Why Organic Food May Not Be Healthier For You

Sep 4, 2012
Originally published on September 19, 2012 4:13 pm

Yes, organics is a $29 billion industry and still growing. Something is pulling us toward those organic veggies that are grown without synthetic pesticides or fertilizers.

But if you're thinking that organic produce will help you stay healthier, a new finding may come as a surprise. A new study published in the Annals of Internal Medicine finds scant evidence of health benefits from organic foods.

"There's a definite lack of evidence," says researcher Crystal Smith-Spangler at Stanford University School of Medicine, especially when it comes to studies of people.

She and her colleagues collected 200 peer-reviewed studies that examined differences between organic and conventional food, or the people who eat it.

A few of these studies followed people who were eating either organic or conventional food and looked for evidence that the choice made a difference in their health.

One study, for instance, looked at whether eating organic food while pregnant would influence the likelihood of eczema and other allergic conditions among children, and another looked at whether eating organic meat would influence the risk of a Campylobacter infection, a bacterial food-borne illness. When the researchers looked at the body of evidence, they found no clear benefits. But they say more research is needed.

It's important to note, though, that such studies have a really hard time uncovering subtle effects of our environment, or what we eat, on our health. Too many other powerful influences get in the way. Also, these studies only followed people for a very short time — about two years or less. That's hardly enough time to document any particular health benefit.

Most of the studies included in this collection looked at the food itself — the nutrients that it contained as well as levels of pesticide residues or harmful bacteria.

As you might expect, there was less pesticide contamination on organic produce. But does that matter? The authors of the new study say probably not. They found that the vast majority of conventionally grown food did not exceed allowable limits of pesticide residue set by federal regulations.

Some previous studies have looked at specific organic foods and found that they contain higher levels of important nutrients, such as vitamins and minerals. We've reported on one particularly ambitious experiment, which is supposed to go on for a hundred years, comparing plots of organic and conventional tomatoes. After 10 years, the researchers found that tomatoes raised in the organic plots contained significantly higher levels of certain antioxidant compounds.

But this is one study of one vegetable in one field. And when the Stanford researchers looked at their broad array of studies, which included lots of different crops in different situations, they found no such broad pattern.

Here's the basic reason: When it comes to their nutritional quality, vegetables vary enormously, and that's true whether they are organic or conventional. One carrot in the grocery store, for instance, may have two or three times more beta carotene (which gives us vitamin A) than its neighbor. That's due to all kinds of things: differences in the genetic makeup of different varieties, the ripeness of the produce when it was picked, even the weather.

So there really are vegetables that are more nutritious than others, but the dividing line between them isn't whether or not they are organic. "You can't use organic as your sole criteria for judging nutritional quality," says Smith-Spangler.

Of course, people may have other reasons for buying organic food. It's a different style of agriculture. Organic farmers often control pests by growing a greater variety of crops. They increase the fertility of their fields through nitrogen-fixing plants, or by adding compost instead of applying synthetic fertilizer.

That can bring environmental benefits, such as more diverse insect life in the field or less fertilizer runoff into neighboring streams. But such methods also cost money. That's part of what you are buying when you buy organic.

So if you really want to find the most nutritious vegetables, and the organic label won't take you there, what will?

At the moment, unfortunately, there isn't a good guide. But a lot of scientists are working on it.

They're measuring nutrient levels in all kinds of crops, and discovering some surprising things, as The Salt reported last week — such as supernutritious microgreens. They're trying to breed new varieties of crops that yield not a bigger harvest but a more nutrient-rich harvest.

The problem is, farmers still get paid by the pound, not by the vitamin. And consumers buy their food the same way. What this really requires is a whole new food system that can track those extra-nutritious crops from farmer's field to consumer's shopping basket.

Maybe, down the road, you will actually see signs in the supermarket that advertise, for instance, iron-rich beans. Maybe they'd be organic, or maybe not.

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This is MORNING EDITION from NPR News. I'm David Greene.


And I'm Steve Inskeep.

Expensive though it may be, a lot of Americans buy organic. In fact, they spend an estimated $29 billion per year on organic food. Hardly a niche enterprise.

GREENE: But here's a headline that might catch your attention. There's a new study from Stanford University concluding that there's hardly any evidence at all of health benefits if you choose organic.

INSKEEP: Here to discuss this are NPR's food correspondents, Allison Aubrey and Dan Charles.

Welcome to you both.

ALLISON AUBREY, BYLINE: Hey there, guys.

DAN CHARLES, BYLINE: Nice to be here.

INSKEEP: OK. A lot of us assume that organic has to be better. Sounds good. Organic. How did the researchers come to the conclusion it makes no difference?

AUBREY: Well, basically, you can look at this and measure this in a couple of ways. You can look at food and measure nutrient content, pesticide residue, that sort of thing. Or you can follow people - people who are eating organic compared to those who are eating conventionally grown food.

So the researchers did both of these. They combed through all of the studies that have been done with people. There were about 17 of them. One of them looked at whether children eating organic had fewer allergies. Another one looked at whether organic would reduce the incidence of food-borne illness. And when they looked at the body of evidence as a whole, they didn't see any clear effect.

GREENE: I feel kind of duped. I mean, I was in a grocery store and was seriously thinking about buying organic raspberries the other day because I figured that, you know, organic, it must be better. I mean, how did this industry explode and become this big without someone at some point earlier saying, you know, we don't know that this is any better.

CHARLES: OK. So the starting point of the organic industry; it's a reaction to the dependence of agriculture on chemicals. And here is a clear difference. You can measure the food - this is the other thing you look at. There are lower levels of pesticide residues on the food when you're looking at organics. And if you're looking...

GREENE: The assumption being that organic might be better if we don't have pesticides in it.

CHARLES: Right. Than if you're looking at conventional...

INSKEEP: And it certainly does feel creepy to be eating a lot of tomatoes with pesticides and thinking that it's building up in your body. But go on.

CHARLES: Right. But here's the question. Does that matter? Does that matter to your health? And the researchers in this study said, no, because even with conventional food, the level of the residues, the amount of pesticides on the food is so low that as far as the scientists are concerned it probably is not going to harm you.

But then there's this other part of it. That is the nutrients in the food. Is there any difference in that?

AUBREY: Right. And in some instances they do document that organically grown food has more nutrients. For instance, we reported on a study that's being done at UC Davis. It's slated to last a hundred years. So far, they're 10 or 15 years into it. Ten years into it, what they found - they looked at levels of antioxidants, so certain compounds. One of them is called Quercetin. And they found, look, significantly higher levels of these compounds here. But what you have to remember is this is one study of one vegetable in one field.

CHARLES: And here's the thing. So this study we're looking at today, they took all of these studies. And there are actually lots and lots of them.

INSKEEP: It's a study of studies.

CHARLES: Dozens and dozens of them.

AUBREY: A meta-analysis.

CHARLES: Right. And they looked at the levels of nutrients in all these different foods comparing organic to nonorganic. And the problem is, yes, there is healthier food, but it doesn't break down along the lines of organic, non-organic. There's huge variation. You go into the supermarket and look at a shelf of carrots. Some of those carrots may have two or three times as much beta carotene - that's the thing that gives you vitamin A - than another carrot.

And the difference has to do with all kinds of things like what variety of carrot they grew or what the weather was like or when they harvested it.

INSKEEP: Wait a minute. So organic labeling started as a way that it's supposed to be convenient for me as a consumer. I want to just make a quick choice, buy something. I'd like to pick organic perhaps, because I think that's going to be better. It turned out to be that that was just something that companies could charge a premium for. They can charge more for that. But in the end, it's not as simple as a label. It's hard to figure out which food is the very best for you. Is that what you're saying?

AUBREY: Well, it actually does cost more to produce things organically.

CHARLES: Yeah. I mean, there are other reasons why you might want to buy organic food. And here we get to sort of the environmental side. If you're the organic farmer, you're controlling your pests with different measures. You're rotating crops. You might be adding nutrients to the soil with different measures. You're putting compost in instead of commercial fertilizer that you buy.

So the result is you might have more diverse insect communities in your field. You might have less runoff of fertilizer into neighboring streams. And that might be more expensive. And that, you could say, is what you're buying when you pay more for organic food.

GREENE: You're buying organic, you're doing good for the world, if not getting a better health benefit. You have a study that you mentioned that is going on for a hundred years. We also talked about that organic doesn't have chemicals. I mean, even though we have this Stanford study, there may be reasons that some would say, I don't want chemicals and, you know, I'm going to wait until we get some final results. I feel better buying organic.

AUBREY: Well, absolutely. This body of evidence is not robust. I mean, that would be a term that scientists would use. Meaning that, you know, we're asking questions that may take decades to answer. When these researchers at Stanford combed through all the literature looking for these human trials, as I said, they found 17. And the longest one in duration was two years. So there's a lot more to learn, I guess we should say.

CHARLES: So, look, I mean, it's kind of a philosophical question you're posing because science will tell us, you know, what it can find out up to the limits of the science. But there is kind of a philosophical position that people will take. It says: I just don't like pesticides. And even though you can't show me evidence that that's going to be bad for me, I'm just not going to take that risk. And I think that is probably also, you know, one of the big factors behind the demand for organic food.

INSKEEP: NPR's Dan Charles, thanks for coming by.

CHARLES: Thank you.

GREENE: And NPR's Allison Aubrey, thank you.

AUBREY: Thanks, guys. Transcript provided by NPR, Copyright NPR.