Caffeine in beverages: How much is too much?

Caffeine is a stimulant that occurs naturally in coffee, cocoa beans, tea leaves, guarana berries and kola nuts. Caffeine stimulates the central nervous system, alleviating fatigue and increasing wakefulness. People differ greatly in their sensitivity to caffeine. If you're susceptible to the effects of caffeine, just small amounts or even one cup of coffee or tea may prompt unwanted effects, such as anxiety, restlessness, irritability and sleep problems. People who are used to drinking more caffeine-laden beverages regularly tend to be less sensitive to its negative effects.

Caffeine content in beverages
The average caffeine content of ground roasted coffee is around 100 mg (milligram) per 150ml (1 cup), of instant coffee it is 80 mg, of decaffeinated coffee is 4 mg, of leaf or bag tea (black) is 60 mg and of decaffeinated black tea is 4 mg. The caffeine in green or ice-tea is about 27 mg and 1 mg per teaspoonful of regular and decaffeinated respectively. Cocoa or hot chocolate has 4 mg of caffeine in a regular cup. A regular bottle (300ml) of soft drink containing caffeine has between 35 – 44 mg of caffeine whiles energy drinks contain between ¬ 76 – 280 mg of caffeine per regular can (250ml).

Recommended amount
Coffee can be taken as part of a healthy balanced diet in moderation. An intake of up to 400mg caffeine per day is recommended for adults and up to 300mg daily for women of reproductive age who are planning a pregnancy or who are pregnant. However, for some women the safe margin is around 150mg/day. This translates to an average of 3 cups of coffee or tea daily for most adult consumers and 2 cups for women planning a pregnancy and during pregnancy. Children have developing nervous systems as such it is important to moderate their caffeine consumption. Children between 10 and 12 years should not consume more than 85 mg of caffeine a day (children 4 to 6 should not exceed 45 mg, while those 7 to 9 years should not exceed 62.5 mg). For children, major sources of caffeine include soft drinks and chocolate.

It is vital to remember that the amount of beverage recommended to meet these guidelines depends on both the size and strength of each serving as well as the intake of other caffeine containing foods.

Caffeine and pregnancy
In early pregnancy, caffeine might be dangerous to the developing foetus because it can readily cross the placenta and can affect foetal heart rate and breathing. A foetus does not have a sufficient metabolic system to cope with the increase in heart rate that results from this jolt of caffeine. In severe cases, the result can be a spontaneous abortion. In less severe cases, caffeine can contribute to low birth weight. Because the risk of miscarriage is highest in the first three or four months, caffeine intake should be most strictly monitored during early pregnancy. Several studies have found an increased risk of spontaneous abortion and low birth weight in pregnant women who consumed more than 150 mg/day of caffeine. Pregnant women who consume as little as 200 milligrams of caffeine per day can double their risk of miscarriage. Evidence suggests that, at levels over 500 milligrams per day, caffeine may delay conception.

Caffeine and Health
Caffeine can interfere with sleep. Sleep loss is cumulative, and even small nightly decreases can add up and disturb your daytime alertness and performance. Using caffeine to mask sleep deprivation can create an unwelcome cycle. If you drink caffeinated beverages because you have trouble staying awake during the day, the caffeine will keep you from falling asleep at night, shortening the length of time you sleep. Caffeine may also increase the number of times you wake up during the night and interfere with deep sleep, making your night less restful.

Caffeine appears to increase the excretion of calcium, a mineral needed for healthy bones. Calcium is particularly important to prevent osteoporosis, a bone disease characterized by loss of bone strength and seen especially in older people. Excessive intake of caffeine may contribute to a certain extent to bone loss by increasing the secretion of gastric acid which needs neutralising with calcium. That could be worrisome for postmenopausal women who drink their coffee black and don't get enough calcium. One study has shown an increased in bone loss among older women who drank as little as two or three cups of coffee a day, compared with those who drank less or none at all. Moderate caffeine intake and adding milk to the beverage will not cause calcium problems.

Recent research findings suggests that drinking moderate amounts of caffeine does not necessarily lead to life threatening arrhythmias (irregular heartbeat), nor does it increase your risk of arrhythmias. However, some evidence suggests that people with mild hypertension may increase their blood pressure levels by consuming caffeine-laden products.

Heavy daily caffeine use of more than 500 to 600 mg a day, or about four to seven cups of coffee can cause sleeplessness, nervousness, restlessness, irritability, nausea or other gastrointestinal problems ,fast or irregular heartbeat, muscle tremors, headaches and anxiety.

Many young people may mix energy drinks with alcohol, a potentially dangerous combination because the stimulating effects of caffeine can allow them to drink more over a longer period of time, which could lead to alcohol poisoning or risky behaviour.

Caffeine may also have other benefits. It may be useful as part of a weight control program because it increases the rate at which the body burns calories for three or more hours after being consumed. Caffeine's ability to improve physical performance is well known among athletes. Caffeine seems to increase endurance and speed in some situations as such excessive use of caffeine is restricted in international competitions.

Curbing the caffeine habit
Caffeine is not addictive by accepted definitions and according to most authorities. When regular caffeine consumption is abruptly ceased, some individuals may experience headache, fatigue, irritability, nervousness or drowsiness. Fortunately, these symptoms usually resolve after a few days, but they can be avoided if caffeine intake is reduced gradually. For example, drink one less can of soda or drink a smaller cup of coffee each day. This will help your body get used to the lower levels of caffeine and thereby lessen the withdrawal effects.

Read labels carefully and start paying attention to how much caffeine you are getting from foods and beverages. Order decaf tea or coffee whenever possible and when making tea, brew it for less time. This cuts down on its caffeine content. Or choose herbal brands, which don't contain the stimulant.

Drinking caffeinated beverages in moderation is not linked to any health risk for most adults.

The writer is a dietician.email:[email protected]