Caffeine: friend or foe?

Press, 12 October 1985, Page 14

Caffeine: friend or foe?

FDDD AI.ERT

JANICE BREMER

DIETITIAN

“How about a cuppa?” That friendly gesture is rooted in our everyday lives as an excuse to take a break and have a reviver. For younger people who find tea and coffee have less appeal, “things go better with . . .” would gain the same response. The common stimulant in these drinks is caffeine.

We might be drug conscious enough to be cautious about taking alcohol, oral contraceptives, aspirin, and multi-vitamin pills, but what about caffeine?

Out potential problems with caffiene consumption are relatively new.

Little coffee was drunk in New Zealand before the early 19505. Since the introduction of suitable machinery to make instant coffee, there has been an upward trend in coffee consumption.

We now drink more than four times the amount New Zealanders consumed in the 19505. Now we have about two to three cups of coffee a day, per head of population.

An Australian study of two years ago found that only three per cent of the population were true abstainers from caffeine. It was also found that twothirds of the coffee drunk was instant, and only five per cent was decaffeinated. More than two-thirds of people drank both tea and coffee. This seems to be a similar trend in New Zealand.

Our yearly tea consumption figures show that per head of population we drink an average of three to four cups of tea each day (depending on strength). Although coffee contributes more caffeine than tea, collectively they do provide most of our caffeine intake.

The Australian study also found that chocolate and cola drinks — the other main sources of caffeine — make a considerable contribution to the diets of younger people. Even then, it is only aoout eight per cent of caffeine intake of 20 to 25-year-olds. Young children get most of their caffeine from chocolate drinks, Coca Cola, chocolate, and chocolateflavoured foods. However, a child of eight or nine years bf age can consume as much caffeine per kilogram of body weight as an adult having five qdps of coffee, by. eating three

dark chocolate bars, (chunky, six-square type) and drinking two cans of cola, and two cups of cocoa. But does this less-than-deliberate consumption of caffeine do us any harm?

Most authorities who have dared to suggest a limit say that the equivalent of five cups of coffee is unlikely to be harmful. However, our individual tolerance varies. Effects

Caffeine is one of the alkaloids found in food and drink. It has well established effects to:

• Act as a mild stimulant, giving a “lift” to reduce drowsiness and tiredness and improve mental alertness.

0 Act as a diuretic, producing a greater volume of urine than would be produced by just drinking water.

• Release fatty acids into the bloodstream. This is an effect used by athletes to "spare” their carbohydrate stores and extend endurance in events longer than 90 minutes — 2-3 cups of coffee an hour or so before the event.

® Increase our rate of breathing and subsequently the amount of work than can be carried out by the muscles. (Evidence that caffeine improves performance in events relying on strength and power does not provide firm conclusions as that supporting glycogensparing in endurance events). • May raise the metabolic rate after meals, the energy used by the vital processes of the body. This effect has been found to be more of a help in weight reduction for those close to ideal weight, rather than those who are very overweight >

Adverse effects • Coffee may stimulate increased stomach secretions, with side effects of heartburn or reflux.

® Even modest amounts prevent some people from sleeping. • Excessive caffeine may cause lack of appetite, anxiety, loss of weight, irritability, or even severe palpitations, headaches, or nervousness. These symptoms may even be experienced by those drinking normal amounts. • Some people suffer “withdrawal*’ symptoms when they stop drinking caffeine, even at levels of six cups per day. These symptoms — headache, inability to concentrate, nervousness, sleepiness can be' avoided by gradually reducing intake over a period of a week — (weaning). © Other adverse effects of caffeine discussed in the medical literature include worsening of peptic ulcers, heart disease, cancers, kidney diseases, and congenital abnormalities (birth defects).

While we await evidence to support speculation about the effects of coffee and tea on medical disorders, we cannot just wait for evidence about the effects on unborn children. Babies can be born with very high caffeine levels in their bloodstream. Caffeine seems to have a more than double potency in pregnant women. It now seems to be generally recognised that in the early stages of pregnancy, and even before conception, all drugs — including alcohol and smoking — should be avoided. • Tea and coffee consumption can greatly affect the

absorption of iron from our meals. Non-meat iron absorption may be reduced by 60 to 90. per cent by tea consumed at the meal. Coffee may reduce it to around 40 per cent. On the other hand, orange juice enhances the iron absorption to five to six times the rate if tea was drunk at the same meal. Wine and spirits have a slight enhancing effect on iron absorption.

Caffeine levels There is a negative intake of carbohydrate, protein, and fat from coffee or tea. But the addition of milk and sugar to six cups of tea or coffee each day can add up to 1500 kilojoules, or 360 calories. Instant coffee carries about half the caffeine load of filtered coffee.

Tea provides valuable fluoride and folate, and coffee provides nicotinic acid, . but otherwise — apart from a few minerals — these drinks offer little nutritional value.

Moderation can be defined as 250 to 300 mg of caffeine each day for adults, but less than a quarter of this for children (depending on their size). Food alert

® Watch total caffeine intake, select a variety of drinks each day. 9 Keep coffee to times you want to be alert, it helps to counter the sluggish effect of a large meal. • Preferably have tea in between meals to reduce its effect on iron absorption.

In moderation,' tea and coffee contribute to our mental and physical wellbeing without inducing unpleasant side effects, or addiction in the majority of consumers.

“Consumer” magazine reported the caffeine levels of various drinks and foods in their March issue. Listed here are grouped approximate values for some drinks.

mg 1 cup equals 150 ml — check your cup size caffeine 1 cup tea with tea bag — three minute brew 55.0 1 cup “pot-of-tea” brewed 1 minute, weak 35.0 brewed 5 minutes, strong 80.0 1 cup instant coffee 55-75 1 cup decaffeinated 5.6 1 cup percolated 125.0 1 can Coca Cola 30.0 1 teaspoon cocoa U 3.8