The antioxidant activity of citrus juices is 10 times higher than previously thought, according to a new analysis conducted by researchers from the University of Granada and published in the journal Food Chemistry.
Many of the chemicals that naturally occur in plant foods function as antioxidants, removing the free radical chemicals that cause cellular and DNA damage in the body and have been linked to various chronic diseases and many of the symptoms of aging. Citrus fruits are particularly high in antioxidants, and many researchers have suggested this as a potential cause for their many health benefits.
70 percent of antioxidants were going uncounted
To date, researchers have estimated the antioxidant potential of foods by simulating the digestion of food in the small intestine, in order to only measure antioxidants that can actually be used by the body. This method only allows the measurement of antioxidants in liquid form, however.
"The problem is that the antioxidant activity of the solid fraction (the fibre) isn't measured, as it's assumed that it isn't beneficial," researcher Jose Angel Rufian Henares said. "However, this insoluble fraction arrives at the large intestine and the intestinal microbiota can also ferment it and extract even more antioxidant substances, which we can assess with our new methodology."
In order to correct his limitation, the researchers developed a new laboratory method, called "global antioxidant response" (GAR), to simulate the digestion of food not just in the small intestine but the entire gut. This allows an estimate of the antioxidant activity of solid foods.
According to the GAR method of analysis, the antioxidant contents of many foods have been drastically underestimated and will need to be revised. For example, traditional antioxidant activity tests deliver a value of approximately 2.3 mmol Trolox/L for orange juice. The GAR method, in contrast, delivers a value of 23 mmol Trolox/L.
"The antioxidant activity is, on average, ten times higher than that which everyone thought up until now, and not just in juices, but also in any other kind of food analysed with this methodology," researcher Rufian Henares said.
The researchers found that 70 percent of the antioxidant capability of orange juice came from soluble fiber, rather than liquids. Based on the new values, they estimated that as much as 12 percent of the antioxidant content of the Spanish diet comes from citrus juices.
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