Research Perspective and Comments & Analysis
Setting The Record Straight On Pesticide Residues
By Dr. Carl L. Keen, Professor Of Nutrition And Internal Medicine, University Of California, Davis
Physicians, government agencies, nutritionists and environmental groups collectively agree the health benefits of eating a diet rich in fruits and vegetables outweighs the theoretical risks from the pesticide residues that can be found on these foods — when the measured residue levels are within the acceptable limits set by the FDA. This position is supported by numerous peer-reviewed toxicology studies and decades of nutrition research. Regrettably, recent surveys show many consumers believe the opposite position is true and that residues can pose a significant health risk. Cancer is among key consumer concerns.
Recently, my colleagues and I examined the theoretical cancer risk, and benefits associated with a potential increase in the consumption of conventionally grown fruits and vegetables. We began by conducting an analysis of the potential number of cancer cases that might be prevented if half of the U.S. population increased its fruit and vegetable consumption by one serving per day. This number was contrasted by an upper-bound estimate that might be theoretically attributed to the intake of pesticide residues arising from the same level of additional fruit and vegetable consumption.
Our analysis indicated approximately 20,000 cancer cases would be prevented each year by increasing fruit and vegetable consumption by a single serving, while less than 10 cases of cancer would be added as a consequence of an increased consumption of pesticide residues. (Estimated cancer cases from residues are likely an over-estimate of the risk, but we chose to take a conservative approach.) While the concept of benefit/risk calculations is often difficult to embrace, the dramatic difference between benefit and risk estimates for consuming foods with detectable, but allowable, pesticide residues should provide confidence that consumers do not have to be unduly concerned about cancer risk from consuming conventionally grown produce.
Following peer review, a paper summarizing our methodology and findings was published in the Journal of Food and Chemical Toxicology in the fall of 2012. It is our hope this information will be useful for nutritionists and other health professionals who are concerned about the potential negative effects of pesticide residues on fruits and vegetables. We suggest this approach provides a practical way to evaluate risk-benefit issues as they relate to foods, and that it provides an example as to how one might discuss this concept with patients and/or concerned consumers.
Peer-reviewed research consistently indicates a diet rich in fruits and vegetables reduces the risk of certain diseases, improves overall health and leads to a longer life. A recent study from the University College of London published in the Journal of Epidemiology and Community Health in March 2014 found people who consumed seven or more servings of fruits and vegetables daily reduced their risk of premature death by 42 percent. That study also found this level of produce consumption reduced the risk of heart disease by 31 percent and cancer by 25 percent.
Importantly, this study and our study found even slight increases in produce consumption can have a significant impact on health. Their results suggest by eating just one to three servings per day, you reduce your risk of premature death by 14 percent and by 29 percent if you eat three to five servings. Because of these results, the study’s lead author stated: “We all know that eating fruit and vegetables is healthy, but the size of the effect is staggering.”
So why are consumers’ risk/benefit perceptions about produce safety skewed in the wrong direction? One hypothesis is over the past several years consumers have been repeatedly exposed to negative messages regarding the safety of conventionally grown fruits and vegetables. These foods are often referred to as “dirty” or “toxic laden.” This messaging, often aggressively promoted, has almost become mainstream thinking. While the motivations underlying such messaging are typically well intentioned, the result may be that food safety fears have created an inappropriate barrier to increasing the consumption of these healthy foods. This factor has an undermining effect on public health initiatives, which promote healthier eating. For individuals who work in public health, advise patients and/or consumers regarding nutrition, or are part of the scientific community, it is important we engage in issuing our messages to consumers to regain accurate risk/benefit perceptions among consumers. That message is quite simple:
• There is uniform and widespread agreement among health experts that consumption of fruits and vegetables needs to be substantially increased.
Measuring Risk Is Risky Business
The issue of pesticides and produce consumption is a long running one. Before the great Spinach Crisis of 2006 brought the issue of pathogen contamination to the forefront, this columnist spent many a year traveling around the country cautioning trade and consumer groups that concerns over pesticide residues were overblown and that the real problem would be pathogens. This position was vindicated by the pathogen-related episodes of recent years.
Now the pendulum of concern is swinging back to pesticides. It certainly doesn’t help to have groups, such as the Environmental Working Group, coming out annually with its “Dirty Dozen,” and clearly this is scaremongering and fundraising more than science. After all, the very concept of a “Dirty Dozen” is inherently something the industry can never be rid of. Even if the industry reduced pesticide residues by 99 percent tomorrow on all items, there would still be a dozen items that would make this list as the most “dirty” — obviously such calculations bear no reference to risk.
Yet we doubt that these groups and their activities explain consumer attitudes toward pesticides. These attitudes are better explained by the way human beings process risk. People who think nothing of hopping in their cars and zooming off to the nearest farmers market fear the risks of flying in commercial airplanes, which are statistically much safer. Similar dynamics are expressed regarding irradiation of food, GMOs, the proximity of nuclear power plants, cell phone towers and much more.
Most humans are just not very good at doing probabilities, so they enter the lottery and worry about being killed during a shark attack.
The gist of this study is it provides research support for the standard public health message, which is: All the research done shows a health benefit to consumption of produce, and all that research was done with conventional produce. Therefore, when calculating any negative effects from pesticides (or anything else), there is a net positive benefit, and a substantial one, to consuming more fruits and vegetables.
One question is whether the risk of exposure to pesticides is properly calculated here. Organic produce is not grown without pesticides; it just uses only approved pesticides. To properly compare organic to conventional, one needs to compare the risks of each mode of production.
Another question is whether we actually need to worry about the fact that there are scaremongering groups out there. It is annoying to the industry, but is it actually causing a decline in consumption? This research does not address this question.
The authors point out that there is negative messaging and then say “…the result may be that food safety fears have created an inappropriate barrier to increasing the consumption of these healthy foods.”
This “may” be true, but it “may not.” It may push some people into buying organic, and since organic is more expensive, they may buy less. Yet they may also be happy with their choice and buy more.
We have no legitimate studies showing a statistically significant percentage of people who have been exposed to this negative messaging deciding to eat less produce and replace fruits and vegetables with candy bars or meat. Many alternative products have negative perceptions of their own, so it is not clear that consumers will process a belief that there are risks, even disproportionate risks, to mean that they are better off eating other products.
Perhaps the industry should focus on clarifying its own health message.
The assertion is that eating “more produce” is healthier. Yet, once again, we have actually never seen a study that says exactly that.
Imagine a person is at weight stasis consuming 2,600 calories a day. Now, upon hearing he should “eat more produce,” he decides to force himself to have six additional pieces of fruit before he goes to bed, say 500 calories total. Standard tables showing a pound of fat equals 3,500 calories indicates this person will gain 52 pounds a year. Is anyone really claiming that this will enhance health?
In truth, the studies that do exist do not just say eat more produce. They say eat less of other things and replace the caloric content with produce — which is a very different message.
It is also true that many of our outreach efforts focus solely on sweet fruit, which is easy to love. Turning children and others onto more bitter vegetables may wind up being an important challenge for the industry to address if we really want to use produce to boost public health efforts.