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You probably have heard some people saying that drinking six cups of coffee per day has no effect on them and others complaining that it takes only one coffee to make them jittery, aggressive, unable to sleep or to have other symptoms such as chest pains.
The opinions on the health effects of coffee are divided. The information available either promotes the health benefits of coffee or warns about its negative side effects.
The truth, however, is that part of the population can benefit from coffee’s health properties and the other part will only experience negative and detrimental health consequences.
This article describes evidence based health benefits as well as the negative effects of various daily amounts of coffee.
What is in coffee?
In addition to caffeine, the most investigated component, coffee contains more than a thousand compounds, many of which exert important effects on the body, either on their own or in synergy with each other.
One cup of coffee contains a small quantity of minerals and vitamins, but since moderate users drink about 4-5 coffees per day (400mg of caffeine), these amounts contribute significantly to the overall daily nutrient intake.
The image below shows the total amounts of micronutrients for four servings of two of the most popular coffees: espresso and brewed coffee in a plunger.
Please note that the amounts vary depending on factors such as the type of coffee or the method of preparation as shown in this example. The last two columns display the recommended daily allowance of these nutrients for comparison.
Data taken from USDA food database.
Caffeine in coffee
Coffee contains caffeine which is a stimulant drug that affects the nervous system and has an impact on hormones. Caffeine contents in coffee depend on the type of coffee, the amount in a serving and the method of preparation.
A standard coffee serving contains about 100mg of caffeine. However “standards” may vary depending on where you usually get your coffee from. See the article “Caffeine levels in drinks” for more information on coffee and other caffeinated products.
How you react to coffee depends mostly on how you handle caffeine.
Caffeine is the most potent ingredient in coffee and has the biggest influence on how our body reacts to coffee.
Although caffeine has many health benefits, it may also produce a wide range of negative symptoms, depending on the individual’s sensitivity and tolerance to caffeine, and in some rare cases caffeine allergy. (read more..)
Before answering the question if coffee is good or bad for you, it is essential to consider the following points on caffeine:
- Caffeine allergy
- Caffeine sensitivity
Caffeine sensitivity is determined by each individual’s genetic make-up and dictates how well we can handle caffeine.Being caffeine-sensitive or a slow caffeine metabolizer restricts how much coffee you can handle.
Negative rather than positive health effects occur as a result of caffeine intake. (read more..) On the other hand, fast caffeine metabolizers, those that can quickly break down and excrete caffeine, experience a wide range of health benefits from caffeine intake.
- Caffeine tolerance
If you are not highly sensitive to caffeine, it is possible to build up tolerance to caffeine.
This means that after a few days of consuming the same daily amount of caffeine, its symptoms, such as increased energy, euphoric feeling, increased focus and disturbance in sleep, tend diminish and even disappear. In some extreme cases, you can build your tolerance to the point of overconsumption and high dependency (caffeinism), which has detrimental results on your health.
- Caffeine overdose
Caffeine overdose may occur whether you are sensitive to caffeine or not. It depends on the combination of the dose and your level of sensitivity. To avoid caffeine overdose, learn your safe limit.
Is coffee addictive?
Coffee is often described as an addictive beverage, since it contains caffeine and it seems to be hard to quit. Caffeine, although a drug, is not addictive. (read more..)
When is coffee bad for you?
- Coffee contributes to acid reflux in people who suffer from (or are prone to) GERD
Gastroesophageal reflux (GERD)* is often caused by the transient relaxation of the lower esophageal sphincter (LES). LES is a muscle between the stomach and the esophagus that ideally only opens when you swallow food.
If this muscle is relaxed, stomach acid may be pushed up to the esophagus burning its delicate lining.In people who suffer from GERD, this sphincter relaxation occurs more frequently and is easily triggered by some foods, especially coffee. (8)
Decaffeinated coffee, however, has significantly less impact in individuals with reflux disease. (9)
*Different spelling of (e/oe)sophagus
GERD – gastro – esophageal reflux (U.S, Canada)
GORD – gastro – oesophageal reflux (U.K, Australia)
- Coffee is bad for your heart if you are a slow caffeine metabolizer
Slow metabolizers have an increased risk of a non-fatal heart attack when they drink 2-3 cups of coffee per day (200-300mg caffeine). Those who drink 4 cups of coffee have 4 times more risk of heart attack comparing with those that drink 1 cup per day. (read more..)
- Coffee may increase the risk of ovarian cancer
Postmenopausal women who drink five or more caffeinated coffees per day have a higher risk of developing ovarian cancer. (10)
- Breast cancer
No correlation was found between breast cancer and caffeine in one study (11).
However, other studies show the association with a higher risk of fibrocystic breast disease in women who are at the higher risk of developing breast cancer. (12)
- Coffee can contain diterpenes: cafestol and kahweol which increase blood lipids
Cafestol and kahweol (called diterpenes) are potent cholesterol-raising agents contained in coffee.Filtered and instant coffees contain the least amount of these compounds, since the filtering process traps the diterpenes.
The highest levels of diterpenes per cup are found in Turkish coffee, French press, espresso and boiled coffee consumed in Scandinavia.
Please note that there is evidence that cafestol and kahweol have anti-cancer properties and are good for the livers’ health. (16)
- Health effects of additives taken with coffee
When coffee is consumed with any other additives besides water, it may have an additional impact on health, especially with the average daily amounts of coffee (4-5 cups).
Adding sugar to coffee increases greatly the calorie intake and adds high amount of fructose, augmenting the risk of metabolic syndrome.
Drinking coffee with milk may cause lactose intolerance symptoms in some individuals and add to the calorie intake. Non-dairy creamers contain all sorts of unhealthy ingredients, such as hydrogenated soybean oil, high-fructose corn syrup and monosodium glutamate.
- Coffee may be not recommended for some people due to its caffeine contents.
- Individuals with caffeine allergy, slow caffeine metabolizers, children, women who are pregnant or at risk of developing breast cancer should avoid or limit coffee intake to the minimum.
- Drinking more coffee than your level of sensitivity allows may induce unpleasant overdose symptoms.
- Overconsuming when you are not sensitive to caffeine may lead to caffeinism and the risk of developing serious medical conditions such as GERD.
When is coffee good for you?
Health benefits of coffee drinking
Most health benefits are achieved by the majority of the population with an intake of 3-5 coffees per day.
Individuals who are allergic to caffeine should avoid coffee and those that are caffeine sensitive should reduce the caffeine intake to the point where symptoms are not detectable (e.g. select decaf over standard coffee).
- Coffee reduces gout incidence and flare-ups in some people
The consumption of coffee is associated with a lower incidence of gout and may reduce gout flare-ups in some people.
This positive effect is due to coffee’s (not necessarily caffeine’s) ability to decrease uric acid in the blood. (Note: the consumption of tea is not associated with decreased uric acid). (17, 18, 19) A large observational study showed that intakes of 4-5 coffees per day, have a 40% lower risk of gout and of at least 6 cups per day a 59% lower risk, when compared with zero intake. (20)
However, there are some claims stating that consuming large amounts of coffee can cause an increased risk of recurrent gout attacks and flare-ups, but they are not confirmed by studies.
- Coffee consumption doesn’t increase the risk of cancer, and possibly lowers the risk of some cancers
Coffee consumption is not linked to the risk of cancer mortality. (21)
Studies on coffee and colorectal cancer are somewhat conflicting although more studies show positive effects.
One large systematic study review has found no association between caffeinated coffee and colorectal cancer in men and women. This means that it neither increases nor decreases the risk of cancer in the colon or rectum. (22) Another more recent large study, however, found that individuals who drink caffeinated coffee have a lower risk of developing colon cancer, specifically proximal tumors, while decaffeinated coffee drinkers show lower risk in both colon and rectal cancers. (Tea has shown no association with colorectal cancer risk). (23)
Individuals who had two cups of decaffeinated coffee daily showed a 52% lower incidence of rectal cancer compared to those who never consumed decaffeinated coffee.
Coffee consumption is significantly related to a decreased risk of liver cancer, although it is not known which compound or synergy of compounds have these protective properties.
Skin cancer – Melanoma
Two recent large studies have shown a reduction of risk of cutaneous melanoma. It was found that four or more cups of caffeinated coffee per day decreased the risk of melanoma by up to 25%, but decaffeinated coffee hasn’t shown a significant reduction of this risk.
No association between coffee and gastric cancer was found in a large systematic review and meta-analysis. (28)
- Caffeine and multiple sclerosis (MS)
Studies on the association between coffee and MS are inconclusive. However, the most recent study (2016) showed that a high intake of caffeinated coffee is related to around 30% lower risk of multiple sclerosis. It is thought to be due to caffeine’s neuroprotective properties, and its ability to suppress pro-inflammatory cytokine production. More studies are needed, however, to confirm the findings of the caffeine involvement. (29)
- Coffee hydrates rather than dehydrates
Drinking coffee was previously thought to have diuretic effects due to its caffeine content. However, many studies have disproved this belief and showed that coffee has rather hydrating effects due to its liquid content. (read more..)
- Coffee and heart disease
For fast metabolizers (medium to high caffeine users), long term intake of between 3-5 cups daily of coffee shows the biggest reduction of risk of cardiovascular disease (CVD). Consumption of large amounts of coffee was not associated with increased risk of CVD. (30, 31) Fast metabolizers also show a 22% lower risk of heart attack by having 2-3 cups of coffee per day (200-300mg caffeine).
- Coffee reduces risk of Alzheimer’s
- Coffee reduced risk of dementia
Drinking 3-5 cups of coffee per day is associated with a decreased risk of developing dementia by 65%. Caffeine, antioxidant capacity and increase of insulin sensitivity is believed to cause these effects. However, more studies are needed. (34, 35)
- Coffee reduces risk of Parkinson’s disease
- Coffee and Diabetes 2
Individuals with type 2 diabetes have a reduced risk in overall mortality, and mortality associated with cardiovascular disease (CVD) and coronary heart disease (CHD). (44)
A large study found that the risk of developing type 2 diabetes mellitus was 35% lower for those who drink at least 6 cups of coffee per day and 28% lower for those who drink 4-6 cups, comparing to those who consumed less than 2 cups per day. (45)
Another study, only considering the male population, found that those that consumed 6 or more cups of coffee per day had a 54% lower risk in developing type 2 diabetes mellitus compared to those who didn’t drink coffee at all. (46)
- Coffee reduces risk of Liver diseases
Individuals with chronic liver diseases are encouraged to drink at least 3 cups of coffee per day, since it has positive effects on liver health. It is believed that the synergy of multiple compounds in coffee provides the liver some protective properties.
Coffee intake showed protective properties against alcoholic and non-alcoholic cirrhosis and reduced the risk of mortality from cirrhosis.
Coffee intake also lowers the rate of developing hepatocellular carcinoma, improves antiviral therapy in hepatitis C patients, and reduces the severity of non-alcoholic fatty liver disease symptoms and the risk of developing liver cancer. (47, 48, 49)
By contrast, decaffeinated coffee, tea and cola-drinks have not been associated with these protective properties. Therefore, it is believed that these properties are due to the synergy of caffeine with other coffee compounds. (50)
- Coffee reduces risk of depression and suicide
Several observational studies show that caffeinated coffee is associated with a decreased risk of depression and that suicide risk associated with depression is lower in individuals with a higher consumption of coffee.
An amount of 4-5 coffees per day is the most optimal in risk reduction and is associated with 20% lower risk of developing depression and 53% lower suicide risk. However, the risk is 58% higher with a usage of at least 8 cups of coffee per day compared to moderate coffee drinkers. (51, 52, 53, 54)
Please note that these are only observational studies which don’t actually prove that coffee causes the reduction of the risks of depression and suicide.
- Coffee and Mortality rate
Large studies show that regular and long term coffee consumption is associated with a lower incidence of deaths from all causes, specifically due to heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections.
The exact reasons are unknown but it is thought to be associated with the more than 1000 compounds contained in coffee, including caffeine and antioxidants, such as polyphenols.
The optimal daily amount of coffee for both men and women is 4-5 coffees per day. This intake guarantees a 12% decrease in death risk in men and 15% in women. (55)
The risk of all-cause mortality and mortality associated with cardiovascular diseases is slightly reduced in decaffeinated coffee drinkers. (56)
Many health benefits of coffee can be attributed to caffeine. The positive effects are associated with fast caffeine metabolizers.
If you are sensitive to caffeine, however, these benefits may not apply. Caffeine:
- improves learning capacity, alertness and mood;
- helps to burn fat during exercise;
- decreases the risk of gout;
- improves heart health, if you are a fast caffeine metabolizer;
- reduces the risk of depression and suicide;
- reduces the risk of developing dementia, Alzheimer’s and Parkinson’s disease;
- reduces the risk of type 2 Diabetes Mellitus;
- has protective properties in liver diseases;
- increases physical performance in athletes.For more detailed information, read the article “Is caffeine bad for you?”
Is decaf coffee bad for you?
What is decaffeinated coffee?
Decaffeinated (decaf) coffee is coffee with the caffeine removed. The process of decaffeination doesn’t remove all the caffeine from coffee, although the remaining amounts are very small. (See caffeine table)
Small amounts of antioxidants are also lost through the decaffeination process, although the overall antioxidant contents still remain very high.
According to the FDA guidelines, decaffeinated coffee must have 97% of the caffeine removed. However, since coffee beans may have varied contents of caffeine, decaf coffees may have different caffeine levels too.
The amount of caffeine ranges from none to 13.9mg per 16oz serving in decaffeinated coffees and from 3 to 15.8mg per shot in decaffeinated espresso.
During the process of decaffeination, a small percentage of antioxidants is removed, resulting in about 15% less antioxidant activity compared to standard coffee. (57)
Most studies are done using regular coffee containing caffeine. This most likely because this is what most coffee drinkers have, and because caffeine is its most potent component.
The main difference between the health benefits and negative health effects of caffeinated and decaffeinated coffee are the impact of caffeine and its synergy with other coffee compounds.
Many health benefits of decaffeinated coffee are believed to be due to the high amounts of antioxidants which may have protective properties in cardiovascular diseases, cancers and type 2 diabetes.
From the studies mentioned above, the association between decaffeinated coffee was found with:
- Reduced risk of gout
- Reduced risk of rectal and colon cancer
- Reduced risk of type 2 Diabetes
- Although studies generally show no association with Parkinson’s, Alzheimer disease and dementia (it is thought to be due to the effects of caffeine), some observational studies show that there may be some connection between high amounts of antioxidants. More studies are needed.
- Lower incidence of death from all causes, heart, respiratory, stroke, injuries, accidents, diabetes and infections. More studies are needed to find out which constituents of coffee are responsible.
- Reduced risk of liver cancer, although it is not known if it is due to caffeine or other compounds
- Hydrating properties due to liquid contents.
Negative effects of decaffeinated coffee
- Reflux, although much lower risk than in regular, caffeinated coffee
Decaffeinated coffee is better than regular coffee for these individuals:
- With high sensitivity to caffeine;
- Sufferers of reflux;
- Pregnant women;
- When taking medications which interact with caffeine
- Decaf coffee is quite healthy and regular intake of decaf coffee has many positive health effects.
- It is a great alternative for those who enjoy the taste but cannot drink coffee due to caffeine contents.