Good news for those who drinks coffee!

Caffeine is a drug that is naturally produced in the leaves and seeds of many plants. It's also produced artificially and added to certain foods. Caffeine is defined as a drug because it stimulates the central nervous system, causing increased alertness. Caffeine gives most people a temporary energy boost and elevates mood.
Caffeine is not stored in the body, but you may feel its effects for up to 6 hours.

Caffeine is usually thought to be safe in moderate amounts. Experts consider 200–400 mg of caffeine a day to be a moderate amount for adults.

It is difficult to link precise intake levels of caffeine to specific health effects because tolerance to caffeine differs widely from person to person. For healthy adults, a small amount of caffeine may have positive effects, such as increased alertness or ability to concentrate. However, some people are more sensitive to caffeine. For them, a small amount could cause insomnia, headaches, irritability and nervousness.

It would be very difficult to consume enough caffeine for a lethal overdose. One would have to drink several hundred cups of coffee or ingest at least 75 caffeine tablets to reach toxic levels, however.

Caffeine may not be addictive in the classic sense, but the body does build up a tolerance over time. Some people find it difficult to function without at least one cup of strong coffee or tea in the morning. The stimulating effects of caffeine are caused by a central nervous reaction. The heart rate increases, blood vessels expand and the brain receives more oxygen. This effect can last up to an hour.

There is such a thing as caffeine withdrawal. Regular consumers of coffee or sodas may experience painful headaches if the body is denied caffeine. These headaches are caused by excess blood collecting in the area around the brain and sinus cavities. Without the stimulation provided by caffeine, the blood vessels shrink, restricting the flow of blood. The traditional cure for caffeine withdrawal is to ingest more caffeine. This is also why many headache medications contain small amounts of caffeine.

Caffeine is a strong diuretic - it makes you urinate more than usual. Apparently this is due to increasing the blood flow through the kidneys.

It can produce insomnia - delaying the onset of sleep and reducing total sleeping time. It has a small effect on respiration by increasing blood flow through the lungs and increasing the supply of air by relaxing bronchiolar and alveolar smooth muscle. That's why it's proving effective in treating the breathing problems of some prematurely born infants.

Caffeine increases the level of circulating fatty acids. This has been shown to increase the oxidation of these fuels, hence enhancing fat oxidation. Caffeine has been used for years by runners and endurance people to enhance fatty acid metabolism.

Caffeine can speed up metabolism. Also, it can help the body break down fat about 30% more efficiently if consumed prior to exercise. (You must be exercising to get this benefit, though.) Additionally, caffeine can keep blood sugar levels elevated, leaving you feeling less hungry.
Caffeine has been found to enhance physical performance and endurance if it isn’t overused. This, combined with its effect of fat burning during exercise, can actually enhance workouts and enable you to get in better shape if you take it at the right time.

Caffeine accelerate heartbeat that causes burning more calories.
According to a study performed in Canada, people who drinks coffee before exercise are more endurable, besides they spend more oxygen during exercise. Spending oxygen is directly connected to metabolism speed.

Changes, caffeine makes in your physiology, can have both positive and negative consequences:
Caffeine can affect your sleep by keeping you awake longer, thereby shortening the amount of sleep you get, and giving you less time in the restorative stages of sleep, which takes a toll on your level of alertness the next day and overall health.
Interestingly, though, caffeine doesn’t affect the stages of sleep the way other stimulants do, so it’s a better choice than speed or other ‘uppers’ to use if you need to stay awake.

Caffeine may increase alertness in tired individuals and enhance performance of certain tasks. Many people find caffeinated beverages can help them stay alert when they work, study or exercise.

It helps prevent muscle fatigue.
A Canadian researcher, Prof Howard Green, has carried out experiments looking at the role of caffeine in helping to overcome muscle fatigue in the quadriceps (thigh) muscles.
In his Canadian experiments, muscle fatigue was induced electrically and then caffeine tablets were taken which were the equivalent of 8-10 cups of coffee. Within an hour the effect of reducing fatigue could be noticed. It probably does this by making more calcium available to the muscles.

In whole body exercise caffeine can increase the performance of muscles. The theory is that it does this by making more fatty acids available to the muscles than usual and that delays depletion of glycogen reserves. It's known that depletion of glycogen from the muscles is tied in with fatigue. This kind of benefit should be relevant to endurance events such as running and cycling.

Drink coffee or a glass of non-sugared fluid containing caffeine one hour before exercise. Consuming caffeine before exercise reduces muscle pain. Caffeine brakes (down) the biochemical reactions while flexing muscles and thus reduces the pain.

You can feel the effects of caffeine in your system within a few minutes of ingesting it, and it stays on your system for many hours—it has a half-life of four to six hours in your body. While in your body, caffeine affects the following hormones:
* Adenosine- Can inhibit absorption of adenosine, which calms the body, which can make you feel alert in the short run, but can cause sleep problems later.
* Adrenaline- Caffeine injects adrenaline into your system, giving you a temporary boost, but possibly making you fatigued and depressed later. If you take more caffeine to counteract these effects, you end up spending the day in an agitated state, and might find yourself jumpy and edgy by night.
* Cortisol- Can increase the body’s levels of cortisol, the “stress hormone”, which can lead to other health consequences ranging from weight gain and moodiness to heart disease and diabetes.
* Dopamine- Caffeine increases dopamine levels in your system, acting in a way similar to amphetamines, which can make you feel good after taking it, but after it wears off you can feel ‘low’. It can also lead to a physical dependence because of dopamine manipulation.

Caffeine has many metabolic effects. For example:
* It stimulates the central nervous system.
* It releases free fatty acids from adipose (fatty) tissue.
* It affects the kidneys, increasing urination, which can lead to dehydration.

Caffeine is a drug, popularly consumed in coffee, tea, soft drinks and, in smaller doses, chocolate. While we seem to have a love affair with these products, there’s been quite a bit of confusion and even controversy surrounding caffeine lately. Is it good or bad for us? The answer we can find only within us.