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Cardiovascular disease is a main cause of morbidity, disability, and mortality all around the world. Atherosclerotic cardiovascular disease is the number one cause of death in the United States and other developed countries (Lloyd et al. 2010). Hyperlipidemia, which results from abnormalities in lipid metabolism, leads to the development of atherosclerotic plaques and is one of the key risk factors of CVD (Jain et al., 2007). Risk of heart attack is 3-fold higher in subjects with hyperlipidemia than in subjects with normal lipid status (Yusuf et al., 2004).
Cardiovascular diseases are recognized as multifactorial diseases. Risk factors for the development of CVD have been identified, which includes older age, male sex, a positive family history, hypertension, diabetes mellitus, dyslipidemia, obesity, andcigarette smoking (Ezzati M., et al 2007). All around the world high cholesterol is one of the major health concerns affecting people. According to the World Health Organization, about 39% of the people worldwide cholesterol (WHO, 2013).
Cholesterol is one of thecardinal substances in sustaining the normal functions of the body, including the cell structures and manufacturing of hormones. High cholesterol, can lead to increased risk of heart disease and stroke. High cholesterol treatments target Low Density Lipoprotein (LDL), which is often referred to as the "bad cholesterol". LDL is known as "bad" because it transport cholesterol from the liver to body cells and often results in plaque formation in the arteries(National Heart Lung and Blood Institute, 2012).
Many clinical trials show an increased risk of heart disease when there is an elevated level of LDL, making LDL the primary target of therapy (Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults, 2011).Oxidation of LDL is thought to play an important role in the atherogenesis. In the initial stages of atherosclerosis, LDL accumulates in the intima of lesion-prone sites of the arterial wall (Schwartz et al., 1991).
The possible involvement of oxidative processes early in atherogenesis has stimulated the idea that dietary antioxidants may have a preventive effect in cardiovascular disease (Gey, 1995). Epidemiological data and randomized trials indicate a protective role of dietary oxidants against CVD (Stephens et al., 1996). Flavonoids derived from tea have been demonstrated to efficiently scavenge a variety of free radicals. Indeed, the potent antioxidant properties of tea polyphenols are thought to be one of the mechanisms underlying their putative protective action against CVD. When the complex nature of atherosclerosis is considered, tea may have a protective role against CVD via a number of different mechanisms, one of which is its antioxidant activity. (Report of the Dietary Guidelines Advisory Committee, 2010).
Tea is the most consumed beverage in the world besides water. Consumption of tea is in the forms of green, oolong, and black tea, which are originated from the leaves of the plant Camelliasinensis. Green tea polyphenols have been extensively studied as reducing cardiovascular disease (CVD) agents (Zaveri, 2006; Cooper et al., 2005). Green tea is prepared by drying, not fermenting, freshly harvested tea leaves and therefore contains more antioxidants than fermented teas. Freshly harvested leaves are immediately steamed to prevent fermentation, yielding a dry, stable product, steaming process destroys the enzymes responsible for breaking down the color pigments in the leaves and allows the tea to maintain its green color during the manufacturing processes. As green tea is fermented to oolong and then to black tea, polyphenol compounds (catechins) in green tea are dimerized, such that these teas may have different biological roles (Cheng, 2000).
Approximately 2.5 million tons of tea leaves are produced annually worldwide, with 20% produced as green tea, which is consumed in Asia, some regions of North Africa, the United States, and Europe. Green tea has been found beneficial than black tea in terms of antioxidant activity due to the higher content of (âˆ’)-epigallocatechingallate (Cheng, 2000). Catechins, a class of low molecular weight polyphenols, are major polyphenols of green tea, which comprises of one third of total dry weight of green tea. Green tea contains poly phenolic compounds, (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin-3-gallate (ECG) and (-)-epicatechin (EC). The major catechin is (âˆ’) epigallocatechin-3-gallate (EGCG). The biological effects of tea polyphenols are focused on the effects of EGCG, including the prevention of LDL oxidation, reduction of platelet aggregation, lipid regulation, and inhibition of proliferation and migration of smooth muscle cells (Cabrera et al ., 2006).
The cardio-protective effect of flavonoids from green tea can be attributed to not only antioxidant, anti-thrombogenic and anti-inflammatory properties but also improvement of coronary flow velocity reserve (Hirata et al., 2004; Cheng, 2004). The beneficial effect of green tea against atherosclerosis has been referred to the antioxidant activity of the flavonoids (Rietveld and Wiseman., 2003). Antioxidants are compounds that protect cells against the damaging effects of reactive oxygen species such as free radicals. An imbalance between antioxidants and reactive oxygen species results in oxidative stress, leading to cellular damage. Catechins are hypothesized to help protect against these diseases by contributing, along with antioxidant vitamins and enzymes, to the total antioxidant defense system (Abdel-Raheimet al., 2009).
Chinese green tea has been shown to significantly prevent endothelial-cell induced LDL oxidation and suppress lipoxygenase activity. Because LDL oxidation is a characteristic feature of atherogenesis and lipoxygenase is involved in the process, the intake of green tea, hence, reduces the risk of coronary heart disease. Green tea has also been shown to lower plasma cholesterol by increasing fecal bile acids and cholesterol (Yang and Koo., 2000). Green tea also has an anti-inflammatory effect (Cheng., 2003). Green tea might be a preventive agent for chronic inflammatory diseases (Sueokaet al., 2001).
Green tea catechins affect lipid metabolism by different pathways and prevent the appearance of atherosclerotic plaque. Its intake decreases the absorption of triglycerides and cholesterol and these findings are in accordance with the fact that it increases excretion of fat (Raederstorffet al., 2003).
The project at hand has been planned:
To determine and compare the nutritive value, along with total phenolic contents, of Lipton green tea and locally available green tea.
To examine the effect of green tea on cardiovascular diseases.
To compare the consequences of both Lipton green tea and locally available green tea on cardiovascular diseases.