Soy consumption linked to memory improvement, antidepressant and skin-protective effects

The Soybean Processing and Utilization Division of the Korean Society of Food Science and Technology held a symposium July 3 at the Daejeon Convention Center on the theme of "Health Effects of Soy Foods and Soy-Derived Compounds." Researchers presented the latest findings demonstrating the health benefits of soy foods and derived compounds such as isoflavones.

The symposium was chaired by Lim Tae-gyu, a professor at Sejong University. Presentations covered the memory-improving effects of fermented soybean jang products, by Park Sun-min of Hoseo University; the antidepressant effects of peptides derived from soy protein isolate, by Kim Hyun-jun of Gyeongnam National University of Science and Technology; the skin-protective effects of isoflavones against fine dust-induced damage, by Kim Jong-eun of Korea National University of Transportation; and the effects of soy protein-derived compounds on bone metabolism, by Oh Nam-su of Korea University.

Park Sun-min of Hoseo University presented findings that traditional fermented soy products — soy sauce and cheonggukjang — may contribute to memory improvement through the gut-brain axis. In a study in which rats with induced memory impairment were fed a diet supplemented with 1 percent soy sauce for seven weeks, inflammatory cytokines in the hippocampus decreased and memory function improved.

In a gerbil model with induced ischemia, cheonggukjang also improved cerebral blood flow and the gut microbiome environment, alleviating declines in memory and cognitive function. Postbiotics produced during fermentation were found to play an important role in memory improvement through the gut-brain axis.

Kim Hyun-jun of Gyeongnam National University of Science and Technology reported that a low-molecular-weight tyrosine-containing peptide derived from soy protein isolate hydrolysate (SPH) alleviated depression-like behavior induced by chronic stress. When SPH was administered to a chronic immobilization stress (CIS) mouse model, blood corticosterone levels fell and both antistress and antidepressant effects were observed.

Kim Jong-eun of Korea National University of Transportation presented findings that orobol, a derivative of the soy isoflavone genistein, suppressed tumor formation and growth in a UV-induced skin cancer model and reduced collagenase expression in a skin aging model, demonstrating skin-protective effects. Orobol is present in trace amounts in fermented foods.

Oh Nam-su of Korea University said a soy protein material (MRPF) combining Maillard reaction and lactic acid bacteria fermentation may help improve bacterial vaginosis and postmenopausal osteoporosis through the gut-vaginal axis and gut-bone axis. In an osteoporosis model in particular, the material preserved bone microstructure and bone density while increasing beneficial gut bacteria.

"The soy protein material showed improvement effects in animal models of bacterial vaginosis and postmenopausal osteoporosis," Oh said. "This suggests its potential as a functional soy protein material acting through the gut-vaginal axis and gut-bone axis."