Drinking coffee at night can help you sleep better? Here's the explanation

Coffee lovers often say that they must have a cup of coffee in the morning to be energetic and ready for work; others say that a cup of coffee at night helps them sleep better. So what does coffee do to us? The answer to this question starts with caffeine.

The discovery of caffeine and its pharmacological effects

In the mid-19th century, German chemist FF Lunger coined the word "caffeine". The first half of the word is the German word for "caffeine".

The word for coffee is kaffee, with the chemical suffix -ine at the end. The French translation is cafeine, while the English form is caffeine. Caffeine is an alkaloid (a naturally occurring compound that is mostly a stimulant) that can be used as a natural pesticide; I think that’s a bonus, as large animals love it (they digest coffee beans effortlessly, which is the basis for its effectiveness). In the tropics, where competition for survival is fierce, plants have evolved increasingly complex means of protecting themselves—most of the plants that grow there contain alkaloids that can alter one’s mind. In addition to coffee, more than 60 plants contain caffeine, including tea plants, kola nuts, yerba mate (popular in South America, with leaves similar to tea leaves), and guarana berries . If we refer to the etymological origins of the word caffeine, we have to say that its true definition should be “coffee chemical.”

The "coffee chemical" is the most widely used drug in the world today, surpassing nicotine and even alcohol. According to New Scientist magazine, about 90% of North Americans consume caffeine every day (coffee accounts for about 75%). Humans are so addicted to its energizing effects that more and more consumer products are incorporating synthetic forms of caffeine. The most obvious examples are carbonated beverages, soft drinks, and the now popular energy drinks, but also ice cream, chewing gum, and even shaving gel.

How much caffeine is in coffee?

A 200ml cup of filtered coffee (such as hand-poured coffee) usually has about 120mg (0.12g) of caffeine - and this figure can vary greatly - or 600mg/L . It is estimated that about 12 tons of caffeine are consumed worldwide each year, equivalent to 800 billion cups of coffee. Caffeine usually accounts for 1.2% to 2.5% of green coffee solids and about 0.7% of dry coffee cherries. Robusta varieties were once famous for their extremely high caffeine content, but there is evidence that variety, planting factors and processing methods are also factors that affect caffeine content. Most studies in recent years have concluded that the melting point of caffeine is 178℃, and that deeper roasting can sublimate caffeine molecules, but the weight and density of coffee beans are also decreasing overall, so the decaffeination effect is offset and the actual proportion of caffeine remains basically unchanged . So if someone chooses coffee based on the relationship between caffeine content and roasting curve, he may not be good enough.

Caffeine is very soluble, so in theory, the amount of caffeine lost in the finished product should be almost or completely independent of brewing technique . Of course, the brewing ratio (the ratio of coffee to water) can affect the relative amount of caffeine in the finished product, so it is best to measure the caffeine content based on the grams of coffee beans you use rather than the amount of coffee itself.

People generally believe that caffeine has no taste, but this is actually incorrect. Pure caffeine is extremely bitter , and even if the content in coffee is not high, 10% of the overall bitterness comes from it - enough for us to distinguish the subtle difference between normal coffee and decaffeinated coffee.

How does caffeine affect the human body and when does it take effect?

The body metabolizes caffeine so quickly that its effects are felt almost immediately. Caffeine reaches its peak effect after about 30 minutes, and after three hours, the effect is reduced to half of its peak. It takes about 12 hours for caffeine to be completely excreted from the body, but this time varies from person to person , depending on factors such as hydration, food, exercise, smoking and drinking, race, age, and even gender. In their book Caffeine World: The Science and Culture of the World's Most Popular Drug, Bennett Allen Weinberg and Bonnie K. Biller note that a non-smoking Japanese man who drinks coffee with alcohol feels the effects of caffeine "five times longer than a British woman who smokes, abstains from alcohol, or uses oral contraceptives."

The physiological and psychological effects of caffeine on the brain and sympathetic nervous system are rapid and specific , and shamefully, are rarely what the human body does on its own. Caffeine first unleashes the physiological mechanisms that make us sleepy, then takes over, activating neurons that in turn stimulate the pituitary gland, which raises the body’s heart rate and causes a dramatic release of blood sugar and adrenaline.

Caffeine can achieve this effect because it is similar to adenosine molecules at the chemical level and can deceive neurons (nerve cells) in the brain. When the human body consumes a lot of energy, the concentration of adenosine increases and attaches to neurons like expanding bubbles, causing brain function to slow down and fatigue to set in. Caffeine is like the evil doppelganger of adenosine. It deceives neurons and replaces the position of adenosine. This unconventional phenomenon is called "competitive inhibition", that is, caffeine competes with and replaces the adenosine receptors on neurons, thereby inhibiting the effect of adenosine.

Since caffeine replaces adenosine, can neurons return to normal? The magic of caffeine is that it has the exact opposite effect of adenosine, and can actually stimulate neurons faster than usual. The pituitary gland is a pea-sized gland located at the base of the brain. It receives signals from neurons and stimulates the sympathetic nervous system to enter "fight or flight" mode - the human body's emergency plan. At this time, the pupils dilate, the heart rate increases, and the blood sugar stored in the kidneys is released. It is this two-pronged physiological attack mechanism that makes caffeine so effective in refreshing.

As early as the 19th century, the negative effects of caffeine in coffee were pointed out by coffee opponents, including Charlie Post, who invented the decaffeinated "healthy" coffee substitute "Boston", which was called "America's favorite coffee substitute". Like most drugs, it is difficult to avoid the potential side effects of consuming (or even abusing) caffeine, and you may face the risk of withdrawal symptoms if you quit completely. As we gradually develop a tolerance to caffeine, we actually create additional adenosine receptors - when we really need a break, the body sends sleepy molecules through adenosine to help us relax. Of course, you can drink coffee anytime to relieve fatigue, but the bad news for caffeine addicts is that they don't use coffee at all. Because adenosine creates more receptors to attach to, fatigue is amplified - in other words, you are dragging yourself down. Heavy caffeine users may even experience mood swings if they can't replenish their caffeine. This is because caffeine is related to the production of serotonin, which regulates human mood, appetite and sleep.

Clinical trials have not yet proven that excessive caffeine intake has permanent negative effects, but a large number of recent studies show that caffeine may be a powerful positive force in the fight against various mental illnesses . For many years, people have believed (and now have confirmed) that caffeine can slow down memory loss in old age , and many recent studies have also found that moderate caffeine intake in mice can prevent protein deposits in brain cells - which happens to be a typical feature of Alzheimer's disease. Experiments also indicate that caffeine may be a powerful drug for preventing and treating Parkinson's disease.

If the above scientific explanation makes you drowsy, just remember: drink good coffee in moderation (such as 1-3 cups of hand-brewed specialty coffee a day, or order a latte/cappuccino at a cafe). It makes us happy and healthy . Just remember these three points.