Organic Food Has a Higher Nutrient Content

Interview by Arty Mangan

ARTY: The Organic Center did a study comparing the nutritional values of organic versus conventionally grown food, what were the findings.

CHARLES: Out of the eleven nutrients with an ample number of samples to compare nutrient levels, the nutrient density in the organic samples were higher in eight of the eleven, and that includes nitrates. The level of nitrates was actually higher in the conventional food, but because that’s a health disadvantage, we credited organic as superior on the basis of that nutrient.

The highest ratio in favor of organic was in the case of quercetin, where it was 2.4 on average. In the case of total phenolics, the average difference was ten percent. In the case of total antioxidant capacity, it was 24 percent. In the case of vitamin E, it was 15 percent. 

There were two nutrients where conventionally grown crops were higher. One is beta-carotene, the conventional food was eight percent higher for that nutrient, and in protein, where the conventional samples were on average ten percent higher. We discounted the importance of the protein finding because the Western diet contains protein to excess. It’s not a limiting nutrient. The greatest deficiency in nutrient intake is in total antioxidant capacity, and that’s why we felt that the 24 percent advantage for organic production in total antioxidant capacity is really a very significant finding.

ARTY: How does the plant respond differently in an organic system?

CHARLES:  The part of this report that I’m most proud of is a section that’s entitled The Plant Physiology Behind Nutrient Density; it’s on pages nine through eleven. This section of the report explains why vitamin C is typically higher in organic fruits and vegetables, whereas, beta-carotene is typically higher in conventional. It has to do with the role of nitrogen in supporting plant growth.

In order for a plant to start manufacturing vitamin C, the plant has to be triggered to go into its reproductive phase. A plant doesn’t do that until it starts to feel stressed from a lack of nutrients in the soil or adverse weather conditions.  In the summer when it starts to get really hot or dry, the plant says to itself, I’ve got to stop growing foliage and getting bigger, and I need to start putting my energy into setting seed, into the reproductive phase of the plant growth cycle.

In conventional production, where there’s typically ample amounts of nitrogen and a lot of extra foliage grown, the production of vitamin C gets delayed until later in the year. Whereas, on the organic farm, because there’s less readily available nitrogen in the soil, the trigger is flipped earlier so that instead of directing its energy to vegetative growth, the plant directs its energy to reproductive growth. The vitamin C biosynthetic pathway is part of the early stages of setting seed and precedes the reproductive cycle in the plant. So, because it happens earlier in the case of organic production systems, you get more vitamin C. That happens earlier in organically grown plants largely due to less nitrogen supporting an artificial continuation of the vegetative growth phase.

ARTY: Why do organic plants produce more antioxidants?

CHARLES: We believe that the plant physiology literature is actually quite clear on this point. The general finding is that conventional production systems with their near sole focus on enhancing yield levels by applying more nitrogen, in particular, but more of all fertilizer elements, and ample water to push both rapid growth and the production of large fruit – big apples, big grapefruit, large grapes – stimulates hyper production in conventional agriculture that dilutes nutrient levels through what agronomists labeled in the early ‘80s the “dilution effect.”

The dilution effect is driven by high levels of nitrogen and other nutrients in conjunction with ample water supplies. Imagine a plant in a field or a tree in an orchard, the plant and the tree are going to utilize the nutrients and the moisture that’s within the reach of their root systems. Plants can’t get up and move to some other place if they feel that they’re in an excessively nutrient-enhanced environment.

If they happen to be in a field where the farmers have applied lots of nitrogen fertilizer or lots of manure and compost, and indeed excessive nitrogen from any source, the plant roots are going to take that nitrogen up. They can’t turn that process off. Because they’re drawing up excessive nitrogen, the plant has to do something with it, because it’s drawn it up into its stem and leaf structure. The thing that the plant can do with extra nitrogen without causing a problem to itself and the plant’s natural development during the growing season is it converts the extra nitrogen into carbohydrates.

Of course, most carbohydrates are sugars. That’s why, when you buy these unusually large conventional apples, or any fruit, they tend to be incredibly juicy. They have a lot of moisture in them, and they are incredibly sweet, from the extra carbohydrates manufactured from the extra nitrogen and water in the system. The plants pull up the extra nitrogen and water and convert this extra dose of nitrogen through photosynthesis into simple sugars, which reduces the solids in the fruit and it increases the sugar content.

Those two things also directly dilute or reduce the concentration of other phytonutrients, the levels of which do not go up in proportion to the carbohydrates and the moisture. That’s why you get dilution of the antioxidants, dilution of the vitamin C, dilution of the vitamin E, and also dilution of some of the minerals. The plant doesn’t bring up any more of those from the soil, nor does it manufacture any more of them, but the amount that it does produce is diluted by this extra moisture and extra sugar that the plant has made in response to the excessive nitrogen.

ARTY: If we look at the organic plant, antioxidants are, in effect, part of its immune system. Isn’t there an enhancement effect in the organic system that contributes to the 24% increase in antioxidants?

CHARLES: Absolutely. That’s the second part of the story. Most antioxidants are produced in response to either a biotic or abiotic stress. The stress can come from drought, excessive water, too much sunlight or solar radiation, high salt levels in the soil, an insect chewing or sucking on the leaves, and plant diseases or fungi or bacteria. Many scientists have documented instances where plants in an organic system up-regulate or overproduce certain phytonutrients because of the plant’s natural response to climatic conditions or pests.

Sometimes this response can be remarkably significant. For example, one study involving Muscadine grapes showed that the level (or concentration) of resveratrol produced by certain varieties of red grapes increased up to four times higher in a field not sprayed with the standard fungicide program compared to a conventional farm where the standard fungicides had been sprayed to control botrytis and mold. On organic farms, grape plants produce more resveratrol and in some fields and seasons, the resveratrol actually brings about almost the same degree of disease control as the fungicides applied on nearby conventional vineyards.

This Muscadine grape study is one of the most dramatic in the literature because of the four-fold increase in one cultivar. That’s a very big increase. Most studies show a ten, twenty or forty percent increase; some studies show a doubling and a few are tripling, but four fold. That’s very unusual.

There are more than a dozen major categories of phytonutrients, like flavonols, flavonoids and stilbenes, most of which have some degree of antioxidant capacity. These different categories are triggered by different external stimuli, whether they’re biotic in nature, i.e., a pest attack or fungi attack, or abiotic, stress from the environment – drought or intense sunlight. For example, the dark pigment in red grapes, in red and black raspberries, in blueberries, in all of our dark-skinned fruits and vegetables are from stilbenes.

Stilbenes are a family of phytonutrients and are triggered by solar radiation, by sunlight. One of the ways farmers can control stilbene content in their harvest is through canopy management. If you have a dense canopy that shades your fruit, you’re not going to have as high a level of stilbenes. If you open up your canopy so a lot of sunlight gets in, not only will you have high stilbene content, but you may also have some scalding on your fruit.

Stilbene content is very much concentrated in the peel and the tissues just below the peel. If the role of the stilbene is to protect the inside of the grape, the inside of the berry, the inside of the fruit from solar radiation, it’s totally logical that the plant would concentrate it in the peel. It’s also true that stilbenes are highly correlated with unique flavors, particularly in wine. They both protect the plants from the damage of ultraviolet radiation from sunlight and also confer to plants some of their really unique flavors.

On the other hand, we know from a lot of studies that in situations where there’s no unusual climatic stress on the plants, and not a lot of pest pressure in the organic part of the field, there will still be higher levels of some nutrients in the organic plants, and that’s why we think this dilution effect is also part of the explanation. You can’t explain all the differences observed simply because organic plants are under more stress, because sometimes they’re not.

Does organic management on average and in general increase nutrient density, for the nutrients that we really care about, because we don’t get enough of them in our typical diet? The answer is unequivocally yes. The published data that we’ve seen suggests that the nutrient boost is about 25 percent. It can be as high as up to four fold and it can even be negative in some years in some fields, but on average it’s about 25 percent.

Most Americans are getting between three and four servings of fruits and vegetables a day, and they really should be getting five to eight. We all need to approximately double our daily intake of fruits and vegetables. If we can increase average nutrient levels and intakes by 25 percent just by eating organic rather than conventionally grown fruits and vegetables, that’s the equivalent of one extra serving.  Plus, the organic fruit and vegetables will, on average, taste better, which helps reduce the time before a person reaches out for that next serving.  Many studies show that the lack of taste is the major reason why so many kids pass up the chance to consume more fruits and vegetables when they are provided a chance to do so as part of school lunch programs.