传统发酵食品中D-乳酸的免疫调节作用研究

鉴于人类机体只存在可快速代谢L-乳酸的L-乳酸脱氢酶，世界卫生组织提倡在食品及医药行业中使用L-乳酸取代DL-乳酸。然而事实上，D-乳酸在诸多传统发酵食品（例如酸奶、奶酪及泡菜等）中大量存在且具悠久食用历史。从营养学角度来看，这存有较大争议，亟待业界澄清。针对上述疑惑，我们进行初步探索却意外发现：D-乳酸抗炎活性远强于L-乳酸且未见明显毒副作用。本项目将主要围绕“D-乳酸是否和如何影响机体免疫调节” 这一科学问题展开，拟从食品营养学及食品毒理学的视角，重点考察D-乳酸作为传统发酵食品免疫调节功能物质基础的安全性和有效性，并阐明其作用机制，以期为未来益生菌定向筛选和个性化应用新策略的制定提供科学依据和理论基础。

Lactic acid has two optical isomers: L(+)-lactic acid and D(–)-lactic acid. Due to the absence of D-lactate dehydrogenase (D-LDH), D-lactic acid is metabolized slower than L -lactic acid in human. To this end, L-lactic acid is classified as generally recognized as safe for use as a food additive, while the maximum acceptable daily intake for D-lactic acid is 100 mg/kg body weight (WHO, 1967). It must be pointed out that D-lactic acid is an ingredient of many fermented foods such as yogurt, cheese, sauerkraut and kimchi. And therein lies the great paradox for nutritionist. To clarify the issue above, we performed a preliminary study and surprisingly revealed that D-lactic acid possessed much better anti-inflammatory activity than L-lactic acid both in vitro and in vivo. Inspired by those findings, we hypothesize that D-lactic acid in fermented foods might functionally mediate immune regulation. The objective of this study is to evaluate the potential of D-lactic acid in host immune regulation and clarify its underlying mechanism of actions. This study might give an insight into the role of D-lactic acid in host physiological homeostasis, and provide a strong rational for application of D-lactic acid-produced probiotic lactic acid bacteria in human health promotion and chronic disease intervention in future.