Outside of water coffee is the most popular beverage on earth.  It’s consumed in practically every culture throughout the world and its use goes back to antiquity.

It wouldn’t have survived this long if it was inherently dangerous, but about 1/3 of Americans drink an average of 3 or more cups per day.  At that level is there a point when drinking coffee becomes detrimental to your health?  Are there certain circumstances that make drinking coffee more dangerous than others?

The Health Benefits and Health Risks of Coffee

Coffee is both simple and complex.  It’s nothing more than soaked beans passed over hot water, but the composition of coffee has a lot of variables.  A single cup of coffee is believed to contain more than 100 different compounds, many of which are biologically active.

The most potent of which are chlorogenic acid, cafestol, caffeine, and kahweol, which exert a wide variety of effects on your body.  They increase your metabolism, blood pressure, and cholesterol while simultaneously controlling your blood sugar and acting as a powerful antioxidant.  The coffee bean stands side by side with other mighty superfoods such as green tea, red berries and cocoa when it comes to its ability to protect your cells against oxidation, yet it can potentially have the unintended consequence of reducing athletic performance (by constricting arteries) or increasing the risk of cardiovascular disease for people who have high blood pressure.

The Good, The Bad, The Unknown

The benefits and potential drawbacks of drinking coffee can be summed up as follows:

The Good:

• It’s very benign and safe for practically anyone, even for heavy drinkers
• The coffee bean has a high concentration of phenolic compounds which give coffee some ability to reduce free radicals, blood sugar levels, and perhaps protect against some forms of cancer
• Most perceived drawbacks of coffee (increased risk of pregnancy, increased risk of cardiovascular disease, etc) have not withstood the test of scrutiny
• Many of the potential drawbacks of coffee are due to the presence of caffeine, and are not specific to the coffee bean itself
• The caffeine content in coffee can slightly raise your base metabolic rate
• Coffee stimulates your central nervous system, resulting in increased mental acuity

The Bad:

• It can increase blood pressure and cholesterol, although its ability to do this varies (the brewing method and your initial BP can have a lot to do with what kind of effect coffee will have)
• It causes your body to lose water, which can disrupt fluid balance if you drink too much of it
• Coffee has a mild effect on neurological receptors within the brain and can be mildly addictive
• It decreases insulin sensitivity (which is odd since it simultaneously reduces blood sugar)
• It can reduce nutrient absorption

Cholesterol and Blood Pressure

The two most persistent observed drawbacks of persistent coffee consumption is that it can raise LDL (“bad”) cholesterol levels and blood pressure in some people.

The cholesterol raising effect is mostly due to two compounds called cafestol and kahweol, by reducing bile acid synthesis within the body.  Curiously enough, this effect is very dependent on how the coffee is brewed.  This was first noticed when epidemiological studies found that the cholesterol raising effects of coffee were consistently found in Scandinavia but not in western Europe and America.

It turns out that where a positive relationship was found when people made their coffee by boiling it instead of traditional brewing.  Cafestol and kahweol are usually removed by the coffee filter.

A typical cup of coffee has around 100 mg of caffeine, and it’s well established that chronic caffeine consumption elevates your blood pressure levels.  By how much is unclear, but the effect seems to be persistent enough that people who already have hypertension would probably do well by cutting back on their daily dosage of brew.   Beyond that the results really vary.  Eventually your body adjusts to the caffeine levels which lessens its effect, but people vary in their adaptation to caffeine.  The amount of caffeine in your cup also varies quite a bit too.  The average is around 100mg, but the variability of caffeine content is very high.  One study found that the same cup of coffee from the same store had caffeine levels that varied by 100% over six consecutive days.

When it comes to blood pressure and cholesterol, neither of these observations should sound big alarms.  Coffee really is pretty harmless, especially if you’re drinking less than three cups per day.  But sensitivity to caffeine can depend on a lot of things and it’s possible you might be harming yourself if you’re always drinking it throughout the day.

The Nutrients in Coffee Give A Little and Take A Little

Coffee contains trace amounts of a variety of micronutrients.  Not enough to thrive, but possibly enough to prevent complete deficiency.  In fact, coffee might even be the main source of dietary antioxidants for the majority of the western world. (That says more about the SAD than it does about coffee).  The majority of its antioxidant effects stem from a compound called chlorogenic acid, and is probably the reason why coffee might reduce your blood sugar.  It’s a powerful reducer within the body, and like other phenols, it has a strong tendency to cling to certain molecules and remove them from your bloodstream….like glucose and its metabolites.

However the nutrients in coffee also have a dark side.  Phenols remove all sorts of stuff from your body, including iron and possibly zinc and calcium.  In many cases the consumption of coffee has been shown to reduce the amount of dietary minerals that are metabolized by your body since chlorogenic acid and phytate can both chelate with metals and render them insoluble within your digestive system.

Almost Entirely Harmless Except At Very High Dosages

For the vast majority of people drinking an occasional cup of coffee poses no substantial health risks.  This makes sense since people have been drinking coffee almost since the beginning of recorded history and nothing remarkably bad has happened because of it.

I believe the health risks associated with drinking coffee are J-shaped.  A little bit of coffee has no effect and likely confers benefits, but potential risks might creep up if you regularly drink more than 4-5 cups a day.  If nothing else it might make giving up coffee more difficult.

People regularly report physical and mental discomfort when they have to kick a longstanding coffee habit since the brain can suffer from a withdrawal from caffeine.

But should you give up your morning cup for fear of bodily damage? No.

References

Jee, Sun ha, et. al. “Coffee, Caffeine and Blood Pressure: A Critical Review.”

URL: http://hyper.ahajournals.org/content/33/2/647.short

Battig, K. “The Cardiovascular Effects of Everyday Coffee Consumption”

URL: http://www.ncbi.nlm.nih.gov/pubmed/1411413

Neuhauser-Berthold, M., et. al. “Coffee Consumption and Total Body Water Homeostasis As Measured by Fluid Balance and Bioelectrical Impedance Analysis”

URL: http://www.karger.com/Article/Abstract/177975

Tunnicliffe, Jasmine, et. al. “Coffee, glucose homeostasis, and insulin resistance: physiological mechanisms and mediators”

URL: http://www.nrcresearchpress.com/doi/abs/10.1139/H08-123#.Ug_j2NfD9jo

Higdon, Jane, et. al. “Coffee and Health: A Review of Recent Human Research”