Cows graze in the green grass of mountainous countryside during sunset in New Zealand.
Opinion: Ten years ago, the world’s leading cancer agency, the International Agency for Research on Cancer (IARC), concluded that nitrate was in some cases “potentially carcinogenic to humans.”
Previous Week, Authors of a report Published with a joint fund of MBIE and Fonterra. Optional in luggage “It is highly unlikely that nitrates in drinking water or in food will present an increased risk of cancer,” it said.
What is the reason for the deviation of opinion – especially since last week’s authors acknowledged that there is a viable mechanism?
First, their focus on the average New Zealander highlights the real danger posed by nitrate contamination in drinking water. in fact, 800,000 New Zealanders may be exposed to nitrates in drinking water. Above cancer-related levels in international studies.
* Nitrates in water or food potentially increase New Zealand’s risk of cancer.
* Emergency action is needed because studies have linked nitrate to birth defects.
* Bowel cancer NZ questions the link between the disease and low nitrate levels in drinking water.
* Call to prioritize nitrate management in Wyma fields.
* Is New Zealand’s drinking water dangerous? Leading international study links nitrates to bowel cancer.
The main author guessed later. That is, for people who drink nitrate-containing water near the current limit of 11.3mg per liter, their total nitrate consumption may come from drinking water.
Second, the analysis assumes that the amount of nitrate in drinking water within an hour of eating is zero health risk. The authors did not provide any new evidence to substantiate this assumption.
It is thought that antioxidants بنیادی mainly vitamin C خوراک in food, especially fresh fruits and vegetables, inhibit the binding of nitrates to the formation of carcinogenic chemicals in the digestive system.
However, there is great uncertainty around the level and frequency of antioxidant intake that is necessary for any level of nitrate consumption to reverse this process. Simply put, how many oranges do you need to eat to reduce the 1mg / L nitrate in your water?
Last week’s authors did not take into account changes in antioxidant levels. Fresh fruits and vegetables are often expensive, and this is not surprising. Vitamin C intake is related to income.. This is a major health equity problem if it relies on zero risk based food and plenty of antioxidants in the entire population.
Since the IARC published its findings, four additional epidemics investigating nitrate and colorectal cancer have been published. All three found an association between nitrate and colorectal cancer, while a study of older women in Iowa found no statistically significant association.
The largest study, with 2.7 million participants over a 33-year period, found that drinking nitrate with cancer reduced the risk of cancer by 10 times.
Critics of these studies are quick to point out their limitations without considering whether they can explain the findings, especially in the context of possible biological mechanisms.
We have published one. Fully cited blog. Outline some of our key concerns around the MBIE-Fonterra report and its findings.
Overall, the weight of the evidence, including the new report, does not support such conclusive conclusions about the potential cancer risk of nitrate contamination in drinking water.
Unsupported results harm communities concerned with the risks posed by nitrate contamination, as well as policymakers in their efforts to assess risk and policy options.
However, we fully acknowledge that there are still major research questions and uncertainties in many areas, which we are trying to answer collectively in order to protect public health.
Dr. Tim Chambers and Professor Simon Hales are in the Department of Public Health, University of Otago, Wellington.