Is Coffee Bad For You?

By Doug Cook


is coffee bad for you Growing up I used to berate my mother for drinking coffee. When I was 16, I read a pamphlet on nutrition. I can’t remember much more than two salient points. One of them: coffee is taboo. When I asked my grandmother for a firm definition of “taboo”, she simply replied, “forbidden”. That was enough to convince me that coffee was somehow partly responsible for much of what plagues our health. (In my mother’s defense, I would later learn that she was known for her awful coffee so even if it were somehow unhealthy, her coffee was never strong enough to be of concern.)

The idea that coffee was a source of ill health stuck with me for a couple of years until my last year of high school, when I tried drinking a cup of what I would now consider really bad coffee with friends, during the intermission of the annual school play. My next memory involves using a Melita coffeemaker – a simple carafe with an open cone filter on top in which I would pour freshly boiled water over the waiting grounds, recently discovered at the Second Cup, the new gourmet-coffee kid on the block at that time – I had arrived! 

Despite my own personal reconciliation with coffee, it remains at odds with many people and continues to have a bum rap. But why? What is it about coffee exactly that makes it seen as a vice rather than a virtue? 

They say if you repeat something often enough, it becomes accepted as truth. This, in my opinion, is what has earned coffee a bad reputation. Among other sins, coffee is said to:

  • increase heart disease risk

  • increase blood pressure

  • be linked to pancreatic cancer

  • cause dehydration

  • leach calcium from the bones, causing osteoporosis

To be fair, early research seemed to support many of these claims. However, much of the research done decades ago is often not of the same caliber as today’s research. 

For example, studies were often poorly designed. Researchers may not have accounted for coffee drinkers’ other behaviors, such as smoking. Coffee drinking and smoking were two behaviors that often occurred together and if a researcher was investigating coffee’s relationship to heart disease without taking into consideration the impact of smoking, they might erroneously conclude coffee was to blame when in fact smoking was the villain. 

Thus, researchers might conclude, wrongly, that coffee causes heart disease. The wrong message gets out, is widely publicized, and becomes “common knowledge”. Such “knowledge” becomes part of the cultural norm and what follows next is a case of broken telephone. 

As a dietitian I see many clients and patients who are confused and frustrated about food. They receive conflicting messages about nutrition from the mass media (such as TV, magazines or newspapers) or from their friends. These messages often lack context and/or history, something a sound bite rarely – if ever – provides. Misguided public perception ensues, and an issue may become black-and-white. 

Unfortunately for food, this results in a “good for you” or “bad for you” mindset. Nothing is this simple, of course. Regrettably, when a food is seen as “bad” people may avoid it unnecessarily. They may feel guilty or anxious when they consume that food.

Coffee and high blood pressure

Coffee has had its share of “bad for you” messages. Many clients have worried, for example, that coffee will cause high blood pressure. Blood pressure will increase after drinking a cup of coffee but will return to pre-coffee consumption levels within a couple of hours. If a person starts to consume coffee more regularly, the blood pressure-raising effect wanes as the person habituates or adapts. 

We might also ask: How much coffee causes sustained high blood pressure? Are we talking about a cup in the morning or a pot? If we don’t define “moderate consumption” or put it into context, we might assume that a teacup’s worth is the same as a Super Big Gulp.

Thus, although coffee does raise blood pressure, especially in new drinkers, don’t jump to the conclusion that coffee is bad for you, or that it will lead to high blood pressure in all people. The real question is whether long term moderate coffee consumption leads to high blood pressure. If you look at all the collected evidence, the answer is that it does not. Having said this, for those with high blood pressure or those who are prone to developing it, reducing or eliminating coffee may be beneficial. 

Coffee and hydration

A similar misconception is seen with coffee and hydration. I can’t tell you how often I hear this one or read about it in fitness magazines. The mantra goes something like this: “For every cup of caffeinated beverage consumed, drink an extra glass of water to prevent dehydration.” 

To save you the suspense, this is false. This myth started in the late 1970s. One of the earliest studies that fueled this idea involved subjects being given either a drink of plain water or a drink that had 250 mg of caffeine (the equivalent of about 2.5 small cups of coffee), after both groups had abstained from consuming caffeine for three weeks. The researchers then collected urine output for 3 hours after consuming the caffeine. Since people urinated more immediately after consuming the caffeine drink, the researchers concluded that caffeine ultimately dehydrated the participants.

However, researchers didn’t look at the long term effects. They didn’t monitor urine output for longer than 3 hours. This is an important point: while there is a small increase in urine output in the first couple of hours after caffeine consumption, the body compensates for this loss during the rest of the day by decreasing urine production later. 

To get a truer picture of water balance (or hydration status, as it’s known), researchers would need to compare the total amount of water consumed and the total water lost over a 24 hour period. In this case, the 24-hour view would show that eventually, the body compensates for extra trips to the loo.

We also now know that when a person is what’s referred to as “caffeine naïve” (in other words, new to caffeine consumption), they will have a stronger response to whatever is being measured – whether this is heart rate, blood pressure or urine output – so that the effect will be magnified. With regular consumption of coffee, however, caffeine’s stimulatory effects often become less effective. The poor caffeine newbies were probably sprinting to the bathroom, but more experienced java ninjas might not even feel a bladder flutter.

The production of nutritional “truth”

Changing our ideas about something is difficult when it’s been ingrained into our consciousness. This is no less true for the scientific community. People can be reluctant to accept facts that contradict their beliefs. Even scientists fall victim to this. 

I think it’s human nature to get lost in the details, and to have trouble judging whether an idea makes sense in a larger context. We hear about a new study almost daily and the latest one seems to contradict the one before. It’s important not to become reactionary. And it’s a good thing to ask “so what?” 

This is where my dietitian voice creeps in. I hear myself proclaiming our mantra of “balance, variety and moderation”, something that can difficult to put into real life practice. Anything can be “bad” or “good”, depending on how much is consumed, and whether that food displaces other foods. If you eat nothing but carrots, for example, you’ll probably displace many other important foods… and you’ll literally turn yourself orange from the beta-carotene (a condition known as carotenemia). But it doesn’t mean that carrots are “bad”. 

Coffee and antioxidants

OK, so coffee isn’t the demon beverage that will make you pee your liver out or your blood vessels explode. Does that make it a health food? Yes… and no.

Coffee is a complex beverage. Its best known for its caffeine content, but it also contains many other different compounds that include antioxidants such as phenols, which are also found in wine, green tea, apples, and chocolate. “Antioxidants” is a fancy word for compounds that protect our cells and tissue from the ravages of oxidation. 

Oxidant production is a part of life. Oxidative chemicals are produced as part of our metabolism as we breathe oxygen and digest food for energy. These compounds can also be produced from pollutants like smog, smoking, alcohol, and sunlight. Fortunately we are protected by two sources of antioxidants: antioxidants that our bodies produce and those we get from the food we eat. Think of antioxidants as shields that protect you from the onslaught of the enemy’s arrows. 

Here’s an idea of how coffee might be beneficial. The Journal of the American Medical Association performed a systemic review – an examination of the combined results of many different studies – that found that habitual coffee consumption was associated with a lower risk for Type 2 diabetes. The antioxidants may protect the cells of the pancreas that produce insulin from damage, essentially extending their warranty so they can keep doing their job. Or, this lowered risk may be due to one of coffee’s other compounds, such as chlorogenic acid (an almost noxious-sounding participant). Chlorogenic acid as been shown to help reduce blood levels of glucose (blood sugar). 

There is equally impressive research showing that coffee may protect against Parkinson’s, dementia, and cardiovascular disease. However, it’s still not clear how this works. We know that coffee contains antioxidants, and that it does have some health benefits, but we aren’t completely clear which constituents of coffee are responsible.

Should we drink to our health?

Many of these studies suggest that we have to drink a lot of coffee to reap the benefits. For instance, the systemic review on coffee and Type 2 diabetes found that the protective effects seemed to require an intake of about 5-7 cups per day – probably not realistic or desirable for many people. Is there a point where the increasing amounts of caffeine ingestion outweighs any potential benefit? The jury is still out on that one. 

Thus, it’s probably still best to follow Governmental guidelines on caffeine consumption. 

  • For adults, the upper limit is about about 400 to 450 mg per day, or about the amount found in three to four 6-ounce (177 mL) cups per day. 

  • Women who are pregnant or nursing do not have to eliminate caffeine entirely. Up to 300 mg per day is considered safe. 

  • For children, the intake limit is 45 mg per day for ages 4-6, 53 mg per day for ages 7-9, and 85 mg per day for ages 10-12. (But really, do you want caffeinated children on your hands?)

Coffee is one of the world’s most popular beverages. It is mainly enjoyed for its taste and aroma, either alone or with friends. While it has been unfairly vilified over the years, more recent research demonstrates that it’s not to be seen as a vice but rather as a wonderful beverage which nature in her wisdom has given us. As with all things, it is to be enjoyed, if not revered, in moderation with an ease of mind and guilt free.  


By Doug Cook| March 17, 2011
Categories:  Eat

About the Author

Doug Cook

Doug Cook

Doug Cook, RD MHSc is a Registered Dietitian Nutritionist and Diabetes Educator who uses a holistic and science-based approach to his practice.

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