Wine and coffee, I just want one glass ~ Scientists: You are right, you should quit drinking!

Produced by: Science Popularization China

Author: Denovo

Producer: China Science Expo

Coffee has now become an indispensable part of many people's lives. Whether it is for refreshing the mind or as a leisure ritual, it is deeply loved.

Every once in a while, the topic of coffee always becomes a hot search topic, from discussing which beans have a more unique flavor, to sharing the skills of hand brewing coffee, to the research on the health effects of coffee, almost every time it can arouse enthusiastic attention. The popularity of coffee is not only a taste enjoyment, but also a reflection of a life attitude. No wonder it has become a hot topic for the public to discuss after dinner.

Drink coffee

(Image source: generated by the author’s AI)

Why does coffee have so many benefits?

The main ingredients of coffee include caffeine, polyphenols and dietary fiber, which give coffee a variety of unique effects. Caffeine is a natural central nervous system stimulant that can specifically bind to adenosine receptors and inhibit the action of adenosine in the brain. Adenosine is a neurotransmitter that can make us feel tired. The accumulation of adenosine in the brain increases a person's sleepiness, and the binding of caffeine blocks this process, thereby increasing the excitability of neurons, making people feel energetic and more focused.

In addition, caffeine can inhibit the activity of phosphodiesterase (PDE). Phosphodiesterase (PDE) is an enzyme that degrades cyclic adenosine monophosphate (cAMP). By inhibiting phosphodiesterase, caffeine prevents the decomposition of cAMP, causing cAMP to accumulate in cells, which in turn stimulates the release of a variety of hormones and neurotransmitters including adrenaline, norepinephrine, dopamine, etc. The release of these substances can enhance the body's stress response, such as increasing heart rate, blood pressure, and metabolic rate. In addition, adrenaline also promotes fat decomposition, releasing fatty acids into the blood, and providing the body with additional energy, so coffee can often be used to reduce fat and improve athletic performance.

Effects of caffeine intake on the health of various organs in the human body

(Image source: Reference [6])

The caffeine in coffee has anti-inflammatory effects, while polyphenols are powerful antioxidants. Moderate coffee consumption not only reduces the risk of cardiovascular disease, but is also closely associated with a decrease in the incidence and mortality of a variety of cancers, including breast cancer, endometrial cancer, liver cancer, and gallbladder cancer.

Caffeine can also effectively reduce the risk of type 2 diabetes by regulating insulin sensitivity. In addition, caffeine can slow down the process of neurodegeneration in Parkinson's disease by antagonizing the action of adenosine receptors. However, although many studies have found the potential health benefits of coffee, the current evidence does not support the view that "coffee can prevent disease." If you feel unwell, it is recommended to see a doctor as soon as possible and follow the doctor's advice.

Recently, scientists from Italy and the United States have revealed some new potential for caffeine - caffeine may be the secret weapon to help people quit alcohol addiction.

Can drinking coffee really help you quit drinking?

Why is drinking addictive? Scientists have found that alcohol (ethanol) itself does not directly bring pleasure. When alcohol is ingested, ethanol is metabolized in the liver to produce substances such as acetaldehyde. These metabolites can act on the "mesolimbic pathway" in the brain, which is composed of the amygdala, ventral tegmental area of ​​the midbrain, and nucleus accumbens , thereby promoting the release of large amounts of dopamine. Dopamine is a neurotransmitter closely related to the experience of pleasure and reward. Its release brings a sense of relaxation and pleasure, thereby stimulating our desire to continue drinking.

Mesolimbic pathway

(Image source: Wikipedia)

However, long-term drinking can cause adaptive changes in the central nervous system, especially the mesolimbic pathway, at the molecular and cellular levels. For example, the number and sensitivity of dopamine receptors in the brain may decrease, causing individuals to need to consume more alcohol to get the same pleasure as before. As tolerance increases, people will gradually increase their drinking and eventually become dependent on alcohol. According to statistics, about 2.5 million people die from alcohol-related diseases each year worldwide.

Researchers conduct experiments to observe the effects of alcohol and caffeine on the brains of male rats

(Image source: Reference [2])

In 2020, scientists fed male rats drinks containing caffeine and alcohol and were surprised to find that caffeine actually made the rats averse to alcohol.

Their recent further research shows that this phenomenon is related to caffeine preventing alcohol from being converted into salsolinol. Specifically, when alcohol is ingested, ethanol is metabolized into acetaldehyde, which, under certain conditions, combines with dopamine in the brain to produce salsolinol. Caffeine prevents this process, indirectly regulating the release of dopamine and reducing the addictiveness of alcohol.

Caffeine blocks the production of squalane, which is similar to the μ-receptor antagonist naltrexone, which is approved by the U.S. Food and Drug Administration (FDA) for the treatment of alcohol use disorder, further supporting its use as a potential treatment for alcohol addiction.

Metabolic pathways of dopamine and norsolaine in the brain

(Image source: Reference [3])

I really recommend adding some milk to your coffee.

According to two studies published in Food Chemistry and Journal of Agricultural and Food Chemistry in 2023 from the University of Copenhagen, Denmark, adding milk to coffee can enhance its anti-inflammatory effects.

The topic of drinking coffee with milk became a hot search on Weibo

(Image source: Screenshot of the author’s Weibo)

This study revealed that the polyphenols in coffee react with the proteins in milk to significantly enhance the anti-inflammatory effect. This is because polyphenols can enhance their ability to inhibit immune cell inflammation after combining with amino acids. The principle is that polyphenols react with the sulfhydryl groups of amino acids to form covalent adducts, which changes the structure of polyphenol molecules and enhances their biological activity.

Studies have shown that adducts such as CA-Cys and CGA-Cys have stronger anti-inflammatory effects in immune cells than polyphenols alone, and they enhance immunomodulatory effects by regulating immune signaling pathways, such as Toll-like receptor and NOD-like receptor signaling pathways, and inhibit the production of inflammatory factors such as TNF-α and PGE2. In addition, these adducts show stronger inhibitory effects in regulating inflammatory responses, indicating that they have potential advantages in anti-inflammatory and immunomodulatory aspects.

Polyphenols are natural antioxidants found in coffee, tea, red wine, as well as fruits and vegetables. They neutralize free radicals in the body, reducing oxidative stress and thus lowering inflammation. Inflammation is a response mechanism of the body's immune system, but long-term or excessive inflammation can lead to health problems, such as arthritis. Polyphenols, as powerful antioxidants, can effectively slow down this inflammatory process. However, relatively little research has been conducted on the interaction between polyphenols and other molecules, especially proteins.

It is really recommended to add milk to coffee

(Image source: generated by the author’s AI)

In this study, scientists compared artificially induced immune cell inflammation with different doses of a mixture of polyphenols combined with amino acids. The results showed that the combination containing polyphenols and amino acids was more effective than the treatment containing polyphenols alone, doubling the anti-inflammatory ability. This means that when we add milk to coffee, the proteins in the milk react with the polyphenols in the coffee, which may effectively enhance the anti-inflammatory effect.

In addition, similar reactions may not only occur in the combination of coffee and milk, but other protein-containing foods and polyphenol-containing fruits, vegetables, tea, etc. may also produce similar health benefits.

Other effects of coffee

In fact, coffee is a very interesting subject for nutritional epidemiology, because usually a person either drinks coffee every day or does not drink it at all, which makes the data of relevant studies more accurate. Therefore, there are endless studies on the effects of coffee on the human body.

Polyphenols in coffee

(Image source: generated by the author’s AI)

Recently, a research team from Harvard University in the United States analyzed medical data of more than 22,000 people from the United Kingdom and the United States, as well as public data of more than 54,000 people in other research cohorts, and found that in addition to the significant effects of caffeine on the nervous system, the polyphenol compounds rich in coffee (such as chlorogenic acid and quinic acid) also have unique effects on the digestive system.

The research team divided the population into three groups based on their coffee drinking habits: high coffee intake group (drinking more than 3 cups a day), never coffee intake group (drinking no more than 3 cups a month), and moderate coffee intake group (moderate drinking between the two).

Microscope photo of Lawsonia saccharolyticus

(Image source: Reference [5])

Subsequently, the researchers used multi-omics analysis, machine learning and other methods to analyze the relationship between the intestinal flora of different populations and coffee drinking. The intestinal flora is the community of microorganisms living in our intestines, which plays a key regulatory role in the human body's metabolism.

The results showed that the gut microbiomes of people with "high" and "moderate" coffee intake had significant differences in composition compared with those of people who "never" consumed coffee.

Overall, the number of most microorganisms in the intestine increased significantly with the increase of coffee intake. Among them, the bacteria with the biggest difference between different populations is Lawsonibacter asaccharolyticus. Lawsonibacter asaccharolyticus is an acid-resistant and bile-resistant probiotic that can survive in the intestine and promote the growth of beneficial bacteria. It helps prevent intestinal infections and relieve problems such as diarrhea and constipation by balancing intestinal flora, enhancing immune function and improving intestinal barriers.

Levels of this probiotic were about eight times higher in coffee drinkers than in non-coffee drinkers, which could have profound implications for people's health.

Conclusion

Although many studies have shown that coffee has positive effects on health, its benefits still depend on moderate drinking and individual differences. We may look forward to more studies in the future to reveal the health secrets behind coffee and help us have a deeper understanding of this ordinary yet extraordinary daily drink!

References:

[1] Deehan GA, Brodie MS, Rodd Z A. What is in that drink: the biological actions of ethanol, acetaldehyde, and salsolinol[J]. Behavioral Neurobiology of Alcohol Addiction, 2013: 163-184.

[2] Bassareo V, Maccioni R, Talani G, et al. Receptor and metabolic insights on the ability of caffeine to prevent alcohol-induced stimulation of mesolimbic dopamine transmission[J]. Translational Psychiatry, 2024, 14(1): 391.

[3] Kurnik M, Panula P, Bugajski A, et al. Salsolinol: an Unintelligible and Double-Faced Molecule—Lessons Learned from In Vivo and In Vitro Experiments[J]. 2017.

[4] Manghi P, Bhosle A, Wang K, et al. Coffee consumption is associated with intestinal Lawsonibacter asaccharolyticus abundance and prevalence across multiple cohorts[J]. Nature Microbiology, 2024: 1-15.

[5] Sakamoto M, Iino T, Yuki M, et al. Lawsonibacter asaccharolyticus gen. nov., sp. nov., a butyrate-producing bacterium isolated from human faeces[J]. International Journal of Systematic and Evolutionary Microbiology, 2018, 68(6): 2074-2081.

[6] van Dam RM, Hu FB, Willett W C. Coffee, caffeine, and health[J]. New England Journal of Medicine, 2020, 383(4): 369-378.

[7] Poojary, Mahesha M., et al. "Covalent bonding between polyphenols and proteins: Synthesis of caffeic acid-cysteine ​​and chlorogenic acid-cysteine ​​adducts and their quantification in dairy beverages." Food Chemistry 403 (2023): 134406.

[8] Phenolic Acid–Amino Acid Adducts Exert Distinct Immunomodulatory Effects in Macrophages Compared to Parent Phenolic AcidsArticle link copied!