BLACK TEA FOR GOOD HEALTH

Provision of diet for the maintenance of physical and mental health is the basic right of every individual and the outcome related to diet on health has been matter of concern since ancient times.  In the late 20th century more emphasis was paid towards health and nutrition that provides a tremendous opportunity to the food processors for marketing healthy food products. The tenet “Let food be the medicine and medicine be the food,” espoused by Hippocrates nearly 2,500 years ago. It is gaining more attention particularly due to increase consumer’s focus in those foods containing health promoting ingredients or physiologically active components known as functional/nutraceutical foods. Such foods are considered to play a key role in disease prevention and maintaining good health.
Functional foods are widely accepted as an adjunct to conventional therapies for enhancing general well being of body that induces resistance against diseases. Modern era bestowed disastrous contribution regarding progression of diseases in humans, induced by the many factors like sedentary life style, polluted environment and unhealthy foods. Nature always acts as helping hand for mankind but such blessings are always hidden and invite the humans for exploration. Tea and its constituents are examples of such compounds contain the solution for the prevention and curing of these evils. Health benefits of the tea are generally attributed to the polyphenols that are secondary plant metabolites, further subdivided into flavanol and flovonol. Tea prominent phytochemicals are theaflavin, thearubingins and theabrownin belong to flavanols while, flavonols are composed of quercetin, kaempferol and myricetin. Theaflavins and thearubigins oxidation help to develop typical color and flavor of black tea. Classically the pigments of black tea have been divided into orange-colored theaflavins (TFs) and brownish thearubigins (TRs) however, former comprises a group of four constituents namely theaflavin, theaflavin 3-gallate, theaflavin, 30-gallate, and theaflavin 3, 30-digallate. The group formation occurs due to reaction between quinones derived from a catechins and gallocatechins. They contributed towards tea brisk, astringent taste and bright golden color to the tea infusion. Likewise, TRs are heterogeneous group of phenolic pigments, molecular mass in the range 700–40,000 Da. They are water soluble, acidic and rust-brown in color that gives the richness to tea taste.
Being a functional drink, black tea provides protection against various maladies and has proven evidences that it is effective against cancer. It inhibits the progression of malignant tumor by inhibiting transcriptional activation of activator protein-1 that is involved in tumor formation. Moreover, it blocked cyclooxygenase-2 gene expression implicated in carcinogenesis and adversely effect the growth factor-mediated cell signaling thereby  block nuclear factor-B mediated cell signaling,  arrested cell cycle progression and inhibited DNA synthesis and cell proliferation.
Diabetes mellitus and its complications are one of the leading causes of death counts in developed and developing countries. According to an estimate, at the end of year 2030, approximately 376 millions peoples will be affected worldwide by diabetes. Currently, Pakistan is ranked at 6th position; it will replace Japan from 5th place at the end of 2030. As a functional drink, black tea acts as a anti-diabetic agent by enhancing the protein, fat and carbohydrate metabolism improving Insulin activity and possibly by preventing b-cells damage. Similarly, tea reduces blood glucose level an indicator of diabetes by suppressing the activity of glucose transporters in the intestinal epithelium that is common in aging population. Furthermore, reduction in oxidative damage to lymphocyte DNA has been observed in diabetic patients receiving quercetin and tea.
Oxidation of low-density lipoprotein (LDL) is recognized as an important factor leading to atherosclerosis and there are several reports indicating that tea inhibits the oxidation of LDL in vitro Studies. The antioxidant effect of tea polyphenols, theaflavin and tea catechins on LDL and VLDL (very low-density lipoproteins) oxidation indicate their effectiveness against aforementioned threats, having lipoprotein bound antioxidant activity greater than that of tocopherol. In a research study, decreased serum lipid concentration and increased resistance of LDL to oxidation were observed by taking 600 or 900 mL tea per day. Neurological and psychological effects of tea are due to theanine by acting as a neurotransmitter in the brain and decreases blood pressure significantly in hypertensive subjects. Tea ingestion induces a rapid increase in alertness and improves mental capacity due to presence of caffeine. Owing to antibacterial effect of black tea, stomach transit time is increased thus improves the gastrointestinal health. As a functional drink, black tea exerted inhibitory effects against microorganisms like Vibrio chol-erae, Salmonella typhi, Campilobacter jejuni, Campi- lobacter coli, Helicobacter pylori, Shigella, Salmonella, Clostridium, Pseudomonas, Candida, Mycoplasma and Cryptococcus.
Succinctly, it is concluded that black tea has a lot of health benefits nevertheless; caffeine is an alarming factor in this contest. However, it is suggested that a comprehensive study will be executed to enhance the meticulousness regarding the role of black tea as a functional drink.
Caffeine over consumption: a human threat
Caffeine (3,7-dihydro-1, 3,7-trimethyl-1H-purine-2, 6 Dionne),  present about 2 to 4 % of dry basis however, the availability of nutrients in soil affects caffeine content in plants. Caffeine is the most widely consumed behaviorally active substance in the world. Average caffeine consumption in humans can range in different cultures and nations from 80 to 400 mg/person per day. In humans, approximately 80% of caffeine is demethylated to paraxanthine and approximately 16% is converted into theobromine and theophylline in the liver. About 3% of caffeine ingested and more than a dozen of its metabolites can be found in urine. No doubt its moderate consumption provide multiplicity of the health benefits including reduced risk of gallstones formation in humans especially in women and lowers the risk of developing type 2 diabetes in humans. It is also related to decrease the incidence or risk of Parkinson’s disease. But its over consumption is a constant source of danger for the user so its harmful effect should be examine that act as a check on its consumption. Caffeine has a diuretic effect and in healthy volunteers the acute administration of caffeine causes a short-term increase in dieresis. Excessive caffeine consumption causes addiction and lead to caffeinism, a condition that has serious behavioral and physiological side effects. In addition to that caffeine consumption causes the urinary excretion of substances such as sodium, potassium, chlorides, magnesium, and calcium in healthy young females. Chronic caffeine consumption increases the risk of osteoporosis (A disease in which the bones become extremely porous, are subject to fracture, and heal slowly) and hip fracture. functional activation of the shell of the nucleus accumbens, an area involved in addiction and reward, was only induced by the highest dose of caffeine 10 (mg/kg). Effect of the caffeine on the cardiovascular system with a slight increase in blood pressure and heart output. It also undergoes biotransformation in the human body to form mentholated derivatives of uric acid. High caffeine consumption causes less chance of pregnancy and/or lead to miscarriage in women. It amplified the increases in blood pressure and heart rate associated with higher levels of self-reported stress and these observed blood pressure elevations reach a maximum 30 to 60 minutes after caffeine administration and persist for several hours. As a result these repeated daily blood pressure elevations and increases in stress reactivity caused by caffeine consumption could contribute to an increased risk of coronary heart disease in the adult population. Moreover, chronic caffeine intake affects renal structure, function and blood pressure in patients with Autosomal dominant polycystic kidney disease (ADPKD). Autosomal dominant polycystic kidney disease (ADPKD) is a common inherited disorder frequently associated with renal failure, hypertension and other abnormalities. Hence chronic caffeine intake increase in severity of hypertension in patients with ADPKD, it may be wise for patients with this disease to limit their intake of caffeinated coffee to four or fewer cups per day.
Different scientist studied the contribution of caffeine to the homocysteine-raising effect of coffee in humans. A high plasma total homocysteine concentration is associated with increased risk of cardiovascular disease. Consequently caffeine is partly responsible for the homocysteine-raising effect of coffee and consumption of unfiltered or filtered coffee raises total homocysteine concentrations in healthy volunteers.
 It was observed that caffeine have the ability to block adenosine receptors at low concentrations even after a single cup of coffee, but other mechanisms of action such as inhibition of phosphodiesterase and mobilization of intracellular calcium demand higher concentrations of caffeine. In addition the CNS effects of caffeine are mediated particularly by its antagonistic actions at the A1 and A2A subtypes of the adenosine receptors. Adenosine A1 receptors are present in almost all brain areas. Consequently the intake of a high dose of caffeine is not reinforced by positive and pleasant behavioral effects.
Caffeine causes a harmful effect on renal inner medullary collecting duct cells. It was toxic and very strong additive. Consequently the chronic excess ingestion of no steroid anti-inflammatory drugs such as caffeine causes renal medullary necrosis. It was strongly suggested that caffeine in beverages like tea and coffee increases the risk of hypertension and its regular intake increases BP. Further more found that caffeine and diterpenes present in unfiltered coffee increase the risk of coronary heart disease while the lower risk of coronary heart disease among moderate coffee drinkers might be due to antioxidants found in coffee.