Does choosing organic over conventional foods protect against cancer? What are the effects of pesticides on cancer risk?
In a review of the growing evidence on human exposure and pesticide toxicity, the evidence linking pesticide exposure to cancer is said to be so overwhelming that the role of pesticides in the development of cancer is “unquestionable.” However, most of the evidence showing DNA damage from pesticides comes from occupational exposure among farmers and field workers, the pesticide industry itself, or those living in high-spray areas, as you can see at 0:35 in my video. Pesticides and Cancer Risk.
There is evidence linking non-professional pesticide exposure to DNA damage—in this case, the separation of single- and double-stranded DNA in the sperm of men with high levels of pesticides circulating in their bodies—but that was in China, where average pesticide concentrations are four times higher than in other parts of the world.
Another way pesticides may help tumor growth is as a side effect of cancer vaccines. Natural killer (NK) cells are our body’s first line of defense against cancer cells and virally infected cells. Pesticides have been shown to cause harmful effects on these immune cells, reducing their ability to kill tumor cells. For example, if you put a bunch of NK cells in a petri dish with human leukemia cells without pesticides, your natural killer cells can clean house and wipe out more than half of the cancer. But if you drip pesticide on it, the NK cells are so disabled that the cancer wins the day, as you can see below and at 1:37 in mine. video.
But how much pesticide are we talking about? The researchers used the highest level found in people actively spraying pesticides. But what about looking at residual pesticides left in common products? Is choosing organic to prevent cancer worth the investment?
Pesticides are detectable in the blood and urine of more than 90% of the US population, regardless of where they work or live. We know it comes from the food we eat because crossover experiments where people are switched between eating conventionally grown food and organic food show that you can turn the urinary concentration of pesticide metabolites on and off like a light switch. But that doesn’t mean pesticides are bad for us.
The health consequences of ingesting pesticide residues from conventionally grown foods are not yet known, but a recent study found that people who reported a higher frequency of eating organic foods had a 25% lower risk of developing cancer. This study is the first to examine the relationship between frequency of organic food consumption and cancer risk, controlling for a number of other factors. Doesn’t it matter that organic consumers are young? The researchers controlled for that and still found a very low cancer risk. But maybe organic consumers get less cancer because they are richer or more educated or have thicker skin, or maybe they exercise more or eat less meat or smoke less. No, the researchers controlled for all of that and still found a significantly lower cancer risk in organic consumers. Maybe their diet was different in other ways, though—more fruits and vegetables overall, or less junk food? No, they still found a very low cancer risk. The researchers concluded, “Our results show that higher consumption of organic foods is associated with a lower overall cancer risk.”
That was the most complex study of its kind to date, but there was an earlier study that was even larger, and it found little evidence of a reduction in the number of all cancers except perhaps one type of blood cancer—non-Hodgkin lymphoma. You can see the data below and at 3:59 in mine video.
The data show no difference in overall cancer rates between those who never choose organic and those who do often or regularly; the only significant results were a lower risk of non-Hodgkin lymphoma and an increased risk of breast cancer. Could it be that women who choose an organic diet are more vigilant about breast cancer screening, and that explains the higher rate of diagnosis? We really don’t know.
Of course, our main concern is not just cancer but the cause of death—the risk of premature death. As it turns out, high blood levels of the pesticide known as beta-hexachlorocyclohexane are associated with significantly shorter life spans. How do we lower our standards? Decades ago, there was a study that found that the breast milk of a vegetarian mother had less beta-hexachlorocyclohexane than the milk of her non-vegetarian sister, who was also breastfeeding at the time. The vegetarian sister apparently had levels of that pesticide that were about a third lower, compared to her meat-eating sibling, as you can see below and at 4:48 in mine. video.
That’s not surprising, since this class of chlorinated pesticides is fat soluble, so they’re mostly found in animal foods.
A recent study failed to look at beta-hexachlorocyclohexane, but did look at polychlorinated biphenyls (PCBs) and found they were linked to an increased risk of death. Also, toxins are found in the same types of foods: eggs, dairy products, and animal fats. Therefore, it is not surprising that the blood of those who eat a vegan diet was found to be “less contaminated than animal animals” in terms of a whole series of PCBs, including those found in studies associated with increased mortality; but vegans did not have lower levels of beta-hexachlorocyclohexane.
Bottom line: If you are concerned about the negative health effects of pesticides and pesticide-type compounds, you may want to reduce your intake of animal products. But when it comes to fruits and vegetables, the benefits of eating organically grown produce probably outweigh any potential risks of pesticide exposure. Therefore, concern about the dangers of pesticides should not stop us from stuffing our faces with as many fruits and vegetables as possible. That would give us a huge health benefit, while the potential lifelong damage of any pesticides on those same fruits and vegetables has been estimated to shorten a person’s lifespan by just a few minutes, on average, which is nothing compared to the nutritional benefits of eating more fruits and vegetables.
Doctor’s Note
For more on organic food, see the related posts below.
