NUTRITION

Everything you need to know about coffee

Coffee continues to attract the interest of scientists and consumers alike. The energizing and thought-activating nature of coffee makes it one of the most popular beverages around the world. For many years it was suspected of having harmful effects, but the latest research is more optimistic. In fact, scientific reports point to the positive health aspects of consuming coffee brew!

Nutritional value and properties of coffee

There are around 1,000 other chemicals in coffee in addition to the well-known caffeine. Among others, it contains carbohydrates, fats, water, protein, plant acids, tannins, alkaloids, minerals (magnesium, potassium), B vitamins (mainly niacin) and aromatic substances. The substance content varies, depending on whether the beans are raw, roasted or a finished brew. It also depends on the type and origin of the coffee. Its energy value is low at only 2 kcal/100 ml of coffee brew without extra ingredients. However, it is often assumed that coffee does not contribute additional calories to the diet.

Caffeine not as black as it is painted

Caffeine is the most important active substance responsible for the stimulating effect of coffee. It is very rapidly and almost completely absorbed from the gastrointestinal tract into the circulatory system, where it reaches its maximum concentration after about one hour. The effects of caffeine on the human body manifest themselves most frequently with:

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

The caffeine content of coffee varies and depends, among others, on the type, the processes it has undergone (e.g. roasting), and the method of preparation.

Did you know that...

  • There is up to twice as much caffeine in the popular Robusta coffee as in the mild-tasting Arabica?
  •  In instant coffee (85 mg/125 ml) there is slightly less caffeine than in black coffee (65 mg/125 ml), but in the same amount of espresso the amount can be even more than four times higher (60 mg/30 ml)?
  • Caffeine is also present in products such as tea, chocolate, cocoa, energy drinks such as cola, as well as supplements and medicines?

How much caffeine can you consume?

A moderate intake of caffeine is considered to be around 200 mg per day, equivalent to 3-4 espressos or 3 cups of instant coffee. In other sources, the reported recommended value is up to 400 mg per day for healthy adults. This amount does not impair health, e.g. it does not increase the risk of cardiovascular diseases, and does not reduce the bone mineral density of those who consume adequate calcium.

What happens when you drink too much coffee?

Despite the experts’ definition of a recommended safe daily intake of caffeine, in many people a far smaller amount can have adverse effects.

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

  • excessive excitability,
  • anxiety,
  • arrhythmia,
  • insomnia,
  • headaches,
  • stomach issues.

It can also lead to addiction. The lethal dose of caffeine, on the other hand, is approximately 5-10 g or 150-200 mg/kg of body weight.

What does coffee contain?

  • Polyphenols

The group of ingredients that give flavour and aroma to coffee includes polyphenolic compounds (mainly chlorogenic acid, quinic acid and caffeic acid). These substances are characterised by complex biological effects. Among other things, they have anti-inflammatory, anti-bacterial and anti-cancer effects (due to their antioxidant activity and uptake of free oxygen radicals), they reduce oxidative modification of LDL (and are therefore responsible for inhibiting the formation of atherosclerotic plaque), and they also have the ability to bind heavy metals from the diet.

  • Oxalic acid

There are also significant amounts of oxalic acid in coffee. Its content reported in studies varies, depending on the method used and the sample (e.g. coffee powder, brew, ground coffee, instant coffee). Coffee can contain from 1 mg to even more than 600 mg of oxalic acid in 100 g. Its excess is detrimental, especially for people struggling with deficiencies in components (e.g. calcium, iron, manganese, magnesium) or patients with kidney problems. For healthy people, it will not pose a risk.

  • Acrylamide

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

How does coffee work?

The caffeine contained in coffee influences faster emptying of the stomach and accelerated intestinal transit – which is why most of us have to go to the toilet almost immediately after drinking it... Did you know that, according to research, drinking coffee as early as 6 hours before going to bed can shorten sleep by an hour? How to drink coffee wisely?

  • To maintain a healthy sleep, it is advisable to have this brew by 5 pm at the latest.
  • Don’t drink coffee on an empty stomach. It can contribute to hyperacidity and reflux.
  • It is a good idea to have coffee 1-2 hours after a meal.

Coffee with or without milk?

According to scientific studies, the addition of milk does not reduce the effect of caffeine and does not have a significant effect on the prolongation of gastric residence time, and therefore reduced absorption. However, the addition of milk to coffee may reduce the bioavailability of polyphenols, including chlorogenic acid, which has glycolytic (insulin-sensitising) and anti-inflammatory effects. It is worth bearing in mind that coffee can also impair the absorption of medicines (e.g. levothyroxine for hypothyroidism). In this case, there should be an interval of at least 30 minutes between taking the dose and drinking coffee.

Does coffee dehydrate?

A cup of coffee is primarily water. Research has shown for many years that it does not cause fluid loss, but caffeine alone can. However, this effect is only observed with large doses of the compound drunk at once and over a short period of time. In addition, regular drinking of the brew eliminates this effect and even helps to regulate the water balance.

Coffee and slimming

Moderate consumption of coffee can be a beneficial factor in a slimming treatment. This is because coffee has the effect of inhibiting the absorption of carbohydrates and fats. In addition, the chlorogenic acid it contains reduces body fat. To achieve the desired effect, coffee should be consumed without sugar and milk or cream, as these additives also increase the calorie content of the brew. Coffee, or rather the caffeine in it, has a proven thermogenic effect (increasing body heat).

Coffee can also inhibit the feeling of hunger, which affects slimming. This is due to the fact that substances in coffee (not just caffeine alone) increase the secretion of hormones responsible for feeling satiety. Additionally, according to a study by Smith et al. published in “The Journal of Nutrition” in 2020, young women who drink 2-3 cups of coffee a day (including decaffeinated coffee) have lower total body fat, as well as visceral fat, than those who drink less coffee. For men, the correlation was not as apparent.

Health effects of coffee

The beneficial effects of coffee consumption include:

  • Reduced risk of type 2 diabetes. The substances in coffee (caffeine, chlorogenic acid and magnesium) have a beneficial effect on glucose and insulin metabolism. They reduce fasting glucose concentrations, improve glucose utilisation and increase cellular sensitivity to insulin. Drinking three cups of coffee a day reduces the risk of diabetes by 21 percent and five cups by 29 percent.

Drinking coffee may help prevent certain types of cancer. A recent report by British researchers on the effects of coffee on the liver shows that it may have a beneficial effect on this organ. Heavy coffee drinkers have a 40-50 percent lower risk of liver cancer compared to non-coffee drinkers.

  • Many scientific studies report that drinking at least four cups of coffee a day can reduce their risk by 15-20 percent. For lung or bladder cancer, the data is inconclusive. In their development, adverse effects of coffee are not excluded.
  • A coffee habit reduces the risk of developing Alzheimer’s disease by around 30 percent, while others say the effect is much greater, up to 65 percent.
  • Moderate coffee drinking (3-4 cups a day) can reduce the risk of heart disease by 11-15 percent, but this effect does not occur with high coffee consumption.
  • Moderate coffee consumption does not result in a deterioration of bone mineral density and therefore an accelerated development of osteoporosis in people who consume the recommended amount of calcium daily.
  • There is a consensus of opinion in the literature on the effect of coffee on osteoporosis risk. This issue needs to be considered in the context of calcium content in a diet.

Administered 30 minutes before training at a dose of 3-5 mg/kg of body weight, it can improve high-intensity sprint performance. Consumption of caffeine 30-60 minutes before training increases the ability to exert effort and reduces the feeling of fatigue during endurance exercise.

Summary

As research shows, coffee has a multidirectional effect, both in terms of health and performance. Due to the ubiquity of the beverage, scientists continue to take a closer look at its effects and its impact on the human body. Although it is worth remembering that all nutritional studies are subject to error, due to the impossibility of limiting other factors that may also have an impact on a particular aspect, it seems that coffee, thanks to its content of multiple compounds, can have a positive effect on health. This is why it is worth including it in your menu, with a safe dose in mind. Often, the ideal dose should be chosen individually, due to possible interaction with medicines or the polymorphism of the gene responsible for its metabolism.

 

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