"Life-extending magic weapon" may also be a "weapon of harm"? These 9 types of people should drink less coffee!

For modern people, coffee has gradually become a popular drink and a daily must-have for many office workers.

Currently, many studies have mentioned that drinking coffee regularly is good for health, such as refreshing the mind, relieving fatigue, preventing type 2 diabetes, and preventing certain cancers. A recent study by a research team from Soochow University showed that drinking coffee can actually offset the harm caused by long periods of sitting - the risk of death for those who sit for ≥6 hours a day and do not drink coffee is 1.58 times that of those who sit for less than 6 hours a day and drink coffee; among people who do not drink coffee, the longer they sit, the higher the risk of all-cause death.

Even so, coffee is not suitable for everyone. There are 9 types of people who cannot drink coffee blindly and must pay special attention.

1. People with poor sleep

Coffee contains a high level of caffeine, which has a certain refreshing effect. Caffeine has a similar structure to adenosine, a metabolite of the body's energy source adenosine triphosphate (ATP), and can compete with receptors that cause fatigue and sleep signals, exerting biological activity that promotes wakefulness and improves fatigue.

Because of this, many office workers rely on coffee to cheer themselves up and work hard.

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Studies have shown that caffeine is absorbed quickly by the human body, reaching its peak 15 minutes to 2 hours after drinking, spreading throughout the body and crossing the blood-brain barrier. Its half-life in adults is generally 2.5 to 4.5 hours. Therefore, drinking coffee 5 hours before going to bed will not have much impact on normal people's sleep. For example, if you go to bed at 10 p.m., then drink coffee before 5 p.m.

However, different people have different tolerance levels to caffeine. People who already have poor sleep, insomnia, or sleep disorders should try to drink less or no coffee.

2. People with arrhythmia

Although it is normal to have an accelerated heartbeat after drinking coffee, it still needs to be taken seriously, especially for people who already have arrhythmia.

Arrhythmia is mainly caused by abnormal electrical conduction of the heart, which results in an irregular, too fast or too slow heartbeat. More than 80% of American doctors recommend that patients with palpitations or arrhythmia quit or reduce their caffeine intake.

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Other studies have shown that for most people, even patients with arrhythmias or people at high risk of arrhythmias, although there is no clearly defined threshold for the harm of caffeine, caffeine intake below 400 mg per day seems to be safe and may even have a protective effect against arrhythmias; however, for people with malignant arrhythmias and people at high risk of arrhythmias who are sensitive to caffeine, they should try to avoid caffeine intake.

400 mg of caffeine is equivalent to no more than 4 cups of pure coffee (150 ml/cup). If it is purchased coffee, you can calculate the number of cups by comparing the caffeine content per cup on the package label; if it is a small bag of 1.8~2 grams of instant coffee, generally no more than 5 bags per day.

3. People with stomach problems

Coffee can stimulate the gastrointestinal tract and increase the secretion of gastric acid.

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This will not affect health for people with normal stomach function. However, for people who already have stomach problems, such as gastric ulcers, excessive gastric acid secretion, and gastroesophageal reflux disease, frequent or excessive coffee drinking may cause symptoms such as nausea, vomiting, acid reflux, and heartburn.

4. Patients with irritable bowel syndrome

Irritable bowel syndrome is a very common functional bowel disease, and patients may suffer from frequent diarrhea and constipation.

Caffeine can stimulate the secretion of gastric acid and cholecystokinin in the digestive system, thereby promoting colonic motility and causing symptoms such as diarrhea. Generally speaking, patients with irritable bowel syndrome are more sensitive to caffeine, and drinking it may increase gastrointestinal discomfort and diarrhea symptoms. Reducing caffeine intake can reduce the occurrence of symptoms related to irritable bowel syndrome.

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5. People with severe anemia

The polyphenols, tannic acid and other ingredients in coffee have no effect on the absorption and utilization of heme iron. Generally speaking, we mainly rely on heme iron to supplement iron and blood in our diet, such as lean meat, pork liver, duck blood, clams, etc., and coffee only affects about 6% of the iron in a meal. Therefore, healthy people do not need to worry about anemia caused by drinking a few cups of coffee.

However, the polyphenols, caffeine, phytic acid and other plant components in coffee will combine with iron, snatch the position of iron ions, reduce the absorption rate of iron, and thus affect the absorption of non-heme iron. Therefore, for people who are already severely anemic, it is recommended to reduce coffee intake appropriately to avoid affecting the body's iron storage level. (For a detailed explanation of whether coffee can cause anemia, interested readers can click on this article "Will coffee "take" away the iron in your body and cause anemia? The truth is not that simple...")

6. People with osteoporosis

The caffeine and tannic acid in coffee do affect calcium absorption, and the diuretic effect of caffeine will increase calcium loss, but this has little effect on healthy people. Some studies have mentioned that the negative effect of caffeine on calcium absorption is very small, and only 1 to 2 tablespoons of milk can completely offset it.

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Based on a large amount of population data, food safety regulatory agencies such as the European Food Safety Authority, the US Food and Drug Administration, Health Canada, and the Australian New Zealand Food Standards Agency believe that a daily caffeine intake of 400 mg or less for healthy adults will not have adverse effects on cardiovascular function, behavior, reproduction and development, or bone health, and there is no risk of acute poisoning. Therefore, healthy people do not need to worry about drinking coffee causing osteoporosis.

However, for people who already have osteoporosis, the "Chinese Expert Consensus on Diagnosis, Treatment and Management of Osteoporotic Pain in the Elderly (2024 Edition)" recommends avoiding excessive coffee consumption.

7. Glaucoma patients

Studies have shown that the caffeine in coffee can cause abnormally high intraocular pressure in glaucoma patients, which is a risk factor for the development of glaucoma. High intraocular pressure can cause optic nerve damage and visual impairment, and in severe cases can lead to blindness.

Therefore, glaucoma patients should avoid drinking high-caffeine beverages such as coffee in their daily lives to prevent further damage to the eyes due to increased and fluctuating intraocular pressure.

8. Children and adolescents

The internationally recommended safe caffeine intake for children and adolescents is no more than 2.5-3 mg per kilogram of body weight. In other words, for a child or adolescent weighing 40 kg, the caffeine intake is 100-120 mg, which is about one cup of coffee. Of course, it is best not to drink it.

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This is because children who are in their growth and development period have a weaker ability to metabolize caffeine than adults, which will not only affect their sleep but also their physical development.

The "Guidelines for Snacks for Chinese Children and Adolescents (2018)" also mentioned that foods containing caffeine will have a negative impact on children's brain development and function. Therefore, children aged 12 and under are prohibited from consuming caffeine and drinking caffeinated beverages such as strong tea and coffee.

9. Pregnant and lactating women

The "Scientific Consensus on Coffee and Health" states that pregnant women are not recommended to drink coffee, and if they do, they should not drink more than 2 cups a day. Although the Canadian Ministry of Health, the American College of Obstetricians and Gynecologists, the American Pregnancy and Childbirth Association and other organizations believe that a small amount of coffee can be consumed during pregnancy (no more than 150-300 mg of caffeine per day, about 2 cups), pregnant women should not be encouraged to drink coffee.

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Therefore, for women who do not have the habit of drinking coffee, it is recommended not to drink coffee during pregnancy and breastfeeding; and for women who have always had the habit of drinking coffee, it is best to limit the amount of coffee they drink.

Summarize

Although drinking coffee is good for health, it should be limited. The "Scientific Consensus on Coffee and Health" recommends that the average adult's daily caffeine intake should be controlled within 400 mg.

Different people have different tolerance levels to caffeine. It is recommended that the 9 groups of people mentioned in the article and people who are sensitive to caffeine should limit or avoid caffeine intake according to their own circumstances.

References

[1]Zhou H, Nie J, Cao Y, et al. Association of daily sitting time and coffee consumption with the risk of all-cause and cardiovascular disease mortality among US adults. BMC Public Health. 2024;24(1):1069. Published 2024 Apr 17. doi:10.1186/s12889-024-18515-9

[2] Zhang Manyu, Fan Hongling, Zhai Wenchao. Research progress on the correlation between caffeine and arrhythmia[J]. Journal of Integrated Traditional Chinese and Western Medicine for Cardiovascular and Cerebrovascular Diseases, 2024, 22(8): 1433-1437

[3] Qin Xian, Song Jun, Hou Xiaohua. Research progress on lifestyle and dietary management of irritable bowel syndrome[J]. Gastroenterology, 2018, 23(7): 436-439

[4]Heaney, R P. “Effects of caffeine on bone and the calcium economy.” Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association vol. 40,9 (2002): 1263-70. doi:10.1016/s0278-6915(02)00094-7

[5] Chinese Society of Food Science and Technology. Scientific consensus on caffeine [J/OL]. Journal of Chinese Institute of Food Science and Technology: 1-6 [2024-05-17]. http://kns.cnki.net/kcms/detail/11.4528.TS.20240416.1351.007.html.

[6] Xiong Haibo, Yi Hong, Liu Xin, Dai Yubing. Meta-analysis of the effect of caffeine on intraocular pressure in patients with glaucoma[J]. Laboratory Medicine and Clinic, 2015, 12(16): 2362-2363.

[7] Cao Huijuan, Liu Jianping. A systematic review of the correlation between caffeine intake during pregnancy and miscarriage[J]. Chinese Journal of Practical Gynecology and Obstetrics, 2014, 30(12): 945-950.

[8]Lisowska A, Kasiak P, Rząca M. Assessment of caffeine intake in groups of pregnant and breastfeeding women: A cross-sectional analysis. Clin Nutr ESPEN. 2023 Oct;57:151-157. doi: 10.1016/j.clnesp.2023.06.041. Epub 2023 Jun 29. PMID: 37739650.

Review | Ruan Guangfeng, Deputy Director of Kexin Food and Health Information Exchange Center