## 1 Introduction  
Human beings are constantly striving for the development of methods for the prevention and treatment of diseases. In the Global Burden of Disease (GBD) 2019 data, the prevalence of cardiovascular disease has approximately doubled over the past 30 years [1]. In addition, cardiovascular diseases are linked to risk factors for metabolic diseases, such as obesity and diabetes [2]. Therefore, lowering the prevalence of metabolic and cardiovascular diseases is considered one of the biggest challenges of today. It is well known that increases in the prevalence of metabolic and cardiovascular diseases are closely related to lifestyle patterns, such as physical activity and dietary habits [3, 4]. Therefore, unlike other diseases, substantial efforts to prevent metabolic and cardiovascular diseases have focused on lifestyle corrections prior to medical treatment. As part of this, food and food ingredients that help prevent metabolic and cardiovascular diseases are attracting attention. In particular, interest in plant-derived phytochemicals is growing [5, 6]. The most commonly consumed food in the world is grains (e.g., oats, barley, and buckwheal), which are a source of carbohydrates. In general, people around the world, on average, get almost 50% of their daily energy intake from carbohydrates [7, 8, 9, 10]; accordingly, the impact of grain quality on health cannot be overlooked. Previously, many people preferred refined grains with a soft texture. However, interest in whole grains has increased continuously as various nutrients and active ingredients contained in whole grains have been revealed. More than 80% of whole grains consist of endosperm, and the hull contains germ and bran (Figure 1). Most of them consist of carbohydrates, but they also contain proteins, vitamins, and minerals. In particular, germ and bran contain dietary fiber, B vitamins, minerals, and various phytochemicals [11]. However, most of the germ and bran are removed through the milling process [12]. Many studies have shown that various nutrients and active ingredients in whole grains, especially in the germ or bran, are effective in improving chronic diseases, including metabolic and cardiovascular diseases [13; 14; 15; 16; 17; 18]. Representatively, there are phenol- and dietary fiber-derived compounds. In addition, it contains various tools, which are vitamin E with strong antioxidant activity. They are known to be involved in blood glucose and lipid metabolism, as well as having antioxidant and anti-inflammatory effects [19; 20; 21; 22]. Due to the influence of these various bioactive compounds, it has been reported that whole grain consumption is the main factor affecting mortality due to cardiovascular disease [23]. Indeed, three servings of whole grains per day was associated with a reduced risk of mortality from cardiovascular diseases in a meta-analysis [24]. In another meta-analysis study with various cohorts, it was also reported that consuming three servings of whole grains reduced the relative risk of mortality from metabolic diseases and cancers, as well as cardiovascular disease prevalence [25]. However, the associations between various bioactive compounds in whole grains and risk factors for metabolic and cardiovascular diseases have rarely been reviewed. Therefore, a literature review was performed to evaluate the characteristics and functions of active ingredients in whole grains and the effects of whole grain consumption on metabolic and cardiovascular diseases. In particular, we describe recent findings on phenol-, vitamin E-, and dietary fiber-derived bioactive compounds, which are representative bioactive compounds in the following four major groups (including eight compounds): whole grain-specific polyphenols, including alkylrescornols (ARs), avenuethramides (Avns), ferulic acids (FA), and \(\gamma\)-oryzanol (OZ); flavonoids, including rutin; vitamin E, including locotrienol and \(\alpha\)-tocopherol; dietary fiber, including \(\beta\)-glucan (Figure 2). Figure 1: Whole grain wheat composition.