What Drinking Coffee Actually Does To Your Body


Its effects may appear to be magical, but there’s a lot happening under the surface when you’re enjoying your morning mug.

Whether you just like the taste of coffee, drink it out of habit, or truly rely on it for energy, it’s no secret the drink has magical powers. But have you ever thought about what it’s actually doing after you gulp down your morning mug?

Coffee comes from a bean, so it contains phytonutrients and polyphenols, chemical compounds found in plants that are believed to have antioxidant benefits, Dana Hunnes, Ph.D., M.P.H., R.D., senior dietician at UCLA Medical Center and adjunct assistant professor at the Fielding School of Public Health, tells SELF. “But for the most part, caffeine tends to be the nutrient in coffee that people are most aware of and that’s the best studied.”

From your brain to your bowels, coffee does work on your body. Here’s what’s really happening when you drink it.

The caffeine enters your bloodstream and quickly finds its way to your brain, where it works as a stimulant and boosts alertness and energy.

“The chemical enters your bloodstream fairly quickly,” Hunnes says. It can take as few as 10 minutes from drinking for caffeine to start working. Caffeine binds to adenosine receptors in the brain. Adenosine is a nervous system depressant, meaning its presence suppresses arousal and promotes sleep. When caffeine intrudes and binds to the receptors, adenosine’s effects are lessened, and we become stimulated. This increased brain activity then stimulates the release of adrenaline, which is what gives us that big burst of energy and attentiveness associated with a morning cup of Joe. Studiesalso have connected caffeine consumption to a boost in memory.

The downside is that drinking too much can cause insomnia.

“If you have caffeine later in the day, it can actually predispose you to develop insomnia or make it worse if you already have it,” Rachel Salas, M.D., an associate professor of neurology at Johns Hopkins Medicine who specializes in sleep medicine, tells SELF. It can keep anyone up if they drink it too close to bedtime, but if you’re prone to develop insomnia, a coffee habit can be the trigger that causes a chronic problem. Salas suggests stopping coffee (and all other caffeine) consumption at noon if you think it may be impacting your ability to fall asleep at night. If you can’t function before your morning cup, it’s a red flag you need to take a look at your sleep habits. Coffee is a helpful crutch when you’re tired, but it’s not going to actually give you more energy in the long term. Only good sleep can do that.

That’s partially because caffeine stays in your system for hours and hours.

“The way we metabolize coffee is called a half-life,” Hunnes says. In most people, caffeine’s half-life is 4 to 6 hours. “It takes about 6 hours to reduce the amount of caffeine in our blood by about 50 percent,” she explains. So if you drink a 200 mg cup at 9 AM, by 3 PM you’ll have 100 mg left, and by 9 PM you’ll have 50 mg. Keep in mind, that’s the average half-life—how quickly you metabolize caffeine really depends on your individual body chemistry and genetics.

Caffeine also impacts our pleasure centers, which improves our mood…and keeps us hooked.

“It can help you be more alert and reactive, but it can also help pep you up and impact your mood,” Salas says. Like most drugs, caffeine in coffee increases the levels of feel-good chemical dopamine in our brains. (Other stimulants like cocaine have the same effect, but just much stronger.) This can improve our moods and increase happiness. But for daily drinkers, this can create dependence, resulting in withdrawal symptoms when you go without—it’s why habitual users tend to wake up grumpy and get headaches if they don’t get their fix.

Too much caffeine can have a negative impact on mood and mental health.

High doses can mess with your brain chemistry too much, and cause jitteriness and nervousness. Studies have shown that high doses of caffeine can increase anxiety and panic attacks. Those who already struggle with these mental health challenges tend to be more sensitive to caffeine and its mood-altering effects.

Drinking large amounts of coffee can cause a spike in blood pressure and heart rate.

Studies have suggested that coffee increases heart rate, thanks to caffeine’s impact on hormones and neurotransmitters. But drinking coffee in moderation—one to three cups per day–shouldn’t have a noticeable impact on a healthy adult. According to the Mayo Clinic, some habitual drinkers may have a slightly higher blood pressure, while others develop a tolerance and are not affected in the long term. There isn’t a clear explanation as to why caffeine causes this increase in blood pressure, but it’s likely due to increased adrenaline and other hormonal responses brought on by the stimulant.

Coffee stimulates bowel movements, and may even reduce the risk of gallstones.

Ever notice you really have to hit the bathroom after a cup of coffee? Experts believe caffeine directly stimulates the colonic muscles, prompting bowel movements. Plus, if you’re drinking it hot, the warm liquid itself can help relax the colon and prompt muscle contractions, adding to the laxative effect. When the muscles in the gallbladder specifically are stimulated, it increases emptying, which can reduce the risk of gallstones.

It’s a myth that coffee is dehydrating.

“It’s a very mild diuretic,” Hunnes says. “But it’s not really much of a dehydrator.” She says that if you were to drink a huge amount in one day, say 8 cups (which is not recommended), and have no other fluids all day, you might experience slight dehydration. But coffee contains a lot of water, and it counts toward your daily fluid intake just like a plain glass of H2O would.

Coffee may suppress appetite and boost calorie burn, but it’s not a magic weight-loss bullet (sorry).

Coffee is a known appetite suppressant and may stimulate thermogenesis, or the process our bodies use to create heat, which theoretically leads us to burn more calories. But there’s not much evidence that these effects are large enough to result in significant or long-term weight loss, the Mayo Clinic says. Black coffee is a good low-cal way to get your fix, but choking it down for its supposed weight-loss benefits probably won’t bring any noticeable changes.

Another Perk for Drinking Coffee


Nearly 60 percent of Americans drink coffee, and for many the habit is a daily one.1 Coffee drinking has long been viewed as more of a vice or a crutch to get a quick energy boost to power through the day, but this view is now changing as the health benefits of coffee continue to be revealed.

This is good news for those of you who sip on a cup of joe in the morning, as it turns out this may be a quite healthy way to start your day.

However, please remember that coffee is one of the most heavily pesticide sprayed crops in the world. If you drink it please be sure to get organic and ideally fair traded, This is less than 3% of all coffee.

Daily Coffee Boosts Colon Cancer Survival

Among people with advanced (stage III) colon cancer, drinking four or more cups of caffeinated coffee daily lowered the risk of cancer recurrence or death during the study by 52 percent compared to those who drank no coffee.

Drinking two or three cups per day was also beneficial, lowering the risk of recurrence or death by 31 percent.

The researchers stressed that other caffeinated beverages, such as soda, did not have the same effect. No link was found between decaffeinated coffee and risk of colon cancer recurrence either.

Further, a causal link was not found. This means it could simply be that coffee drinkers tend to follow a healthier overall lifestyle that’s contributing to the lower risk. However, the antioxidants and other beneficial plant compounds in coffee have been linked to a lower chronic disease risk before.

In fact, coffee has been linked to a lower risk type 2 diabetes as well, a condition known to increase the risk of colon cancer. It’s likely that compounds in coffee may lower the risk of multiple chronic diseases via similar pathways.

As reported by the New York Times:2

The researchers’ hypothesis is that the factors that increase risk for Type 2 diabetes, such as obesity, a sedentary lifestyle, and high insulin levels, also drive colon cancer, Dr. [Charles S.] Fuchs [director of the Gastrointestinal Cancer Center at Dana-Farber Cancer Institute in Boston] said.

And many studies have shown that coffee consumption is associated with a lower risk for Type 2 diabetes, a chronic illness that may increase the risk of colon cancer.

‘We believe that activating the energy pathways that contribute to heart disease and diabetes is also relevant for the proliferation of cancer cells,’ Dr. Fuchs said, while also stressing that more research was needed.

The analysis determined the lowered risk associated with coffee was… because of the caffeine. One hypothesis is that caffeine increases the body’s sensitivity to insulin, so it requires less of the hormone. That, in turn, may reduce inflammation, which is a risk factor for diabetes and cancer.”

What Else Does the Research Say About Coffee and Cancer?

While a number of individual studies have suggested coffee consumption might increase your cancer risk, when multiple studies are analyzed, such as is the case with meta-analyses, the association disappears, and, in fact, becomes protective.

For instance, one 2007 meta-analysis found an increase in consumption of two cups of coffee per day was associated with a 43 percent reduced risk of liver cancer3 – a finding that has been confirmed by more recent research.

Not to mention, coffee appears to have additional benefits for liver health, slowing down the progression of liver disease to cirrhosis, improving responses in people with hepatitis C, and lowering the risk of death in people with cirrhosis.4

The potential benefit of coffee for liver health appears so strong that researchers have stated daily coffee consumption should be encouraged in people with chronic liver disease.5

Another meta-analysis involving 59 studies revealed an increase in consumption of one cup of coffee per day was associated with a 3 percent reduced risk of cancers.6 According to the researchers:

“[C]offee drinking was associated with a reduced risk of bladder, breast, buccal and pharyngeal, colorectal, endometrial, esophageal, hepatocellular, leukemic, pancreatic, and prostate cancers.”7

There’s even research showing coffee consumption could lower your risk of skin cancer. Drinking four cups of caffeinated coffee daily might reduce your risk of melanoma, the most dangerous form of skin cancer.8

According to researchers:

“[C]offee constituents suppress UVB-induced skin carcinogenesis, induce cell apoptosis, protect against oxidative stress and DNA damage, reduce inflammation in epidermal cells, and inhibit changes in DNA methylation.”9

Women who consumed more than three cups of coffee a day had a significantly lower risk of basal cell carcinoma (non-melanoma skin cancer) than those who consumed less than one cup per month.10

Roasted Coffee Contains More Than 1,000 Compounds, Many of Which May Help Fight Cancer

Coffee has multiple potential anti-cancer pathways. As mentioned, caffeine is one of them, as its been shown to both stimulate and suppress tumors depending on the cancer and when it’s administered.11

Polyphenols in coffee, such as lignan phytoestrogens, flavonoids, and polyphenols are also known to have anti-cancer properties, as does caffeic acid, which inactivates several pathways involved in the development of tumors – including cell cycle regulation, inflammatory and stress response, and apoptosis.

Researchers noted in the journal BMC Cancer:12

“There are two specific diterpenes in coffee, cafestol and kahweal, which produce biological effects compatible with anti-carcinogenic properties, including the induction of phase II enzymes involved in carcinogen detoxification, specific inhibition of the activity of phase I enzyme responsible for carcinogen activation, and stimulation of intracellular antioxidant defense mechanisms.

Coffee is also a major source of the chlorogenic acid that contributes to its antioxidant effect. Intake of chlorogenic acid has been shown to reduce glucose concentrations in rats and intake of quinides, degradation products of chlorogenic acid, increases insulin sensitivity.

Chronic hyperinsulinemia and insulin resistance are confirmed markers of high risk for some cancer sites.”

The Benefits of Coffee: From Your Heart to Your Brain

The benefits of coffee are becoming so well established that, for the first time, a government advisory committee included a mention of caffeine in its recommendations for the 2015 edition of Dietary Guidelines for Americans. The report said Americans could safely consume up to five cups of coffee a day, or approximately 400 milligrams (mg) of caffeine, with no detrimental effects.13

The recommendation was based on an evaluation of multiple meta-analyses and other studies evaluating the link between coffee and chronic diseases, including cancer, type 2 diabetes, heart disease, Parkinson’s, and Alzheimer’s. Here’s a sampling of what the research shows:

Heart Health

In a study of more than 25,000 people, those who drank a moderate amount of coffee – defined as three to five cups daily – were less likely to have calcium deposits in their coronary arteries than those who drank no coffee or more coffee daily.14

A large part of arterial plaque consists of calcium deposits (atherosclerosis), hence the term “hardening of the arteries.” Coronary artery calcium can be a significant predictor of future heart disease risk.

In addition, one study showed moderate coffee drinking reduces your chances of being hospitalized for heart rhythm problems. 15 Another study found it may trigger a 30 percent increase in blood flow in your small blood vessels, which might take some strain off your heart.16

Another study, a meta-analysis that included data from 11 studies and nearly 480,000 people found drinking two to six cups of coffee a day was associated with a lower risk of stroke.17

Multiple Sclerosis and Parkinson’s Disease

Drinking four to six cups of coffee a day is associated with a lower risk of multiple sclerosis, as is drinking a high amount of coffee over five to 10 years. According to researchers, Caffeine has neuroprotective properties and seems to suppress the production of pro-inflammatory cytokines.”18 Higher coffee and caffeine intake are also associated with a lower risk of Parkinson’s disease.19

Dementia

Caffeine promotes production of the neurotransmitters serotonin, dopamine, and noradrenaline, and triggers the release of brain-derived neurotrophic factor (BDNF), which activates brain stem cells to convert into new neurons, thereby improving your brain health.

Among people with mild cognitive impairment (MCI), those with higher blood levels of caffeine (due to coffee consumption) were less likely to progress to full-blown dementia.20 Caffeine/coffee intake is associated with a reduced risk of dementia or delayed onset, particularly for those who already have MCI,” the researchers said.

Premature Death

Research published in the New England Journal of Medicine has even shown that coffee consumption is inversely associated with premature death. The more coffee drank, the lower the risk of death became, including deaths from heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections.21

Coffee Is the Number One Source of Antioxidants in the US

Another reason why coffee may have such dramatic effects on Americans’ health is because it is the number one source ofantioxidants in the US diet. The research, which was presented at the 230th national meeting of the American Chemical Society, showed that Americans get more antioxidants from drinking coffee than from any other dietary source, with researchers noting “nothing else even comes close.”22

Examples of the antioxidants in coffee include significant amounts of hydrocinnamic acid and polyphenols. Antioxidants are nature’s way of providing your cells with adequate defense against attack by reactive oxygen species (ROS) or free radicals.

Free radicals are a type of a highly reactive metabolite that is naturally produced by your body as a result of normal metabolism and energy production. They are your natural biological response to environmental toxins like cigarette smoke, sunlight, chemicals, cosmic, and manmade radiation, and are even a key feature of pharmaceutical drugs. Your body also produces free radicals when you exercise and when you have inflammation anywhere in your body.

As long as you have these important micronutrients, your body will be able to resist aging caused by your everyday exposure to pollutants. If you don’t have an adequate supply of antioxidants to help squelch free radicals, then you can be at risk of oxidative stress, which leads to accelerated tissue and organ damage.

While fruits, such as berries, and vegetables are ideal sources of antioxidants, many Americans don’t eat the recommended amounts each day. This is why coffee, which is consumed widely on a daily basis, represents such a large dietary share of antioxidants. If you’re not a coffee drinker, you can easily boost your antioxidant intake by eating fresh produce – and even if you do drink coffee, getting your antioxidants from a wide variety of sources is still important.

Is Decaf Coffee a Healthy Choice?

The coffee beans used to make decaffeinated, or decaf, coffee undergo a process to remove most of the caffeine. In order to be labeled decaffeinated, the coffee must have 97 percent of the original caffeine content removed.23 This may be preferable for those who are highly sensitive to caffeine (for instance experiencing jitters after one regular cup), but there are some considerations. For starters, some of the research on coffee’s health benefits have shown caffeinated coffee to be more effective than decaf (the featured colon cancer study is one such example).

In particular, caffeinated coffee has also been linked to a lower risk of liver damage, increased metabolic rate, reduced risk of depression and suicidal thoughts, and enhanced athletic performance while decaf coffee has not.24 The process used to decaffeinate the coffee is also important to be aware of.

One of the most commonly used methods is Direct Process, which uses the chemical methyl chloride to remove the caffeine from coffee beans. Starbucks, for instance, uses this process on most of its decaf brews (although it also offers a “naturally processed” decaf Sumatra blend).25

The National Cancer Institute lists methyl chloride as a possible carcinogen, so it’s something you’re better off avoiding (trace amounts are sometimes detected in decaf coffee, although typically at levels below 1 part per million). Natural Process decaffeination uses either ethyl acetate (a plant hormone) or carbon dioxide to remove caffeine, while the Swiss Water process uses only water. Only the carbon dioxide or Swiss water methods are allowed in coffee that’s certified organic. If you choose to drink decaffeinated coffee, be sure to choose one that is decaffeinated using one of these latter two methods.

Another option, if you’re simply looking for a lower-caffeine blend, is to choose Arabica beans, which naturally have about half the caffeine content of Robusta beans. 26 Also, keep in mind that even decaffeinated coffee is not caffeine free (a typical cup of decaf may contain 3 to 18 milligrams (mg) of caffeine, compared to between 140 to 300 mg in a regular cup.

This is an important distinction for pregnant women to be aware of. Public health agencies suggest pregnant women limit daily caffeine to 200 mg (or about two cups of coffee a day). However, caffeine can significantly impact the growing fetus. It is able to freely pass through the placenta, and since caffeine does not provide any benefits to your baby, only potential hazards, I strongly recommend pregnant women avoid ALL forms of caffeine.

How to Ruin a Good Cup of Coffee…

If you want to drink coffee for its health benefits, drink your coffee black, without sugar, non-dairy creamer or cream, or flavorings. If you are dousing your cup of coffee in creamer, non-dairy creamer, sugar, and other sweeteners and flavorings, you are missing out on the therapeutic benefits and potentially harming your health.

The natural blend of polyphenol antioxidants are part of what makes coffee so healthy. However, some research suggests that adding dairy to your coffee may interfere with your body’s absorption of beneficial chlorogenic acids.27 Meanwhile, if you add sugar to your coffee you’ll spike your insulin levels, which contributes to insulin resistance.

Also, coffee beans are one of the most heavily pesticides-sprayed crops. So, you should select only coffee beans that are certified organic. Remember, you will obliterate any positive effects if you consume coffee that’s been doused in pesticides or other chemicals. Whenever possible, purchase sustainable “shade-grown” coffee to help prevent the continued destruction of our tropical rain forests and the birds that inhabit them.

There are many who say shade-grown coffee tastes better as well. In addition, you’ll want to purchase whole bean coffee that smells and tastes fresh, not stale; if your coffee does not have a pleasant aroma, it is likely rancid. Grind it yourself to prevent rancidity, as pre-ground coffee may be rancid by the time you get it home. If you use a “drip” coffee maker, be sure to use non-bleached filters. The bright white ones are chlorine-bleached, and some of this chlorine will leach from the filter during the brewing process. Bleached filters are also notoriously full of dangerous disinfection byproducts, such as dioxin.

Finally, while it appears coffee in moderation is beneficial, be careful not to overdo it, as some studies have found adverse effects when about 10 cups a day or more are consumed. When referring to a “cup” of coffee, most research considers it to be five to eight ounces with about 100 mg of caffeine. In contrast, a small cup at many coffee houses starts at 12 ounces while a large cup may hold 20 to 24 ounces. Simply be aware of how much you’re actually consuming.