## 4 Discussion  
A polyphenol-rich diet is associated with several health benefits, including a reduction of the risk of cardiovascular diseases, type 2 diabetes, obesity, and metabolic syndrome. Over the last few years, growing attention has been paid to polyphenols from grapes for their potential to reduce cardiovascular and metabolic disease onset due to their ability to improve associated risk factors [43], reduce oxidative stress [44] and inflammatory status [45], and increase antioxidant capacity [46]. Furthermore, increasing \(\beta\)-glucan intake has been associated with improved glycemic control and a subsequent reduction in diabetes development. Barley \(\beta\)-glucans form a highly viscous solution in the stomach and small intestine, thereby prolonging nutrient transit and absorption through the gut, and have the ability to affect glucose and lipid metabolism. Many studies have demonstrated the LDL cholesterol-lowering effect of products enriched with \(\beta\)-glucan, whereas a number of other studies have not. Regarding the study of the acute consumption of grape seed flour-enriched bakery products, no similar clinical trials exist in order to directly compare the results of the present study. Limited data concerning grape seed extract intervention studies in healthy cohorts exist in the literature; therefore, comparisons between those findings and the ones demonstrated by our study were performed. Furthermore, concerning barley flour and \(\beta\)-glucan addition in crackers, we are the first to report their acute effect in a healthy cohort as the literature findings retrieved indicated their effect on other bakery products. Therefore, we were the first to assess the effects of the administration of crackers enriched either with 10% grape seed flour or with 40% barley flour with added \(\beta\)-glucan along with a high-fat and high-carbohydrate meal on the metabolic profiles and antioxidant status among a cohort of 12 healthy volunteers. In the literature, human intervention studies have studied the acute and long-term effects of daily grape seed or pomace supplementation in the form of extracts or powders. Some researchers observed beneficial effects in glycemic and lipid profiles, although others recorded no impact of their action. In regard to lowering lipid profiles, it was reported that the acute administration of 300 mg/kg of a procyanidin-rich grape seed extract along with a high-polyunsaturated-fat meal to eight healthy individuals could reduce postprandial oxidative stress by increasing plasma antioxidant status. However,no statistically significant differences were observed in LDL cholesterol and triglyceride levels [47]. The consumption of a high-carbohydrate meal along with 100 or 300 mg grape seed extract by eight healthy adults significantly reduced postprandial glucose levels up to 2 h after treatment [48]. In a similar manner, the intake of grape pomace extract along with a high-fat meal in 18 normal and overweight healthy women managed to reduce uric acid in the normal-weight subjects. Extract consumption did not change the glucose response in all participants, although there was a tendency for a time effect. Triglyceride levels were reduced but not at the significance level, demonstrating a significant time effect, whereas total, HDL-, and LDL-cholesterol post-prandial levels were similar to baseline [49]. Only one human intervention study concerning the enrichment of products with grape pomace was retrieved. Twelve healthy participants (men aged 20-40 years old) followed a 3-day low polyphenol diet prior to the beginning of the study, and they consumed, on two different days separated by a one-week washout period, after an overnight fast, either a polyphenol-rich drink (1.562 g gallic acid equivalents (GAE)) or a control drink, followed after 3 h by the consumption of a standard meal. The standard meal contained 18% protein, 30% fat, and 52% carbohydrate (960 kcal).