ON HOT days many of us reach for an ice-cold glass of water, but we may be better opting for a cup of tea. According to the European Journal of Clinical Nutrition and a growing number of British dieticians, drinking three or more cups of tea a day can be just as good as drinking water, not only because it counts towards your recommended daily intake of two litres of water, but because it has many added benefits.

Black tea contains flavonoid polyphenols, which are plant compounds that have anti-oxidant, anti-bacterial and anti-inflammatory properties which prevent cell damage. A recent overview of tea studies found that drinking three or four cups of tea a day can cut your chances of having a heart attack, bolster protection against tooth plaque and decay - as tea contains natural fluoride - and strengthen your bones, thus reducing your risk of osteoporosis.

However, while drinking black tea can substantially improve the ability of your arteries to relax and expand, which keeps your blood pressure healthy, according the European Heart Journal, taking milk in your cuppa - as 98% of Brits do - ruins all the good work. German researchers found that caseins in milk reduced the concentration of catechins, which help dilate blood vessels by producing nitric oxide.

Black tea also scores less well as it blocks the absorption of dietary iron because it contains tannins (an astringent phenolic compound) and phytates (the stored form of phosphorus). These bind with iron molecules making it unavailable for other bodily functions, such as transporting oxygen around your body and maintaining your immune system.

Green tea, which is more commonly drunk in Asian countries, such as China and Japan, has not undergone any fermenting so it's believed to have greater anti-oxidant properties and more catechins than black tea. However, it is an acquired taste as it's very earthy.

A Japanese study published in the Journal Of The American Medical Association found that regular green tea drinkers reduced their risk of fatal cardiovascular disease by almost a third. However green tea enthusiasts are quick to point out that the health benefits accrue over the long-term. In order to improve your anti-oxidant levels and to help guard against free radical damage, you should ideally be drinking five cups of green tea a day for a year . Free radicals interfere with your cell structure so they can't replicate in a healthy manner.

The west has recently become more aware of the health benefits of white tea. This is not black tea with milk added, but is made from new growth buds and young leaves of the plant Camellia sinensis. The leaves are steamed and then dried which means it retains the high concentrations of flavonoid catechins which are present in fresh tea leaves.

As white teas contain buds as well as leaves (other teas are mainly leaves), the dried tea doesn't look green but has a pale appearance. A study from Pace University in the US found that white tea had more anti-viral and anti-bacterial properties than green tea.

White tea may have the power to battle cancer-causing cells and many different types of cancer, such as colon, prostate and stomach cancers. Flavonoids (a class of antioxidants) inhibit the growth of cancer cells and prevent the development of new ones.

Studies show that white tea can thin the blood and improve artery function. It helps lower high blood pressure and maintain a healthy heart. By promoting strong, healthy blood vessels, white tea guards against the ravages of a stroke. Antioxidant catechins have been found to reduce cholesterol, and white tea is teeming with them.

Cholesterol is a special type of fat, necessary for health. There is good cholesterol and bad cholesterol, and white tea increases the good while decreasing the bad. This helps prevent hardening of the arteries and blockage of blood flow. By thinning the blood, lowering blood pressure and reducing cholesterol, white tea protects the heart and the entire circulatory system.

Researchers have also discovered that people who drink two or more cups of white tea a day are almost 50% less likely to die after suffering a heart attack.

And white tea has also become the doyenne of anti-ageing beauty products recently because it hunts down damaging free radicals, protects your skin and helps reverse the signs of ageing caused by stress, the sun and a poor diet. Both Origins and Estée Lauder have incorporated it into their moisturisers and eye products.