequency with which they ate certain foods and it was found that the associations between ingested nitrate and prostate cancer were only observed in men who consumed less fiber, fruit and vegetables, or vitamin C. “The antioxidants, vitamins, and polyphenols in fruits and vegetables could act as inhibitors of the formation of nitrosamines in the stomach, which are compounds with carcinogenic potential ”, explains Carolina Donat-Vargas.
“On the other hand, vitamin C has shown remarkable antitumor activity,” he adds. “And fiber, for its part, benefits intestinal bacteria, which exerts a protective effect against toxins derived from food, including nitrosamines.” In individuals with lower fiber intakes (≤11g/day), a higher nitrate intake multiplied by 2.3 the probability of suffering from prostate cancer, while in those with higher fiber intakes (>11g/day ), a higher nitrate intake was not associated with a higher probability of prostate cancer.
The researchers hope that their findings will help raise awareness about the potential harmful effects of contaminants in water on the environment and human health and that those responsible will take measures to reduce nitrate levels for what they propose, for example, “to end with the indiscriminate use of fertilizers and pesticides” and promote diets that prioritize global health by reducing the consumption of foods of animal origin, especially meat.
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