Nitrate in tap and bottled drinking water may be a risk factor for prostate cancer

Nitrate is present in tap water and bottled water, largely due to the use of fertilizers in agriculture and the manure produced by intensive livestock farming.

The nitrate ingested during a person’s adult life through the consumption of tap and bottled water may be a risk factor for prostate cancer, especially in the case of aggressive tumors and in younger men. This is the conclusion of a study conducted in Spain and led by the Barcelona Institute for Global Health (ISGlobal), a center supported by the “la Caixa” Foundation. The findings were published March 8 in the journal Environmental Health Perspectives.

The study also suggests that diet plays an important role. The researchers discovered that eating a lot of fiber, fruit/vegetables and vitamin C could reduce the negative effect of nitrate in drinking water.

Ingestion of waterborne nitrate and trihalomethanes

The aim of the study was to assess whether there was an association between the intake 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 rainfall. “Nitrate is a compound that is part of nature, but we have changed its natural cycle,” explains Cristina Villanueva, an ISGlobal researcher specializing in water pollution. The new study looked at whether long-term exposure to nitrite during adulthood could lead to cancer.

THMs are by-products of water disinfection, ie chemical compounds formed after drinking water has been disinfected, usually with chlorine. Unlike nitrate, for which the only route of entry is through the mouth, THMs can also be inhaled and absorbed through the skin while showering, swimming in pools, or washing dishes. Long-term exposure to THMs has been associated with an increased risk of bladder cancer, but evidence of the relationship between THMs and other types of cancer is very limited to date.

Prostate cancer and long-term exposure to nitrate and THMs in drinking water

To evaluate the possible link between prostate cancer and long-term exposure to nitrate and THM 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 38-85 years who had not been diagnosed with cancer at the time of the study. The average nitrate and trihalomethanes each participant had been exposed to since age 18 was estimated based on where they had lived and the type (tap water, bottled water or, in some cases, spring water) and the amount of water they had drunk during Their whole life. Estimates are based on available data from drinking water controls carried out by municipalities or concessionaires, from analyzes of bottled water of the most widely distributed brands, and from measurements at various Spanish locations supplied by groundwater.

The findings showed that the higher the nitrate intake, the greater the association with prostate cancer. Participants with a higher intake of nitrate via water (life average of more than 14 mg per day) were 1.6 times more likely to develop low- or intermediate-grade prostate cancer and almost 3 times more likely to develop an aggressive prostate tumor than participants with a lower nitrate intake (lifetime average of less than 6 mg per day).

“It has been suggested that aggressive prostate cancers, which are associated with a poorer prognosis, have underlying etiological causes other than slow-growing tumors with an indolent course, and our findings confirm this possibility,” said ISGlobal researcher Carolina Donat-Vargas, lead author of the study. “The risks associated with the intake of nitrate through water are already observed in people who consume water with a nitrate content below the maximum level allowed by European guidelines, which is 50 mg nitrate per liter of water.”

Drinking water does not mean you will get cancer

The authors noted that this study provides only the first evidence of the association, which needs to be confirmed by further research. So there is still a long way to go before we can establish a causal relationship. “Exposure to nitrates through drinking water doesn’t mean you’re going to get prostate cancer,” said Donat-Vargas. “Our hope is that this study, and others, will encourage a review of permitted nitrate levels in water to ensure there are no risks to human health.”

Although dietary intake of THMs was not associated with prostate cancer, THM concentrations in domestic tap water have been associated with the development of these tumors, suggesting that inhalation and dermal exposure may play an important role in overall exposure . Further studies that correctly quantify exposure to THMs through multiple pathways are needed to draw definitive conclusions.

Fiber, fruits, vegetables and vitamin C to prevent prostate cancer

Participants also completed a food frequency questionnaire, which provided individual nutritional information. A striking finding of the study was that the link between ingested nitrate and prostate cancer was only observed in men with lower intakes of fiber, fruits/vegetables and vitamin C. “Antioxidants, vitamins and polyphenols in fruits and vegetables can reduce the formation of nitrosamines – compounds with carcinogenic potential – in the stomach,” explained Donat-Vargas. “In addition, vitamin C has shown significant anti-tumor activity. And fiber, in turn, benefits the gut bacteria, which protect against food-derived toxins, including nitrosamines. In participants with a lower fiber intake (=11 g/day), a higher nitrate intake increased the risk of prostate cancer by a factor of 2.3. However, in those with a higher fiber intake (>11 g/day), a higher nitrate intake was not associated with an increased risk of prostate cancer.

The research team hopes this study will help raise awareness of the potential environmental and human health impacts of pollutants in water, and convince authorities to ensure tighter control of this natural resource. Measures proposed by the study’s authors to reduce nitrate levels include “ending the indiscriminate use of fertilizers and pesticides” and encouraging diets that prioritize the health of the planet through the consumption of reduce animal products. 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 tumors diagnosed. 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. The currently recognized risk factors – age, ethnicity and family history – cannot be changed. However, it is suspected that certain environmental exposures may contribute to the development of prostate cancer, especially in the advanced and more aggressive forms. Therefore, it is vital to continue researching the environmental factors that may contribute to the development of this cancer so that action can be taken to prevent it.

Reference: “Long-term exposure to nitrate and trihalomethanes in drinking water and prostate cancer: a multi-case 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.
DOI: 10.1289/EHP11391