Researchers on coffee

July 29, 2006

Researchers stir up heated debate over a cup of coffee

http://www.theaustralian.news.com.au/story/0,20867,19942257-23289,00.html

Evidence is filtering through on the health benefits of coffee, writes Marie McCullough

July 29, 2006

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."

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

Not long ago, in the 1970s and 1980s, coffee's name was mud, 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 1000 years, this ubiquitous liquid remains quite mysterious. The human body much prefers to get antioxidants from vitamins. If vitamins are the Prada of antioxidants, flavonoids are clothes picked off a kerb.

``By and large, flavonoids are recognised by the body as foreign substances. That's why they're extensively metabolised to make them more water-soluble so they can be excreted,'' says Balz Frei, a biochemist at Oregon State University. "I have my doubts that these compounds are really making a difference in terms of antioxidant protection.''

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 (2006;166:1311-1316), an 11-year study of 28,000 post-menopausal women in Iowa found coffee drinkers had fewer incidences of type 2 diabetes than non-drinkers. This doesn't prove the 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 per cent decrease in diabetes risk turned up among the nurses who drank only one cup a day, while the Iowans had to have 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, says Harvard epidemiologist Walter Willett, who led the nurses' study.

Population studies from the US, 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 (2006;166:1190-1195). Among 125,500 members of the Kaiser Permanente health plan, heavy alcohol drinkers cut their chance of cirrhosis by 20 per cent per cup of coffee a day; four cups correlated with an 80 per cent risk reduction. Liver enzyme levels also were healthier in imbibers of both coffee and alcohol.

Some researchers speculate that when the liver metabolises coffee, this somehow inhibits the chronic liver inflammation involved in metabolising lots of alcohol.

In any case, physician Arthur Klatsky, who led the Kaiser research, hopes the inconclusive link will not be used to rationalise immoderate drinking. "It doesn't mean it's OK to drink a lot of alcohol if you drink a lot of coffee,'' Klatsky says.

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, diarrhoea 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 Oregon State University's 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 the 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.

Agencies