PHILADELPHIA – Over the centuries, coffee has been cursed for making soldiers undependable, women infertile, peasants rebellious and worse.

In England in 1674, for example, the anonymous authors of the Women’s Petition Against Coffee complained that they were suffering in the bedroom because men were constantly in coffeehouses, slurping that “nauseous Puddle-water”:

“That Newfangled, Abominable, Heathenish Liquor called COFFEE … has … Eunucht our Husbands … that they are become as Impotent as Age.”

It makes you wonder what those guys were putting in their daily grind besides cream and sugar.

The point is, coffee has always been more than a beverage, and its health effects have always been controversial. After all, coffee is chock-full o’ the drug 1, 3, 7-trimethylxanthine – better known as caffeine (even decaf has caf) – plus a whole latte has other chemicals and additives.

Recently, the buzz on brew has been good. Glug enough of it, research suggests, and you’ll lower your risk of diabetes, liver cirrhosis, Parkinson’s disease, gallstones and suicide. You’ll also sprint better.

But not long ago, in the 1970s and ’80s, coffee’s name was mud. It was connected – tenuously or incorrectly, experts now say – to pancreatic cancer, heart attacks, birth defects, miscarriage, osteoporosis and other ill effects.

The surprising thing is that even after a thousand years, this ubiquitous liquid remains quite mysterious. So sit back, sip some drip, and ponder the latest research.

Seven out of 10 studies that followed huge groups of people for many years, including Finnish twins and American nurses, have linked coffee to a reduced risk of type 2 diabetes. Last month in the Archives of Internal Medicine, an 11-year study of 28,000 postmenopausal women in Iowa found that coffee drinkers had less type 2 diabetes than nondrinkers.

This doesn’t prove perk is protective. Eating lots of nuts was linked to just as much diabetes-risk reduction in another analysis of the nurses’ diets.

Furthermore, while the circumstantial evidence is abundant, it’s confusing. A smallish 20 percent decrease in diabetes risk turned up among the nurses who drank only one cup a day, while the Iowans had to guzzle six or more to see such a benefit. It’s also unclear what ingredient is at work, since decaf appears more protective than caffeinated coffee in some studies, but not others.

Even if coffee is beneficial, “I don’t think it would be the basis for urging changes in coffee consumption because there are many other ways to reduce risk of type 2 diabetes,” such as losing weight, said Harvard epidemiologist Walter Willett, who led the nurses study.

Population studies from the United States, Japan, Europe and Norway suggest coffee protects the liver from the effects of alcohol.

The first report of a strong link, published in 1992, was updated last month in the Archives of Internal Medicine. Among 125,500 members of the Kaiser Permanente health plan, heavy alcohol drinkers cut their chance of cirrhosis by 20 percent per cup of coffee a day; four cups correlated with an 80 percent risk reduction. Liver enzyme levels also were healthier in imbibers of both coffee and alcohol.

Some researchers speculate that when the liver metabolizes coffee, this somehow inhibits the chronic liver inflammation involved in metabolizing lots of alcohol. (Fans of coffee enemas claim it helps the liver cleanse itself of toxins.)

In any case, physician Arthur Klatsky, who led the Kaiser research, hopes the inconclusive link will not be used to rationalize immoderate drinking.

“It doesn’t mean it’s OK to drink a lot of alcohol if you drink a lot of coffee,” Klatsky said.

While not technically addictive, caffeine increases the production of dopamine, a brain chemical crucial to pleasure and motivation.

The brain cells that make dopamine stop working in Parkinson’s disease, and studies using animal models suggest caffeine wards off Parkinson’s by protecting these cells.

The dopamine connection may explain why both the Kaiser Permanente study and the Nurses Health Study found that coffee drinkers were significantly less likely to commit suicide.

And it may explain why several population studies found coffee drinkers had less Parkinson’s disease – if they were male. In yet another coffee conundrum, several studies found no such benefit for females.

Why? One guess is that estrogen interferes with coffee’s protective effect. In several studies, coffee drinking correlated with reduced Parkinson’s risk in postmenopausal women who had never taken menopausal estrogen supplements, but not in those who used the supplements.

Like all drugs, the world’s favorite pick-me-up has side effects. Caffeine increases blood pressure and heart rate. It can cause palpitations, insomnia, tremors, diarrhea and increased urination. Caffeine withdrawal can cause headaches, drowsiness, depression and grumpiness. Unfiltered coffee, popular in Scandinavian countries, increases bad LDL cholesterol. A study this year found high levels of various inflammatory substances in the blood of coffee drinkers in Greece.

Plus, coffee drinkers tend to be smokers.

No wonder the beverage’s effects, particularly on the cardiovascular system, continue to be deciphered and debated.

Frei and colleagues at the Pauling Institute reviewed the vast, ever-growing coffee research and concluded that people who have high blood pressure, insomnia, or other sensible reasons to eschew brew should do so.

But for most adults, “there is little evidence of health risk and some evidence of health benefits” for up to four cups a day.

Hazelnut, anyone?

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(c) 2006, The Philadelphia Inquirer.

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Java junkies rejoiced a year ago when University of Scranton researchers concluded that for Americans, coffee is the number-one source of antioxidants – those marvelous molecules that neutralize harmful oxygen renegades.

The scientists reported that the typical American drinks 1.6 cups of joe a day, containing 1,299 milligrams of antioxidants called flavonoids. The runners-up weren’t even close: tea (294 mg), bananas, (76 mg), and dry beans (72 mg).

But this research was done in test tubes, not in the human body, which much prefers to get antioxidants from vitamins. If vitamins are the Prada of antioxidants, flavonoids are clothes picked off a curb.

“By and large, flavonoids are recognized by the body as foreign substances. That’s why they’re extensively metabolized to make them more water-soluble so they can be excreted,” said Balz Frei, a biochemist at Oregon State University’s Linus Pauling Institute. “I have my doubts that these compounds are really making a difference in terms of antioxidant protection.”

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