Despite this, there are also more cautious studies. These tend to report on the risks of consuming caffeine, especially in children and young people, pregnant and lactating mothers, and individuals with underlying health conditions.
As you are sipping your first or your umpteenth cup of the day, find out what the latest research says about the safety of coffee and what coffee does to our bodies to cause the health miracles that everyone is talking about.
How much caffeine are we consuming?
Caffeine occurs naturally in tea leaves, coffee beans, and cocoa beans. Synthetic caffeine is also added to other drinks, some food products, and certain medications.
The levels of caffeine in coffee depend on the type of coffee used and how it was prepared. An average 8-ounce cup of brewed coffee contains between 95 and 165 milligrams of caffeine, while a single shot of espresso contains between 47 and 64 milligrams.
In the United States, 89 percent of adults consume caffeine - mostly in the form of coffee, tea, and, to a lesser extent, soft drinks. Men consume slightly more caffeine (on average, 240 milligrams per day) than women (who drink, on average, 183 milligrams per day).
Energy drinks make up only a small proportion of the caffeine intake of adults, but consumption did increase significantly between 2001 and 2010.
The majority of U.S. children (79 percent) also consume caffeine, with older children consuming more than younger ones.
Children below the age of 12 tended to consume caffeine in the form of tea, soda, and flavored dairy products, while older children mostly consumed coffee.
What happens inside our bodies?
Coffee contains a remarkably complex collection of molecules. Chief among them is, of course, caffeine, the central nervous system (CNS) stimulant that helps many of us to wake up in the morning and get through our day.
But there are also other antioxidant substances that help to mop up free radicals in our cells and activate DNA repair, as well as anti-mutagen molecules that stop cancer-causing DNA mutations from occurring. However, it's not all good news: coffee also contains carcinogens.
So what happens to the caffeine? Caffeine spreads throughout the body after it is taken up in the intestine. It takes quite a long time to be metabolized, which means that it is present in our bodies for some time after we consume it.
How we metabolize caffeine depends on our age. The half-life - that is, the amount of time taken to break down half the caffeine in our system - in adults is estimated to be between 3 and 7 hours.
But in newborns this is much higher, with numbers cited to be in the range of 65 to 130 hours.
Genetic variations make some people more susceptible to the effects of caffeine, by affecting both how quickly it is broken down and by how strong an effect it has on organs. Other things also affect caffeine metabolism.
The enzymes that break down caffeine are also responsible for breaking down steroids. In women, oral contraceptives are thought to double the half-life of caffeine in the body. In pregnant women, caffeine also stays in the body significantly longer.
What happens to the other molecules in coffee? The chief antioxidant and flavor molecules in coffee are chlorogenic acids. These are also found in apples, pears, and other fruits, as well as in vegetables and plants.
They are absorbed in the intestine and partly metabolized by our gut microbes. They are now able to exert their strong antioxidant effects on a range of cells.
The health benefits of coffee have been attributed to both the caffeine and the other antioxidant molecules in the drink. But what is the scientific evidence behind these claims?
The science behind the health benefits
Interestingly, decaffeinated coffee has many of the same health benefits as regular coffee. So much so that in mice, both caffeinated and decaffeinated coffee showed significant anti-aging effects.
A recent study compared the effect of coffee and caffeine from other sources on the length of telomeres, which are caps that protect the ends of chromosomes during cell division. Telomeres are used as a measure of aging; the structures get shorter when cells age.
Short telomeres are associated with a higher risk of death. As caffeine consumption increased in U.S. adults, telomeres were significantly shorter.
However, with increasing coffee consumption, telomeres were longer. Coffee consumption might therefore prolong life, while caffeine consumption could shorten it.
But caffeine itself has also been linked with potential health benefits. For example, researchers recently showed that caffeine can boost the levels of an enzyme that might prevent Alzheimer's disease.
Others have investigated the anti-inflammatory properties of caffeine and its metabolites. Older adults who had lower levels of inflammation were healthier than those with higher levels of inflammation, and the low inflammation group had significantly greater levels of caffeine metabolites in their blood.
If coffee is this good for us, shouldn't we all be drinking it?
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