from our newsletter, broadcast on
Wednesday May 28, 2014
There is little or no decrease in the incidence of cancer associated with consumption of organic food, according to a recent large prospective study from The University of Oxford and published in the British Journal of Cancer. The study found that, with the exception of non-Hodgkin lymphoma, there was no clear evidence to support the belief that the risk of cancer is lower in people who mainly choose organically produced foods than in people who eat conventionally produced foods.
The main reason why consumers buy organics is because they perceive them to be healthier. While organic foods have roughly the same amount of nutrients as conventionally grown foods (organic have a higher amount of phosphorus), organics are less likely to be contaminated by detectable pesticide residue. Pesticide exposure has been linked, not conclusively, to certain cancers, particularly non-Hodgkin lymphoma, soft tissue sarcoma, and breast cancer.
“There are many reasons why people may choose organic food, including their beliefs on potential benefits for taste, health and the environment. It has been suggested that pesticide residues in non organically-produced food might increase the risk for cancer. This is the only large study to address this question. Our paper does not show evidence of any overall reduction in risk of cancer,” says Professor Tim Key, study author.
Researchers looked at the relationship between the reported frequency of consumption of organic food and subsequent cancer incidence, both overall and for 17 individual cancer sites or types in a large prospective study of middle-aged women in the United Kingdom.
At the beginning of the study, 30% of women reported never eating organic food, 63% reported sometimes eating organic food and 7% reported usually or always eating organic food. When researchers followed up these woman nine years later, they found 53,769 cases of cancer. Compared with women who reported never eating organic food, there was actually a small increase (9%) in risk of breast cancer in women who reported always eating organics. Socio-economic status and whether or not the woman was a smoker had no effect on the results.
Now, interestingly, women who reported always or usually consuming organics were more likely to participate in physical activity, and less likely to smoke or eat red meat and processed meat than those women who never consumed organic food. However, these women also consumed more alcohol and had fewer children – factors associated with an increased risk of breast cancer. At the same time, the women in this category are more likely to have attended breast cancer screenings, and therefore would be more likely to be diagnosed.
“The association with breast cancer was statistically significant but very small in magnitude. There is no hypothesis suggesting that organic food would increase breast cancer risk. The small association may well be due to ‘residual confounding’ – we adjusted as carefully as possible for other known risk factors for breast cancer, some of which were more prevalent in the women who chose organic food, but it is difficult to completely eliminate the impact of this type of confounding. So we cannot say with certainty why this small increase in risk is present, but it is unlikely to be due to any real hazard,” says Key.
Meanwhile, epidemiological studies have reported higher risks of soft tissue sarcoma among farmers and forestry workers, possibly resulting from exposure to pesticides. Researchers in this study found no significant association between organic food consumption and risk of soft tissue sarcoma. The only reduced cancer risk (by 21%) found was for incidence of non-Hodgkin lymphoma in women who usually or always ate organic food compared with women who reported never eating organic food.
Exposure to pesticides in the general population is mainly from residues on food, and both the U.S. and the UK regularly test levels in the food supply. The concentration, however, is generally found to be low. In fact, a recent report from the UK Pesticide Residues Committee, for the quarter ending December 2012, shows that pesticide residues were detected in 30% of food samples tested, but were above the maximum permitted level in only 1% of the food samples.
In a similar review performed by the USDA’s Pesticide Data Program (PDP), the 2012 data summary shows that when pesticide residues are found in/on foods, they are nearly always at levels below the tolerances set by the EPA. Excluding water, residues exceeding the established tolerance were detected in 0.53% of the samples, and 4.3% of the samples had residues with no established tolerance for the specific commodity tested.
“The result of our analysis was no overall difference in cancer risk by reported organic food consumption, suggesting that choosing organic foods is unlikely to affect an individual's overall risk of cancer. The results for non-Hodgkin lymphoma suggest that there could be a reduction in risk for this one type of cancer (which would not be big enough to influence the overall cancer risk), but the results from this single study are not nearly enough to establish this, and more research will be needed to confirm if there is indeed a link,” adds Key.
Click here to download a link to the USDA’s 2012 PDP Report.