Nitrate is present in tap water and bottled water, mainly due to the use of fertilizers in agriculture and manure produced by intensive animal husbandry.
Nitrate ingested during a person’s adult life through the consumption of tap water and bottled water may be a risk factor for prostate cancer, particularly in aggressive tumors and in younger men. This is the conclusion of a study carried out in Spain and led by the Barcelona Institute of Global Health (ISGlobal), a center supported by the “la Caixa” Foundation. The results were published March 8 in the journal Environmental Health Perspectives.
The study also suggests that diet plays an important role. Researchers have found that eating plenty of fiber, fruits/vegetables, and vitamin C can reduce the negative effect of nitrate in drinking water.
Ingestion of waterborne nitrates and trihalomethanes
The objective of the study was to assess whether there was an association between the ingestion of waterborne nitrate and trihalomethanes (THMs) and the risk of prostate cancer. Nitrate and THMs are two of the most common contaminants in drinking water. The nitrate present in the water comes from agricultural fertilizers and manure from intensive livestock farming; it is washed into aquifers and rivers by precipitation. “Nitrate is a compound that is part of nature, but we have modified its natural cycle,” explained Cristina Villanueva, an ISGlobal researcher specializing in water pollution. The new study investigated whether long-term exposure to nitrite throughout adulthood could lead to cancer.
THMs are by-products of water disinfection, that is, chemical compounds formed after drinking water is disinfected, usually with chlorine. Unlike nitrate, for which the only route of entry is ingestion, THMs can also be inhaled and absorbed through the skin when showering, swimming in pools, or washing dishes. Long-term exposure to THMs has been associated with an increased risk of bladder cancer, but evidence for the relationship between THMs and other types of cancer is, to date, very limited.
Prostate cancer and long-term exposure to nitrates and THMs in drinking water
To assess the possible association between prostate cancer and long-term exposure to nitrates and THMs in drinking water, a research team led by ISGlobal studied 697 cases of prostate cancer in Spanish hospitals. between 2008 and 2013 (including 97 aggressive tumors), as well as a control group consisting of 927 men aged 38 to 85 who had not been diagnosed with cancer at the time of the study. The average nitrates and trihalomethanes that each participant had been exposed to since age 18 were estimated based on where they had lived and the type (tap water, bottled water or, in some cases, well water) and the amount of water he had drunk throughout their lives. The estimates have been made on the basis of available data from drinking water controls carried out by municipalities or concessionary companies, analyzes of bottled water of the most widely distributed brands and measurements carried out in different Spanish locations supplied by groundwater.
The results showed that the higher the nitrate intake, the stronger the association with prostate cancer. Participants with a high waterborne nitrate ingestion (lifetime average of more than 14 mg per day) were 1.6 times more likely to develop low-grade or moderate-grade prostate cancer and nearly 3 times more likely to develop an aggressive prostate tumor than participants with low nitrate intakes (lifetime average less than 6 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 results support this possibility,” said explained ISGlobal researcher Carolina Donat-Vargas, lead author of the study. “The risks associated with the ingestion of waterborne nitrates are already observed in people who consume water with nitrate levels below the maximum level authorized by the European directives, which is 50 mg of nitrate per litre. of water.”
Drinking water does not mean you have cancer
The authors noted that this study merely provides the first evidence of the association, which will need to be confirmed by further research. Therefore, there is still a long way to go before a causal relationship can be asserted. “Being exposed to nitrates through drinking water does not mean you will develop prostate cancer,” commented Donat-Vargas. “Our hope is that this study, and others, will encourage a review of permitted levels of nitrates in water, to ensure there is no risk to human health.”
Although waterborne ingestion of THMs was not associated with prostate cancer, THM concentrations in residential tap water were associated with the development of these tumors, suggesting that inhalation and dermal exposure can play an important role in total exposure. Further studies that properly quantify exposure to THMs by multiple pathways are needed to draw firm conclusions.
Fibre, fruits, vegetables and vitamin C to prevent prostate cancer
Participants also completed a food frequency questionnaire, which provided individual dietary information. A striking finding from the study is that the association between nitrate ingestion and prostate cancer was only seen in men with low fiber, fruit/vegetable, and vitamin C intake. , vitamins and polyphenols in fruits and vegetables can inhibit the formation of nitrosamines – compounds with carcinogenic potential – in the stomach,” explained Donat-Vargas. “Furthermore, vitamin C showed significant anti-tumor activity. And fiber, for its part, benefits gut bacteria, which protect against food-borne toxins, including nitrosamines. In participants with a low fiber intake (=11 g/day), a higher nitrate intake increased the probability of prostate cancer by a factor of 2.3. However, among those who consumed more fiber (>11 g/day), higher nitrate intake was not associated with an increased likelihood of prostate cancer.
The research team hopes that this study will help raise awareness of the potential environmental and human health impacts of pollutants in water, and persuade authorities to ensure tighter control of this natural resource. Among the measures proposed by the study authors to reduce nitrate levels are “ending the indiscriminate use of fertilizers and pesticides” and encouraging the adoption of diets that prioritize the health of the planet by reducing the consumption of foods of animal origin. food, especially meat.
Prostate cancer: the most common cancer in Spanish men
Prostate cancer appears to be on the rise worldwide. It is currently the most common cancer in Spanish men, among whom it accounts for 22% of all diagnosed tumors. However, its causes remain largely unknown and it is one of the few cancers for which the International Agency for Research on Cancer (IARC) has not identified a clear carcinogen. Currently recognized risk factors – age, ethnicity and family history – are not modifiable. However, it is suspected that certain environmental exposures may contribute to the development of prostate cancer, especially in its advanced and more aggressive forms. Therefore, it is essential to continue to explore the environmental factors that may contribute to the development of this cancer, so that steps can be taken to prevent it.
Reference: “Long-Term Exposure to Nitrate and Trihalomethanes in Drinking Water and Prostate Cancer: A Multicase–Control Study in Spain (MCC-Spain)” by Carolina Donat-Vargas, Manolis Kogevinas, Gemma Castaño-Vinyals, Beatriz Pérez-Gómez, Javier Llorca, Mercedes Vanaclocha-Espí, Guillermo Fernandez-Tardon, Laura Costas, Nuria Aragonés, Inés Gómez-Acebo, Victor Moreno, Marina Pollan and Cristina M. Villanueva, March 8, 2023, Environmental Health Perspectives.