A great drink - but beware the pitfalls

Three cups of tea contain the equivalent amount of anti-oxidants found in six apples.

(China Daily) Tea is my cure-all: Earl Grey when I need soothing; green tea as a mid-afternoon pick-me-up: pu'er tea if I'm feeling a bit posh and a good strong cup of English Breakfast tea (in fact from India or Africa) to wake me up first thing.

Of course there is a huge variety of teas available both in China and internationally, but all of these true teas are made from the leaves of the Camellia sinensis plant in one form or another.

Infusions made with different plants (ie chrysanthemum, jasmine, chamomile) are not technically "tea" but instead should really be referred to as a "tisane".

True tea is split into three categories.

First up are both green and white teas which are made from young leaves and buds - these are then steamed or burned to deactivate some of the innate chemicals.

The second category is oolong tea - here, leaves are bruised and crushed, then allowed to oxidise awhile before they are heated and dried.

The final group is black tea, where the leaves are rolled and broken extensively, and allowed to oxidise completely before drying. These are referred to (technically incorrectly) as fermented teas.

Teas from all these groups have a number of extremely beneficial health properties and are a rich source of many different natural compounds called flavonoids. Green tea is much higher in flavanols called catechins, while black tea contains greater amounts of theaflavins and thearubigins. All types of tea contain good amounts of similarly named flavonols like quercetin and rutin.

All you need to know is that these all have potent anti-oxidants which can help to protect you against heart disease, stroke, cancer and neurodegenerative diseases. Of course, tea should not be considered a replacement for fruit and vegetables that contain other nutrients, but a 1999 study showed that three cups of tea contain the equivalent amount of anti-oxidants found in six apples.

Tea plants gather fluoride in their leaves and so may contribute significant amounts to the daily intake of tea drinkers. In the US, the recommended "Adequate Intake" (AI) of fluoride is 3-4 mg per day for adults and 0.7-2.0 mg for children. A cup of tea contains around 0.3mg-0.5mg, and this figure doubles if the water used is already fluoridated.

Fluoride's chief role is in reducing dental cavities, although it also contributes to healthy bones and protecting against osteoporosis. In addition to fluoride, the flavonoids and tannins in tea can reduce the harmful activity of bacteria in the mouth, so all in all, tea (without sugar) can help to keep your teeth healthy.

Camellia sinensis contains caffeine, so all teas (unless they go through a decaffeinating process) will contain caffeine. Green tea tends to have slightly less than oolong and black teas. An average cup of black tea (around 200ml) has about 40mg caffeine - this is compared to a cup of brewed coffee, which has about 100mg. That leaves room for 7-8 cups of tea per day as 300mg caffeine per day is considered a safe intake for adults.

Caffeine can act as a diuretic (causing you to lose water) but only if consumed in large amounts at one time ie 6-8 cups, or 250-300mg caffeine. On the other hand, tea drunk in a lesser quantity can make a valuable contribution to daily fluid intake.

People suffering from anaemia (iron deficiency) should be careful when they drink tea - the tea's tannins heavily reduce iron absorption from the food you are eating. This effect is even greater if you have milk in your tea, as the calcium competes with iron for absorption. Conclusion? Have your cuppa in between meals, not with them.

This nutrition-related column is written by Nina Lenton, a qualified dietitian living and working in Beijing. Contact her at nina_lenton@hotmail.com.