How long does it take for caffeine to work?

by Mark Miller March 17, 2016

How long does it take for caffeine to work?

Ten minutes after that first sip of coffee, the subtle but invigorating effects of caffeine kick in, making getting out there and facing the day seem less daunting.

And in a surprising finding, one study found that decaffeinated coffee, which contains only 2 to 3 percent of the caffeine of regular coffee, also contributes (slightly) to a person’s alertness.

How long does it take caffeine to kick in?

You might feel drowsy and incapable of functioning at a high level until the caffeine hits your bloodstream. You may go from 0 to 60 in about 10 minutes, but you hit top speed after about 45 minutes, when 99 percent of the caffeine from your coffee, tea or energy drink has entered the bloodstream fully. Then it takes many hours for the caffeine to dissipate.

These findings were reached by researchers from the University of Barcelona in a study published in December 2008 in the journal Progress in Neuro-Psychopharmacology and Biological Psychiatry. The journal article is not available without paying a fee.

The 10-minute finding contradicted previous studies that showed alertness does not increase until after 30 or 45 minutes, says an articlein Science Daily about the research article.

“Forty-five minutes is the time needed for maximum caffeine concentration to be reached in the blood, but levels reach half this concentration after just a few minutes,” Science Daily reports.

To measure caffeine’s effects on the human body, the researchers analyzed 668 university students, 238 of them male. Their average age was 22. They sampled the levels of caffeine in their blood at 10, 20 and 30 minutes. They took the measurements two times during the day after the students drank coffee, at midday and in the late afternoon, to serve as a control if there were possible differences caused by time of day.

Men get more caffeine kick

Another surprise finding: Men obtain more of the stimulating effects of caffeine, than women.
The lead researcher, Ana Adan, told Science Daily, “Although both the men and women saw an improvement in their activity levels with the coffee, which increased in later measurements, we observed a greater impact among the males.”

Though the women in the study were less affected by caffeine, they obtained more alertness from the decaffeinated coffee than the men did.

The study says the invigorating effects of decaf gave “a small subjective improvement in the participants’ state of alertness.”

“If a person cannot drink normal coffee, a decaffeinated one might provide some benefits. It remains to be evaluated whether these effects are simply subjective, or if they do have an impact on performance,” Adan told Science Daily.

Many ways to take caffeine

There are, of course, different ways to ingest caffeine. People who chew caffeinated gum or suck caffeinated mints might find their alertness level increases quickly because the body absorbs the compound quickly through the thin membranes of the mouth. Also, many energy drinks have greatly concentrated amounts of caffeine in a few ounces of liquid, which are drunk quicker than, say, an 8 or 10-ounce cup of hot coffee. The faster the caffeine is consumed, the faster it hits the bloodstream.

Another thing that might affect the rate of caffeine uptake into the bloodstream is the concentration of the chemical in the product being consumed. In other words, some types of coffee and other products contain more caffeine than others, depending on the type of beans it’s made from and the brewing process. So drinking a 6-ounce cup with 100 mg of caffeine may have less of an effect than a 6-ounce cup with 167 mg.

Also, as the Viter Energy Mints Blog wrote before:

When people talk about having “a cup of coffee,” they don’t necessarily mean 8 ounces (236 milliliters). For example, many people go for the large size of coffee at McDonald’s restaurants and Starbucks, at 20 ounces (591 milliliters). Or at home, they may have a 12- to 16-ounce mug.

So when you read guides online that say an 8-ounce cup of drip java has about 163 mg of caffeine, you can more than double the amount of the stimulating chemical for a 20-ounce size. Drip coffee is the kind that drips through a filter to produce that cup or mug of the elixir that so many people say they can’t start their day without.

That Viter Energy Mints Blog explores all about the amounts of caffeine in the many types of coffee. Another of our blogs detailed amounts of caffeine in other products, including chocolate, tea, medicines and energy drinks.

More caffeine, more buzz

The amount of stimulation a person gets from coffee and other caffeinated products varies by the amount of caffeine.

According to a LiveStrong articleabout how long caffeine stays in the system:

Caffeine’s stimulant effect on the central nervous system is dose-dependent; the more caffeine consumed, the stronger the stimulant effect. It blocks a neurotransmitter called adenosine, which is a central nervous system depressant and has a calming, slowing effect on the brain. When adenosine is blocked, the adrenal glands begin secreting adrenaline, which is the chemical associated with the body’s “fight or flight” response. This response is characterized by increases in heart rate, body temperature, blood pressure and blood sugar levels. When caffeine blocks adenosine, it also leads to increased dopamine levels, which are associated with an elevation in mood.
Another thing to keep in mind when consuming caffeine (about 80 percent of American adults do so), is that the chemical’s half-life is about five or six hours. This means about half the coffee you ingested five hours ago is still in your body five hours later.

Mark Miller
Mark Miller


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