## 1 Introduction  
Nowadays, cardiovascular diseases have become life-threatening worldwide. There are many causes of cardiovascular events, such as hypercholesterolemia. Hypercholesterolemia is the state of having a high level of lipids in the bloodstream due to increased total cholesterol, triglycerides, and low-density lipoprotein (LDL) levels. According to the Department of Mental Health, Thailand, the number of hypercholesterolic patients has increased annually, due to the higher rate of a high-fat diets, lack of exercise, and unhealthy eating behavior. The excessive consumption of fatty foods leads to high blood lipid levels, which further develop into cardiovascular disease [1]. In patients with mild hypercholesterolemia, there are many effective ways to manage and prevent high lipidlevels in the bloodstream, such as changing dietary behavior, doing more exercise, or even taking supplement products [2]. It is suggested that soy, red yeast, vitamin C, and probiotics can help to improve blood lipid profiles [3; 4; 5].  
Oxidative stress has been defined as the imbalance between reactive oxygen species (free radicals) and antioxidant defenses, which leads to tissue damage because of the oxidation reaction [6]. A previous study [7] reported that high LDL levels are associated with the oxidative stress state caused by lipid peroxidation. The oxidant LDL will lead to foam cell generation, and will become further atherosclerosis.  
Probiotics are live microorganisms that, when administered in adequate amounts, provide a health benefit to the host. _L. paracasei_ displays probiotic properties, including acid and bile tolerance, adhesion to mucosal and epithelial surfaces, antimicrobial activity, and bile salt hydrolase activity. _L. paracasei_ can lower cholesterol levels both in humans and animal models. There are several pathways involved in cholesterol-lowering; for example, deconjugating bile salts into bile acids and excreting them out of the body via feces to promote the use of cholesterol as a substrate in order to synthesize more bile acids [8]. The antioxidant effects of _L. paracasei_ have been reported by many processes, including up-regulating antioxidative activity, promoting the production of glutathione (GSH), and down-regulating the production of malondialdehydedehyde (MDA), which is a reactive oxygen species (ROS) [9]. Moreover, probiotics can stimulate an immune response by increasing immunoglobulin production, and through the enhancement of macrophages and lymphocyte activity, the stimulation of the \(\gamma\)-interferon output, and the stimulation of both the acquired and innate immune response via immunoglobulin A (IgA) secretion and phagocytosis induction [10]. Moreover, they provide assistance in detoxification and the removal of toxins such as lipopolysaccharide from the body [11].  
_L. paracasei_ HII01 was isolated from northern Thai pickles and was reported for its beneficial effects on fatigued, obese, and diabetic subjects [12]. However, there is a limited number of studies on hypercholesterolemia Thai subjects. Therefore, the current study was conducted to investigate the effect of _L. paracasei_ HII01 supplementation on cholesterol and oxidative stress levels in Thai subjects with hypercholesterolemia.