For many of us, any study suggesting our coffee-drinking habits might be good for us is a reason to celebrate (and to raise our mugs of hot delicious Americanos in toast)! And as luck would have it, a number of research studies show that drinking coffee in moderation could legitimately provide a range of health benefits, including reducing the risk of certain cancers, stroke, diabetes, Parkinson’s disease, Alzheimer’s disease, cardiovascular disease, gout, gallstones, and depression, along with protecting against antibiotic-resistant bacterial infections and cirrhosis of the liver. It can even reduce muscle soreness after a workout! There are even studies that show that coffee drinkers are plain old less likely to die (from any cause), suggesting that drinking coffee every day can have a life-extending effect. In fact, a meta-analysis from 2014 found that drinking four cups per day was associated with a 16 percent reduction in all-cause mortality (as well as a 21 percent reduction in cardiovascular disease mortality).
Even more recently, two important prospective cohort studies, published on the same day in the Annals of Internal Medicine, confirmed a mortality-reducing effect of coffee across a wide spectrum of populations. The first study—encompassing 10 different European countries and a total of 521,330 people—found that the highest coffee consumers (28 oz per day for men and 23 oz per day for women) had significantly lower all-cause mortality (12 percent lower for men, 7 percent lower for women) compared to people who didn’t drink coffee at all. This study also found that the highest coffee consumers had lower risk of death from digestive diseases (59 percent lower for men and 40 percent lower for women), and that the highest coffee-consuming women (but not men) had a 30 percent reduction in cerebrovascular diseases and a 22 percent reduction in circulatory diseases.
The second prospective cohort study confirmed that coffee’s mortality benefits hold true for non-white ethnic groups (an important finding, because data for coffee and mortality is sparse for non-whites, and there are many instances where dietary variables have different effects depending on a person’s ethnic background). Analyzing data from the Multiethnic Cohort, this study looked at 185,855 African Americans, Native Americans, Japanese Americans, Latinos, and whites and found that even after adjusting for smoking and other potential confounders, drinking at least two cups per day was associated with an 18% reduction in total mortality. Only in Native Hawaiians did coffee’s inverse association with total mortality not reach statistical significance. (Coffee also appeared protective against death from heart disease, stroke, cancer, diabetes, kidney disease, and respiratory disease in this analysis!)
Some of these effects are owed to the antioxidants, polyphenols, and bioactive compounds found in coffee (including some with insulin-sensitizing and anti-inflammatory properties). Some of the health benefits of coffee are also directly attributable to its caffeine content (which is why drinking tea—which is rich in antioxidants and polyphenols while also containing caffeine—is also associated with good health). This is partly why many of the health-protective effects of coffee are not seen with decaf coffee. In addition, the decaffeination process tends to strip the coffee not only of much of its caffeine content, but also of many of its antioxidants and polyphenols (potentially leaving behind a few of the more harmful substances that can be found in coffee).
So, what’s the catch? Despite many potential benefits, coffee can also be a double-edged sword. For one, coffee is made from a seed (not a legume, but the pit of the coffee fruit). Right away this should put us on the alert since seeds tend to contain protective compounds to prevent digestion and thereby ensure the survival of the plant species. A large percentage of people report that coffee upsets their stomach or gives them heartburn. This is because coffee stimulates the secretion of the main gastric hormone gastrin, resulting in excessive secretion of gastric acid and speeding up gastric peristalsis (even decaf coffee has this effect). Coffee also stimulates release of the hormone cholecystokinin (CKK), which stimulates release of bile from the gallbladder. In a healthy individual, this release of bile salts is likely sufficient to neutralize the highly acidic chyme. However, deficiencies in gallbladder function are associated with metabolic syndrome. In the case of reduced gallbladder function or excessive coffee consumption, highly acidic chyme travels through the small intestine where it irritates and inflames the lining of the intestines. This is also clearly a good argument for consuming coffee with food.
Although caffeine does have benefits in many cases, people who are genetically slow caffeine metabolizers (involving reduced activity of the CYP1A2 enzyme) may not receive the heart-protective benefits of coffee, but instead experience high blood pressure and an increased risk of having a heart attack. Due to the disruptive effects of caffeine on sleep, consuming caffeinated coffee late in the day can have a negative impact on sleep quality. Another one of the detrimental effects of consuming caffeine (whether from coffee, tea, chocolate, or energy drinks) is the effect that it has on cortisol. Caffeine acts to increase cortisol secretion by elevating production of adrenocorticotropic hormone by the pituitary gland. Excessive cortisol production can lead to a variety of health issues, including an overactive immune system, disrupted sleep, impaired digestion, and depression. When you consume caffeine, your cortisol level increases (dependent on what your cortisol management is like to begin with and how much caffeine you consume) and can stay elevated for up to six hours. With daily consumption, your body will adapt somewhat and not produce quite as much cortisol, but complete tolerance to caffeine does not occur. Very importantly, if you are a habitual consumer of caffeine, your cortisol will increase more dramatically in response to stress (like that guy cutting you off in traffic) than someone who doesn’t consume caffeine. If you have difficult managing stress as it is, caffeine is not helpful to you.
One key study showed that moderate coffee consumption in healthy individuals correlated with increased markers of inflammation in their blood. People who drank more than 200 mL (that’s one large cup in my house) of coffee every day (equivalent to 37.3 mg of caffeine) had increased circulating white blood cells and several key inflammatory cytokines (chemical messengers of inflammation, usually restricted to the site of injury or infection). When cytokines circulate in the blood, they cause low level inflammation everywhere in the body. This chronic systemic inflammation is exactly one of the situations we are trying to prevent with adoption of a Paleo diet! These increases in markers of inflammation were persistent even after adjusting for other health and lifestyle factors (such as age, sex, weight, exercise, and smoking).
Several compounds in coffee (namely cafestol and kahweol) have cholesterol-raising effects, and can cause higher LDL and total cholesterol in some individuals (although they may also have a protective effect on the liver, and help explain the association between coffee consumption reduced risk of liver cancer). These compounds are largely removed via paper filtration, so their presence depends on how the coffee is prepared.
In a nutshell (er, a coffee bean husk), coffee offers a variety of pros and cons that are extremely context dependent. For many people, coffee is a fine addition to a Paleo diet (especially when consumed in moderation, in filtered form, early in the day, and with a meal rather than on an empty stomach). People with gallbladder problems, who metabolize caffeine more slowly, or who simply experience adverse side effects like an upset stomach or heartburn should proceed with caution where coffee is concerned.
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