No wonder millions of people around the world drink it: caffeine-containing beverages, such as coffee and tea, are the most popular psychoactive drug. But should we be concerned about the ever-increasing array of drinks that contain caffeine?

In this fact sheet, Leanne Cooper from Sneaky's examines caffeine, its sources, and its effect on the body - providing you with all the necessary information to make the final decision.

Caffeine facts

Caffeine is found in the leaves and beans of the coffee tree, in tea leaves, guarana berries, and in small amounts in cocoa and the kola nut . If you enjoy a cup of Rooibus, you will be pleased to learn that this tea comes from a different plant and contains no caffeine. Caffeine also turns up as an ingredient in cold medications, appetite suppressants and pain relievers, and can be helpful against some headaches and of course to combat drowsiness.

Surprisingly, it's the leaves of the tea plant that contain the most caffeine, around 5% compared to 1-2% for coffee beans. Plants cleverly use caffeine for survival as it repels many insects .

As most of us know, caffeine stimulates our central nervous system (CNS), helping to keep us alert (that get-up-and-go feeling) and overcome listlessness.

What's in a cuppa?

Depending on what you read, the amount of caffeine in food will vary. A 150 ml cup of tea varies from 30-100 mg of caffeine. A determining factor is how the tea is made. Adding milk, sugar, using loose leaves or teabags (strong loose-leaf tea provides the most caffeine) all create a different result.

Coffee beans come in two flavours: Robusta, which has more caffeine, and Arabica. A 150 ml cup of drip-percolated coffee typically has a caffeine content of 100-150 mg; instant coffee has 60-100 mg per 150 ml, depending on the brand. An espresso comes in at around 90 mg per 150 ml. This is good news for those mums who sneak in an espresso after dropping off the kids at school.

A 200 g block of chocolate contains the equivalent of about 550 mg of combined methylxathines (caffeine-like compounds and other stimulants). A 30 g bar has between 20-60 mg caffeine-like effect. This may be something to note if you have a child who is overly active and enjoys the odd chocolate bar.

Given our teenagers are the ones who consume the greatest quantity of soft drinks, caffeine intake is something to keep an eye on.

A 375 ml cola drink contains around 40 mg of caffeine while a 250 ml energy drink contains around 80-100 mg caffeine - about the same as a shot of espresso. No wonder we have trouble keeping up with our teenagers!

The rate at which our bodies metabolise caffeine depends on our liver and its ability to deal with such drugs. While it's been found that women can clear drugs such as caffeine from their liver faster than men, this is influenced by hormone levels and medications. It takes longer for women to clear such drugs when they are pregnant or on the oral contraceptive pill.

Caffeine is rapidly absorbed in less than an hour. After this, it has a half-life (the time it takes for the total amount taken in to be reduced or cleared to half) of 3½ to 6 hours.

Note: Caffeine content is highly unpredictable in coffee and tea, especially in tea. Preparation is a huge factor and colour is a very poor indicator of caffeine content. Teas such as the green Japanese Gyokuro contain far more caffeine than much darker teas like Lapsang Souchong, which have very little. Even approximate caffeine contents assigned to teas are generally very inaccurate.

WHAT IS THE EFFECT OF CAFFEINE?

When drunk in moderation, for most of us caffeine is harmless and can even have benefits. However, keep an eye on your intake and that of your children - whether it is green tea or chocolate.

As well as being a central nervous system stimulant, caffeine is also a diuretic (increases the loss of fluid through the kidneys) and affects our body in a number of ways.

Short-term effects include:

• Contraction of the muscles, which can cause twitching.
• An increased heart rate.
• Slowing of blood flow to the stomach.
• More sugar is released from the liver into the bloodstream.
• Breathing tubes open up.
• A cup of coffee before bedtime may make it harder to sleep. You'll also find that you sleep deeper for shorter periods and have shorter dream cycles. As a result, you feel less rested when you wake up. However, some tolerance to caffeine can lessen these effects.

Benefits include:

• As an antioxidant, it may help prevent heart disease and some cancers. Coffee also contains flavonoids, which are also antioxidants.
• Assisting premature babies experiencing breathing difficulties. Minute amounts of caffeine given intravenously can stimulate a newborn baby's brain to tell the lungs to inflate.
• Shift workers or others suffering from fatigue may benefit from caffeine's properties as a stimulant.

Have a coffee and sober up?

Now that's a question for alcohol drinkers - and the answer is: no chance. Not even a strong cuppa can make you sober after a few drinks. While caffeine may make you feel more alert, it will not alter your blood alcohol level.

Withdrawal

I am sure many of you have experienced this feeling even if you might not admit it. To date, caffeine is not considered addictive but it can be habit-forming. As we develop a tolerance towards it, so we need more in order to produce the same sensations. In effect, we need to drink more to 'top up' our reserves.

Withdrawal symptoms (usually starting within 12-24 hours, peaking at 48 hours and lasting for between 1 and 5 days) occur because after a day or so without caffeine the brain begins to struggle on its own.

Other symptoms may include nausea, fatigue, drowsiness, anxiety, vomiting and irritability. In extreme cases, symptoms may include depression, inability to concentrate and diminished motivation to initiate or to complete daily tasks at home or at work.

IS YOUR COFFEE MAKING YOU NERVOUS?

Those of you who are self-confessed coffee addicts may be interested to learn that a high intake of caffeine is clinically associated with a number of psychological conditions.

The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) states:

The four caffeine-induced psychiatric disorders include caffeine intoxication, caffeine-induced anxiety disorder, caffeine-induced sleep disorder, and caffeine-related disorder not otherwise specified (NOS). Excessive caffeine intake, also known as caffeine-ism, may result in panic disorders, anxiety, bipolar disorder, and schizophrenia. A growing number of medical professionals believe caffeine-intoxicated people are routinely misdiagnosed and unnecessarily medicated.

How much is too much?

As we know, caffeine affects people differently according to their body's ability to deal with it. As a general guideline though, you should consume less than 600 mg per day - around four cups of strong drip-percolated coffee, or five or six cups of tea (less is recommended for pregnant or breastfeeding women).

This nutritionist believes that one to two cups a day is fine for the average person. However, if certain circumstances put you outside this category, abstaining isn't going to hurt.

Pregnancy

Caffeine is quickly absorbed and reaches a peak concentration in blood within an hour of ingestion: it also has negative impacts on the unborn child. Studies have shown that women who drink in excess of one cup of coffee a day are only half as likely to conceive as those who drink less than a cup a day. The odds are even worse for women who drink more than two and a half cups a day (they are nearly five times less likely to conceive as women who do not drink coffee at all) (Wisborg, 2003).

Studies also suggest that caffeine reduces fertility in men by damaging the sperm. Caffeine has been reported to negatively influence the production of hormones that control fertility, for example it may reduce the rate by which an egg successfully implants in the uterus.

Unfortunately, we don't fully understand the impact of caffeine on human development. We do know that as little as two or three cups of brewed coffee every day during pregnancy can result in lowered infant birth weight, prematurity, poor reflexes and slowed neuromuscular development . There is a far clearer picture of the effect of caffeine on infants and children.

But it's not all bad news. As we've noted briefly above, caffeine has a therapeutic effect on premature and near-miss SIDS infants. Caffeine's minor effect on respiration (increasing blood flow through the lungs and increasing the supply of air) appears to be useful in treating breathing problems of some prematurely born infants.

Breastfeeding

While the actual amount that a mother consumes - which then turns up in breastmilk - is variable, it is estimated that 0.06% to 1.5% of the amount ingested crosses into breastmilk. The half-life of caffeine is between 3-7 hours (women not on the pill will be at the longer end). However, for newborns - who metabolise caffeine very slowly - the half-life is 80 hours.

Caffeine has an affinity with the fatty, creamy layer of breastmilk and consequently tends to be most concentrated two hours after we drink it. Caffeine can also reduce milk supply and may be associated with recurrent mastitis (ABA, 2004). In some studies, it's been found that mothers who consume lots of caffeinated drinks have lower iron levels in their breastmilk. This may explain why there are more instances of iron deficiency anaemia in countries where lots of coffee is consumed. Babies of mothers who drink large amounts of caffeine can show signs of agitation, jitteriness, constipation and general unsettledness. So cutting back on caffeine could be the answer to a good night's sleep - for both you and your bub!

Because caffeine is a diuretic, drinking too much may lead to dehydration amongst breastfeeding mums. With bub taking between three and five cups of fluid a day from mum, staying hydrated is extremely important.

But even if you are breastfeeding, you don't need to completely deny yourself the small pleasures in life such as the occasional tea or coffee. However, keep your intake to one or two cups once in a while, ideally after feeding. The American Academy of Paediatrics suggests that breastfeeding mums consume no more than three cups of coffee a day (that is equivalent to less than 300 mg/day); they also warn that smoking increases the effect of caffeine in the body, so mothers who smoke should reduce this amount even further.

Created by Leanne Cooper, nutritionist mother of two and director Sneakys. The information provided is not meant to replace medical advice .

Contact details for Leanne Cooper and Sneaky's: PO Box 313 Manly NSW 1655: Ph: 02 9400 9759: Web: www.sneakys.com.au

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