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How harmful is coffee?

This question originally appeared on Quora. Answer by Jon Kapecki, scientist.

I’ve addressed the health aspects of coffee in several previous Quora postings. The bottom line, however, is that coffee, as well as its main psychoactive component, caffeine, appears to have both health benefits as well as raise some concerns. But except for a small segment of the population, such as those with a medical condition and possibly those who are pregnant, modest consumption of coffee (and hence caffeine) is not detrimental, at least so far as current medical research suggests.

In a past Quora posting, I've addressed the question and highlighted those who should specifically avoid caffeine. If you suffer from high blood pressure, GERD, glaucoma (perhaps), or other ailments for which caffeine can have a negative effect, any reduction of intake is likely to be at least somewhat beneficial.

While we’re on the subject, however, let’s clear up a few misunderstandings. At moderate levels, coffee does not dehydrate you. Caffeine is indeed a mild diuretic, but the water that accompanies it in the coffee or tea that you drink more than makes up for that. A major review from researchers at the University of Connecticut (in The International Journal of Sport Nutrition and Exercise Metabolism, published June, 2002) found virtually no statistically significant difference in urine volume after drinking coffee versus water. Other later studies largely confirm this. I doubt that coffee depletes the body's water reserves either.

Caffeine does not increase cholesterol levels. Other components of coffee, possibly terpenes, may increase cholesterol levels, particularly LDL (currently viewed as the bad stuff) and triglycerides, for heavy java drinkers, but it appears that these suspect materials are largely removed by coffee filters. If you’re worried about this, but still want to drink coffee, retire that French press or percolator (which makes bad coffee anyway), and get something like a cheap brand of coffee.

In fact, in one of the largest (130,000 participants) and most recent retrospective studies of coffee consumption and health (in the Annals of Internal Medicine for June, 2008), no relationship was found between the amount of coffee the folks in the study consumed and an increased risk of death from any cause, including cancer or cardiovascular disease. More recent studies suggest that coffee may even modestly reduce the risk of contracting diabetes.

So if you like coffee, drink up - but like everything in life, do it in moderation.

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