**4.1 Tea phytochemicals in diabetics**

Diabetes mellitus, a highly alarming disease worldwide is associated with high levels of blood glucose other than normal which is associated with insufficient insulin production or its ineffectiveness.

Polyphenols in green and black tea are very effective in reducing hyperglycemia and insulin resistance which can manage the blood glucose in diabetes [31, 35, 36].

Thus, tea polyphenols present potential nutraceuticals for various facets of type 2 diabetes mellitus. In type 2 diabetes, insulin tolerance is developed following major metabolic disorder which led to numerous health complications reducing the quality of life and increasing the mortality rate [37]. It has become evident from various *in vivo* experiments that polyphenol phytochemicals and their additive food products modulate metabolism of carbohydrates and lipids, reduce hyperglycemia, insulin resistance, and improve many other metabolic process related to prevention and suppression of diabetics [35]. Consumption of black or green tea on daily can suppress the diabetic cataract and lower the glucose level in blood [36]. Similarly


#### **Table 3.**

*Role of major phytochemicals of tea in different diseases.*

oolong tea has profound effect in treatment of type 2 diabetes [35]. However, further clinical study is required to develop nutraceutical products to apply in diabetic patients for prevention and cure. It was reported in an investigation in Japan that daily intake of about 6 cups of tea could reduce the diabetes affected people [38]. Recently, significant contribution of black tea polyphenol viz. theaflavins and thearubigins were found very effective in oxidative stress related diseases such as diabetes [31]. Therefore, tea nutraceuticals are very much promising in control and treatment of diabetes.

It has been reported that polyphenols have the hypoglycemic effects which are associated in reducing intestinal absorption of dietary carbohydrates affecting glucose metabolism, improvement of β-cell function and insulin action, inducing insulin secretion, and anti-inflammatory and anti-oxidative activity [39].

### **4.2 Tea photochemicals in cardiovascular diseases**

The cardiovascular diseases such as hypertension (high blood pressure), coronary heart diseases (heart attack), cerebrovascular disease (stroke), heart failure, peripheral vascular diseases, etc. have been increasing day by day. The major causes of these are foods habits, chemicals used in food and food products, chemicals used in cultivation as well as lack of awareness.

Green tea consumption has been found to be effective in reduction of cardiovascular related disorders through decreased serum cholesterol and triglyceride. It has been reported in a study carried out in Japan that regular green tea consumption (≥500 mL) reduced the mortality rate in women in cardio vascular diseases by 31% as compared to those who consume non-regularly [40].

The green consumption has the effect of reducing the risk of coronary heart diseases by lowering the hyperlipidemia and total body cholesterol in body [41]. Moreover, EGCG the major catechin in green tea has been shown its usefulness in cardioprotective effects (inhibiting the formation of cardiac hypertrophy), antithrombotic and antiplatelet activities which are associated with cardiovascular diseases [42]. The theaflavin and thearubigins in black tea functional drinks are valuable against lipid and glucose related abnormalities especially high cholesterol and LDL levels [31].

#### **4.3 Tea phytochemicals in obesity**

Obesity has been considered as a serious concern globally effecting large number of peoples. It is associated with accumulation of excess body fats which stimulate various disorders in body such as hypertension, osteoarthritis, hyperlipidemia, heart attack, etc. [43] It is identified as a major factor in many metabolic syndrome such as stroke, heart failure, hypertension, diabetics, arthritis, etc.. The oolong tea food products also were also found to be very effective in decrease of in weight of obese people [44]. The green tea catechin, EGCG has been found to be beneficial on obesity [45]. Catechins in tea helps in weight management and consumption of green tea catechins results significant reduction in body weight in human [46].

#### **4.4 Tea phytochemicals in oral diseases**

Tea phytochemicals are useful in treatment and prevention of various types oral diseases which include tooth decay and oral cancers [47, 48], dental plaque and dental caries [49]. The tea extract and fluoride in tea can prevent the carcinogenic activity of oral bacteria such as *Escherichia coli, Streptococcus salivarius*, and *Streptococcus mutans* [50].
