Abstract
Soy bean isoflavones are structurally similar to estrogen, and exhibit weak estrogenic activity. In 2006, Food Safety Commission of the cabinet office set the upper limit of isoflavone (aglycone equivalent) intake from Foods for Specified Health Uses (FOSHU) at 30 mg/day for additional consumption with a normal diet. However, the upper limit for isoflavones was not established in the so-called health foods containing soy protein and isoflavones. We evaluated the respective soy protein and isoflavone contents in 10 health foods including 5 FOSHU by the ELISA and HPLC methods. The soy protein content of eight of these foods was determined to be within 90-118% of that reported on the label, and two protein powders for junior use contained about a half of the soy protein content reported on the label. The isoflavone aglycone content in FOSHU containing soy protein was detected to be 90-122% of the labeled content, while the isoflavone content of two soy protein-fortified foods with no label exceeded 30mg per one serving. It might be necessary to pay attention to junior athletes not excessively consuming these soy protein powder foods.
