Jan. 31, 2007 — Flavonoids — the powerful, plant-based antioxidant compounds that have been linked to disease prevention — are found in a variety of fruits, nuts and vegetables. But, as a recent government report points out, the amount you get depends on the kind of plant you eat, and how much stress it has endured.
In its most comprehensive study yet on the healthy compounds, the U.S. Department of Agriculture not only suggest that certain varieties of fruits, nuts and veggies contain more antioxidants than others, but that flavonoid content varies widely between individual samples. For example, a market may display a tub full of red delicious apples, but flavonoid levels in each individual apple may vary.
The research showed that the difference may be due to stress, which appears to increase the healthful properties of produce. Nutritionist David Haytowitz, one of the study’s authors, explained to Discovery News that taxing conditions — such as those created by more natural farming methods — appear to force plants to release greater amounts of flavonoids and other beneficial compounds.
"Insect attacks and weather conditions can be stressful to plants," he explained. "Even harvest times are important, as early morning harvests are less stressful than those conducted around noon, since the midday sun adds to a plant’s stress."
Such factors may explain why one flavonoid varied from 31 to 114 milligrams in 3 ½-ounce samples of the same variety of sweet red cherry.
Another factor is color, which is chemically linked to many antioxidants. Raw blueberries, blackberries, cranberries and strawberries all ranked very high for several flavonoids that have been shown to reduce inflammation and to rid the body of damaging free radicals.
"We are interested, because they may help to prevent coronary vascular disease, cancer and other diseases," said Haytowitz, who added that color does not always indicate antioxidant content.
"Green tea and green leafy vegetables happen to be high in flavonoids, but that is not related to their color, which comes from chlorophyll," he explained.
Bananas ranked high for compounds called flavan-3-ols, even though the flesh of this fruit is creamy white.
