## 6 Conclusions  
Major bioactive compounds abundant in whole grains, such as polyphenols, flavonoids, antioxidants, and fiber, have been demonstrated to have preventive effects on cardiovascular and metabolic diseases. Alkylresorcinols, averthramides, ferulic acid, and \(\gamma\)-oryzanol are representative polyphenols in whole grains, especially in rice bran or oat, and show preventive effects against impaired glucose intolerance, diabetes, vascular diseases, hypertension, and dyslipidemia. Rutin, one of the types a flavonoid rich in buckwheat, improved insulin sensitivity, glucose tolerance, lipid metabolism, and hypertension-related parameters. Doctorienol, which are antioxidants that are generally derived from RBO and \(\alpha\)-tocopherol, found in a variety of foods, also show hypolipidemic and hypoglycemic effects in vivo and in humans. In particular, the anti-hyperlipidemic effects of tootrienol are attenuated by interactions with \(\alpha\)-tocopherol. Soluble fiber, including \(\beta\)-glucan from oat and barley, decreased lipid profiles by inhibition of cholesterol or fatty acid synthesis and absorption, as well as blood glucose levels, with improved glucose intolerance and insulin resistance. As described above, the preventive effects of bioactive compounds derived from whole grains on cardiovascular and metabolic diseases are well-established; therefore, whole grains are often consumed as a healthy food. Indeed, various studies have revealed that whole grain food consumption improves metabolic parameters. In a meta-analysis, intake of 3 servings, or 90 g, of whole grains per day was related to 19% and 22% reduced risks of coronary artery disease and cardiovascular diseases, respectively [25]. In addition, an overall inverse association between whole grain and metabolic syndrome has been identified, while a positive association has been detected for refined grain consumption in a meta-analysis of several observational studies [99]. The favorable effects of whole grain foods on cardiovascular and metabolic diseases have also been observed in clinical intervention studies. A higher consumption of a whole grain-enriched diet was associated with higher concentrations of lipid metabolites and decreased postprandial insulin levels compared to those for the intake of a refined wheat cereal diet in subjects who have metabolic syndrome [100]. Supplementation of a low-fiber diet with oat bran also improved non-HDL-C and TC compared to levels for the control diet [101]. The consumption of tartary buckwheat, a whole grain food, decreased the levels of insulin, LDL-C, and TC in patients who have T2D [102]. However, a non-significant association was observed in another study. Whole grain consumption did not alter metabolic disease parameters, anthropometric measurements, or body composition in those who were healthy, overweight, or obese and consumed whole grain wheat for 8 weeks compared to parameter values for the refined wheat product consumption group [103]. However, the amount of intake and study duration varies by studies. In addition, specific doses of bioactive compounds derived from whole grain foods and appropriate treatment duration of the studies described in this review are also still inconclusive. Thus, more studies of the relationship between the intake of bioactive compounds or whole grains and metabolic and cardiovascular diseases for specific guidelines should be conducted. Taken together, these results indicate that bioactive compounds rich in whole grains, including alkylresorcinols, avenanthramides, ferulic acid, \(\gamma\)-oryzanol, rutin, locotrienol, \(\alpha\)-tocopherol, and \(\beta\)-glucan, as well as whole grains as a whole food, play important roles in the prevention of cardiovascular and metabolic diseases. However, data for the effects of individual bioactive compounds from well-designed human studies are still lacking, and the interactive effects of various bioactive compounds on the regulation of cardiovascular and metabolic diseases are still unclear.