Is caffeine addictive? Symptoms of caffeine addiction Why are some people insensitive to caffeine?

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Does drinking coffee give you heart palpitations? Can't sleep if you drink coffee? The caffeine contained in it is the substance targeted by the public. But is caffeine really that bad?

Q1. Is there more caffeine in deep-roasted coffee or light-roasted coffee?

Many people think that deep-roasted coffee is bitter, so deep-roasted coffee has a high caffeine content. However, caffeine is actually a substance with good thermal stability and is less likely to be destroyed by heat. The study found that there was no significant difference in caffeine content in water extract of coffee with different roasting degrees, so deep-roasted coffee beans did not have more caffeine.

However, because deep-roasted coffee is relatively light, if you want to make the same amount of coffee, you may use more coffee beans, of course, the total amount will be more. Therefore, the caffeine content of deep-roasted coffee "beans" is not more, but the caffeine content of deep-roasted "coffee" may be higher.

Q2. Why can't you sleep after drinking coffee?

In theory, ​, caffeine itself does not have a "refreshing" effect, but keeps us awake. The sleep mechanism of the human body is very complex, including GABA, adenosine and other nerve conduction substances, which mainly regulate the human "physiological clock". Among them, adenosine is the key substance of the switch mechanism (sleep onset) that starts sleep. When adenosine binds to the receptor in the brain, it turns on the sleep switch and makes us "fall asleep."

Caffeine is a purine alkaloid with a very similar structure to adenosine, so caffeine intake competes with adenosine for the receptor (adenosine 2A), so it does not inspire a "sleep reaction" and therefore cannot sleep.

Q3. Why are some people insensitive to caffeine?

Although caffeine competes with adenosine for receptors, this receptor (adenosine 2A) may reduce the sensitivity of caffeine to this receptor because of its genotype. The gene of this receptor is ADORA2A. Studies have found that this gene has genetic polymorphism (single nucleotide polymorphism, SNP) on 1083 base pairs, changing from the original CC type to the CT or TT type.

Note: genetic polymorphism refers to a single point of nucleotide mutation in the gene code (codon), which is composed of three nucleotides, such as AAC. A single nucleotide mutation means that there is only one nucleotide mutation, such as the transformation from AAC to AAT, which will affect gene expression or subsequent protein translation, thus resulting in human "polymorphism".

Because the adenosine gene is at position 1083, the shift from C to T affects the receptor's sensitivity to caffeine, and this variation is also reflected in caffeine uptake behavior. A 2007 study in the American Journal of Clinical Nutrition found that people with CC or CT types consumed less high caffeine, while people with TT types were able to tolerate caffeine, so they consumed more caffeine.

So, if you're not sensitive to caffeine, you may have a TT genotype in your genes.

Q4. Why can people in Europe and America drink so much coffee every day?

For caffeine-related receptors or enzymes in the human body, apart from adenosine 2A receptors, the most important is the cytochrome P450 system in the liver, which also controls the metabolism of many drugs. Similarly, genes control the mechanisms of cytochrome P450, one of which is CYP1A2.

There are also many positions of SNP in the gene fragment of CYP1A2, especially the point mutation (A to C) at position 163mainly controls the metabolism of caffeine. The 2008 Journal of Pharmacogenomics found that most of the 163s of CYP1A2 in Asians have the C type, which makes Asians have a lower ability to metabolize caffeine than people in Europe and the United States, which prolongs the half-life of caffeine in the body, so the same intake of caffeine products delays the effect in Asians, which may also be one of the reasons why Asians are less tolerant to coffee.

Q5. Can long-term caffeine intake cause palpitations?

Many people who drink coffee will feel palpitations, but in fact it is not necessarily caused by caffeine, while some people say that long-term caffeine intake is more prone to palpitations. However, a study published in the 2006 issue of the Journal of the American Heart Association gives such an answer.

Of the nearly 1400 subjects in the study, 61 per cent ate a cup of caffeine a day. The subjects wore electrocardiographic monitoring equipment to monitor their heart condition for 24 hours, monitoring early ventricular or early atrial contraction. It was found that there was no significant correlation between the frequency of early cardiac contraction per hour or the number of times throughout the day and caffeine intake.

Therefore, caffeine is not one of the inducing factors of palpitation in the long run.

Q6. Caffeine has withdrawal?

Coffee abstinence disorder (caffeine withdrawal syndrome) is the thing that people are most worried about. It seems that as long as you drink coffee, you will become addicted, and if you don't drink coffee, you will have addiction withdrawal syndrome. Is that true?

Indeed, caffeine withdrawal is listed in the Diagnostic guidelines for Psychiatry (DSM--5), as well as in the physician's Diagnostic Manual (ICD--10), and there are studies to explore whether caffeine withdrawal is as serious as rumored.

Data from the 2004 issue of the Journal of Psychiatry (Psychopharmacology) show that:

50% of people have headaches.

13% of people have problems with functional abnormalities.

12Murray developed symptoms after 24 hours.

20Murray 51 hours is the peak period of symptoms.

Last 2murmurfor 9 days.

This figure is somewhat similar to that of the 1992 New England Journal of Medicine:

52% of people have headaches.

8% of people have fatigue problems.

11% of the people showed decreased vitality.

8% of people have anxiety reaction.

11% of people have the problem of depression

However, in fact, the subjects in these studies consumed higher amounts of coffee products, consuming 2.5 cups of coffee (239 mg caffeine) per day as outlined in the New England Journal of Medicine, and in another study with similar results, subjects ate six cups of coffee a day, which is different from the coffee intake habits of Taiwanese, so I don't think the problem of caffeine withdrawal in Taiwan should be serious.

Q7. Can drinking coffee lead to osteoporosis?

In October 2017, there was a news report that a 30-year-old girl ate four cups of black coffee a day, and the condition of osteoporosis was just like that of the elderly, and this also brought out our fear that coffee would lead to osteoporosis.

Caffeine does activate the activity of osteophages in bones and promote the release of bone calcium into the bloodstream. A study in the International Journal of Osteoporosis in 2006 found that daily coffee intake and the risk of osteoporosis significantly increased. This risk is also related to caffeine intake.

Does this mean that drinking coffee can lead to osteoporosis? No, in fact, the biggest problem is insufficient calcium intake. The above data, provided that calcium intake is below 700mg, the study found that if calcium intake is above 700mg, coffee and caffeine intake is not significantly associated with the risk of osteoporosis.

However, our current calcium intake is really not good. According to the results of the National Nutrition Survey, our calcium intake is only about 600 mg, so if we want to drink coffee healthily, we must first eat enough calcium. There is also literature in the Journal of the American Medical Association that milk can eliminate the bone risk caused by coffee, so I think latte is a good way to drink coffee.