What are the benefits of buying organic foods? Are they safer? Do they make you healthier?
¿Te has preguntado si existe una manera natural de bajar tus niveles de presión arterial, protegerte contra el alzhéimer, perder peso y sentirte mejor? Resulta que sí la hay. El doctor Michael Greger (FACLM), fundador de NutritionFacts.org y autor del rotundo éxito de ventas del New York Times "How Not to Die" (Comer para no morir), nos presenta la nutrición basada en la evidencia para añadir años a nuestra vida y vida a nuestros años.
Welcome to Nutrition Facts. I’m your host, Dr. Michael Greger, and I’m here to ask you, what is the most important decision you’ll make today, is it how you’ll get to work, who you’ll set up a meeting with, what friend you’ll call for lunch? Well, as it turns out, probably the most important decision you’ll make today is what to eat. What we eat on a day-to-day basis is the number one determinant of our health and longevity—literally. Most premature deaths in the United States are preventable and related to nutrition. So, we’re going to explore some smart nutrition choices based, naturally, on facts. Here, we refer to the science, the research, the available data published in the peer-reviewed medical literature right now. That’s why I wrote my book, How Not to Die, and why I created my nonprofit site NutritionFacts.org and, now, this podcast.
The benefits of consuming an abundance of conventional produce or soy foods far outweigh the risks of pesticides, but why accept any risk at all when you can choose organic?
There appears to be no consistent differences in the level of vitamins and minerals in organic versus conventionally grown produce, but organic fruits and vegetables have more phenolic phytonutrients. Here’s the research.
Are organic foods safer or healthier than conventional alternatives? Two separate questions. Some consumers are interested in getting more nutrients, whereas others are more concerned about getting less pesticides. Let’s do nutrition first. Hundreds of studies reviewed, and they didn’t find significant differences for most of the traditional nutrients like vitamins and minerals, and so concluded that despite the widespread perception that organically produced foods are more nutritious, they didn’t find robust evidence to support that perception. They did, however, find higher levels of phenolic phytonutrients.
These so-called secondary metabolites of plants are thought to be behind many of the benefits ascribed to eating fruits and vegetables and organic fruits and vegetables had between 19% and 69% more of a variety of these antioxidant compounds. The theory was that these phytonutrients are created by the plant for its own protection. For example, broccoli releases the bitter compound sulforaphane when the plant is chewed, to ward off those who would eat it. Bugs take a bite and go, ew this tastes like, broccoli! But pesticide-laden plants are bitten less by bugs and so may be churning out less of these compounds, whereas plants raised organically are in a fight for their lives, and necessarily have to produce more protection. That was the theory anyway, but we don’t have good evidence to back it up. More likely it has to do with the fertilizer. Plants given high-dose synthetic nitrogen fertilizers may divert more resources to growth rather than defense.
These antioxidants may protect the plant, but what about us? More antioxidant phytonutrients in organic vegetables and, so, yes, more antioxidant activity–but also more antimutagenic activity. They exposed bacteria to a variety of mutagenic chemicals like benzopyrene, the polycyclic aromatic hydrocarbon found in barbequed meat, or IQ, the heterocyclic amine found in grilled/broiled/fried meats as well as cigarette smoke, and there were fewer DNA mutations in the Petri dishes where they added organic vegetables compared to the Petri dishes where they added conventional vegetables.
Preventing DNA damage in bacteria is one thing, but what about effects on actual human cells? For example yes, organic strawberries may taste sweeter and better, and have higher antioxidant activity and more phenolic phytonutrients, but let’s stack them up head-to-head against human cancer cells. Extracts from organically grown strawberries suppressed the growth of colon cancer cells and breast cancer cells significantly better than extracts from conventional strawberries. Now, this was dripping strawberries directly onto cancer cells growing in a lab, but as we saw, there are real life circumstances in which strawberries come into direct contact with cancerous and precancerous lesions, reversing the progression of esophageal cancer, and so presumably organic strawberries would work even better, but they weren’t tested.
So, although in vitro studies show higher antioxidant and higher antimutagenic activity, as well as better inhibition of cancer cell proliferation, clinical studies on the impact of eating organic on human disease simply haven’t been done. Based on antioxidant phytonutrient levels, organic produce may be considered 20% to 40% healthier, the equivalent of adding one or two servings’ worth to a 5-a-day regimen. But organic produce may be 40% more expensive, so for the same money you could just buy the extra serving’s worth of conventional produce. So, from a purely nutrients-per-dollar standpoint, it’s not clear that organic foods are any better. But people may buy organic foods to avoid chemicals, not just because they are more nutritious–which brings us to the next question: Are organic foods safer?
Organic food consumption appears to reduce exposure to pesticide residues and antibiotic-resistant bacteria. Here’s why: The stated principles of organic agriculture are “health, ecology, fairness, and care” but if you ask people why they buy organic, the strongest predictor was concern for their own health or their family’s. People may spend more for organic more for selfish, rather than altruistic, motives. Although organic foods may not have more nutrients per dollar, consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria.
Food safety-wise, they found no difference in the risk of contamination with food poisoning bacteria in general. Both organic and conventional animal products were commonly contaminated with Salmonella and Campylobacter, for example. Most chicken samples were found to be contaminated either way with Campylobacter, about a third with Salmonella, but the risk of exposure to multidrug-resistant bacteria (resistant to multiple classes of antibiotics) was lower with the organic meat. So, they both may carry the same risk of making us sick, but food poisoning from organic meat may be easier for doctors to treat.
What about the pesticides? There is a large body of evidence on the relation between exposure to pesticides and elevated rate of chronic diseases such as different types of cancer, diabetes, neurodegenerative disorders like Parkinson’s, Alzheimer’s, and ALS, as well as birth defects and reproductive disorders, but they’re talking about people who live or work around pesticides. Take Salinas Valley California, for example, where they spread a half million pounds of the stuff. Daring to be pregnant in an agricultural community like that may impair childhood brain development, such that pregnant women with the highest levels running through their bodies, as measured in their urine, gave birth to children with an average deficit of about seven IQ points. Twenty-six out of 27 studies showed negative effects of pesticide on brain development in children. These included attention problems, developmental disorders, and short-term memory difficulties.
If you compare kids born with higher levels of a common insecticide in their umbilical cord blood, those who were exposed to higher levels are born with brain anomalies–and these were city kids. So, presumably this was from residential pesticide use.
Residential exposure to pesticides, like using insecticides inside your house, may be a contributing risk factor for cancers like childhood leukemia, suggesting that awareness be increased among populations occupationally exposed to pesticides about their potential negative influence on the health of their children–though I don’t imagine most farmworkers have much of a choice. Pregnant farmworkers may be doubling the odds of their child getting leukemia and increase their risk of getting a brain tumor.
So, conventional produce may be bad for the pregnant women who pick them, but what about our own family when we eat them?
Well, first of all, just because we spray pesticides on foods in the fields doesn’t mean it ends up in our bodies when we eat it–or at least we didn’t know that until this study was published in 2006.
Researchers measured the levels of two pesticides running through children’s bodies by measuring specific pesticide breakdown products in their urine. It’s clear that eating organic provides a dramatic and immediate protective effect against exposure to pesticides commonly used in agricultural production. The study was subsequently extended. Can you guess when the kids were eating organic? What about adults, though? We didn’t know, until now. Thirteen men and women consume a diet of at least 80% organic or conventional food for seven days, and then switched. And, no surprise, during the mostly organic week, pesticide exposure was significantly reduced, and not just by a little, a nearly 90% drop in exposure.
So, it can be concluded that consumption of organic foods does provide protection against pesticides, but does that mean protection against disease? We don’t know—the studies just have not been done. Nevertheless, in the meantime, the consumption of organic food provides a logical precautionary approach.
Yes, test-tube studies show advantages of organic produce, such as better cancer cell growth suppression, but what about in people, not Petri dishes?
The medical literature has been historically hostile to organic foods, blaming, in part, erroneous information supplied by the health food movement for our ignorance of nutrition, but until a few generations ago, all food was organic. So, it’s kind of ironic that what we now call conventional food really isn’t very conventional for our species.
By eating organic we can reduce our exposure to pesticides, but it remains unclear whether such a reduction in exposure is clinically relevant. I talked about some of the test-tube studies comparing health-related properties of organic vs. conventional foods—higher antioxidative and antimutagenic activity, as well as better inhibition of cancer cell proliferation, but in terms of studies on actual people rather than Petri dishes, there isn’t much out there.
Why can’t you just compare the health of those that buy organic to those that don’t? Organic consumers do report being significantly healthier than conventional consumers, but organic consumers also tend to eat more plant foods in general, and less soda and alcohol, processed meat or milk, and just eat healthier in general, so no wonder they feel so much better.
Therefore, there is an urgent need for interventional trials, or studies following cohorts of people eating organic over time. The Million Women Study in the UK, the first to examine the association between the consumption of organic food and subsequent risk of cancer. The only significant risk reduction they found, though, was for non-Hodgkin’s lymphoma. This is consistent with data showing a higher risk of developing lymphoma in those who have higher levels of pesticides stored in their butt fat, which they only looked at because studies on farmworkers found higher rates of lymphoma.
Parental farmworker exposure is also associated with a birth defect of the penis called hypospadias, and so researchers decided to see if moms who failed to choose organic were at increased risk. And indeed, they found that frequent consumption of conventional high-fat dairy products was associated with about double the odds of the birth defect. Now, this could just be because those that choose organic have other healthy related behaviors, or it could be that high-fat foods, like dairy products, bioamplify the fat-soluble toxicants in our environment.
There are two other general population studies that have raised concerns: one found about a 50% to 70% increase in the odds of ADHD among children with pesticide levels in their urine common among US children, and another that found triple the odds of testicular cancer among men with higher levels of organochlorine pesticides in their blood–90% of which comes from meat, fish, and dairy, which may help explain rising testicular cancer rates in many Western countries since World War II.
What about interventional trials? All we have in the medical literature so far are studies showing organically grown food provides health benefits to fruit flies, raised on diets of conventional versus organic produce then subjected to a variety of tests designed to assess overall fly health and, what do you know, flies raised on diets made from organically grown produce lived longer. Hmm, insects eating insecticides don’t do as well. Not exactly much of a breakthrough.
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Thanks for listening to Nutrition Facts. I’m Dr. Michael Greger.
This is an approximation of the audio content, contributed by Allyson Burnett.