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.
The new method also allowed the researchers to create a mathematical model to help determine which storage or processing methods could maintain the highest antioxidant content in various juices.
“This technique and the results derived from it could allow dieticians and health authorities to better establish the values of the antioxidant capacity of foods, ” Henares said.
Orange juice prevents cancer, stroke
The antioxidants in orange juice are believed to be behind many of its health benefits, including prevention of cancer and stroke. A 2013 study in the journal Nutrition and Cancer: An International Journal reviewed all the research on orange juice and cancer prevention, concluding that antioxidants in orange juice helped prevent cancers of the blood, breast, colon and liver.
“OJ could contribute to chemoprevention at every stage of cancer initiation and progression,” the researchers wrote. “Among the most relevant biological effects of OJ is the juice’s antigenotoxic and antimutagenic potential.”
A 2012 study published in the journal Stroke found that women with a high amount of antioxidants known as flavanones in their diet were 19 percent less likely to suffer blood-clot-related stroke than women with the lowest flavanone intake. Eighty-two percent of the flavanones consumed in the study came from oranges and orange juice, while another 14 percent came from grapefruits and grapefruit juice.