Visiting Professor guest post: Organic foods

There are lots of reasons consumers give for buying organic foods, but a few reasons are very common.  Among them is the notion that organic foods are better for you.  Really?  Are organic fruits and veggies better for you?  Depends on what you mean by ‘better for you’.  But as far as we know, the answer is probably ‘no’, especially if you’re buying organic fruits and veggies (F&V) at the store.  It might seem crazy, but there’s no good evidence to support the notion that you will be more healthy by shopping for organic F&V.  There are some complicated reasons for this, and some areas we aren’t quite sure about yet, but I’ll try to explain.

If ‘better for you’ means ‘fewer pesticide residues,’ you’re right.  But if you think ‘fewer pesticide residues’ means ‘better for you,’ that gets murky.  Why do we apply pesticides?  We do it to protect our food from pests and diseases.  It’s cheaper and more productive than destroying blight-infected tomatoes, individually wrapping apples in a protective barrier, or throwing away heads of cabbage with worms.  But why do those things matter?  It turns out we’re just consumers.  Two big things we look for when buying F&V are appearance and cost.  If a person has a choice between a spotty, more expensive apple and a uniformly bright and shiny lower-cost apple, he’ll probably choose the latter.  And which would be better, buying 2 heads of cauliflower because it’s pretty and low-cost (conventional), or buying one head because it has a slight cosmetic defect and costs a little more (organic)?  You guessed it; in terms of your health, it’s more likely that 2 heads are better than 1.  If that isn’t complicated enough, consider that there are no good long-term human studies concerning the health effects of pesticide residues ingested from food.  There’s no evidence that eating conventional F&V, even with the elevated risk of consuming more pesticide residues, is worse for you than eating organic F&V.  But there is evidence that eating more F&V is better for you than eating less.  So why eat less?

Some of the best health care in Minnesota comes from the Mayo Clinic.  What?  Who cares about the Mayo Clinic?  In Minnesota, we worship the Mayo Clinic. [undeserved pride] They represent some of the finest health care in the country [/undeserved pride].  And what does the Mayo Clinic have to say about pesticides on our food?  “Most experts agree…that the amount of pesticides found on fruits and vegetables poses a very small health risk.”

But what about nutrients—don’t organic foods have more nutrients or something good in them?  Maybe they do have fewer nitrates (which may be bad for you, especially if you’re too young to read this), but that really depends on how the specific growers use fertilizers.  Maybe some organic produce tends to have more vitamin C, but that can vary too.  And even if the organic tomato you’re eating has more vitamin C than the conventional tomato you passed up, is that physiologically relevant?  Does it matter to your body?  We don’t have any good evidence that it is.

Why am I being so down on organics?  Mostly because I like to play devil’s advocate.  I buy a lot of organic F&V.  There are some reasons to buy organics that may be more legitimate than “it’s better for me”.  Sadly, research seems to indicate that I buy organic F&V to make myself feel good for buying it, not because it’s actually better for me.  But in general, eating healthy means eating more fruits and vegetables.

Charlie Rohwer is a horticultural scientist at the University of Minnesota Southern Research and Outreach Center.  He has an MS from Michigan State University and a PhD from the U of M.  He currently studies vegetables and things that make them good for you.

25 thoughts on “Visiting Professor guest post: Organic foods”

  1. There is no ironclad PROOF that eating food with pesticide residues is bad for you. But there is certainly evidence. For just one example, this.

    I guess it depends on whether you think it makes sense to exercise precaution when it comes to your health and your food intake. Right now, the regulatory system around food additives and pesticides/herbicides assumes that the chemicals are safe until they are proven otherwise. (At which point, the industry will switch to another, similar chemical which may be just as toxic but which is less well studied or at
    least less regulated. E.g. the replacement of methyl bromide with methyl idoide.)

    So what it really comes down to is: would you rather assume that all chemicals are safe until they are proven dangerous? Or would you rather acknowledge that there are limits to our understanding of the things we create, and that chemicals which have not been rigorously tested (which is the vast majority of those in use) MAY be dangerous, and as such minimizing one’s exposure is perhaps worth doing?

    Of course, this all completely sidesteps the question of the environmental and energy footprint of agriculture. But that’s another conversation…

  2. For the President’s Cancer Panel, please see “What Individuals Can Do: Recommendations” in Part 3 re: organic foods and pesticide exposure.

  3. Another reason I buy organic when I can is that I try to buy it locally as well. Sustainable local agriculture on a small scale is important to some people (including myself). I can get organic produce at the Farmer’s Market for a good price typically. Also, I agree with GreenEngineer in that we seem to assume all chemicals that increase producticity are good until proven otherwise. I like innocent until proven guilty in my criminal courts, but not necessary the food court.

  4. Sure, conventional f&v haven’t been proven worse for health, but they’ve also not been proven to NOT be worse for health. See, I can spin the words, too. And at this point, without sufficiently compelling evidence, it’s all spin. So for now, I’ll take the more cautious approach with my family’s health and assume there’s risk in each chemical use until sufficient evidence proves each individual substance safe.

  5. Laura, to be fair I don’t think Charlie is “spinning” words. Like any responsible scientist, he can only make recommendations based on solid evidence. And Joe, I’m sure Charlie would provide citations if you’d like them. (We try to keep them off the blog for the most part to keep it readable.)

  6. Like any responsible scientist, he can only make recommendations based on solid evidence.

    Of course. But when does the absence of evidence become evidence of absence (of harm)?

    One or a few tests or experiments can fail to find indications of danger or harm. But a negative result is not (should not be) the same as determining a substance to be “safe”. Declaring a substance actually _safe_ should require a vast body of studies and tests run under a range of different circumstances and populations.

    This of course does not provide “proof” but can establish a preponderance of evidence, which is the best you can do in this kind of situation. But until that level of exhaustive investigation is done, any substance (particularly one lacking a long history of use) should be thought of as an unknown, and treated accordingly. To do otherwise is to make a conclusion on insufficient evidence, and is not appropriate for a scientist.

    It may be that most scientists would agree with these sentiments. Unfortunately, that’s not how industry, the media, or the public interpret those scientific findings in most cases.

  7. I don’t think anyone is suggesting pesticides are safe or harmless in this particular post. The question is more nuanced – if, for instance, you couldn’t afford (or find) organic veggies and didn’t have space to grow them, would you be healthier avoiding veggies altogether?

  8. One point I tried to make is that disdain for ‘conventional’ agriculture because conventional food is bad for us is misguided. Conventional fruits and vegetables are good for us, no doubt about it. Eat them! Are organic F&V good for us? Yes. Eat them too. Daniel, as the investigator in the article was quoted, “Although kids should not stop eating fruits and vegetables, buying organic or local produce whenever possible is a good idea.” That is the point Linda was making clear for me above (thanks!).

    When the EPA registers pesticides, they are supposed to use a “No Observable Effects Limit”, which is an amount of the pesticide that doesn’t cause a measured effect in the animals it was tested on. This amount is reduced by a factor of 10 because we are not lab animals, by another factor of 10 because some people vary in their sensitivity to pesticides, and another factor of 10 because children are especially susceptible (NOEL in humans is assumed to be 1,000 times lower than the measured NOEL in the lab animals). Registration also takes into consideration how likely it is a consumer will be exposed to that pesticide and how important that pesticide is for growers. Foods test positive for residues all the time (over 70% of the time by some estimates). And sometimes a residue on food exceeds the limit set by the EPA. In a recent USDA study, tolerances were exceeded only 0.5% of the time (USDA PDP, 2008). If produce has 1 molecule of a pesticide on it, is it harmful to your health? At what point does the amount of pesticide on the apple you’re eating outweigh the benefit you’re getting by eating an apple? 30 molecules? 1 molecule more than the tolerance? We don’t know, and it’s different for everybody. But obviously, the ‘tolerance’ is merely a best guess for a level at which we can assume the risk of ingestion is minimized if a grower thinks it needs to be used to protect a crop. That’s all it is. But consider that the USDA, who oversees organic certification, makes no guarantees that organic foods are safer or more nutritious.

    Is this registration process ideal? Well, some would argue that using data from the people who are trying to sell the product isn’t right, or it’s a conflict of interest when income for the office that regulates pesticides comes from the companies who are trying to get their products approved. Or that longer-term studies need to be done. Or that active ingredients (or their breakdown products) might be more toxic when measured as a formulated product, complete with surfactants and “other ingredients”. But who is going to do an independent, long-term, controlled study on the effects of a specific pesticide formulation in humans? It’s not easy to afford that kind of study or to get it approved by ethics boards. I agree with GreenEngineer, I think: it’s not an ideal process. But it can change, as it did in 1996 when registration rules got tougher and retroactive (FQPA:, especially for carbamates and organophosphates, Daniel!).

    You might assume that 1 molecule of something called “pesticide” is more dangerous than 0 molecules. But “pesticide” is a loaded word. I killed some dandelions in my rock mulch (which I inherited with the house, I did not choose rock mulch) with household vinegar. That makes vinegar a pesticide. Plants make their own pesticides, and we eat them all the time. Broccoli makes glucosinolates, raspberries make egallic acid, ginger makes 6-gingerol. The plants use these things to ward off pests and diseases. We like these foods because they taste good, and at the dose we eat them at, they’re usually good for us. Poppies make opiates to drug animals, and for good reasons and in the right amounts, opiates can be good for us. But too much opium, and bad things happen. I don’t think it comes down to a choice between “all chemicals safe until proven dangerous” or “minimizing exposure is reasonable”. The first option is erroneous (you can’t buy a pesticide until the EPA has reviewed its safety somewhat), and the second should always be practiced. Minimize exposure to things that may or may not be bad for you. But again, my point is that you should also strive to maximize things that are good for you—fruits and veggies! And LauraP, I’m not saying conventional F&V haven’t been proven worse for health—they’re BETTER for your health compared to low F&V intake! There are lots of epidemiological studies showing benefits of F&V consumption that used conventional F&V. And ‘chemical’ is a loaded term too (just ask Garden Professor Jeff Gillman…).

    Daniel, the recommendation from the President’s Cancer Panel is pretty good—it says choose “to the extent possible” food grown without pesticides (and to wash your food!). But (devil’s advocate again) are organic bananas safer than conventional bananas? I’m peeling off the outside before I eat it! Same with sweet corn! The universality of that suggestion is misplaced, I think. As an aside, it also seems weird that the document is associating “chemical fertilizers” with increased cancer risk. But that does look like an interesting study you found there about OP and ADHD! I hadn’t seen that.

    GreenEngineer, like Linda said, I’m not saying pesticides are 100% safe. Knowing what is an acceptable risk, in order to eat healthy foods, is difficult for anyone (including the EPA).

    And yes, I sidestepped LOTS other issues surrounding the topic, it would take too much space! But again, full disclosure, I buy organic (and local) F&V all the time. I can find lots of other reasons to do so.

    Here’s some interesting, relevant reading:

    Institute of Food Technologists Scientific Status on Organic Foods
    (Here’s a synopsis).

    Trewavas and Stewart, 2003. Paradoxical effects of chemicals in the diet on health. Curr. Opin. Plant Biol. 6:185–190.

    Chen, M. 2005. Organic fruits and vegetables: Potential health benefits and risks. Nutrition Noteworthy 7(1). [last sentence: “Very few actual benefits have been demonstrated, and, at present, the best recommended diet remains as one that is balanced and rich in fruits and vegetables, regardless of organic or conventional origin.”]

  9. I love this blog and I love this post!!

    Charlie, I think I’m getting the jist of what you are saying. My family eats organic and conventional f&v. We are trying to increase that amount while eating less red meat, less processed foods, and less junk food. Based on the ADHD study and other studies, we prioritize which f&v we buy organic, because it is a health and financial decision for us and out two small children. No wonder that Michelle Obama has stayed clear of the organic vs conventional debate in her “Let’s Move” campaign for children’s health. Her first priority is for children to eat more f&v, and this is a HUGE issue for underprivileged children and their families. There are too many f&v “food deserts” in our cities and states and especially popular culture.

  10. Post request: In response to the ADHD and OP study, Jeff or the like, do homeowners (& their children) generally pick up organophosphate residue in conventionally treated landscapes which are on commercial turf programs? (I know treated landscapes have huge variance in how they are treated, so I am attempting to generalize with a typical turf-centered landscape that is commercially treated.) This question also assumes that oral ingestion of OP residue is equal to skin ingestion, which is probably not the case. But, skin contact can lead to oral ingestion. But, I may be qualifying too much.

  11. Daniel, That study on ADHD is interesting, but I haven’t been able to read the paper itself yet — I’m planning on doing a post about it on Thursday — kind of a “what to look for before you believe the hype” piece. I’ll also talk a little about other studies already done on OP insecticides.

  12. Thanks, Jeff. I, also, meant to reference your book with the EIQ of OP, but I can’t find it (and it’s driving me crazy).

    Also, in reference to the Pres. Cancer Panel, they seem to give a blanket statement concerning pesticide use in the landscape. Yet, just as Charlie stated re: their statement on organic foods, isn’t this too general of a statement? It’s not the poison but how one uses it, organic or conventional.

  13. I think we are forgetting one of the most important issues surrounding organic food and that is the soil that is used to grow it. Studies have found that organic methods are better for the health of the soil which in turn is better for the F&V growing in it.

  14. “It turns out we’re just consumers.” Excuse me, some of us are not “just comsumers” but actual “people” who want “food” instead of “food like substances” and purchasing organic is one way of “voting” for a food choice and letting our industrialized food like substance system know some of us “people” want a change in our food system.

  15. Okay, I have a question: Charlie, lets just say I happen to buy a f/v that is in the 70% of testing positive for residues. Does that wash off with water, or water and soap? Perhaps that is a way some of us on a lower budget (who still love our f&v) can eat something while decreasing any risk of exposure – be it real or perceived. I love all this information and the discussion – thanks for stimulating my thinking!

  16. great discussion

    Is it really feasible for most people to avoid eating non-organic f&v(never mind the other food groups?

    …about as feasible as avoiding “made in china”

    wish i could grow my own, but the front yard just isnt big enuf

    gp’s please keep up the good work


  17. I would not advise someone to forgo F&V just because they can’t afford organic. If you’re on a budget, eat as well as you can afford. But I would argue that organic, local, and fresh (which are not all the same thing, but all of which are important) is worth prioritizing. In many people’s minds, cable TV is a necessity and good quality F&V is a luxury. That’s bass ackwards.

    In the name of doing the best you can with what you have, organic is much more important for some foods than others. here’s a list.

  18. This is quite the interesting discussion. I just watched the documentary Food Inc and that makes me want to watch what I eat very closely.

    You are correct in saying organic, local and fresh are not the same thing.

    Regardless, thank you for the list! I made sure to bookmark it for future use

  19. Timely article:  Wild Birds Opt for Conventional Food Over Organic. 

    A three-year study by Newcastle University has found that wild birds are not swayed by the organic label, but instead prefer the more protein-rich, conventional food that will help them to survive the winter.

    Published in the Journal of the Science of Food and Agriculture, lead researcher Dr Ailsa McKenzie said the findings were likely to be of “considerable interest to the general public in the debate over the relative merits of consuming organic food.”

  20. A three-year study by Newcastle University has found that wild birds are not swayed by the organic label, but instead prefer the more protein-rich, conventional food that will help them to survive the winter.

    Published in the Journal of the Science of Food and Agriculture, lead researcher Dr Ailsa McKenzie said the findings were likely to be of “considerable interest to the general public in the debate over the relative merits of consuming organic food.”

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