Some people swear by a cup of coffee in the morning. Others refuel throughout the day, and some skip it altogether. One question that invariably comes up during Dr. Fuhrman’s Weight Loss Detox or Nutritarian Coaching certificate Q&As is whether it’s OK to drink coffee, or if it must be avoided completely. So let’s take a closer look.
When it comes to coffee consumption, there’s good news and bad news.
Here’s the good: Drinking coffee regularly is linked to a lower risk of several chronic diseases, and coffee contains beneficial antioxidants.
Here’s the bad: Caffeine causes temporary increases in blood pressure and blood glucose and disrupts your sleep.
So the question is: Does coffee really have health benefits? How concerned should we be about caffeine intake?
Cardiovascular disease, type 2 diabetes, and cancer
The associations between coffee consumption and lower risk of several chronic diseases has been reported, including cardiovascular disease, type 2 diabetes, liver disease, Parkinson’s disease, Alzheimer’s disease, prostate cancer, breast cancer, and depression. Plus, moderate coffee consumption (2-4 cups/day) is also associated with lower all-cause, cardiovascular, and cancer mortality, regardless of caffeine content.
The relationship between coffee drinking and health is complex, and there is variability between individuals in caffeine metabolism. But the antioxidant content of coffee might explain some of these observations of lower disease risk.
Coffee is more than just caffeine. The coffee bean is rich in polyphenols, 98 percent of which are chlorogenic acids, which have antioxidant and anti-inflammatory actions. Caffeine itself has some antioxidant properties. For people who consume the low-nutrient typical Western diet, coffee is a significant source of antioxidant phytochemicals. Overall, antioxidant phytochemicals help prevent cardiovascular disease by reducing oxidative stress and inflammation, and enhancing vascular function. Plus, oxidative stress and inflammation are major contributing factors to cancer and other chronic diseases.
But hang on before you reach for that grande. The antioxidant content – and the resultant antioxidant effect – of coffee is variable.
Studies that have investigated coffee’s effects on antioxidant status and oxidative stress have provided conflicting evidence on whether drinking coffee improves the body’s antioxidant status. Coffee may increase the body’s natural antioxidant glutathione and reduce oxidative DNA damage, but evidence is mixed on other antioxidant measures, such as blood antioxidant capacity, antioxidant enzyme activity, and oxidative protein and lipid damage.
This could be because chlorogenic acid content varies widely between batches of coffee. One reason for the variation is the roast of the coffee, with darker roasts having lower chlorogenic acid content.
Short-term caffeine intake is thought to impair insulin sensitivity. In studies lasting a few hours, coffee has increased blood glucose. However, studies of longer duration show different results.
In studies lasting weeks, drinking coffee daily was associated with lower blood glucose or no change in blood glucose after a meal. A meta-analysis found no significant difference between coffee and control groups in fasting blood glucose or insulin resistance, and observational studies suggest coffee drinking is linked to a lower risk of type 2 diabetes.
The short-term increase in blood pressure associated with caffeine intake likely does not have a significant long-term impact on cardiovascular health. In patients with hypertension, caffeine acutely increases systolic and diastolic blood pressure within about an hour. However, longer-term studies (a few weeks) generally have found no increase in blood pressure with coffee consumption compared to a caffeine-free control diet or decaffeinated coffee.
Epidemiologic studies that follow participants for many years do not suggest that regular, long-term coffee consumption increases blood pressure. Caffeine itself has both blood pressure-raising and -lowering effects, and chlorogenic acids (coffee antioxidants) have blood pressure-lowering effects. Therefore, it’s likely that moderate consumption of coffee does not increase or decrease blood pressure.
But for people who already have high blood pressure, especially severe hypertension, caffeine could be risky. A study that followed over 18,000 Japanese adults for about 19 years found that greater coffee consumption was associated with an increase in the risk of death from cardiovascular disease, but only among participants with grade 2-3 hypertension (systolic blood pressure above 160 mm Hg or diastolic blood pressure over 100 mm Hg. Compared to participants with grade 2-3 hypertension who did not drink coffee, those who drank two or more cups a day had double the risk of death from cardiovascular disease.
The downsides to coffee
There are a few negative effects of coffee that are worth considering. Coffee, especially when it is prepared without a paper filter (such as in a French press), contains cafestol and kahweol, which can increase LDL cholesterol. Plus, many people find coffee unpalatable without adding sugar or high-calorie sweetened creamers, which promote weight gain.
Observational studies have reported an increase in the risk of bone fractures associated with coffee consumption in women – this is likely because caffeine promotes urinary excretion of calcium. There have also been increases in risk for low birth weight, preterm birth, and childhood leukemia associated with high coffee intake during pregnancy.4
Coffee also contains some acrylamide – a potentially carcinogenic compound found in fried and dry cooked starchy foods – due to the roasting process. There is also evidence that high caffeine intake is linked to vitamin D deficiency, though the cause is not yet clear.
Caffeine is a stimulant, and it is addictive. Repeated use of caffeine quells withdrawal symptoms, and these withdrawal symptoms make it very difficult to discontinue caffeine use. The stimulant effect also appears to cause some people to feel anxious or jittery.
Caffeine is also frequently used to counteract the effects of sleep deprivation, but caffeine use cannot take the place of adequate sleep.
Caffeine cannot replace sleep
Many people – think college students cramming for finals, or long-haul truck drivers – use coffee to stay awake. But the truth is, while caffeine might keep your eyes open, it won’t make you less sleep-deprived.
Caffeine promotes wakefulness by blocking signals in the brain that promote sleepiness, but it does not reverse all the cognitive deficits associated with sleep loss. Sleep deprivation leads to diminished cognitive function: attention, alertness, complex cognitive functions, and the speed of cognitive and motor functions are all compromised. Caffeine withdrawal itself causes discomfort and reduced daytime performance: headaches, anxiety, and slower motor functions. Some studies have found cognitive and other daytime performance benefits associated with caffeine use, but it is difficult to tell whether these are true benefits or just reversal of the negative effects of caffeine withdrawal.
Caffeine has a highly variable half-life, and therefore has a highly variable effect on people’s sleep. There is additional variability due to typical caffeine consumption and timing, genetics, age, sex, and body weight. However, studies measuring sleep in laboratory settings suggests that caffeine use (even up to 16 hours before sleep) reduces sleep quantity or quality. Many people end up in a cycle: feeling fatigued in the morning leads to more caffeine use, which leads to poorer sleep the next night.
Caffeine and appetite
Despite caffeine’s reputation as an appetite suppressant, the research overall does not suggest coffee or caffeine decreases appetite or subsequent calorie intake.
Should I drink coffee or not?
Whether coffee has clinically relevant benefits for blood glucose or the cardiovascular system remains unclear. It is likely that coffee is a significant source of dietary antioxidants for people on a low-nutrient Western diet.
Adding coffee to an already healthful diet is unlikely to provide any further benefits, and there are some negatives to consider, such as sleep disruption and acrylamide exposure. However, there’s no evidence that a daily cup of coffee poses any risk to healthy adults. For those with hypertension or high risk for osteoporosis, or those who are pregnant, caffeine could be harmful.
My experience and opinion overall is (even though one cup a day is not been determined to be harmful), that it is better to avoid coffee, especially if you desire more than one cup a day, for the following reasons:
1. The beneficial phytonutrients and supposed benefits have no value to healthful eaters especially those eating other beans.
2. The addictive properties of caffeine can enable less sleep, which can age the brain and shorten lifespan.
3. The withdrawal symptoms (mental buzz or headache) from coffee/caffeine can be reduced/treated by eating food, thus increasing caloric intake in some people. We want to be instinctually connected to our hunger signals and not have them perverted.
4. Roasted and darkened foods containing acrylamide are not health promoting, and addictive substances like caffeine are not healthful.
5. Hot beverages can result in chronic micro-burns to the tongue and oral palate increasing risk of tongue and throat cancer.
Full disclosure: I personally am not a coffee drinker and I am glad I never became addicted.
If you do drink coffee, of course, avoid adding sugar or high-saturated fat dairy products, and consider water process decaffeinated coffee to avoid the stimulant effect.