Does Eating Organic Reduce Cancer Risk?
A recent study claims to confirm what a lot of people felt they already knew: eating organic can reduce your risk of getting cancer. But a closer look at the details reveals a different story.
Monica Reinagel, MS, LD/N, CNS
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Does Eating Organic Reduce Cancer Risk?
When you ask people about the safety of our food supply, pesticides nearly always top the list of concerns. Specifically, people worry that exposure to pesticides in their food increases the risk of cancer.
On a gut level, this seems like a no-brainer. When we consume food that has been treated with pesticides, we consume trace amounts of these chemicals. And many of these compounds have been categorized as possible or probable carcinogens. How could taking in more pesticides NOT increase our cancer risk?
And yet, the available evidence didn’t seem to line up with this seemingly obvious conclusion. In 2014, for example, a ten-year study of more than a half million British women found that those who always ate organic food had essentially the same risk of getting cancer as those who never did.
This year, however, a French study seemed to find the opposite. Researchers analyzed the diets of almost 70,000 people and concluded that “a higher frequency of organic food consumption was associated with a reduced risk of cancer.”
Finally, a study confirmed what a lot of people felt that they already knew: eating organic can reduce your risk of getting cancer. Duh. Case closed.
Having looked at the details of this study, I’m not ready to close that case just yet. But before we dig into that, let’s take a brief detour to examine another closely-related belief: Eating more fruits and vegetables reduces cancer risk.
Why Would Eating Fruits and Vegetables Decrease Cancer Risk?
According to the FDA’s Pesticide Monitoring Program, your biggest dietary exposure to pesticides is from the non-organic fruits and vegetables you consume. The more non-organic fruits and vegetables you eat, the higher your likely pesticide exposure. And pesticides give you cancer, right?
And yet, some studies suggest that people who eat more fruits and vegetables have lower incidence of cancer—even if they are eating conventional fruits and vegetables.
For example, a long term study of almost 200,000 women found that those who averaged five or more servings of fruits and vegetables a day cut their risk of breast cancer by 10% compared with those who ate 2.5 servings a day or fewer (which is close to average intake).
Now, a 10 percent reduction in risk is fairly modest. Instead of 10 out of 200 women getting a breast cancer diagnosis, only nine out of 200 did. Still, if you’re that one who dodged the bullet, those extra servings of peas and carrots will probably seem more than worth it.
Other studies have found only a weak association between fruit and vegetable consumption and cancer risk—or none at all. This surprises a lot of people. After all, we talk so much about all the cancer-fighting phytochemicals found in fruits and vegetables. You’d think the cancer fighting effect of eating them would be more dramatic.
I think the link between fruit and vegetable intake and cancer risk might be more indirect. Eating more fruits and vegetables can help you maintain a healthier body weight—and that is unequivocally associated with lower cancer risk.
But the point I’m trying to make here is that if pesticide exposure increased cancer risk, we might expect to see more cancer in people who ate more conventionally-grown fruits and vegetables, because their exposure to pesticides would be larger. And yet this does not appear to be the case. While eating more fruits and vegetables may not reduce your cancer risk as much as we might have hoped, it certainly doesn’t increase it.
So with that in mind, let’s look at the details of this French study.
Does Buying Organic Reduce Your Pesticide Exposure?
The authors (like many consumers) hypothesized that those who ate a lot of organic foods would have a lower risk of developing cancer because of a lower exposure to pesticide residues.
To test this hypothesis, the researchers came up with something called the Organic Food Score. To calculate this, they asked participants to say how often they consumed 16 different categories of organic foods. If you usually consumed a category of organic food, you got two points. Consuming organic sometimes got you 1 point, and never eating organic for that category earned you 0 points. The points for all 16 categories were then tallied up for a score from 0 to 32.
Although each category was weighted equally in the score, they were hardly equivalent in terms of their potential pesticide load. For example, two of the 16 categories (dairy products and eggs) are foods that generally have no detectable pesticide residues.
Asking how frequently someone chooses organic instead of conventional also doesn’t really tell you anything about how much someone is consuming. Some of the categories in the organic food score are things that you might consume occasionally or in very small quantities, such as condiments, herbal tea, or vitamin supplements. Other categories are daily staples like bread and milk. How can these contribute equally to your organic food score?
If I drink only organic wine and take only organic vitamins, but never eat organic fruits and vegetables, I’d get the same score as someone who ate only organic fruits and vegetables but settled for conventional marmalade and coffee.
The authors wanted to test their hypothesis that reduced exposure to pesticides would be associated with a lower cancer risk. But, in my opinion, the Organic Food Score that they developed is an extremely poor proxy for pesticide exposure.
But perhaps people who buy organic foods more frequently (or at least say that they do) have a lower risk of cancer for reasons that have nothing to do with pesticides. High scores on the Organic Food Score might reflect more disposable income, or greater health consciousness, or beliefs or fears about food and health—all of which may in turn be associated with other healthy habits.
And, in fact, the researchers found that “a higher frequency of organic food consumption was associated with a reduced risk of cancer.” Those with the highest organic food scores had a 25% reduction in cancer risk compared those with the lowest. That was the headline.
But if you look more closely, you’ll find there are some really weird things about this data. If organic food consumption (or pesticide exposure) were associated with cancer risk, you’d expect to see some sort of dose effect: the more organic foods you eat, the lower the risk. And for certain kinds of cancers, this was the case.
For example, with skin cancer, the risk went down as the organic food score went up. But for other types of cancer, including colorectal cancer, prostate cancer, and premenopausal breast cancer, those with organic food scores in the middle of the range had a higher risk than those with the lowest scores.
Here’s a graph that might make it easier to see what I’m talking about.
Perhaps the strangest case is for non-Hodgkins lymphoma. Those in the highest category, with average organic food score of 19, had an 86% reduction in risk compared to those in the lowest category, who had an average score of less than 1. But those in the second highest category, whose scores averaged 10, had a 20% increase in risk compared to those with scores of less than 1. To me, that’s a red flag for some funky data.
Then again, when you consider how the organic food score was derived, it makes sense that the relationship between that score and cancer risk would be all over the place. Because asking people how often they buy organic wine or coffee is not a very effective way to assess their dietary pesticide exposure.
To their credit, the researchers also calculated a simplified score based only on the six categories of foods that represent the major sources of dietary pesticide exposure: fruits, vegetables, soy-based products, grains and legumes, breads and cereals, and flour. Unfortunately, the results of this secondary analysis were just as problematic; those with higher organic scores (suggesting lower pesticide exposure) frequently had much greater risk than those with lower scores.
The Bottom Line
Despite the hoopla and headlines that accompanied this study, I don’t think these results make a very strong case that eating organic reduces your cancer risk. The best evidence to date indicates that eating fruits and vegetables is (mildly) protective, irrespective of whether they are conventional or organic.
There may be other good reasons to buy organic produce, such as reducing the amount of synthetic pesticides that wildlife and agricultural workers are exposed to or supporting your local organic farmer. By all means, choose organic when it’s available, affordable, and as fresh as the conventional options. Just promise me that you won’t limit your intake of fruits and vegetables due to concerns over pesticides. If you’re worried about your cancer risk, that energy would be far better spent pursuing a healthy body weight and an active lifestyle.
In the Nutrition Diva archives, I have episodes on the five most important things you can do to reduce your cancer risk, as well as tips on how to reduce your exposure to pesticides. And if you have questions or comments about today’s episode, I’d love to hear from you. You can post those below or connect with me on Facebook or Twitter.
About the Author
Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes’ most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation’s leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.