Tea, coffee, and energy drinks have one thing in common: they contain caffeine. Below, "Ask the Doctor" gives you a detailed introduction to the effects of caffeine on the human body.

1. Increased blood pressure

Caffeine can cause a short-term spike in blood pressure, and sometimes even a long-term spike. The reasons for this are not entirely clear, but it is thought that caffeine may block the secretion of a hormone that relaxes arteries and lowers blood pressure. It is also possible that caffeine promotes the secretion of adrenaline, which can raise blood pressure.

People with high blood pressure or heart problems must be especially careful before consuming caffeinated foods and it is best to consult a doctor.

2. Increase your heart rate

Caffeine can make your heart beat faster, which is not a problem in most cases. But if you take too much or are sensitive to caffeine, your pulse may beat too fast or last too long. This can feel like an abnormal heart rhythm, palpitations, or a missed beat.

3. Refreshing and making people more alert

Caffeine can stimulate people's energy and emotions, just like a shot of chicken blood, making people more alert. When you feel sleepy in the morning or have to stay up late to work overtime, drinking a cup of strong tea or coffee is very effective.

Our bodies cannot store caffeine all the time, but it can have effects for up to 6 hours. But drinking too much is not necessarily a good thing, as it can make people nervous and tense.

4. Helps Fight Disease

Caffeine may help prevent kidney stones and inflammation, and there is also research suggesting that regular caffeine intake may help prevent certain neurological diseases, such as Parkinson's, Alzheimer's, Huntington's, multiple sclerosis, and epilepsy, but evidence is still to be added.

5. Polyuria

Caffeine is a diuretic, which means it makes people urinate more easily. For people who are not used to caffeine, 300 mg of caffeine can produce a diuretic effect.

For healthy people, this polyuria is not a big problem and generally does not cause dehydration.

People who consume a little caffeine every day will develop a higher tolerance to caffeine, and the diuretic effect will be greatly weakened.

6. Better athletic performance

During endurance activities, such as running, cycling or swimming, caffeine can make people faster and with less muscle pain. The effects are more pronounced when caffeine is in a non-liquid form, such as a caffeine tablet.

Eating some one hour before exercise will allow the body to fully absorb the caffeine and achieve better results. 200-400 mg of caffeine is enough, and more will not have any better effect.

7. Promotes Recovery After Workout

Studies have found that after exercise, caffeine can regenerate and store glycogen, promoting body recovery, and the effect is better when taken together with carbohydrates.

It is important to note that you should not consume too much caffeine, otherwise you may continue to be excited, affect your sleep, and be detrimental to your body's recovery.

8. Affects sleep

Too much caffeine, especially in the afternoon or evening, can make it difficult to fall asleep. People who are sensitive to it may suffer from insomnia even after drinking a little. Older people may have a greater impact on their sleep due to caffeine intake.

Therefore, it is best not to drink tea, as well as caffeinated beverages such as coffee, tea, chocolate, sports drinks, etc. in the afternoon or late evening.

9. Causes headaches

People who are used to consuming some caffeine every day may experience headaches, also known as rebound headaches, once they stop consuming caffeine.

If you stop smoking all at once, the pain may be worse, but if you cut back a little bit every day, it will be better.

How much caffeine is "too much"?

This depends on a person's weight, diet, medications, and overall health. For most adults, 400 mg of caffeine a day is fine, but 600 mg may be too much. Because the caffeine content of each tea or coffee is different, it is difficult to say how many cups you can drink at most. You can judge based on your body's reaction. If you feel that your sleep is affected or you urinate too frequently or your heart beats uncomfortably after drinking, then it is too much.

You should limit your caffeine intake if you experience any of the following reactions:

• Gastrointestinal problems;
• Headache;
• Muscle twitching
• Palpitations.

"Ask the Doctor" - a team of doctors from the ancient city of Xi'an, sharing scientific and practical health knowledge with you.