It seems obvious that fewer pesticides and more nutrients would be better for us. However there appears to be a constant battle between conventional sources and the natural health industry about this topic.
For some reason that isn’t clear to me, the mainstream media and medical establishment seem very attached to the idea that organic produce is no healthier or safer than conventional produce.
They often point to a study performed at Stanford in 2012 as proof of this claim, as if it were the final word. After all, it’s Stanford!
New study confirms that organic produce is higher in
antioxidants and lower in pesticide residues.
But it turns out the Stanford study wasn’t nearly as conclusive as the media made it out to be. I wrote an article critiquing it shortly after it was published, and Mark Sisson also weighed in. In short, the Stanford researchers 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. What’s more, according to the researchers own conclusion, “consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria.” (1)
New analysis of 343 studies finds that organic really is better
A new study published in the British Journal of Nutrition is the latest addition to the debate. It’s the largest meta-analysis (i.e. review of studies) that has been published on this topic to date, covering 343 individual studies looking at the composition of crops and food. (2)
The study found that organic crops had higher levels of certain antioxidants—such as phenolic acids, flavonols and anthocyanins—and that eating organic foods could boost a person’s antioxidant intake by up to 40% (the equivalent of two portions of fruits or vegetables a day).
Some “experts” have claimed these results are meaningless because “antioxidants are not essential nutrients.” But while antioxidants in plants may not be essential, in the sense that we cannot live without them, a growing body of evidence suggests that they are crucial for optimal health.
In fact, recent research has revealed that what we call “antioxidants” in plants are actually “pro-oxidants” that gently stress our bodies. Rather than killing us or making us sick, however, these compounds promote adaptations that make us healthier and stronger and may extend our lifespan. The science writer Moises Velasquez-Manoff describes this phenomenon in a recent article called “Fruits and Vegetables Are Trying To Kill You:
…these plant “biopesticides” work on us like hormetic stressors. Our bodies recognize them as slightly toxic, and we respond with an ancient detoxification process aimed at breaking them down and flushing them out.
Consider fresh broccoli sprouts. Like other cruciferous vegetables, they contain an antifeedant called sulforaphane. Because sulforaphane is a mild oxidant, we should, according to old ideas about the dangers of oxidants, avoid its consumption. Yet studies have shown that eating vegetables with sulforaphane reduces oxidative stress.
When sulforaphane enters your blood stream, it triggers release in your cells of a protein called Nrf2. This protein, called by some the “master regulator” of aging, then activates over 200 genes. They include genes that produce antioxidants, enzymes to metabolize toxins, proteins to flush out heavy metals, and factors that enhance tumor suppression, among other important health-promoting functions.
Some scientists have even gone as far as suggesting that antioxidants (or more accurately, “pro-oxidants”) are primarily responsible for the health benefit we get from eating plants. Thus, the finding that we may get 40% more antioxidants from eating organic produce is not insignificant.
Pesticide residues and toxic metals are not harmless
In addition to finding higher levels of antioxidants in organic produce, the study authors also found lower levels of cadmium—a toxic, heavy metal—and lower levels of pesticide residues. On average, cadmium and pesticide levels were 48% and 400% lower, respectively, in organic produce than in conventional varieties.
Cadmium (Cd) is a highly toxic metal that accumulates in the human body. It is classified as a category I carcinogen—which means it contributes to cancer development—and has been linked to an increased risk of everything from Alzheimer’s disease, to thyroid problems, to cardiovascular disease, to hormone imbalance. (3, 4, 5, 6) It’s fairly obvious, therefore, that we should do everything we can to minimize our exposure to cadmium.
The question of how exposure to pesticide residue in foods impacts human health is still controversial. That said, there is more than enough evidence to warrant caution—and that is especially true for children and pregnant women. Reports over the past few years have linked pesticide exposure in children to ADHD, intelligence/IQ, and numerous other problems. Researchers have also begun to identify mechanisms through which pesticides can disrupt the development of children even at very low exposures. (7)
Why local trumps organic when it comes to nutrient content
As I’ve argued before, the most significant factor in determining the nutrient content of fruits and vegetables is not whether they are grown organically or conventionally, but how long they have been out of the ground before they are 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).
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. (8) 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. (9)
Jo Robinson goes into great detail on this topic in her excellent book, Eat On The Wild Side. In fact, she argues that the fruits and vegetables we eat today are almost unrecognizable to what our ancestors ate in terms of nutrient content, in part because of the effects of industrial food production.
So while it certainly makes sense to eat organic, if you’re interested in maximizing the nutrient density of your food, eating foods that are grown locally and consuming them as close to harvest as possible is even more important. This means shopping for produce at farmer’s markets or using a CSA, or even better, growing your own backyard fruits and veggies.
Final thoughts and recommendations
Before I share recommendations, it’s worth pointing out that this new study was funded by the European Union and the Sheepdrove Trust, an organic farming charity. One might argue that the involvement of the Sheepdrove Trust constitutes a conflict of interest.
Unfortunately, such conflicts are the rule rather than the exception in most nutritional and medical research. Critics of the Stanford study have pointed out that the Freeman Spogli Institute, which supported the research, has received millions of dollars in funding from Cargill (the world’s largest agricultural business) and the Bill & Melinda Gates Foundation, which has deep ties to agricultural and biochemical companies like Monsanto. In addition, one of the co-authors of the study, Dr. Ingram Olkin, has accepted money from the tobacco industry’s Council for Tobacco Research, which is a fraudulent front organization for Big Tobacco.
When a study is funded by an organization with a vested interest in the result, we should certainly be cautious when interpreting those results. However, such a funding source does not by definition make the study worthless. We can still evaluate it on its own merits.
With that in mind, I think the findings of this new, large study are sound and consistent with the majority of the previously published evidence—especially as it relates to higher levels of pesticide residue and heavy metals in conventional produce.
Here’s what I’d suggest given what we know:
Buy organic, locally grown produce as much as possible. This typically means shopping at farmer’s markets and/or joining a local community supported agriculture (CSA) program.
It’s particularly important for young children and women who are trying to conceive, pregnant, or breastfeeding to eat organic, because they are more susceptible to being harmed by pesticide residue and heavy metals.
If you have limited access to organic produce, due to financial or geographical reasons, try to at least buy organic varieties of the fruits and vegetables that are grown with the highest amount of pesticide when grown conventionally. The Environmental Working Group maintains a list of these, which it calls the “Dirty Dozen”. It also maintains a list of the “Clean Fifteen”, which are the fifteen varieties of fruits and vegetables that are relatively safe to buy conventionally. You can see both lists here.
Written by: Chris Kresser @ chriskresser.com