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Coffee: What's the scoop on its health effects?

Over the years, coffee's been linked to illnesses such as cancer and cardiovascular disease. But for every study that implicates coffee as a possible health risk, another seems to find no such link.

So what's the scoop on coffee?

If you're going to have a vice, coffee is probably one of the least harmful — as long as you drink it in moderation.

Few grounds for concern

Caffeine is the ingredient that gives coffee its kick. It's a stimulant that wakes you up, gives you energy, increases your alertness and quickens your reaction time.

Drinking too much caffeine can have noticeable effects. But evidence that coffee causes serious health problems is weak, and problems are usually limited to people who drink large quantities — about eight cups or more a day.

Research into coffee's effects continues. But at this point, here's what we know about coffee and:

Cancer — A few studies have suggested that some of the hundreds of substances in coffee may contribute to pancreatic or bladder cancer. But more recent studies haven't confirmed this. If there is an association between coffee and cancer, it's limited and found only at very high levels of coffee consumption.

Cardiovascular disease — Coffee has been linked to elevated cholesterol levels and an increased risk for coronary artery disease and heart attack. But a 1996 study of more than 121,000 female nurses found that after researchers adjusted for cigarette smoking among coffee drinkers, coffee consumption — even at high levels — didn't increase heart attack risk.

There's some evidence compounds in coffee increase cholesterol levels. But the compounds aren't found in filtered or instant coffee, which most people drink. If you boil your coffee or drink espresso, which isn't filtered, you may want to limit how much you drink.

Caffeine can intensify certain heart rhythm problems. It can also cause a temporary rise in blood pressure. However, elevated blood pressure generally occurs in people who drink coffee only occasionally. Still, if you have high blood pressure, your doctor may recommend that you avoid or limit caffeine.

Osteoporosis — Caffeine increases the amount of calcium excreted in your urine. At least one study has suggested that caffeine may increase your risk for hip fracture. However, you'd have to drink large amounts of caffeine every day for it to have any noticeable impact on bone density.

Fibrocystic breast changes — Evidence that coffee can lead to fibrocystic breast changes, in which benign but painful lumps develop in your breast, appears to be weakening. However, caffeine may aggravate the condition.

Caffeine comparison

Type of coffee, 6-ounce cup	Milligrams of caffeine per serving*
Brewed, drip method	115
Brewed, percolator method	80
Instant, 1 rounded teaspoon	65
Decaffeinated	2
Flavored, regular and sugar-free	25-75
Espresso (1.5 to 2 oz.)	100

*Amounts can vary

Not a benign brew

Coffee isn't harmless, though, depending on how sensitive you are to caffeine, even a couple of cups of coffee can affect your;

Nervous system

Too much caffeine can make you nervous, restless, anxious and irritable. It can also increase your heart rate, make panic attacks worse and cause insomnia.

Digestive system

Caffeine causes the band of muscle separating your esophagus and stomach to relax. This allows stomach acids to back up into your esophagus, producing heartburn. Caffeine may also irritate existing stomach ulcers by increasing stomach acid secretion, and cause constipation, diarrhea and gastrointestinal upset.

Bladder

Caffeine's been known to cause bladder irritation in some people. It's also a mild diuretic, causing you to urinate more.