Advice Column, Fertility, Health, Lifestyle

Coffee: Good or Bad for you?

  • Paarl Dietitians
  • Category Advice Column, Fertility, Health, Lifestyle

The health effects of coffee are quite controversial. Depending on who you ask, it is either a super healthy beverage or incredibly harmful. But despite what you may have heard, there are actually plenty of good things to be said about coffee. For example, it is high in antioxidants and linked to a reduced risk of many diseases as well as improved sports performance. Some studies have even shown that coffee drinkers live longer. 

The truth is… there are some important negative aspects to coffee as well (although this depends on the individual). Coffee contains caffeine, a stimulant that can cause problems in some people and contribute to anxiety and disrupt sleep. 

This newsletter takes a detailed look at coffee and its health effects, examining both the pros and cons.


Coffee is one of the most popular drinks worldwide, with around two billion cups being consumed in a day. With Finland drinking more coffee than any other country in the world.

Coffee is a major dietary source of caffeine and has received considerable attention regarding health risks and benefits. Caffeine is a chemical compound which acts as a stimulant when consumed. Many of us are aware of the effects of caffeine on our bodies as we try to wake up in the morning, or stay awake at the end of a long day. However, for some individuals, excessive caffeine consumption (more than 2-3 cups of coffee or 200 mg of caffeine per day) can have negative consequences on their bodies including an increased risk of nonfatal myocardial infarction (heart attack).

Caffeine metabolism – rate of breaking down caffeine

After drinking a cup of coffee, most of the caffeine gets absorbed by the body and circulates for a few hours while slowly degrading in our body. 95% of caffeine is broken down inside the liver using an enzyme called Polymorphic Cytochrome P450 1A2 enzyme (CYP1A2).

How long the caffeine stays in the body is measured by the half-life of the substance. The half-life is how long it takes for half of the caffeine ingested to be metabolized or eliminated from the body. In most healthy adults, the half-life of caffeine ranges from 2 to 4 hours. The longer the half-life (or the longer it takes for the caffeine to breakdown) the more severe the caffeine related symptoms.

The half-life of caffeine as well as the way you handle caffeine and the intensity of the symptoms depend on a variety of factors such as:

  • The amount of caffeine consumed
  • Liver function
  • What drugs or medications are taken at the time of caffeine intake
  • Levels of enzymes that break down caffeine (polymorphic cytochrome P450 1A2 enzyme)
  • Overall health status
  • Age

The majority of the population can handle moderate amounts of caffeine very well (around 400ml or 2 cups of coffee) and can enjoy its health benefits with only a few minor negative effects. However, in some cases the effects of caffeine on the body and health can be more negative than positive.

The positive or negative effects of caffeine on health mainly depend on an individual’s genetic predisposition. How we react to caffeine is dependent largely on genetics & varies between individuals.


Not everyone responds to a single cup of coffee (or other caffeinated beverage) in the same way. Depending on a person’s genetic make-up, he or she might be able to guzzle coffee right before bed or feel wired after just one cup, based on research (Java gene study).  

DNA plays a big part in how much coffee we can drink, to the point that some of us should avoid or at least reduce coffee or other caffeinated drinks. There are a number of genes that determine how well we can take a caffeine hit, since they influence the rate of the breaking down of caffeine, sensitivity and tolerance to caffeine and also the rate of breaking down other harmful substances induced in the body by caffeine. 

There are a few genes responsible for how efficiently we deal with caffeine in our diet:

  • Gene CYP1A2 (Cytochrome P450 1A2) is responsible for releasing the liver enzyme that determines how quickly our bodies break down caffeine.
  • Gene COMT (Catechol-0-Methyl Transferase) is responsible for making an enzyme which controls the breakdown of stress hormones called catecholamines. Caffeine increases the release of catecholamines. 


There are two variations of the CYP1A2 gene which affect how quickly a person metabolizes caffeine – one that helps metabolize caffeine faster and another that helps metabolize it slower.

Those who produce less of this metabolizing enzyme (polymorphic cytochrome P450 1A2) are referred to as SLOW METABOLIZERS and then take longer to rid the body of caffeine, staying longer in the system in higher amounts and making its side effects feel more intense and prolonged. Slow metabolizers are regarded as being caffeine sensitive. These individuals usually feel the effects after drinking one or two coffees. Common caffeine sensitivity symptoms include jitteriness, increased heartbeat, nausea; sweating, dizziness, diarrhea, insomnia, headache.

The other variant of the gene causes the liver to metabolize caffeine very quickly – referred to as FAST METABOLIZERS. These individuals metabolize caffeine about four times more quickly than people who are slow metabolizers.


The COMT gene has a number of variations – one variation causes low COMT enzyme activity. So the less active the COMT enzyme is, the bigger the concentration of catecholamines.  When caffeine is in high concentrations, there is a further increase in the release of catecholamines. High amounts of catecholamines increases the probability of damage to cells in the heart muscle resulting in an increased risk of a heart attack.  The risk of a heart attack grows if you are a slow metabolizer and have low COMT activity.


Slow metabolizers are caffeine sensitive, thus frequent coffee consumption are associated with health risks. The increased disease risk may be due to the fact that caffeine hangs around longer in a slow metabolizer, it has more time to act as a trigger of heart attacks.

Caffeine Intake Amount Risks/Benefits for SLOW metabolizers
1-2 cups coffee (200 mg)/day Does not increase heart attack risk
2-3 cups coffee (300 mg)/day Increased risk of heart attack by 36%
4 cups coffee or more/day Increased risk of heart attack by 64%
4 cups coffee or more/day for persons below 50 years Increased risk of heart attack by four fold
2-3 cups coffee (300 mg)/day for women, planning to get pregnant  Increased risk of recurrent pregnancy loss or reduced fertility
1 cup coffee (100 mg)/day for pregnant women Increased risk of miscarriage

If one is a slow metabolizer of caffeine, then one should decrease the amount of caffeine intake to reduce the risk of disease e.g. high blood pressure or nonfatal heart attacks. Moreover, females who are pregnant or plan on being pregnant and are slow metabolizers of caffeine should cut back on consuming caffeine to lower their risk of miscarriages and to increase fertility.

Negative health effects of coffee for SLOW metabolizers

  • Menopause: Caffeine use is associated with greater vasomotor symptom bother (e.g. hot flashes and night sweats) in postmenopausal women.
  • Infertility and miscarriage: Caffeine rapidly crosses the human placenta and reaches a similar concentration in the fetus. If you are a slow metabolizer and consume 2-3 coffees per day, the risk of infertility and miscarriage increases. An increase of 100mg of caffeine intake per day (equivalent to 1 cup of coffee) is associated with a 7% higher risk of loss of pregnancy, and a 13% higher risk of a lower birth rate. 
  • Sleep: Caffeine can affect sleep quality, especially if you are a slow metabolizer. Therefore, it is recommended to abstain from caffeinated drinks for a minimum of 6 hours before sleep time (on average, it should be avoided after 5pm).
  • Anxiety: In slow metabolizers the intake of caffeine may induce symptoms of anxiety. 
  • Heart health: Slow metabolizers have an increased risk of non-fatal heart attack, if they drink 2-3 cups of coffee daily (200-300mg caffeine). 
  • Blood pressure: Caffeine raises blood pressure. The increase in blood pressure is small, of about around 3mm Hg. Nevertheless, these changes may negatively affect individuals (slow metabolizers) at high risk of cardiovascular diseases.


The trend among fast metabolizers is quite the opposite. Those who drank one to three cups of coffee daily had a significantly reduced risk of heart attacks – suggesting that for them coffee is protective. Fast metabolizers clear caffeine from their systems rapidly, allowing the antioxidants, polyphenols and coffee’s other healthful compounds to kick in without the side effects of caffeine.

Caffeine Intake Amount Risks/Benefits for FAST metabolizers
2-3 cups coffee (300 mg)/day Decrease heart attack risk by 22%
1 cup coffee (100 mg)/day for pregnant women No increased risk of recurrent pregnancy loss or miscarriages

Health benefits of coffee for FAST metabolizers

  • Cognitive function and psycho-motor performance: Caffeinated beverages, such as coffee or tea, if consumed throughout the day, improve alertness, learning capacity, mood, memory and psychomotor performance.
  • Gout: Long term caffeine consumption is associated with decreased risk of gout.
  • Heart health: There is a 22% lower risk of heart attack by having 200-300mg caffeine per day (2-3 cups of coffee).
  • Skin cancer: Two recent, large studies on the effects of coffee on skin cancer have found that caffeinated coffee consumption is associated with a reduction of a risk of malignant melanoma by up to 25%. Because decaffeinated coffee didn’t show a significant association with the risk of melanoma, scientists think that this may be due to caffeine. More studies on caffeine are planned to confirm these theories.
  • Cognitive decline: Coffee may help protect your brain in old age. Several studies show that coffee drinkers have a much lower risk of dementia, Alzheimer’s disease and Parkinson’s disease in old age. Scientists believed that factors responsible for this reduction may be due to caffeine, antioxidant capacity and increase of insulin sensitivity. Studies have shown that coffee drinkers have up to a 65% lower risk of developing Alzheimer’s disease and 32-60% decreased risk of developing Parkinson’ disease.
  • Physical performance of the athletes: Caffeine (specifically as a capsule/tablet or powder) when taken before exercise, is effective in increasing physical performance (especially in high-intensity workouts of prolonged duration). It improves performance by acting on several areas in the body: it increases focus and alertness, boosts energy, causes a higher release of epinephrine (adrenaline), increases the release of body fat for energy usage and aids in burning more fatty acids during exercise. For optimal absorption, it is advisable to take the supplement 60 minutes before the exercise. However, it is also effective when taken 15-30 minutes before exercise. 
  • Diabetes: Habitual caffeine consumption may reduce the risk of type 2 diabetes mellitus – each daily cup of coffee was linked to a 7% reduced risk.


There is no definitive answer to the question of whether coffee is bad or good for you. Caffeine sensitivity is an important factor that determines whether coffee is healthy or not. The bottom line is, are you a FAST or SLOW caffeine metabolizer? 

  • Being caffeine-sensitive or a SLOW caffeine metabolizer restricts how much coffee you can manage, by producing unpleasant overdose symptoms as soon as you surpass your caffeine limit. Negative rather than positive health effects are likely to occur as a result of caffeine intake. Slow metabolizers should decrease total caffeine in the diet. Restrict coffee intake to a maximum of 2 cups per day (equivalent of 200mg caffeine per day) or alternatively opt for decaffeinated options instead. Also be cautious of so-called hidden caffeine found in tea, soft drinks e.g. colas, energy drinks, energy bars or gels, chocolate and many over-the-counter medications.
  • FAST caffeine metabolizer, on the other hand, can quickly break down and excrete caffeine. Caffeine is good for fast caffeine metabolizers and they’ll experience a wide range of health benefits of caffeine intake, as mentioned in the section previously. 
  • The general recommendation, in the absence of DNA testing, is to keep to 2-3 cups of coffee per day (200-300mg caffeine).

The main point is that, if you are sensitive to caffeine, drinking caffeinated beverages will bring you more negative than positive effects, depending on the sensitivity level and on the amount consumed. 

Important: There are some people who definitely want to avoid or severely limit coffee consumption, especially pregnant women. People with anxiety issues, high blood pressure, insomnia or gastroesophageal reflux disease (GERD)    might also want to try limiting coffee for a while and see if it helps. 


Want to know if you are you a slow or fast caffeine metabolizer? The safest option to make sure how you are handling caffeine is to do genetic test that will tell you if you have the fast or slow caffeine metabolizing gene. 

By knowing your genetic makeup, you can adjust your daily caffeine intake accordingly and manage your overall well-being. Why guess if you are putting yourself at risk the next time you drink coffee, eat chocolate, or take cold medicine? Ease your mind and find out.

This greater understanding of the link between coffee and genetics has opened up a wide new area of research. Genetic or DNA testing provide individuals with accurate personal genetic information, which can be used to make simple lifestyle changes to improve overall well-being. Heavy coffee drinkers or anyone else who would like to take advantage of the most recent scientific findings to make positive changes in their lifestyle would benefit from such a test. 

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One Comment

  • keepyoursoulhealthy November 3, 2022 at 1:05 pm

    Very informative content keep it up


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