## 3 Bioactivity of _Chlorella vulgaris_ Compounds
### Lipid-Lowering and Cardiovascular Effects  
Several studies suggest that _C. vulgaris_ can lower lipid levels, contributing to cardiovascular health. Its consumption has been associated with reductions in total cholesterol, LDL cholesterol, and triglycerides, while it may either increase HDL cholesterol or have no significant effect on it [68; 103; 104]. According to Sherafati et al. [105], a systematic review and dose-response meta-analysis assessed the impact of _C. vulgaris_ supplementation on blood lipids. The analysis revealed a significant reduction in total cholesterol (TC) and LDL levels, with a mean difference of -7.47 mg/dL for TC and -7.71 mg/dL for LDL. However, there was no significant effect on triglycerides and HDL levels. The dose-response analysis further indicated that the LDL lowering effect was most pronounced at dosages up to 1500 mg/day, with no significant benefits at higher doses. These lipid-lowering effects, along with the antioxidant and anti-inflammatory properties of _C. vulgaris_, make it an effective agent in preventing atherosclerosis and promoting heart health [44].  
The mechanisms by which _C. vulgaris_ exerts these lipid-lowering effects are multifaceted and involve various biochemical pathways. One of the primary mechanisms is the presence of omega-3 fatty acids in _C. vulgaris_, which are known to have beneficial effects on lipid metabolism. Omega-3 fatty acids can reduce triglyceride levels in the bloodstream by promoting their utilization and oxidation in the liver [106]. In a study involving Wistar strain rats, it was observed that the administration of _C. vulgaris_ led to a significant reduction in triglyceride levels, suggesting that the omega-3 content plays a crucial role in this process [106]. Additionally, the PUFAs found in _C. vulgaris_ may help improve the lipid profile by enhancing the activity of lipoprotein lipase, an enzyme that facilitates the breakdown of triglycerides [106].  
Another important mechanism is the fiber content of _C. vulgaris_, which can decrease intestinal fat absorption. The dietary fiber present in _C. vulgaris_ binds to dietary fats in the gastrointestinal tract, thereby reducing their absorption into the bloodstream. This effect can lead to lower overall lipid levels and improved metabolic health [17]. Furthermore, the presence of bioactive compounds, such as peptides and polysaccharides, may also contribute to the modulation of lipid metabolism by influencing gut microbiota composition and activity, which in turn can affect lipid absorption and metabolism [17]. _C. vulgaris_ has also been shown to exert anti-inflammatory effects, which can further aid in lipid regulation. Chronic inflammation is often associated with dyslipidemia and metabolic syndrome, and the anti-inflammatory properties of _C. vulgaris_ may help mitigate these conditions. By reducing inflammation, _C. vulgaris_ can improve insulin sensitivity and promote better lipid metabolism, leading to lower lipid levels in the body [17]. Moreover, the antioxidant properties of _C. vulgaris_ may play a role in its lipid-lowering effects. Antioxidants help reduce oxidative stress, which is linked to lipid peroxidation and the development of atherosclerosis. By neutralizing free radicals, _C. vulgaris_ can protect lipids from oxidative damage, thereby maintaining a healthier lipid profile.