Studies show marred fruit may pack more nutrition

April 28, 2016

The old saying of don’t judge a book by its cover may also hold true for fruit as some studies are showing that unsightly scars on the outside of nature’s candy might actually reflect a higher nutritional content within.

Take apples, for example. The scars and other blemishes you sometimes see on their skin are a result of the fruit fighting fungus, heat and pests as they grow. While many are quick to turn their back on these less appealing looking fruits, others are showing that some blemished produce pack an unexpected nutritional punch — courtesy of its own battles to survive.

An article explains that a 2014 review of 343 studies found that organic produce had lower pesticide residue and a 20 – 40% percent higher antioxidant content than conventional produce. Those antioxidants include compounds such as flavonoids, phenolic acids, anthocyanins and carotenoids, all produced by plants as defense mechanisms when they are stressed by pests. The study authors suggested that organic crops may be subject to more stress because they may receive fewer pesticides, in lower doses, and with less potent killing effects.

Another study of both conventional and organic apple varieties found higher antioxidant phenols and fruit acids in organic apples. The study authors noted, "The regular consumption of fruit acids is helpful in preventing illness and metabolic disorders. We recommend the consumption of regional organically grown varieties rather than of cultivars from integrated cultivation."

The article explains that though not all pests and diseases are benign, some common apple infestations are the result of harmless fungi that result in sooty "blotch" (dark patches) and fly speck (black dots), but do not harm taste or texture nor infect humans. These blotches are a result of the plant fighting off environmental insults — relying on its antioxidant defenses to do so.

One study showed that an apple covered in scab had more healthy, antioxidant phenolic compounds, called phenylpropanoids, than a scab-free apple peel. Another study showed that apple leaves infected with scab have 10 – 20% more phenolic compounds. Similar research has found high levels of resveratrol in grape leaves infected with fungi or simply exposed to the stress of ultraviolet light. Resveratrol is an antioxidant that's been well-studied for its potential cardio-protective action that protect both plants, and probably the humans who eat them.

This does not mean that we should turn away from conventional agriculture, or make hard and fast assumptions about crops, environmental biologist Brian Ward, said in the article. "There are so many factors contributing to antioxidant content. The most important factor is the plant itself — and the variety. That's genetic. Then there is the soil, its mineral content, and whether conventional or organic fertilizer is used. But yes, there is some interesting data that when plants are stressed by insects or disease, they produce metabolites that are good for us."

Microbiologist Martin L. Pall says that our own innate, potent protective mechanisms can be activated by compounds in fruits and vegetables. In fact, he suggests in a recent research paper, those antioxidants may serve as mild stressors that kick our repair mechanisms into high gear. They activate a molecule in our cells known as Nrf2, which itself can trigger the activity of over 500 genes, most of which have cell-protective functions.

"This is certainly true of compounds like resveratrol," he said. "That part of the story is pretty clear." He says there's intriguing evidence that other plant compounds that increase under stress may be good for our health, too, but those benefits are not as well-documented.

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Category: Food Safety