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Is coffee a magic bean or poison pill? What the research says

By Nicole Ferring Holovach, MS, RD

America's number one drug of choice isn't alcohol or marijuana — it's caffeine. Yes, your morning cup of joe is actually a bona fide pharmacological agent. More than 50 percent of Americans consume this legal drug every day in the form of coffee. Even more people drink coffee just occasionally. Most don't stop at one cup — the average American is knocking back three to four cups per day. But is there anything wrong with that? Should coffee be viewed as a guilty pleasure or as a health-promoting tonic like tea, a beverage that enjoys a much better reputation? Here is the latest on America's favorite fix.

Filtering Through the Research

Research findings over the years have been continually contradictory on whether or not coffee is healthy. That's because coffee can be difficult to study. There is more to coffee than just caffeine. It's a very complex beverage made up of hundreds of different compounds. These compounds can change depending on the type of bean, the method of roasting, and the method of preparation (drip, French press, etc.). Moreover, drinking coffee often accompanies unhealthy behaviors like smoking, lack of sleep, and stress, making it difficult to single out coffee as the cause of the negative health outcome in a study. But regardless of contradictory research, a few solid patterns have emerged.

Coffee's Perks

Like tea, coffee contains antioxidants. These antioxidants are possibly due to coffee's roasting process. Antioxidants can prevent or slow oxidative damage in the body. Think of oxidative damage as rust — a byproduct of wear and tear on the body and getting older. Oxidative damage contributes to many diseases, which is potentially why coffee intake is associated with reduced risk of diabetes, heart disease, cancer, liver disease, and Parkinson's and Alzheimer's diseases. Coffee's benefits could also be due to other beneficial compounds that reduce inflammation and regulate insulin, both of which impact the aforementioned diseases. Coffee may even positively affect certain hormones in the body that play a role in the development of type 2 diabetes.

And then there is of course the caffeine in coffee, which is associated with increased cognitive performance, productivity, and concentration as well as enhanced athletic performance — so drink up before your big exam or race. These beneficial effects of caffeine have been seen in as little as a half cup!

A Note About Decaf

Benefits were seen in prostate cancer studies with decaffeinated coffee as well as caffeinated coffee. But diabetes studies did not find the same benefits with decaffeinated coffee. It's also important to note that most decaffeinated coffee still has some caffeine — about 8 to 14 mg in an 8-ounce cup of decaf (compared to 95 to 200 mg in the same-sized cup of regular coffee). Also, there is some concern over the chemical process used to decaffeinate coffee, but there is no evidence to suggest any harm.

The Bitter Truth

But coffee isn't completely innocent. It can affect sleep patterns and contribute to anxiety. And evidence shows that women who are trying to conceive should cut back on coffee. More than 300 mg of caffeine can affect fertility and has been linked with miscarriage and stillbirth. A growing fetus can absorb caffeine and has no way to metabolize it. Most experts recommend that women who are trying to conceive or who are pregnant limit their caffeine intake to 200 mg or less a day, which is the equivalent of about two small cups or one strong cup of coffee.

Coffee can also affect blood pressure, but only temporarily. It seems that drinking coffee causes an immediate, temporary rise, especially in those people are not used to caffeine. Coffee does not seem to affect blood pressure levels over time.

And diabetics should know that the increase in blood glucose levels that occurs after consuming carbohydrates is exaggerated if caffeine is also consumed.

Bean and Brewing Method May Matter

Coffee aficionados know that coffee tastes different depending on the roast and the method of preparation. A generic cup of joe from the corner store tastes incomparable to a freshly ground dark roast coffee made in a French press. But taste is not the only difference between the two. The way coffee beans are roasted and prepared affects coffee's health benefits.

Roasting coffee beans creates acrylamide, a chemical that forms in starchy foods during high-temperature cooking processes like frying and roasting. In high doses, acrylamide has been linked with cancer and nerve damage. Darker roasts may have more acrylamide than lighter roasts, though this has not been completely proven yet, and even if a dark roast does indeed have more acrylamide, it does not have anywhere near the amount that is linked with cancer and nerve damage.

Researchers don't yet know the exact health impact of the low levels of acrylamide found in food — if there are any at all in such low doses — but that didn't stop California law-makers in February of 2011 from adding acrylamide to California's Proposition 65 list of chemicals known to cause harm to humans. In the case of acrylamide, the Office of Environmental Health Hazard Assessment (OEHHA) within the California Environmental Protection Agency declared that acrylamide is a chemical "known to the State of California to cause developmental and male reproductive toxicity," according to the OEHHA's press release. However, no major, national organizations recommend dietary changes to avoid acrylamide yet. If you're concerned about acrylamide in your coffee, cut back and choose a light roast bean instead of dark.

Unfiltered methods of coffee preparation, like French press or Turkish coffee, increase the amount of diterpenes in coffee. Diterpenes are found in the oily components of coffee. Two types of diterpenes in coffee, kahweol and cafestol, are associated with increased levels of LDL (bad) cholesterol. When you brew coffee with a paper filter, the diterpenes get left behind in the filter. Metal filters and unfiltered coffee do not remove the oily components of coffee. Given this, if you drink coffee daily, it's probably best to brew coffee with a paper filter and save other coffee preparations for special occasions.

The Bottom Line

If you don't already enjoy coffee, there's no reason for you to start drinking it. But for you java junkies, moderate consumption poses minimal health risks for most people and may even have some health perks. The negative effects of coffee tend to emerge in excessive drinking, so avoid heavy consumption. However, while a cup or two might be harmless, if you're drinking coffee all day just to stay functional, there might be an underlying reason for your lack of energy. Get adequate sleep and enjoy coffee as a healthy treat, not a necessity.

Published: November 11, 2011

Nicole is a Washington, DC-based nutrition communications professional, writer, and yoga teacher. She blogs about holistic health at www.WholeHealthRD.com.

See also:

• 18 heart-healthy foods you aren't eating
• Do detox diets work? Dr. James Beckerman reports
• How healthy is your diet? Find out with our free food diary!