FOR YEARS, I have used and recommending green tea for its incredible health benefits. Tea (primarily black tea) is, in fact, the most widely consumed beverage on the planet, while coffee drinking is still extremely popular around the world. All these beverages have a common constituent - caffeine. But what's the truth about caffeine?

Caffeine defined

Caffeine is known chemically as trimethylxanthine. Medically, caffeine is used to stimulate the heart, to dilate the breathing passages in conditions like asthma and also as a mild diuretic to increase urine production.

Recreationally, it is used to provide a boost of energy or create a feeling of heightened alertness. Caffeine by itself is a brain stimulant, and is addictive as its actions are similar to those of the amphetamine drugs.

Caffeine occurs naturally in many plants, including coffee beans, tea leaves and cocoa nuts. It is important to note, however, that in these natural food substances, the caffeine exists not in isolation, but in combination with hundreds of other active chemicals which can modulate the actions of caffeine itself.

In its unbounded wisdom, Mother Nature often creates her own checks and balances that we often override by isolating and using one component of a plant. This is what happens when caffeine is added artificially to a wide range of food products including a variety of beverages.

CAFFEINE IN DIET

Here are the most common everyday sources of caffeine:

Coffee: Typical drip-brewed coffee contains 100mg per six ounce cup. If you are buying your coffee at a restaurant or fast food outlet or drinking it at home or the office out of a mug, you are consuming it in 12-, 14- or 20-ounce containers. You can calculate the number of milligrams based on your normal serving size.

Tea: Typical black tea (regular tea bags) contains 70mg per six ounce cup. Green tea contains 30mg per six ounce cup.

Others: Generally colas (Coca-Cola, Pepsi, Sprite, etc.) contain 50mg per 12 oz can. Cocoa or hot chocolate will contain 20mg per six ounce cup. Typical milk chocolate contains 6mg per ounce.

Anacin contains 32mg per tablet. No-doz contains 100mg per tablet. Dexatrim contain 200mg per tablet.

BENEFITS

Two hundred milligrams of caffeine have been shown to improve alertness and concentration, and studies have suggested it helps some night-shift workers to maintain concentration, potentially reducing the chances of industrial accidents.

Ingesting 300mg (equivalent to three cups of coffee) 30 minutes before workouts results in up to 30 per cent improvement in endurance with faster times, less exertion, less fatigue, and more rapid recovery.

Caffeine is the most active ingredient in many 'diet pills' as it breaks down fat into fatty acids, which are immediately burned. Conversion of fat to energy is about 30 per cent more efficient when caffeine is consumed prior to exercise. However, this breakdown, and burning, occur only when you exercise.

It's been suggested that because caffeine is an antioxidant, it may help prevent the development of some types of cancer.

CAFFEINATED SOFT DRINKS AND CHILDREN

A high-caffeine intake is bad for children. It actually dissolves the calcium in young bones. When a group of 13- to-18-year-olds drank an unsweetened caffeinated drink, the calcium output in their urine increased by 25 per cent. When they drank caffeine plus sugar, their calcium loss was even higher.

Phosphorus, found in most carbonated soft drinks, accelerates bone loss even more. One soda costs a child as much as 120 milligrams of calcium. Furthermore, a soft drink after a workout also depletes children's sodium chloride, and potassium, causing sore muscles and delayed recovery time after exercise.

BEST SOURCE

Yes, caffeine is potentially useful, but how much you consume and where you get it from is very important. I believe that the best source of caffeine is green tea. Why?

Green tea contains much smaller quantities of caffeine than coffee or black tea. It has a powerful energising and fat-burning effect due to other substances it contains, and not just caffeine.

Green tea contains potent antioxidants called polyphenols that can prevent prostate, breast and intestinal cancer. It also has a long list of other health benefits, from lowering cholesterol to preventing tooth decay.

In addition to energising, green tea also has an anxiety-relieving effect. This is due to the presence of a substance called treanine that appears unique to teas.

So when used wisely and in moderation, caffeine can have many health benefits. But I recommend that you get it mostly from green tea.

Email Dr. Tony Vendryes at vendryes@mac.com, visit the website www.anounceof prevention.org, or listen to 'An Ounce of Prevention' on Power 106 FM on Fridays and Saturdays at 8:00 p.m.