The benefits of certain foods, such as orange juice, could be more important than we think, according to a new study suggesting current methods for determining antioxidant activity only tell half the story.

Researchers from the University of Granada developed a method called the global antioxidant response (GAR) that they claim provides a more thorough analysis because it assesses food in its entirety.

The researchers say that current methods for determining antioxidant value reflect only the portion that gets absorbed by the small intestine, called the liquid fraction.

"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," says study author Jose Angel Rufian-Henares.

"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."

Using their GAR method, which simulates gastrointestinal digestion in vitro, on both commercial and natural orange, mandarin, lemon and grapefruit juices, the team found 70 percent of the antioxidant activity was found in the solid fraction, meaning that the numbers could be far greater than previously established.

"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 analyzed with this methodology," says Rufián-Henares.