Weekly Wellness: Deciding how much is too much caffeine

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COLUMBIA - It is a bitter, white crystalline xanthine alkaloid and a stimulant drug. It is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects that feed on the plants.

It is most commonly consumed in infusions extracted from the seed of the plant and the leaves of the bush. It is the world's most widely consumed psychoactive drug, but unlike many other psychoactive substances, it is legal and unregulated. And in North America, 90% of adults consume it daily.

What is it? Caffeine.

Caffeine is a central nervous system and metabolic stimulant that is used recreationally and medically to reduce physical fatigue and to restore alertness. It can increase focus, create faster and clearer flow of thought, and better body coordination.

Caffeine can improve performance during sleep deprivation but may lead to subsequent insomnia. In athletes, moderate doses of caffeine have been found to improve sprints, endurance, and performance.

But there is a fine line as high doses of caffeine can impair athletic performance by interfering with coordination.

Caffeine content can range from as much as 160 milligrams in some energy drinks to as little as 4 milligrams in a 1-ounce serving of chocolate-flavored syrup. Even decaffeinated coffee isn't completely free of caffeine.

Caffeine is also present in some over-the-counter pain relievers, cold medications, and diet pills. These products can contain as little as 16 milligrams or as much as 200 milligrams of caffeine. In fact, according to WebMD.com, caffeine itself is a mild painkiller and increases the effectiveness of other pain relievers.

The Mayo Clinic suggests that up to 400 milligrams (mg) is a safe amount for most adults. This would be the equivalent to four cups of brewed coffee or 10 cans of cola soft drinks or two "energy shot" drinks. There are benefits and drawbacks to caffeine, based on the amount that is consumed.

At high levels (more than 744 milligrams/day), caffeine may increase calcium and magnesium loss in urine. But recent studies suggest it does not increase your risk for bone loss, especially if you get enough calcium.

You can offset the calcium lost from drinking one cup of coffee by adding just two tablespoons of milk. However, research does show some links between caffeine and hip fracture risk in older adults. If you're an older woman, discuss with your health care provider whether you should limit your daily caffeine intake to 300 milligrams or less.

A slight, temporary rise in heart rate and blood pressure is common in those who are sensitive to caffeine. But several large studies do not link caffeine to higher cholesterol, irregular heartbeats, or an increased risk of cardiovascular disease. If you already have high blood pressure or heart problems, though, have a discussion with your doctor about your caffeine intake.

Reviews of 13 studies involving 20,000 people revealed no relationship between cancer and caffeine. In fact, caffeine may even have a protective effect against certain cancers.

Research suggests that heavy daily caffeine (500 - 600 mg) can cause side effects such as insomnia, nervousness, restlessness, irritability, upset stomach, fast heartbeat and muscle tremors.

So if you are a caffeine-lover (like me), try to pay attention to the amount of caffeine you enjoy on a daily basis and keep your intake to 400 mg or less.