Beneficial effects of oral pure caffeine on oxidative stress.

Ingestion of coffee (which is a mixture of over 1000 hydrosoluble substances) is known to protect from type-2 diabetes mellitus and its complications, and other chronic disorders associated with increased oxidative damage in blood and tissues. This protection is generally attributed to polyphenols and melanoidins. Very few studies were conducted on the amelioration of classic blood markers of oxidative stress induced after a few days of caffeine administration, but results vary. To assess whether caffeine could account for antioxidant properties of coffee in the short-term, we tested the ability of pure caffeine ingestion (5 mg/kg body weight/day in two daily doses for seven consecutive days) to improve plasma levels of six biochemical indices in healthy male volunteers (n = 15). These indices were total antioxidant capacity (TAC), glutathione (GSH), oxidized glutathione (GSSG), GSH to GSSG ratio, lipid hydroperoxides (LOOH) and malondialdehyde (MDA). We found that all indices changed significantly (P < .05 or < .01) in a favourable manner, ranging from -41% for GSSG to -70% for LHP levels, and +106% for GSH levels to +249% for the GSG/GSSG ratio. Changes of any given index were uniform across subjects, with no outliers. We conclude that caffeine has unequivocal, consistent antioxidant properties.