2.5. Intervention
inflammation
INFLAMMATION, OXIDATIVE STRESS
The intervention was composed of two factors: treatment and time. The treatment factor served as the antioxidant agent and was a grape drink or placebo. The time factor served as the modulator of the effect of the agent on the oxidative stress challenge (high-fat meal) and was morning or evening. The grape drink consisted of 46 g grape powder (equivalent to 1.5 servings of fresh grapes) reconstituted in 120 mL water. The grape powder was a mixture of fresh black, red and green seeded and unseeded California grapes that had been frozen, ground with food-quality dry ice, freeze-dried and reground. The control treatment was 120 mL of a placebo drink composed of a grape-like powder. The placebo powder closely matched the grape powder in sensory characteristics, dietary fiber content, sugar profile (fructose and glucose) and organic acid (tartaric, malic, and citric) profile. Artificial dyes (FD&C) were used in the placebo in place of natural colorings to avoid the addition of polyphenolic compounds from natural colorings. Flavorings used in the placebo powder contained no polyphenolic compounds or antioxidants. Both powders were prepared in 46 g packets and provided by the California Table Grape Commission (Fresno, CA, USA) for human research. The polyphenol content is listed in High-fat meal: A single high-fat meal was used to provoke an oxidative stress response [Test mealtimes: The laboratory visits began at 7:00 a.m. and 6:00 p.m. These times approximate the beginning of the active and rest diurnal phases, respectively, while accommodating participant availability for testing. Published data indicate higher blood and urine markers of inflammation and oxidative stress during the early active phase compared to the early rest phase [Randomization was performed using an online research randomization generator in blocks of 8 participants. The principal investigator assigned participants to an intervention group.