Effects of regular consumption of vitamin C-rich or polyphenol-rich apple juice on cardiometabolic markers in healthy adults: a randomized crossover trial

The aim of the present study was to investigate the effects of the consumption of two cloudy apple juices with different polyphenol and vitamin C contents on antioxidant status, cardiometabolic and inflammation markers in healthy young adults. Twenty subjects, aged 21-29 years, completed a randomized crossover study. At each 4-week intervention period, the volunteers randomly consumed two glasses (2 x 250 mL/day) of either a vitamin C-rich apple juice (VCR) (60 mg/L vitamin C and 510 mg catechin equivalent/L) or a polyphenol-rich (PR) juice (22 mg/L vitamin C and 993 mg catechin equivalent/L). Blood and urine samples were collected throughout the study, and markers of antioxidant status, glucose metabolism, lipid profile and inflammation were measured. The comparison of the post-intervention minus pre-intervention change revealed differential results in HOMA index, total cholesterol, ICAM-1 and VCAM-1 (P < 0.05) across juices. During the VCR period, plasma antioxidant activity (FRAP) increased (P = 0.031), while ICAM-1 and total cholesterol showed a trend to decrease (P = 0.060 and P = 0.094, respectively). During the PR period, plasma insulin and HOMA increased, and total glutathione decreased (P < 0.05). A joint consumption of apple juice natural antioxidants such as vitamin C and polyphenols might provide mild favorable effects on cardiometabolic markers, as compared to apple polyphenols alone.