Increased cytokine production by monocytes from human subjects who consumed grape powder was not mediated by differences in dietary intake patterns

Recently, in a randomized, double-blind crossover study, we reported that consumption of grape powder by obese human subjects increased the production of the proinflammatory cytokines interleukin (IL)-1β and IL-6 by peripheral blood monocytes after ex vivo stimulation with bacterial lipopolysaccharide compared with the placebo treatment. We hypothesized that dietary grape powder increased the production of these cytokines by stimulated monocytes. To test this hypothesis, we used 24-hour dietary recall data to determine if differences in dietary patterns played a role in increased cytokine production. No differences in total energy, protein, carbohydrates, or fat intake in the diets were observed between the grape powder and placebo intervention periods. There were no differences observed in consumption of meats and poultry, eggs, fish, vegetables, grains, total dairy, or nuts and seeds by the participants between the 2 intervention periods. When participants received the grape powder, the recall data showed decreased intakes of butyric and capric acids (P < .05), and a possible trend toward decreased intake of cheese and total fruit (P < .1). Positive associations between the intakes of margaric acid, butter, total dairy, or whole grain and IL-6 production were observed (P < .05). However, path analysis showed that total energy, protein, carbohydrates, and fats, and individual fatty acids did not influence the production of cytokines by monocytes. The path analysis indicated that the increased cytokine production by lipopolysaccharide-stimulated monocytes from obese human subjects was caused by the grape powder and not mediated by differences in dietary intake.