What happens to our body when we drink coffee?

By Thomas Merritt, Laurentian University

Surely while reading this you have a cup of coffee in your hands. Coffee is the most popular drink in much of the world. So much so that Americans drink more coffee than soda, juice and tea together.

How popular is coffee? To give us an idea, when Prince Harry and Meghan Markle announced that they planned to move their residence to Canada, the international coffee chain Tim Hortons offered them free coffee for life as an extra incentive to move to the North American country.

Given the reputation of coffee, the confusion surrounding how this warm and dark nectar of the gods affects our biology greatly surprises.

The coffee ingredients

The main active ingredients of coffee are caffeine (a stimulant) and a whole series of antioxidants. What do we know about how both influence our body? Broadly speaking, the information we have is fairly simple, but the devil is in the details, and speculation about whether coffee could help or harm is triggered without anyone stopping them.

The stimulating properties of caffeine are what make a cup of coffee the perfect option to wake up. In fact, coffee, or the caffeine it contains, is the most consumed psychoactive substance in the world. It seems to work, at least in part, as a stimulant by blocking the adenosine receptor, a nucleoside that stimulates sleep.

Caffeine and adenosine have similar heterocyclic compounds. The first performs a molecular mimicry by blocking the adenosine receptor, which prevents the body from developing its natural ability to rest when needed.

In addition, this blockage is the reason why excessive coffee consumption can cause agitation and lack of sleep. Fatigue can be postponed until the regulating organisms of the human body begin to fail, at which point nerves occur and even more serious consequences, such as anxiety and insomnia. Adverse effects are usually common and have long been known: the possible relationship between coffee consumption and insomnia was discovered more than 100 years ago.

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The National Film Board of Canada produced a documentary about the historical impact of coffee on culture, called Black Coffee: Part One, The Irresistible Bean.

Unique answers

Each person responds differently to caffeine. At least part of this alteration comes from the different types of adenosine receptors, the molecules to which caffeine adheres and blocks, although there may be other forms of genetic variation.

Some individuals do not process caffeine, so drinking coffee could pose a risk to their health. Moving away from those extremes, however, there are differences in the way we respond to a cup of coffee. Like much of biology, this difference is a product of the environment, of coffee consumption in the past, of genetics and, as implausible as it may seem, of chance.

Perhaps the most attractive thing about coffee is the exciting caffeine shot it provides. But that does not mean that it is the most interesting aspect from the biological point of view.

In a study with rats, it was observed that caffeine caused muscle contractions in animals, so it is possible that it works as a digestive activity stimulant. However, other research has shown that decaffeinated coffee can produce the same effect, so everything points to the existence of a complex mechanism that encompasses other molecules present in coffee.

The benefits of antioxidants

What do we know about coffee antioxidants and the surrounding aura? The truth is that they do not constitute any mystery. Metabolic processes generate the energy necessary for life while producing waste, often in the form of oxidized molecules that can be harmful to themselves or other molecules.

Antioxidants are a broad group of molecules that can eliminate hazardous waste. All organisms produce antioxidants as part of their metabolic balance. Even so, it is not clear if additional antioxidant supplements have the ability to increase these natural defenses, doubt that you have not avoided speculation.

Antioxidants have been linked to almost everything that has to do with health, including premature ejaculation. However, do the highly valued positive effects have any basis? Surprisingly, the answer is, again, a resounding "maybe."

Coffee and cancer

Coffee is not going to cure cancer, but it may prevent it, as well as other diseases. Part of the relationship between coffee and cancer lies in the question of what cancer is: simply explained, it is an uncontrolled cell growth, which indicates when genes are actively expressed and when they are not.

The research group of which I am part studies the regulation of gene expression. Therefore, I am in a position to ensure that neither a good cup of coffee nor an injection of caffeine will cause active or inactive genes at the wrong time to start following the rules.

The antioxidants that coffee contains could have an anticancer effect, since they fight cell deterioration. One type of damage that could help mitigate is that caused by genetic mutations; In fact, cancer is caused by mutations that lead to deregulation of genes.

Elaborate studies have shown that coffee consumption fights cancer in rats. For their part, research carried out with humans indicates that coffee consumption is associated with the reduction of cases of some cancers.

It is interesting to note that coffee has also been related to the decrease in other diseases. High coffee consumption has been linked to the reduction of Parkinson's cases and other forms of dementia. At least one experimental study with mice and cell cultures shows that the protection generated finds its origin in the combination of caffeine and coffee antioxidants.

Similarly, notable consumption has been related to the decrease in type 2 diabetes patients. If there is something that seems common to all diseases, it is their complexity, the combination of effects and the differences between individuals.

After knowing all this information, what can we intuit about the biology of coffee? Well, as I explain to my students, it's complicated. However, as most of the readers of this article know, what is certain is that coffee helps us to open our eyes in the morning.

This is an updated version of an article published in English on January 19, 2020. The original piece claimed that coffee was the most popular drink in the world. The expression "most popular" can accommodate different meanings. Retail coffee sales exceed those of tea, but the truth is that tea is the most consumed beverage worldwide after water.

Thomas Merritt, Professor and Canada Research Chair, Chemistry and Biochemistry, Laurentian University

This article was originally published in The Conversation. Read the original.