Commentary: Coffee, a health drink or an unhealthy addiction?

Recent news reports suggest three cups of coffee a day keeps the doctor away. Public health expert Rob M van Dam evaluates this theory, and examines the benefits and concerns surrounding this much loved beverage.

An empty coffee cup. (Photo: REUTERS)

By Rob M van Dam

SINGAPORE: Regular coffee consumers may live slightly longer than coffee abstainers. That is the conclusion based on results from two studies from the US and Europe recently published in the renowned medical journal Annals of Internal Medicine.

The studies involved hundreds of thousands of participants, whose coffee drinking and other lifestyle habits were assessed through questionnaires, and participant mortality monitored over an average of 16 years.

The US study found that those who consumed two to three cups of coffee a day were 12 per cent less likely to die during the study period compared to non-coffee drinkers. Results from the European study were similar.

Interestingly, these findings did not only apply to caffeinated coffee, but also to decaffeinated coffee, suggesting that components other than caffeine may be responsible.

There are several possible candidates: Coffee is a complex beverage with hundreds of components including vitamins, minerals and antioxidant compounds including polyphenols and lignans.

Also interestingly, the results on coffee and mortality were not only consistent for different ethnic groups in the US and different countries across Europe, but also agree with the results from several previous studies.

Is coffee then a health drink and not an unhealthy addiction?

A cup of coffee is served. (File photo: REUTERS/Jorge Silva)

DETRIMENTAL TO HEALTH?

For decades, researchers suspected that coffee may be detrimental to health. This prompted numerous studies on the link between coffee and a wide variety of disease outcomes.

Coffee has become one of the most thoroughly researched beverages in our diet. From all these studies, a few health concerns related to coffee have emerged.

First, coffee consumption during pregnancy exposes the fetus to caffeine. The fetus has very limited ability to metabolise caffeine, and high caffeine intake by pregnant women has been linked to reduced fetal growth and even miscarriage in some studies.

Although the evidence of this effect is not conclusive, it seems prudent to limit caffeine intake during pregnancy to no more than one cup of coffee per day.  

Second, unfiltered coffee, which includes French pressed coffee or boiled ground coffee contains a compound named cafestol that raises serum cholesterol levels, which can in turn increase the risk of heart disease.

Filtering coffee through a paper filter or a sock, or putting coffee beans through the process of producing instant coffee, removes this compound and produces coffee that does not raise cholesterol levels.

Third, coffee by itself is a very low-calorie drink. Together with tea and water, coffee can be a good alternative to high-calorie beverages such as soft drinks, energy or sports drinks and juices.

However, too often, coffee is a vehicle for sugar and cream, and drinking it with these additions several times a day can lead to excess energy consumption and weight gain.

Finally, if you experience adverse effects of having too much caffeine, such as feeling jittery or having difficulty sleeping, it is of course time to cut down on your consumption.

For the consumption of filtered coffee without too many caloric additions in non-pregnant adults, there are few if any health concerns. Drinking up to six standard cups of coffee per day has not been associated with a higher risk of heart disease, stroke or cancer.

In contrast, coffee consumption has been linked to lowered risks in several chronic diseases such as liver cancer, other liver conditions, and Type 2 diabetes when compared with non-drinkers.

Such links have been confirmed in multiple studies across the world and may be the reason for the lower risk of premature mortality in the recent studies.

A cup of coffee being made at a coffee shop. (File photo: REUTERS/Jorge Silva)

LITTLE REASON TO QUIT

It should be noted, however, that these results are from well-conducted cohort studies, and not from randomised controlled trials, which are the gold standard of medical studies.

In cohort studies, researchers carefully document existing exposure to a food or drink (in this case coffee) and statistically adjust for other risk factors, but do not manipulate the exposure.

As a result, the possibility cannot be completely excluded that there could be other factors about individual coffee consumers that could be responsible for their lower disease risk.

Taken together, however, the overall evidence from research rather convincingly suggests that for most adults, regular coffee consumption can be part of a healthy diet.

Generally, people can reduce their coffee consumption or quit drinking altogether after a few unpleasant days with headaches, thus arguing against coffee drinking being a true addiction.

For now, the current scientific evidence suggests, however, that if you are enjoying your coffee habit, there is little reason to quit. 

Rob M van Dam is associate professor at the Saw Swee Hock School of Public Health at the National University of Singapore, and a member of the National University Health System.

Source: CNA/sl