For the first time ever, a study has proven that eating flavonoids, a type of antioxidant that’s especially concentrated in fruits and vegetables, may boost your immune system.

How did the researchers come to this realization? By watching birds.

Researchers from the University of Freiburg and the Max Plank Institute for Ornithology in Germany offered blackcaps a choice of two foods; they were identical except one contained more flavonoids. Sure enough, the birds chose to eat the foods that contained the extra antioxidants.

Next, they looked into what impact the flavonoids had on the birds’ health. Compared with birds not fed flavonoids, those that ate modest amounts of the healthy antioxidants for four weeks had stronger immune systems.

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