Coffee is among the most consumed — and controversial — beverages in the world. While coffee should be treated with care and avoided altogether by those who metabolize it poorly, it also provides health benefits to many people. Read on to find out what they are – and how to drink coffee responsibly.
Coffee is the second most popular drink in the world, trailing only water and, debatably, tea.
Caffeine, a key component of coffee, is a controversial compound. With 90% of North American adults consuming caffeine daily, it is the world’s most consumed psychoactive drug – and coffee is the delivery method of choice.
Perhaps that’s why, in the fitness world, we’ve traditionally viewed coffee with some suspicion.
But is coffee really bad for us? Should we give up our beloved cuppa joe? If it’s bad, why does it feel so good?
The coffee plant originated in East Africa — according to legend, a goat herder tried coffee cherries after he noticed his goats acting much more energetic after nibbling on the coffee bushes.
The earliest evidence of coffee drinking occurred in the 15th century in Yemen. From Yemen, coffee quickly spread to Egypt and North Africa, and by the 16th century it was being enjoyed by the rest of the Middle East, Persia, and Turkey and soon thereafter Italy and the rest of Europe.
Fast forward to today. Coffee is ubiquitous in our culture. Everywhere you look, there’s a coffee shop on the corner. What effect might our cultural love of coffee have on our health?
Short answer: Well, we’re not completely sure.
Research on coffee’s safety is mixed, for several reasons:
- Metabolism matters. People vary genetically in how well they can process caffeine and coffee.
- Coffee interacts with many hormones and neurotransmitters in the body, such as cortisol, acetylcholine, and insulin. These relationships are complex, and often depend on timing, amount, and people’s individual makeup.
- As a crop, coffee is less like corn or soy, and more like cacao or wine grapes: It’s typically grown and processed in smaller batches by smaller-scale farmers and producers. Variations in soil and climate, as well as later roasting and brewing technique, will change the taste and chemical makeup. It’s hard to standardize the exact chemical compounds in coffee from batch to batch. (By the way, JB likes to roast his own coffee. You can follow along with his process here or see a nice PDF version here.)
So it’s hard to say definitively that coffee is “good” or “bad”; “healthy” or “unhealthy”. Let’s explore this in more depth.
What about my metabolism?
One reason that evidence on the health effects of coffee is so mixed is that people clear caffeine at different rates. Caffeine is broken down and cleared by the liver, and our genetic makeup shapes how quickly and effectively we can do this.
- On one hand, “slow” metabolizers of caffeine don’t process caffeine effectively. These are people who are adversely affected by caffeine, get the jitters, and are wired for up to nine hours after consumption.
- Others just get a boost in energy and alertness for a couple of hours; they are considered “fast” metabolizers of caffeine.
Research in the emerging field of nutrigenomics shows that about half of us have the gene variant that makes us “slow” metabolizers, while the other half enjoy the gene variant that allows them to get away with quad-espressos.
(For more on this, see JB’s interview with nutrigenomics researcher Ahmed El-Sohemy here.)
Thus, whether coffee is better or worse for you depends on how well and quickly you metabolize caffeine.
If you are a slow metabolizer of caffeine and coffee, steer clear (or at least, reduce your consumption). In your case, coffee can do more harm than good, and this may explain why high coffee consumption has been associated with:
- higher risk of miscarriage
- disrupted sleep
- worse PMS symptoms
- increased blood pressure, even in people without hypertension
- non-fatal myocardial infarction (aka a heart attack)
On the plus side, low caffeine consumption still seems relatively safe for most folks, so a few daily cups of tea or squares of dark chocolate shouldn’t harm you (and in fact, may greatly boost your wellbeing!).
And fortunately, not everyone is adversely affected. For those lucky enough to be fast metabolizers, there is good news – and lots of it. Fast metabolizers don’t show the same association between coffee and disease — if you’re a fast metabolizer, coffee might even improve your health!
What about cortisol?
Cortisol is a hormone produced by the adrenal glands. It increases blood pressure, spikes blood sugar and prepares the body for “fight or flight” mode.
Coffee and caffeine tend to transiently increase cortisol levels; however, this depends on several factors, including when you drink coffee, how often you drink it, and whether you have high blood pressure.
Cortisol is normally high in the morning, so if you drink some coffee at 6 a.m. and 10 a.m., you should be fine, as cortisol is naturally elevated at that time of day anyway. However, your body may not appreciate coffee as much in the afternoon or evening, when cortisol normally drops. At that point, consider tea or something decaffeinated.
Again, there’s individual variation: Habitual consumers of coffee seem to be less affected by the cortisol bump, while those with hypertension seem to be more affected.
If cortisol levels are a problem for you, keep your coffee intake to first thing in the morning, and otherwise consume more tea. (Not only does tea have less caffeine, it also has other beneficial, calming compounds such as L-theanine. For more on this, see What You Should Know About Tea.)
What about pesticides?
Coffee plants are heavily sprayed with pesticides, which pose obvious health concerns. Fortunately, the plant’s structure offers some protection. While the outer “berry” does receive a lot of exposure, it’s the interior bean that is roasted and used for coffee, and its exposure is far less. In addition, the roasting process destroys the majority of pesticide residues.
If you’re especially wary of pesticides, choose organically grown coffee. (Hey, it can’t hurt.) And while you’re at it, look for the Fair Trade label, which helps insure that family farmers are paid a fair wage for their crops.
What about my insulin sensitivity?
While a high dose of caffeine tends to decrease insulin sensitivity and glucose tolerance acutely, it doesn’t seem to cause chronic problems. While those at risk of developing diabetes may want to be cautious, overall coffee consumption is actually associated with a 35% decreased risk of developing type II diabetes.
What about my kids?
There’s no clear guideline on when kids can safely consume coffee. Guidelines on caffeine consumption are based mostly on the size of the child, rather than their chronological ages.
Nevertheless, Health Canada recommends:
- no more than 45 milligrams a day for kids aged 4 to 6;
- 62.5 milligrams for kids age 7 to 9;
- 85 milligrams for kids age 10 to 12; and
- no more than 2.5 milligrams per kilogram (2.2 pounds) of body weight for adolescents 13 and up.
All this means that a 110 pound adolescent should not have more than 125 milligrams of caffeine a day — about one 6-8 oz cup of coffee.
Bear in mind, too, that kids may be getting plenty of caffeine from soft drinks, bottled tea, etc. Check out All About Caffeine for more information on caffeine specifically.
Caffeine & dehydration
For years, fitness enthusiasts worried that coffee would dehydrate them. However, a recent review of 10 studies found that consuming up to 550 mg of caffeine per day (or about five 8-oz cups) does not cause fluid-electrolyte imbalances in athletes or fitness enthusiasts.
In another review, researchers concluded that consuming caffeine-containing beverages as part of a normal lifestyle does not lead to fluid losses exceeding the volume of fluid consumed (intake and output were roughly equal), nor is it associated with poor hydration status.
Take-home: Don’t drink coffee as your only beverage, and drink enough water, and you’ll be fine.
Coffee & performance
Let’s be honest — that first morning coffee can transform us from beast to philosopher (or at least, slightly more awake and nicer beast). Coffee, and more specifically its caffeine content, provide many noted mental and physical performance benefits.
Caffeine reduces our rate of perceived exertion, so it doesn’t feel like we’re working as hard as we actually are. People who regularly drink coffee perform better on tests of reaction time, verbal memory, and visuo-spatial reasoning.
Another study found that women over the age of 80 performed significantly better on tests of cognitive function if they had regularly consumed coffee over the course of their lifetimes.
Take-home: A little bit of coffee/caffeine before important tasks requiring alertness and energy can be a good thing.
Coffee & Parkinson’s
Parkinson’s disease is a fatal and incurable brain disease that affects 1 percent to 2 percent of people over 65. Amazingly, at least six studies have found that regular coffee drinkers are up to 80% less likely to develop Parkinson’s.
Researchers have identified a gene called GRIN2A that appeared to protect people who drank coffee from developing Parkinson’s. GRIN2A is linked to glutamate, a compound that is suspected of killing the brain cells that die off in Parkinson’s patients. Glutamate can be affected by another compound called adenosine, and coffee interferes with this process.
However: Only about 25% of the population has the gene variant of GRIN2A that boosts the protective effect of coffee.
Take-home: Coffee may lower Parkinson’s risk, but only in a small subset of people.
Coffee & Alzheimer’s
Speaking of neurodegenerative disorders, Alzheimer’s disease is the most common form of dementia. There is no cure for the disease, which gets progressively worse over time, and eventually leads to death.
What separates the research on Alzheimer’s from most of the other information covered in this article is that it derived from directly controlled trials versus simple observation.
Here, research indicates that people who drink about three cups of coffee a day show a marked reduction in cognitive impairment compared to non-drinkers. Once you got up to four or more cups per day, though, the associated protection disappears.
This protection was not seen with tea or decaf coffee, so the benefit seems to be from the combination of the caffeine and some of coffee’s bioactive compounds.
In fact, new research from the University of South Florida found that this combination boosts blood levels of a critical growth factor called GCSF (granulocyte colony stimulating factor) that seems to prevent the formation of Alzheimer’s disease. People with Alzheimer’s disease have less GCSF than the rest of the population. Increasing GCSF in mice improves their memory.
In the U of South Florida study, the researchers compared the effects of regular and decaf coffee to those of caffeine alone. In both Alzheimer’s mice and normal mice, treatment with regular coffee dramatically increased blood levels of GCSF; neither caffeine alone nor decaf coffee provided this effect.
GCSF seems to improve memory performance in the Alzheimer’s mice in three ways:
- It recruits stem cells from bone marrow to enter the brain and remove the harmful beta-amyloid protein that initiates the disease.
- It creates new connections between brain cells.
- It increases the birth of new neurons in the brain.
As the lead researcher, neuroscientist Dr. Chuanhai Cao, remarked: “Coffee is inexpensive, readily available, easily gets into the brain, appears to directly attack the disease process, and has few side-effects for most of us”.
According to the researchers, no other Alzheimer’s therapy being developed comes close to meeting all these criteria.
Take-home: Coffee seems to contain compounds that may reduce Alzheimer’s risk; and may also be part of a treatment protocol in the future.
Coffee, antioxidants & cancer
While dark chocolate and green tea gather a lot of acclaim for their antioxidant content, coffee actually outshines them both in this department.
In fact, the antioxidants in coffee may make up as much as 50-70% of the total antioxidant intake of the average American! (Which is not necessarily a good thing, because it means that there are a lot of vegetables not getting eaten…)
Despite some general worries about the health effects of coffee, coffee consumption is associated with an overall decreased risk of cancer. In particular coffee consumption has been shown to be associated with a lower risk for oral, esophageal, pharyngeal, breast (in post-menopausal women), liver, colon, and aggressive prostate cancer.
When it comes to the prostate, researchers recently found that men who drank the most coffee (6 or more cups per day) were nearly 60% less likely to develop advanced prostate cancer than non-coffee drinkers. Other research has shown that people who regularly consume two or more cups per day may have a 25% decreased risk of colon cancer.
Again, the research is mixed in part because of the variation in response to coffee.
Take-home: Coffee may lower your cancer risk, but don’t count on it as your only health strategy. And eat some vegetables already.
Coffee & cardiovascular health
Drinking unfiltered types of coffee can increase your levels of LDL (aka “bad”) cholesterol. But overall the data seems to indicate that coffee consumption may moderately reduce your risk of dying from cardiovascular complications.
Take-home: Research is mixed on cardiovascular disease and coffee.
Coffee & overall mortality
A recent study in The New England Journal of Medicine showed that drinking two to three cups of coffee per day was associated with a 10% decreased risk of death for men at any age, and a 13% decreased risk of death for women at any age.
In general, coffee drinkers were less likely to die from heart or respiratory disease, stroke, diabetes, injuries, accidents or infections. (Which makes us wonder… what do they die of? Espresso steamer mishaps?)
Summary & recommendations
Coffee’s not for everyone. And it’s not a magic bullet. Still, it seems to have significant health benefits for those who can tolerate it. This includes:
- better athletic and mental performance
- possibly lower rates of some types of cancer, neurodegenerative diseases, and Type 2 diabetes
- possibly some prevention of premature mortality and cardiovascular disease
Most of the research on coffee is epidemiological. This means studies look at associations rather than cause and effect. Simply because coffee is associated with particular risks and benefits doesn’t necessarily mean that coffee causes all of these risks or benefits.
Just as with all foods (and nutrients for that matter), dosage matters. While some studies have found large intakes (5-6 cups) to have significant benefits, other research suggests that drinking that much coffee is counter-productive.
In general, it appears that drinking some coffee is good, but more might not be better, especially if you are a slow metabolizer. For those who are greatly affected by coffee and caffeine, avoid it altogether or cut down your consumption.
Want a quick and easy test of your coffee consumption? Ask yourself how you feel physically, mentally, and emotionally a few hours after you drink some… as well as if you miss your daily dose.
Also, go black if possible. Pumping your coffee full of cream, sugar, and other exotic additives reduces any potential health benefits by adding unnecessary calories and artificial flavours and sweeteners. (And Frappucinos or chocolate covered coffee beans? C’mon.)
Taking all the data into consideration, it seems that your best bet is about 1-3 cups of coffee (8-24 oz) per day. This will maximize the benefits while minimizing the risk.
And keep this in mind…while there is positive data on coffee, these benefits don’t necessarily include things like energy drinks and caffeine pills. There are many antioxidants and bioactive compounds in coffee that are interacting with its caffeine content to provide the benefits. So, unfortunately, Red Bull doesn’t count.
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