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The Superiority of Organic Fog

July 24, 2008. The title of the report from The Organic Center reads: New Evidence Confirms the Nutritional Superiority of Plant-Based Organic Foods. What is the new evidence? Since the last publication of reviews of studies covered those done through 2000 (none of which found conclusive evidence of the superiority of organic over conventional foods), you might think that the new evidence would consist of the 40 studies done since 2001. After all, those studies measure not just vitamins and minerals,  but polyphenols, antioxidants, precursors of vitamins, nitrates, and protein. But, you would be wrong. This new evidence is a review of the literature going back to 1980.

We identified all peer-reviewed studies published in the scientific literature appearing since 1980 comparing the nutrient levels in organic and conventional foods and screened them in two ways for scientific validity. We assessed how the studies defined and selected organic and conventional crops for nutrient level comparisons.

Surprisingly, this amounted to only 97 published studies over the past 28 years. The researchers "identified 236 scientifically valid “matched pairs” of measurements that include an organic and a conventional sample of a given food." The new evidence would come from evaluating these matched pairs of measurements.

The researchers screened the studies on the basis of experimental design, whether the same cultivars were planted in both the organic and conventional fields, the degree of differences in soil types and topography, the focus of the study, where it was carried out, the definition of organic farming, and the number of years the organic field in a matched pair had been managed organically. Studies were determined to be either “high quality,” “acceptable,” or “invalid.” There were 135 study-crop combinations covered in the 97 studies. 30% of them were deemed invalid. Of the 94 study-crop combinations deemed valid that have been written up in peer-reviewed journals over the past three decades, 55 were deemed invalid because of "the analytical methods used to measure nutrient levels."  Thus, the new evidence comes from 39 of the 97 published studies (40% of the original database).

The researchers then applied "17 decision rules to select the matched pairs from a given study-crop combination that most closely reflected food in its fresh form, grown using routine or typical organic and conventional practices." The long and the short of it is that the researchers compared the levels of 11 nutrients in organic and conventional foods in 236 matched pairs. The researchers report:

The organic foods within these matched pairs were nutritionally superior in 145 matched pairs, or in 61% of the cases, while the conventional foods were more nutrient dense in 87 matched pairs, or 37%. There were no differences in 2% of the matched pairs.

The organic samples contained higher concentrations of ... polyphenols and antioxidants in about three-quarters of the 59 matched pairs representing those four phytonutrients....

Matched pairs involving comparisons of potassium, phosphorous, and total protein levels accounted for over three-quarters of the 87 cases in which the conventional samples were nutritionally superior....

The magnitude of the differences in nutrient levels strongly favored the organic samples. One quarter of the matched pairs in which the organic food contained higher levels of nutrients exceeded the level in the conventional sample by 31% or more. Only 6% of the matched pairs in which the conventional sample was more nutrient dense exceeded the levels in the organic samples by 31% or more.

Of course, what the discerning reader wants to know is do these differences matter? Are those who are spending more money for their organics getting good value? We know they are getting less conventional pesticide and fertilizer residue, but does it matter that they are getting more polyphenols in their fruits? If I'm getting adequate nutrients from conventional fruits and vegetable, why would I pay significantly more for organics even if they supply more nutrients? Sure, I could eat fewer fruits and vegetable and get the same benefit if I switched to organics, but do I really want to eat fewer berries or less broccoli?

We know that the amount of nutrients in most foods is relatively small, so getting 30% more vitamin C, say, from an organic orange (I'm making up this statistic, by the way) means little to me. Oranges aren't my only source of vitamin C. In fact, I don't even eat oranges these days or drink orange juice because of a special diet I'm on. Most of the data presented by the researchers to demonstrate the superiority of organics is given in percentages. It might be more useful to break it down into cost per unit of nutrient alongside a list of various sources of the same nutrient.

The researchers, by the way, don't limit themselves to touting the superiority of organics. Nor do they limit their assertions to superiority in nutrients. Even though none of their criteria for evaluation has anything to do with flavor, they assert:

For every farm and agricultural region there are unique combinations of genetics, soils, climate, and practices waiting to be discovered that have the potential to produce exceptionally nutrient dense and flavorful foods. These are the kinds of fruits and vegetables needed to lure children — and adults — away from high-fat, sugar-laden foods, and in the course of doing so set the stage for sustained improvement in public health. (emphasis added)

Telling a kid that a fruit is organic rather than conventional is unlikely to be much of a lure if the kid has been brought up on high-fat, high-sugar snacks and meals. While it would be healthier for kids to eat fruits and vegetable rather than devour potato chips, pizza, and sodas, the issue is irrelevant to whether organics are nutritionally superior to fruits and vegetables grown conventionally. Likewise, the obesity epidemic is not a matter that will be resolved by choosing organic over conventional. The researchers spend much time agonizing over the poor nutritional quality of the typical diet, but this discussion is out of place here. An obese person is not going to eat a tomato rather than an ice cream cone or a piece of pizza once she's told that the tomato is organic and nutritionally superior to the ice cream, the pizza, and a conventionally grown tomato.

For those who get their protein through corn or soybeans, you might like to know that both those crops have declined significantly in protein over the past few decades. Now, if it could be shown that organic soybeans providing twice the protein as conventional soybeans could be produced for half the cost, then I'd be very impressed and I imagine so would the agricultural community. You'd deserve a Nobel prize if you could produce rice or beans that provide twice the nutrition for half the cost.

One of the more interesting sections of this report on the new evidence of the superiority of organics is called "The Plant Physiology Behind Nutrient Density." It would be difficult not to be impressed by the following (just one of several examples of the differences between organic and conventional farming):

In most high-yield, conventional farming systems where nitrogen is supplied in excess, plants grow vigorously with an abundance of vegetative growth (often requiring aggressive pruning and canopy management), produce extra chloroplasts, and hence elevated levels of carotenoids, but delay the reproductive process and production of Vitamin C. Such plants also experience a buildup of nitrates (a negative for food safety and nutritional quality).

Accordingly, relatively high levels of betacarotene, nitrates, and relatively lower levels of Vitamin C are often found in the same sample of food because they all stem from the same physiological roots.

Conversely, in organic systems, levels of Vitamin C are typically elevated compared to plants grown in high-nitrogen systems, and there is little build up of nitrates, while beta-carotene levels are also somewhat depressed. This allows these plants to better deal with stresses from pests and climatic extremes, because of their enhanced ability to scavenge free radicals via Vitamin C and other antioxidant systems.

The following is also impressive:

The rapidly available nitrogen in the conventional farming system diverts sugars from photosynthesis to produce more proteins and a spike in vegetative growth. And so the plant produces more leaves, and thus more chloroplasts, and then more carotenoids. Whereas in the organic system, the slower and prolonged supply of nitrogen does not trigger a spike in plant growth, allowing more photosynthetic sugars to be available for other metabolic functions such as producing more Vitamin C and polyphenols.

For people who can afford to grow organic, there would be little incentive to grow conventional unless you were trying to feed the hungry around the world or make mega-bucks by selling lettuce to McDonald's or Burger King. For those who can afford to buy organic, the question has to be: is it worth it? I'd like to see a large scale prospective study that compares people who eat mainly organic and those who eat mainly conventional. Do the organic folks live longer? have fewer cases of cancer or heart disease? (Of course, you'd have to control for such things as smoking and drinking, and a few other factors known to affect health and longevity.) Is the quality of their life better? Knowing that there are fewer nitrates or more polyphenols in a grape that is organically grown is really not a very important piece of information by itself. How much of this stuff can my body absorb? How much do I have to eat to get any benefit? If people aren't getting enough nutrients because they are not eating enough fruit or vegetables, how likely is it that they are going to switch to organics when they find out they only need four servings a day instead of five to get their proper nutrition? For people who don't want to eat very much and who have the time and the ability to do the calculations, it might be wise to switch to organics. You might be able to eat less and get the same or better nutritional value from your food.

To sell organics to the rest of us, though, you are going to have to do better than throw out percentages and explain why organic fertilizer is better for plants than conventional.

In any case, when we finally get to the presentation of the data on p. 40 of this 53-page report, we find that the percentages given are even less interesting than we supposed. Actual amounts of any nutrient are not given. If an organic had more of nutrient than a conventional product, it was ranked as "higher" in nutritional value no matter how much more of the nutrient was present. I repeat: having a little more of any nutrient is of little interest. Even two conventionally grown fruits or vegetables will probably vary in nutritional content, even if they come from the same farm. What we want to know is the actual average amount of nutrients in the food. Only then can we determine whether it is worth the extra cost. It is of little interest to me that of 25 matched pairs, 18 of the organics had a higher level of polyphenols than the conventionals. How much higher? Even knowing that on all counts, organics ranked higher in 62% of the matched pairs means little if the actual differences were little. Likewise, knowing that in 23 out of 27 matched pairs, the conventional product had more protein is of little interest on two counts. We don't know the actual differences and quite a lot of us don't rely on plants for our protein.

Table 5.4 on page 42 does provide some data that, while still obscured by using only percentages, gives us some sense of how much more of the nutrients are in organics. In 68 matched pairs, there was one organic  that had more than 50% more of a nutrient: kaempferol. Four of the organics had more than 30% of a nutrient, and two of those were for potassium, a rather readily available nutrient for most of us.

The bottom line? Of the 236 matched pairs, the ratio of superiority of organics was 1.25. If we disregard quercetin (an antioxidant) and nitrates, the ratio is 1.06. This difference is not a difference that makes much difference. It also mitigates the conclusion of the authors that:

The average serving of organic plant-based food contains about 25% more of the nutrients encompassed in this study than a comparable-sized serving of the same food produced by conventional farming methods.

A more accurate claim would be that with a few exceptions, organics contain about 6% more nutrients than conventionals. However, nitrates are not good for you, so organics would be better if you are trying to avoid nitrates. According to Wikipedia, quercetin, a flavonol, is found in many foods. One recent study found that organic tomatoes had 79% more quercetin than those conventionally grown. If they taste as good as or better than fresh tomatoes conventionally grown (not those waxy things picked weeks ago when they were green) and the price is not too exorbitant, I'd buy them. On the other hand, I don't eat too many tomatoes, so I might want to look into alternative ways to get my quercetin: capers. apples, tea (Camellia sinensis), onions, red grapes, citrus fruits, broccoli and other leafy green vegetables, cherries, a number of berries, or the fruit of the prickly pear cactus. I eat berries and leafy green vegetables every day, and am frequently seen putting raw broccoli in my salads. I garnish with a few cherry tomatoes, organic sometimes but usually not. I feel healthier just writing about it, but not superior.

These researchers may have good intentions but many people are going to be suspicious of their methods, which seem to be data mining and cherry picking. If I were trying to sell people on the superiority of organics I think I'd focus on what's not in my product rather than try to make people think that because somebody somewhere can grow a tomato organically that has 80% more of this or that nutrient, organics are superior to conventionally produced foods. In some cases, they are superior. In others, they have more nutrients but not enough to make them "superior." There are many more factors that need to be considered when deciding whether to plant or buy organic or conventional besides average levels of vitamin C or quercetin.

*   *   *

This article is for Tim, who kindly informed me of the study from the Organic Center. Apparently, Tim did not like my article on organic food and farming. He signed his email: Tim (an atheist skeptic Ph.D. scientist who is skeptical of knee-jerk skeptics). I won't take it personally. He also wrote with sarcasm: I'd be interested in seeing how you apply your vast and unbiased knowledge of organic agriculture to analyzing this text. He concluded, without sarcasm: By the way, where is your entry on industrial agriculture? Surely, you couldn't have overlooked the myriad hoaxes that corporate agri-business perpetuates? Such an omission would reveal your political bias, and obviously such an esteemed skeptic such as yourself has none.

Obviously. That's why I'm so well loved in my church.


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