Table of contents
- Types of coffee
- Active ingredients in coffee
- Potential health benefits
- Choosing wisely
- Why has coffee been labelled as harmful in the past?
- Side effects of coffee
- Is coffee safe during pregnancy?
All About Coffee
Coffee is one of the most consumed drinks in the world and one of the most traded agricultural products. Coffee is a more complex beverage than it is generally perceived to be, this is because it doesn’t just contain caffeine but rather hundreds of different compounds.
Coffee is probably most popular for its stimulant properties, providing an extra energy boost. It also plays an integral role in social situations whereby people meet for coffee. In addition to these favourable aspects, there has been research into the potential health benefits coffee provides.
The cultivation of coffee commenced in Arabia and Ethiopia, it has since spread worldwide. Coffee beans can be separated in to two categories:
The Arabica bean is harder to grow. It has a rich flavour and less caffeine than the Robusta bean. For these reasons, it is a more expensive variety.
The Robusta bean grows easily, it is more resistant to diseases and pests and it produces fruit quickly. The flavour and aroma is weaker than that of the Arabica bean.
Photo sourced from theroasterie.com
Caffeine is responsible for that ‘pick me up’ feeling experienced when drinking coffee. This is because it acts as a stimulant for the nervous system and brain (1). Its effect can be closely compared to that of the hormone adrenaline, both inducing an instant increase in heart rate and burst in physical energy and alertness (1).
The science behind the stimulant effect:
Caffeine molecules bind to receptors in the brain that a compound known as adenosine also binds to. When caffeine attaches, there is limited free space on the receptors for adenosine so less can bind (2). Adenosine is responsible for the promotion of sleep by dampening the brains activity (3). When caffeine binds to these receptors in the brain and the heart, it produces the opposite effect to adenosine and rather acts as a stimulant (2). It triggers the activity of dopamine which is responsible for pleasure and arousal. Therefore in the presence of caffeine, there are less compounds acting to promote sleep and more being used that promote alertness and energy.
The picture below demonstrates this mechanism. The yellow ‘C’ represents the caffeine molecule and the ‘A’ represents the adenosine molecule.
Image sourced from caffeineandyou
As you can see, the caffeine molecule binds to the receptors and the adenosine is therefore diverted.
Caffeine is absorbed in the small intestine and stomach (3). It has an effect generally within 30 – 45 minutes after consumption (when the amount circulating through the body is at its peak). Tobacco increases the speed at which caffeine circulates the body and oral contraceptives slow the rate (3).
Due to the popularity of coffee, it is the most widely consumed psychoactive drug in the world (a psychoactive drug is a substance that affects the nervous system, resulting in altered brain function e.g. increased alertness and focus)(3). The quantity of caffeine needed to produce these effects is different for every individual and will depend on variations in body size/ composition and tolerance to caffeine (1). Like any drug, caffeine is addictive (1).
A number of early studies showed the compounds kahweol and cafestol (types of diterpenes found in coffee) were responsible for raising LDL cholesterol levels (bad cholesterol) (3). However, it has since been found that this only applies to unfiltered coffee (3).
These diterpenes are present as oily droplets or in grounds suspended in coffee. For individuals who use paper filters, these problem substances are mostly removed and have little to no effect on cholesterol levels (3). For those who drink non-filtered coffee, the substances remain. However, there appears to be only a mild rise in cholesterol levels for those who have a moderate coffee consumption (3).
Espresso has a higher presence of kahweol and cafestol than filtered coffee but due to its generally small consumption, it likely has little effect on LDL cholesterol (3). Boiled coffee, Turkish coffee and French press coffee are also higher in cafestol and will have a larger impact on cholesterol levels (4). Paper filtered coffee and instant coffee have much lower levels of kahweol and cafestol and are therefore more suitable for individuals with cholesterol concerns (4).
There have been some studies showing kahweol and cafestol to have anti-cancer properties but this research is still in the very early stages (3).
Chlorogenic acid and antioxidants
Chlorogenic acid (CGA) is responsible for the bitter taste of coffee; it is also largely responsible for the acid reflux that some individuals experience after drinking coffee (2). Arabica beans have less chlorogenic acid levels than robusta beans but the concentration in any one coffee can depend on different elements (2). Both decaffeinated and caffeinated coffee have similar amounts of CGAs.
The association between lower rates of heart disease and diabetes in coffee drinkers is likely due to the chlorogenic acid and antioxidants present in coffee (3). Chlorogenic acid is the main antioxidant in coffee (2,3). Antioxidants act to reduce the harmful effects of dangerous molecules known as ‘free radicals’ (1,2). Free radicals can damage tissue and cells such as the lining of blood vessels (3).
There has been research to show that chlorogenic acid potentially inhibits the absorption of glucose by the digestive system, this thereby reduces the spike in blood glucose levels and insulin (3).
Alternatively, there has been research showing a link with chlorogenic acid and an increase in an amino acid (homocysteine) that has been linked with atherosclerosis (the clogging of arteries) (3). However, this effect has not yet been well established and a moderate coffee consumption has actually been linked with a small decrease in risk (3,5).
In the past, coffee has regularly cropped up on the lists of food and drink that have a detrimental effect on health. However, many recent studies have been looking in to the potential health benefits of a moderate coffee consumption. The trending opinion is that the health benefits of coffee tend to outweigh the risks for most people. The recent areas of interest include:
• Blood pressure
Coffee has the ability to raise blood pressure as part of a short term side effect. It has been thought to have negative effects on long-term blood pressure as well. Recent studies have been showing however that coffee does not cause hypertension (high blood pressure) in the long term and that regular coffee drinkers tend to build a tolerance to the hypertensive effects. Some studies have even shown a lowered risk of cardiovascular disease in those with a moderate coffee consumption – This could be due to the antioxidant properties discussed above.
There have been studies finding a lowered risk of some cancers in people who drink coffee. One such study found that the participants who were coffee drinkers had a 50% lower risk of liver cancer and liver disease than the participants who did not drink coffee. There are also potential benefits for lowering the risk of breast, colon, oesophageal, prostate and rectal cancer (2). The potential for this can again be attributed to the antioxidant (phenolics) and anti-inflammatory properties of coffee.
Research is also showing that moderate coffee drinkers are less likely to get type 2 diabetes than non – drinkers. The idea is that some components in coffee can increase your resting metabolic rate (helping with weight management), reduce glucose concentration, increase sensitivity to insulin and slow the rate at which glucose is absorbed by the intestine. Experiments on human fat cells showed that coffee doubled their uptake of glucose, thereby decreasing the amount entering the blood stream (2). There is still uncertainty over the exact compounds that increase the uptake of glucose (2). Additionally, a review of 18 studies consisting of over 450,000 people showed that the risk of type 2 diabetes could be decreased by 7% with each extra cup of coffee consumed each day (6).
For those who already have diabetes and struggle to maintain their blood glucose levels (BGLs), decaffeinated coffee could be trialled to see if the decrease in caffeine lowers BGLs.
• Brain health
Parkinson’s disease: Coffee appears to have a protective role against Parkinson’s disease (some studies have shown up to a 25% decrease in risk for coffee drinkers) (3). However, this has mostly been shown in men, not women (5). A reason for the difference between genders is possibly that caffeine and oestrogen require the same enzyme for metabolism and hence compete with each other (5).
Alzheimer’s disease: A study published in the ‘Journal of Alzheimer’s Disease’ suggested that coffee raises levels of ‘granulocyte colony stimulating factor (GCSF)’. In simpler terms, GCSF is a growth factor that has been linked with the prevention of Alzheimer’s disease. The scientific reasoning behind this theory is that GCSF causes a sequence of events that remove the plaques from the brain associated with Alzheimer’s disease (3,6). The study showed 4 to 5 cups of coffee per day was necessary for the preventative effects (6).
Stroke: The risk of stroke in the long term is also lower with moderate coffee consumption (3-4 cups/ day)(3). However, the chance of stoke occurring immediately after drinking coffee is increased, especially for infrequent drinkers (3).
Antioxidants in coffee (such as CGA) are the major contributors to coffees supposed neuroprotective effects. A possible reason for this being that the brain is a very lipid (fat) rich organ (2).
Although more research is required, evidence is repeatedly confirming the health benefits of coffee drinking (4). One study conducted by Harvard found no link between coffee intake (up to 6 cups per day, equal to 100mg of caffeine per cup) and an increased risk of death from any ailment including cancer or heart disease (4). This study followed 130,000 people over an 18-24 year period.
Though we are not at the point of recommending people drink coffee, research in this area is currently very active. It is therefore suggested that a focus be placed on improving other lifestyle factors opposed to decreasing coffee intake, for example; consuming a healthier diet, cessation of smoking and increasing physical activity (4).
You need to be wise about how you are having your coffee! Adding lashings of sugar, full fat milk, chocolate, cream and shots of syrup very quickly increases your sugar, fat and energy intake which is not good for your health. These practices negate any benefits that could be gained from coffee. An example is provided below to emphasise the difference adding “extras” to your coffee can make.
The image below shows the nutrition information of a coffee beverage, sold by a popular coffee brand. This is just an example though virtually all coffee outlets have similar versions of this drink.
This product illustrates that the way you choose to have your coffee can greatly determine the health implications it will have over time. This particular beverage has a massive 440 calories, high saturated fat content and high sugar content. It may be ok as a one off indulgence but by regularly choosing additions like full cream milk, syrups and whipped cream, weight gain and poor health outcomes are promoted.
Below is an example of another common coffee beverage with a lot of “extras”.
In addition to this, many people enjoy a couple of biscuits, cake, muffin or slice with their coffee. These foods are also generally energy dense and high in fat and sugar so should not be part of a regular coffee routine.
Compare the above coffee beverage to the cappuccino below and you have a far better option that will not significantly add to your daily intake of fat, sugar or energy.
The supposed negative health effects of coffee could partly be put down to study design (4). It has been found that many individuals who drink coffee, are also more commonly partaking in unhealthy lifestyle habits such as smoking, poorer diet and lower levels of physical activity (4). These aspects would have a large impact on the health status and outcomes of the participants.
By having an increased awareness of this, recent studies have been able to select their participants more carefully and to control lifestyle factors that may influence results or at least separate them from coffee consumption (4).
It is caffeine that produces the side effects experienced when you have more coffee than your body can comfortably tolerate or when you have coffee withdrawals. Common symptoms of excess coffee can include:
- A racing heart beat
- A greater level of fatigue after the initial energy burst
These symptoms don’t generally cause any harm but they can be uncomfortable. It is at the discretion of the drinker as to how much caffeine they can have before experiencing such symptoms.
There has not yet been any conclusive evidence on a safe level of coffee consumption for pregnant women (4). It is however advised that coffee intake be decreased for this population as it travels through the placenta to the foetus which is sensitive to coffee and which it metabolises at a slow rate (4).
It is therefore suggested that pregnant women reduce their coffee intake to a low level, no more than 1 small cup per day (4).
Contact us for results focused nutritional advice
This article about coffee was written by our nutritionist Belinda Elwin who is a Dietitians Association of Australia member and Accredited Practising Dietitian.
If you have questions about healthy eating choices or for a personalised meal plan, contact your local doctor who will arrange for you to see a dietitian in Sydney. For healthy eating advice, Contact us today!
1. Better Health Channel. Caffeine. State Government of Victoria. Updated: Jan 2013. Available here.
2. Davies E. Chemistry In Every Cup. Royal Society of Chemistry. Updated 2013. Available here.
3. Harvard Health Publications. What Is It About Coffee?. Harvard Medical School. Jan 2012. Available here.
4. Van Dam R. Ask the Expert: Coffee and health. Harvard School of Public health. Available here.
5. The Harvard Medical School Family Health Guide. Coffee’s Health Benefits. Harvard Medical School. Updated 2006. Available here.
6. HuffPost health Living. Coffee Grounds Are High In Antioxidants, Researchers Find. Huffington Post. Updated Feb 2013. Available here.