Antioxidants in Dark Soy Sauce Have Dramatic Effect

Researchers from the National University of Singapore, Yong Loo Lin School of Medicine, recently investigated the vascular and antioxidant effects of dark soy sauce in human volunteers. The results of the study were published in today's edition of Biochemical and Biophysical Research Communications (2006; 344:906-911; see http://www.sciencedirect.com/science/journal/0006291X). Funding for this research was provided by the Biomedical Research Council (see http://www.a-star.edu.sg/astar/about/action/about_bmrc.do).

The researchers divided 24 volunteers into two groups which were given either rice with 30 mL of dark soy sauce or plain rice with added caramel coloring (placebo). After three days, the groups switched. Analysis showed that the dark soy sauce had a rapid antioxidant effect--on average, 10 times greater than red wine and 150 times greater than vitamins C and E--with an accompanying improved vascular effect. The researchers did not note any effect on blood pressure resulting from the sodium content of the soy sauce.

One finding of note that resulted from this research is the fact that feeding alone--the placebo group--produced an antioxidant effect. Therefore, the authors of this study note researchers need to take this effect into account when using biomarkers as a tool to evaluate oxidative damage to avoid drawing misleading conclusions. Despite the fact that the placebo group demonstrated antioxidant effects, the authors note that the dark-soy-sauce group had "significantly greater" antioxidant effects.

"The next step would be to examine whether long-term feeding of dark soy sauce could prolong the antioxidant activity and ameliorate the adverse consequences of oxidative stress," note the researchers in the Biochemical and Biophysical Research Communications article. This will involve analyzing the effects of repeated, long-term consumption of dark soy sauce.