Answer:Jeffrey Blumberg, PhD, director of Tufts HNRCA Antioxidants Research Laboratory, replies, I am unaware of any studies that have examined the effect of soy milk on the antioxidant activity of tea. However, the basic premise of this interaction is that the protein (mostly casein) in milk binds to the tea flavonoids, particularly the catechins, and thus inhibits their antioxidant capacity as well as bioavailability. As soy milk also contains substantial protein (albeit not casein), a similar reaction is plausible. He cautions, though, that the evidence that cow milk does bind significantly to tea flavonoids and impairs their antioxidant activity and bioavailability is equivocal.