Skip to main content
Part of complete coverage on

Is organic food better for you?

By Aaron Carroll
updated 7:25 AM EDT, Tue August 5, 2014
STORY HIGHLIGHTS
  • A new study says organic foods are more nutritious than conventionally grown food
  • Aaron Carroll: There's little evidence that organic foods are better for people
  • He says higher level of antioxidants in organic foods doesn't lead to better health
  • Carroll: Organic crops are lower in protein, which is an actual nutrient

Editor's note: Aaron E. Carroll is a professor of pediatrics at the Indiana University School of Medicine and the director of its Center for Health Policy and Professionalism Research. He blogs about health policy at The Incidental Economist and tweets at @aaronecarroll. The opinions expressed in this commentary are solely those of the author.

(CNN) -- Recently, a study published in the British Journal of Nutrition said that organic fruits and vegetables are more nutritious.

Aaron Carroll
Aaron Carroll

A press release declared it the "largest study" of its kind. Because of its size and breadth, some people believe that it trumps previous research which showed organic food did not appear to be any safer or more nutritious than conventionally grown food.

Despite the hoopla, I think this study offers little new information and is not very convincing in making a claim that organic food is somehow "better for you."

This new study, like many before it, was a systematic review and meta-analysis. That means it wasn't a new clinical trial or report of laboratory research. It was a specific kind of analysis that allows for a "study of studies." Basically, researchers set out to find all relevant research in a field, and then combine all of it together into one big analysis.

Guide to organic eating
Know when to buy organic
Fresh, organic food for babies

This type of analysis allows for many smaller studies, which might not have much power, to be merged into a study that might allow for more comprehensive inspection. It also allows for research that on its own might not be robust enough to achieve some sort of statistical significance.

Systematic reviews are sometimes preferable to regular review articles because they have reproducible methods. By stipulating how scientists searched for research, how they determined what studies were good enough for inclusion, and what tests were done, systematic reviews allow others to judge the merits of the work, and to test its conclusions if desired.

Clarified: What does 'organic' mean?

But that doesn't mean that systematic reviews are infallible or immune from criticism. In fact, often the results of systematic reviews or meta-analyses can be hotly contested. I'm sure they will be for this study.

In 2009, for example, a group of scientists published a major review of organic versus conventionally grown food, covering research from 1958 through 2008. They reviewed 52,471 articles and found 162 studies that compared crops and livestock products. They deemed 52 of them high enough quality for inclusion in their analyses. They found no significant difference between organic and conventionally grown food with respect to nutrient content.

However, this study was considered by some to be methodologically imperfect.

So in 2012, researchers from Stanford University worked on this topic and published a systematic review and meta-analysis. They looked at research through May of 2011, found 460 studies, and identified 237 that met their inclusion criteria. Of these, 17 were studies of human diets, and 223 were studies of foods themselves.

Again, the result was that there's a lack of evidence that organic foods are significantly more nutritious than conventionally grown food.

Which brings us to the most recent study. The authors of this paper acknowledged the previous reviews, but claimed that they weren't comprehensive enough. So they searched the literature from 1992 through 2011 and reviewed 448 studies. They deemed 343 appropriate for inclusion, which did make this a "larger" study.

But remember that this study didn't include much more "newer" data than the Stanford study did. It simply had more data because it was more permissive in the type of studies that it deemed of high enough quality to be included.

The analysis showed that there were a significantly higher level of antioxidants in organic foods than in conventionally grown foods. It is on this basis that the researchers declared organic food more nutritious. They also found higher levels of pesticides on conventionally grown foods, which they said made them more unsafe.

First of all, it's important to be realistic about what antioxidants can and can't do. They are a type of compound, used by our body, to fight against "free radicals" or chemicals that can cause damage to many structures in the body by stealing electrons from certain molecules. Antioxidants can "give" electrons to free radicals so they don't take from our bodies.

But antioxidants aren't "nutrients." They also aren't all the same. Each one works in a certain way in different parts of the body. More importantly, there is little evidence that more antioxidants will lead to better health.

Vitamin E has shown mixed results in the Women's Health Study, the Heart Outcomes Prevention Evaluation trial, and the GISSI-Prevenzione trial. Beta-carotene was shown to have no effect on heart disease or cancer. Mixtures of antioxidants didn't prevent cardiovascular events in women or cancer heart disease, or death in anyone. These studies all included much larger doses of antioxidants than would likely be received by eating organic fruits and vegetables.

Second, the most recent study also found that organic crops are lower in protein. That's an actual nutrient, and it's being ignored in much of the media reports.

Third, while levels of pesticides may be higher in conventionally grown food, none of the studies have detected levels of chemicals that approach anything near what would be classified as an unsafe level.

Finally, though, this study provides an opportunity to understand how we might think about systematic reviews in general. If it were so obvious that organic foods were nutritionally superior, we would need no meta-analysis. Large studies would find clear benefits with respect to nutrients, and that would be that. We are having this argument because it is hard to find a benefit.

Moreover, when a systematic review finds a benefit that an old study didn't, by being more permissive of the research it includes, that should give us pause. It's entirely possible, of course, for previous work to be flawed and to have left out critical research, but that doesn't appear to be the case here.

It seems that the recent study included everything the old study did, and then added to it research that didn't make the cut the first time. That's potentially problematic.

Of course, it's a judgment call as to which analysis is correct. I tend to favor the Stanford study, because it seems like it was more rigorous in excluding studies with weaker methodologies.

But as with many things, people's predisposed beliefs will likely color their interpretations of which study is correct. Even if you favor the newer study, the differences, while statistically significant, do not provide evidence to support the notion that organic foods are more nutritious.

I would be remiss if I neglected to mention one more thing. The Stanford study was done with no external funding at all. The newer study, though, cost $429,000 and was funded by a charity that "supports organic farming research." That doesn't mean that a conflict of interest tainted the methods or results, but it should at least be acknowledged.

Childhood vaccines are safe. Seriously.

Forgotten vials of smallpox virus found

Read CNNOpinion's new Flipboard magazine

Follow us on Twitter @CNNOpinion.

Join us on Facebook.com/CNNOpinion.

ADVERTISEMENT
Part of complete coverage on
updated 8:27 PM EST, Fri December 26, 2014
The ability to manipulate media and technology has increasingly become a critical strategic resource, says Jeff Yang.
updated 11:17 AM EST, Fri December 26, 2014
Today's politicians should follow Ronald Reagan's advice and invest in science, research and development, Fareed Zakaria says.
updated 8:19 AM EST, Fri December 26, 2014
Artificial intelligence does not need to be malevolent to be catastrophically dangerous to humanity, writes Greg Scoblete.
updated 10:05 AM EST, Fri December 26, 2014
Historian Douglas Brinkley says a showing of Sony's film in Austin helped keep the city weird -- and spotlighted the heroes who stood up for free expression
updated 8:03 AM EST, Fri December 26, 2014
Tanya Odom that by calling only on women at his press conference, the President made clear why women and people of color should be more visible in boardrooms and conferences
updated 6:27 PM EST, Sat December 27, 2014
When oil spills happen, researchers are faced with the difficult choice of whether to use chemical dispersants, authors say
updated 1:33 AM EST, Thu December 25, 2014
Danny Cevallos says the legislature didn't have to get involved in regulating how people greet each other
updated 6:12 PM EST, Tue December 23, 2014
Marc Harrold suggests a way to move forward after the deaths of NYPD officers Wenjian Liu and Rafael Ramos.
updated 8:36 AM EST, Wed December 24, 2014
Simon Moya-Smith says Mah-hi-vist Goodblanket, who was killed by law enforcement officers, deserves justice.
updated 2:14 PM EST, Wed December 24, 2014
Val Lauder says that for 1,700 years, people have been debating when, and how, to celebrate Christmas
updated 3:27 PM EST, Tue December 23, 2014
Raphael Sperry says architects should change their ethics code to ban involvement in designing torture chambers
updated 10:35 PM EST, Tue December 23, 2014
Paul Callan says Sony is right to call for blocking the tweeting of private emails stolen by hackers
updated 7:57 AM EST, Tue December 23, 2014
As Christmas arrives, eyes turn naturally toward Bethlehem. But have we got our history of Christmas right? Jay Parini explores.
updated 11:29 PM EST, Mon December 22, 2014
The late Joe Cocker somehow found himself among the rock 'n' roll aristocracy who showed up in Woodstock to help administer a collective blessing upon a generation.
updated 4:15 PM EST, Tue December 23, 2014
History may not judge Obama kindly on Syria or even Iraq. But for a lame duck president, he seems to have quacking left to do, says Aaron Miller.
updated 1:11 PM EST, Tue December 23, 2014
Terrorism and WMD -- it's easy to understand why these consistently make the headlines. But small arms can be devastating too, says Rachel Stohl.
updated 1:08 PM EST, Mon December 22, 2014
Ever since "Bridge-gate" threatened to derail Chris Christie's chances for 2016, Jeb Bush has been hinting he might run. Julian Zelizer looks at why he could win.
updated 1:53 PM EST, Sat December 20, 2014
New York's decision to ban hydraulic fracturing was more about politics than good environmental policy, argues Jeremy Carl.
updated 3:19 PM EST, Sat December 20, 2014
On perhaps this year's most compelling drama, the credits have yet to roll. But we still need to learn some cyber lessons to protect America, suggest John McCain.
updated 5:39 PM EST, Mon December 22, 2014
Conservatives know easing the trade embargo with Cuba is good for America. They should just admit it, says Fareed Zakaria.
updated 8:12 PM EST, Fri December 19, 2014
We're a world away from Pakistan in geography, but not in sentiment, writes Donna Brazile.
updated 12:09 PM EST, Fri December 19, 2014
How about a world where we have murderers but no murders? The police still chase down criminals who commit murder, we have trials and justice is handed out...but no one dies.
updated 6:45 PM EST, Thu December 18, 2014
The U.S. must respond to North Korea's alleged hacking of Sony, says Christian Whiton. Failing to do so will only embolden it.
updated 4:34 PM EST, Fri December 19, 2014
President Obama has been flexing his executive muscles lately despite Democrat's losses, writes Gloria Borger
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT