Everything you need to know about coffee

Nutritional value and properties of coffee

In addition to the widely known caffeine, coffee contains about 1,000 other chemical substances. It includes carbohydrates, fats, water, protein, plant acids, tannins, alkaloids, minerals (magnesium, potassium), B vitamins (mainly niacin), and aromatic compounds. The content of these substances varies depending on whether the beans are raw, roasted, or brewed. It also depends on the coffee variety and its origin. Its energy value is low, at only 2 kcal per 100 ml of brewed coffee without additives. However, it is often assumed that coffee adds no extra calories to the diet.

Caffeine is not as bad as it is painted

Caffeine is the most important active substance responsible for the stimulating effect of coffee. It is absorbed very quickly and almost completely from the digestive tract into the bloodstream, where it reaches its maximum concentration after about an hour. The effects of caffeine on the human body most often manifest as:

• increased concentration,
• improved alertness and mood,
• reduced fatigue and drowsiness,
• better exercise performance, or faster reaction times.

Elevated caffeine levels persist for about 4 hours in healthy adults, while in pregnant women, this period is 9–11 hours. Additionally, women's bodies eliminate this substance faster than men's.

The caffeine content in coffee varies and depends on factors such as the variety, the processes it has undergone (e.g., roasting), and the preparation method.

Did you know that…

• The popular Robusta coffee variety contains up to twice as much caffeine as the milder-tasting Arabica?
• Did you know that instant coffee (85 mg/125 ml) contains slightly more caffeine than black coffee (65 mg/125 ml), while the same amount of espresso can contain more than four times as much (60 mg/30 ml)?
• Caffeine is also found in products such as tea, chocolate, cocoa, cola-type energy drinks, as well as supplements and medications.

How much caffeine can you consume?

Moderate caffeine consumption is considered to be about 200 mg per day, which corresponds to 3–4 espressos or 3 cups of instant coffee. Other sources recommend up to 400 mg per day for healthy adults. This amount does not negatively affect health, including increasing the risk of cardiovascular disease, nor does it decrease bone mineral density in people who consume adequate amounts of calcium.  

What happens when you drink too much coffee?

Although experts have established a recommended, safe daily dose of caffeine, much smaller amounts can cause adverse effects in many people.  

Excessive, long-term caffeine consumption (above 500–600 mg per day) can cause a number of adverse symptoms, such as:

• hyperexcitability,
• feelings of anxiety,
• arrhythmia,
• insomnia,
• headaches,
• stomach problems.

It can also lead to addiction. The lethal dose of caffeine is approximately 5–10 g or 150–200 mg/kg of body weight.

What does coffee contain?

Polyphenols

Polyphenolic compounds (mainly chlorogenic, quinic, and caffeic acids) are among the ingredients that give coffee its flavor and aroma. These substances are characterized by a complex biological effect. They possess, among other things: anti-inflammatory, antibacterial, and anti-cancer properties (linked to antioxidant activity and the scavenging of oxygen free radicals), reduce oxidative modification of LDL (thereby inhibiting the formation of atherosclerotic plaque), and also have the ability to bind heavy metals from the diet.

Oxalic acid

Coffee also contains significant amounts of oxalic acid. The content reported in studies varies, depending on the method used and the sample (e.g., coffee powder, brew, ground coffee, instant). Coffee can contain anywhere from 1 mg to over 600 mg of oxalic acid per 100 g. An excess is unfavorable, especially for people struggling with nutrient deficiencies (e.g., calcium, iron, manganese, magnesium) or those suffering from kidney problems. For healthy individuals, it poses no threat.

Acrylamide

Coffee is a source of acrylamide, which has been classified by the IARC (International Agency for Research on Cancer) as a compound potentially carcinogenic to humans. Acrylamide can also be found in roasted and instant coffee.

How does coffee work?

The caffeine in coffee promotes faster gastric emptying and accelerated intestinal transit—which is why most of us need to head to the bathroom almost immediately after drinking it... Did you know that, according to research, drinking coffee even 6 hours before bedtime can shorten sleep by an hour? How to drink coffee wisely?

• To maintain healthy sleep, it is worth having your last cup no later than 5:00 PM.
• Do not drink coffee on an empty stomach. It can contribute to hyperacidity and reflux.
• It is best to have coffee 1-2 hours after a meal.

Coffee with or without milk?

According to scientific research, adding milk does not reduce the effect of caffeine and does not significantly affect the time food stays in the stomach, and consequently, does not reduce absorption. However, adding milk to coffee can lower the bioavailability of polyphenols, including chlorogenic acid, which exhibits glycolytic (insulin-sensitizing) and anti-inflammatory effects. It is worth keeping in mind that coffee can also impair the absorption of medications (e.g., levothyroxine used for hypothyroidism). In such cases, you should wait at least 30 minutes between taking your dose and drinking coffee.

Does coffee dehydrate you?

A cup of coffee is primarily water. Research has shown for many years that it does not cause fluid loss, although caffeine itself can – however, this effect is only observed with large doses consumed at once over a short period. Furthermore, regular consumption of this beverage negates this effect and even helps regulate water balance.

Coffee and weight loss

Moderate coffee consumption can be a beneficial component of a weight loss regimen. Coffee helps inhibit the absorption of carbohydrates and fats. The chlorogenic acid it contains also reduces body fat. To achieve the desired effect, coffee should be consumed without sugar, milk, or cream, as these additives increase the calorie content of the drink. Coffee, or more specifically the caffeine it contains, has a proven thermogenic effect (increasing body temperature).

Coffee can also suppress feelings of hunger, which aids the weight loss process. This happens because the substances in coffee (not just caffeine alone) increase the secretion of hormones responsible for satiety. Additionally, according to a 2020 study by Smith et al. published in "The Journal of Nutrition," young women who drink 2-3 cups of coffee per day (including decaffeinated) have lower total and visceral body fat than those who drink less coffee. This correlation was not as significant in men.  

The impact of coffee on health

Moderate consumption of coffee is completely safe and poses no health risks; in fact, it can offer many benefits.

The beneficial effects of coffee consumption include:

• a reduced risk of type 2 diabetes. The substances in coffee (caffeine, chlorogenic acid, and magnesium) have a positive effect on glucose and insulin metabolism. They lower fasting glucose levels, improve its utilization, and increase cell sensitivity to insulin. Drinking three cups of coffee a day reduces the risk of diabetes by 21%, and five cups by 29%.  

Drinking coffee may help prevent certain types of cancer. A recent report by British scientists on the impact of coffee on the liver suggests that it may have a beneficial effect on this organ. For heavy coffee drinkers, the risk of liver cancer is 40-50% lower compared to those who do not drink coffee.

• Many scientific studies report that drinking at least four cups of coffee a day can reduce this risk by 15-20%. Data regarding lung or bladder cancer are inconclusive, and a potential adverse effect of coffee on their development cannot be ruled out.
• The habit of drinking coffee reduces the risk of developing Alzheimer's disease by about 30%, while others suggest the effect is much greater, reaching up to 65%.
• Moderate coffee consumption (3-4 cups per day) may reduce the risk of heart disease by 11-15%, but this effect is not observed with high coffee intake.
• Moderate coffee consumption does not lead to a deterioration in bone mineral density and, consequently, does not accelerate the development of osteoporosis in individuals who consume the recommended daily amount of calcium.

Taken 30 minutes before a workout at a dose of 3-5 mg/kg of body weight, it can improve high-intensity sprint performance. Consuming caffeine 30-60 minutes before training increases exercise capacity and reduces the perception of fatigue during endurance exercise.

Summary

As research shows, coffee has a multifaceted effect, both in terms of health and performance. Due to the popularity of the beverage, scientists continue to scrutinize its effects and impact on the human body. Although it is worth remembering that all nutritional studies are subject to error due to the inability to control for other factors that may also influence a given aspect, it appears that coffee, thanks to its array of compounds, can have a positive impact on health.

That is why it is worth including it in your diet, while keeping a safe dosage in mind. Often, the ideal dose should be determined individually, due to potential interactions with medications or polymorphisms of the gene responsible for its metabolism.

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