They sit side by side on the supermarket shelf: Blueberries, $2.99; organic blueberries, $3.99.
You hesitate before making a decision. You have a vague sense that organic foods are somehow better for you, but aren’t sure precisely what direct benefit your body will get from that extra dollar.
A new meta-study suggests the answer, as best we can tell, is: Not much.
“The evidence does not suggest marked health benefits from consuming organic vs. conventional foods,” a research team led by two Stanford University scholars writes in the Annals of Internal Medicine.
Specifically, they report that studies conducted to date do not contain “strong evidence that organic foods are significantly more nutritious than conventional foods.”
The researchers do conclude that “consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria.” But, they add, even those benefits come with an asterisk.
A research team led by two Stanford-affiliated MDs, Dena Bravata and Crystal Smith-Spangler, analyzed 237 studies examining the benefits of organic foods. Such foods are usually grown without synthetic pesticides or fertilizers, or the routine use of antibiotics or growth hormones.
Only a handful of the studies examined the effects of organic or conventional diets on groups of people. The vast majority—223—compared the levels of either nutrients or contaminants in organic and conventionally grown varieties of various foods.
“Of the nutrients evaluated, only one comparison—the phosphorous content of produce—demonstrated the superiority of organic foods,” the researchers write. They did not find this particularly impressive, given that “near-total starvation is needed to produce dietary phosphorous deficiency.”
They did point to one specific nutritional benefit: Organic milk contains higher levels of beneficial fatty acids than conventional milk. “Otherwise,” they write, “studies measuring nutrient levels among human consuming organic and conventional diets did not find consistent differences.”
Conventional chicken and pork have a higher risk of contamination with bacteria resistant to three or more antibiotics. That said, the researchers note that the extent to which antibiotic use for livestock contributes to antibiotic-resistant pathogens in humans is not clear.
Similarly, conventional produce has a higher risk of pesticide contamination. But it’s uncertain if this has a significant impact on human health, since the researchers found “no studies comparing pesticide levels among adult consumers of organic vs. conventional foods.”
Indeed, they found no studies at all looking at the long-term health trajectories of people who eat organic vs. conventional foods.
Finally, they caution that organic farming practices vary considerably; it’s possible that some specific organic farming methods yield better results than others. But, again, the data is lacking.
The researchers--who received no external funding for their study--note there are environmental benefits to organic farming, and many people prefer the taste of organically grown food.
But all in all, their study shows that while organics may indeed be better for us in the long run, the evidence supporting that claim simply isn’t there—at least not yet.