To provide an agent for preventing, through an increase in the amount of reduced glutathione within the lens, cataract that progresses due to oxidative stress induced by ultraviolet irradiation or aging, diabetes, and prolonged use of steroids, etc. The present invention further addresses the problem of providing food and beverages, such as food and beverage products, health food products, functional food products, and dietary supplement products, which include said cataract preventative agent. The present invention has shown that a yeast extract obtained by a simple method and having a GSH content of 15 mass% or more has an effect of increasing the amount of reduced glutathione within the lens.本發明係提供一種白內障預防劑,藉由增加水晶體中之還原型麩胱甘肽量,來預防因為高齡、紫外線等氧化壓力、進一步為糖尿病或長期使用類固醇等導致病症進展之白內障。並進一步地以提供含有該白內障預防劑之飲食品、健康食品、機能性食品、健康輔助食品等食品類、飲料類為課題。 本案發明者們發現藉由簡單之操作所獲得之GSH含量為15質量%以上的酵母萃取物具有增加水晶體中之還原型麩胱甘肽量的作用。無