Coffee and caffeine: only good news?

several objects in pictures to those participating in the study. The objects were classified as "outside" and "inside". Afterwards, one half of participants received 200 milligrams of caffeine in tablet form, while the other half received placebos. The memory test took place 24 hours later. The test participants were again shown pictures (the same, completely new, and very similar), which were clearly better recognised by the caffeine group.

A cup of coffee contains 80 to 120 milligrams of caffeine. Does a constant coffee-to-go spur the brain? According to other studies, the caffeine effect cannot be increased at will² - and the studies usually say nothing about practical benefits. Perhaps a habituation effect with regular consumption puts the memory into perspective again.

Coffee against excess kilos?

More relevant than ever is the research into the effects of consuming caffeinated beverages, which are among the most common drinks next to water, especially in the western world. A study published in 2016 shows that regular coffee consumption can help you lose weight and even keep it off. In a study³ led by Dr de Zwaan from the University of Hanover (Germany), data from 500 men and women from the German Weight Control Register (in German: Deutschen Gewichtskontroll-Register) were analysed. They consumed more caffeine than the more than 2,000 control subjects of a population sample. In the evaluation, the positive contribution of caffeine to weight stabilisation could be established.

The aim of the German Weight Control Registry, which was designed for a period of 2 years, was to find out which factors are important for long-term weight stabilisation. Among other things, the different dietary habits were also examined and the results compared with a general population sample.

"Significant differences related to the consumption of caffeinated beverages were found between the 500 people from the German Weight Control Register and the general population."

Martina de Zwaan, Head of the Psychosomatics and Psychotherapy Clinic, Hannover Medical School

Lower BMI through coffee consumption?

Participants in the weight control registry who successfully lost weight by at least 10% over 1 year and sustained the reduced weight for at least 1 year consumed significantly higher amounts of coffee and caffeinated beverages compared to the general population sample.

"Caffeine consumption thus appears to be negatively associated with long-term weight gain, meaning you are less likely to gain weight back after losing it if you consume caffeine in larger amounts."

There is also evidence that coffee drinkers have a lower BMI. Caffeine, as a central nervous system stimulant, is thus still considered the most active metabolic component of coffee and is associated with various effects on metabolism: increased energy expenditure, increased heat production and improved fat burning in muscle under physical activity.

How does caffeine work biochemically?

The more active the nerve cells are, the more adenosine is produced, and the more the adenosine receptors are occupied. The nerve cells then work more slowly. This has a chain reaction effect on other areas of the brain and makes people tired. The adenosine control circuit thus protects the brain from energy deficiency, which otherwise occurs in particularly active brain areas during long periods of wakefulness.

Caffeine is similar to adenosine in its chemical structure and occupies the same receptors, but does not activate them. The adenosine can therefore no longer dock after caffeine binding. The nerve pathways do not receive a signal - which is why they continue to work even when the adenosine concentration increases. The adenosine receptors are therefore competitively inhibited by caffeine.

In higher doses, caffeine also prevents the enzymatic degradation of cyclic adenosine-3',5'-monophosphate (cAMP). This cAMP plays an important role in regulation in the cell as a so-called second messenger. Caffeine also inhibits phosphodiesterases, enzymes that are responsible for the breakdown of cAMP.

Thus, the degradation inhibited by caffeine leads to an increase in the cAMP concentration in the cells. Among other things, cAMP leads to the activation of protein kinase A, which in turn mediates a variety of functions, including the release of glucose in the liver and ATP production for muscle contraction in skeletal muscle.

Coffee can be beneficial to health

The moderate consumption of coffee is therefore not associated with a health risk, but in many cases even shows a health-promoting effect. Caffeine itself is not the only decisive factor here. Other ingredients of coffee and tea probably play an important role. An intake of about 300 mg of caffeine per day is considered moderate, with a cup of coffee containing between 80 and 120 mg of caffeine, depending on the type of preparation and variety. Some studies show preventive effects, even at higher intakes. However, excessive consumption can lead to undesirable effects.

There are large individual differences in the tolerance of caffeine. In any case, the consumption of caffeinated coffees and teas can positively support a weight reduction measure. Of course, successful and long-lasting weight loss and maintenance can only be achieved through long-term changes in eating, drinking, exercise and behavioural habits. Coffee is no substitute for diet or exercise - but coffee drinkers seem to have an easier time losing weight.

Does coffee reduce the risk of skin cancer?

Some coffee ingredients can protect against cell damage caused by UVB radiation. Reactions in the test tube don't say much for the real world, so a team of researchers led by Erikka Loftfield from the Yale School of Public Health evaluated data from an already completed American nutrition and health study.

In the study, almost half a million people recorded their eating habits and UV exposure over ten years. In the follow-up study, 2,900 participants were diagnosed with melanoma. Calculations showed that 4 or more cups of coffee a day reduced the risk of skin cancer by 20 percent. The caffeine in coffee seems to be responsible for this effect.

...and do coffee drinkers live longer?

Coffee can apparently not only actively extend working hours, but also life, according to an American study. A team from the Harvard School of Public Health analysed data from more than 200,000 people that had already been collected as part of the Nurses' Health Studies and the Health Professionals Follow-up Study. These are long-term American studies that have been running for over 30 years.

The result: coffee drinkers live longer than people who completely abstain from this hot beverage. Up to 5 cups a day reduce the risk of premature death from cardiovascular diseases. However, it is not entirely clear which ingredients are responsible for this.

Coffee also counts for fluid balance

There is a persistent rumour that coffee dehydrates the body. Studies have shown, however, that coffee has almost the same effect as any other liquid. But caffeine is diuretic. You have to urinate more often, but you do not excrete more water throughout the day. Regular coffee drinkers do not notice the diuretic effect, they get used to it.

The British researcher Sophie Killer already found this out in 2014 in a study with 50 test subjects. They were each given 4 cups of coffee a day for 3 days, then after a ten-day break they were given the same amount of water instead of coffee. The liquids were labelled with a hydrogen isotope. In this way, the researchers knew whether they were incorporated into the body or quickly excreted again. The result is that coffee contributes to the body's water balance in the same way as water ingestion. The glass of water often served with coffee is a nice gesture, but not really necessary.

1. https://www.hopkinsmedicine.org/news/stories/caffeine_memory.html
2. Paiva, I. et al. Caffeine intake exerts dual genome-wide effects on hippocampal metabolism and learning-dependent transcription. J Clin Invest (2022).
3. de Zwaan et al. Caffeine intake is related to successful weight loss maintenance Eur J Clin Nutr. 2016 Apr;70(4):532-4. doi: 10.1038/ejcn.2015.183. Epub 2015 Nov 11.
4. M Yassa: https://www.hopkinsmedicine.org/news/stories/caffeine_memory.html
5. Isabel Paiva, (33 Mitautoren!)… Anne-Laurence Boutillier, and David Blum: Caffeine intake exerts dual genome-wide effects on hippocampal metabolism and learning-dependent transcription. J Clin Invest. 2022; 132(12): e149371. https://doi.org/10.1172/JCI149371.
6. D Icken, S Feller, S Engeli, A Mayr, A Müller, A Hilbert , M de Zwaan: Caffeine intake is related to successful weight loss maintenance. Eur J Clin Nutr. 2016 Apr;70(4):532-4. doi: 10.1038/ejcn.2015.183. Epub 2015 Nov 11.
7. S. C. Killer, A.K. Blannin, A.E. Jeukendrup: No Evidence of Dehydration with Moderate Daily Coffee Intake: A Counterbalanced Cross-Over Study in a Free-Living Population. PLoS ONE, 9(1): e84154, January 10, 2014, doi: https://doi.org/10.1371/journal.pone.0084154.
8. E. Loftfield: https://ysph.yale.edu/news-article/coffee-and-cancer/