Oct 26, 2012 | Chris Kresser
I'm sure by now many of you have heard about the Stanford study claiming that organic foods are no healthier or safer than conventional alternatives.
There were so many problems with this study and the media reporting of it that it's difficult to know where to start. To begin with, their results did not, in fact, support the claim that organic foods are "no healthier or safer" than conventional alternatives. Their data - if we are to take them at face value - suggest only that organic produce is no more nutritious than conventional produce. From their own conclusion:
The published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods. Consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria.According to the authors, organic foods are no more nutritious than conventional foods. But, ahem, eating organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria. Somehow that last bit just slid right by in most of the media coverage of the study. The headlines were all about how organic is no better than conventional in terms of nutrient content, but few articles analyzed the significance of the increased exposure to pesticide and antibiotic resistance bacteria. No mention of the fact that pesticides, herbicides and other harmful chemicals that have been shown to cause health problems - especially in vulnerable populations like children. No mention of the 2010 report issued by a panel of scientists convened to study the effects of environmental toxins on cancer urging Americans to eat organic produce grown without pesticides, fertilizers or other chemicals, because the U.S. government has grossly underestimated the number of cancers caused by environmental toxins. No mention of the especially high risk these chemicals present to unborn children, such as lifelong endocrine disruption, hormone imbalances and other problems.
As important as those omissions are, I'd like to focus instead on nutrient content - since that is what the media coverage of the study primarily focused on. Is it really true that organic foods are no more nutritious than conventional foods?
Did the Stanford researchers stack the deck against organic?
Mark Sisson has written an extensive critique of the Stanford study. He pointed out that it inexplicably omitted or undervalued certain nutrients from the comparison that have already been shown to be more concentrated in organic foods, such as vitamin C, polyphenols and flavonoids. He also references several other studies showing higher content of various nutrients in organic foods.
Mark highlights one study in particular which found that:
differences existed between newly-organic farms and more "mature" organic farms; the longer soil was worked using organic methods, the more nutrient-rich its produce. Thus, it's possible that many of the studies showing little to no difference between conventional and organic were using "young" organic farms that had yet to reach their potential.I think the balance of evidence suggests that organic food is, in fact, more nutritious than conventional food when the full nutrient spectrum is considered. And that's important because we've learned a lot about how important many of the "secondary metabolites" in food that weren't measured in the Stanford study are to human health.
When it comes to nutrient content, local trumps organic
But the most glaring omission in the study, from my perspective, was that the authors didn't once mention the most important factor of all when it comes to the nutrient content of produce: how long it has been out of the ground before it is consumed.
Most of the produce sold at large supermarket chains is grown hundreds - if not thousands - of miles away, in places like California, Florida and Mexico. This is especially true when you're eating foods that are out of season in your local area (like a banana in mid-winter in New York). Consider this:
The average carrot has traveled 1,838 miles to reach your dinner table.Days - maybe more than a week - have passed since it was picked, packaged and trucked to the store, where it can sit on the shelves even longer.
The problem with this is that food starts to change as soon as it's harvested and its nutrient content begins to deteriorate. Total vitamin C content of red peppers, tomatoes, apricots, peaches and papayas has been shown to be higher when these crops are picked ripe from the plant. This study compared the Vitamin C content of supermarket broccoli in May (in season) and supermarket broccoli in the Fall (shipped from another country). The result? The out-of-season broccoli had only half the vitamin C of the seasonal broccoli.
Without exposure to light (photosynthesis), many vegetables lose their nutrient value. If you buy vegetables from the supermarket that were picked a week ago, transported to the store in a dark truck, and then stored in the middle of a pile in the produce section, and then you put them in your dark refrigerator for several more days before eating them, chances are they've lost much of their nutrient value. A study at Penn State University found that spinach lost 47% of its folate after 8 days.
And here's the thing: this nutrient loss happens regardless of whether the produce is conventional or organic.
This is why buying your produce at local farmer's markets, or even better, picking it from your backyard garden, are better options than buying produce shipped from hundreds or thousands of miles away - regardless of whether it's conventional or organic. Fruits and vegetables from local farms are usually stored within one or two days of picking, which means their nutrient content will be higher. And as anyone who's eaten a fresh tomato right off the vine will tell you, local produce tastes so much better than conventional produce it might as well be considered a completely different food.
The research study I'd really like to see is one comparing the following:
- "Industrial" organic produce (i.e. produce harvested more than a week before it's consumed)
- "Industrial" conventional produce
- Local organic produce (i.e. produce harvested within a couple of days of consumption)
- Local conventional produce
Based on the data we have, my guess is both organic and conventional local produce would beat out industrial organic and conventional in terms of nutrient content. So if nutrient content is your only concern, choosing locally grown foods (both organic and conventional) over foods from distant locales is your best bet.
However, if you're concerned about exposure to pesticide and antibiotic-resistance, industrial organic might be a better choice than local conventional (assuming no local organic option is available).
Of course the best choice of the four is to buy local, organic produce: it will have the highest nutrient content and the lowest levels of pesticide and antibiotic-resistant bacteria. And it's also more supportive of fair labor practices, the maintenance of healthy soil and biodiversity and the strength of local communities. There's a lot more to food than nutrition.
If money is tight and you can't afford to buy local, organic produce from farmer's markets exclusively, here's what I'd suggest:
- Choose organic when it matters most. Some foods tend to be higher in pesticides than others. See this list for the 12 fruits and vegetables you should always buy organic.
- Buy local, conventional varieties rather than "industrial" conventional varieties whenever possible.
- Consider joining a CSA program. This is a convenient and often cheaper (than shopping at farmer's markets) way to buy local, organic, seasonal produce. And you get to support your local farmers in the process.
- Start growing some of your own food. This is of course the cheapest alternative of all, and the most satisfying.