Ever wonder why it feels like you can’t get through the day without coffee, tea, chocolate, or your favorite soda or energy drink? Whether it’s a cup of joe to get you going in the morning or a chocolate treat on your break — there’s a reason you feel like you can’t do without them.

The answer is because each time you’re enjoying your favorite beverages and treats, you’re also ingesting a stimulant.

Caffeine is one of the most commonly used stimulants in the world. “It takes only 15 to 20 minutes to get into the bloodstream, yet we feel its effects within an hour, for as long as up to four to 10 hours,” says registered dietitian Beth Czerwony, MS, RD, LD.

How does caffeine affect your body?

Caffeine is generally considered safe. It stimulates, or excites, your brain and nervous system. It can actually benefit you — from increased alertness to being used as a treatment for headaches.

Some studies propose other health benefits too. Caffeine has possible positive effects on inflammation, the lining of your heart and blood vessels and type 2 diabetes. Some research even suggests it might help you live longer.

What are the negative effects of caffeine?

Most healthcare experts recommend that children under age 12 avoid caffeine altogether and women who are pregnant limit their caffeine intake to no more than 200 mg a day.

For adults, consuming as little as 300 milligrams of caffeine (that’s roughly four cups of coffee) in a day can increase your risk of nausea, anxiety, sleeplessness, restlessness and other side effects.

For some adults, when overly used or abused, caffeine can also cause:

• Headaches.

• Irritability.

• Sleeping problems.

• Heart palpitations.

• Gastrointestinal distress.

• Dehydration.

• Tremor.

• Agitation.

• Heartburn.

• Diarrhea.

“If caffeine gives you the jitters or you find you’re becoming too dependent on it, you should consider cutting back,” Czerwony says.

More serious adverse neurologic and cardiac effects may also occur if you consume too much caffeine, and death is even possible. Exceeding 480 milligrams a day has also been linked to:

• Arrhythmias (heart rhythm disturbances).

• Rapid heart rate.

• Cardiac ischemia (narrowing of the heart’s arteries).

• Seizures.

• Hallucinations.

• Muscle breakdown (rhabdomyolysis).

• Death.

How much caffeine can I consume?

The American Medical Association Council on Scientific Affairs defines “moderate” coffee drinking as about 250 milligrams (or about 3 cups of coffee) per day.

To determine how much caffeine is in your favorite beverage or treat, Czerwony suggests starting by reading labels. Caffeine content may vary according to many factors, and different amounts are reported, but consider that the following are estimates:

Coffee — The caffeine in an 8-ounce cup of coffee varies according to whether it’s brewed, instant or decaf. “Contrary to popular belief, even decaf delivers a minor jolt of caffeine,” Czerwony says.

• Standard brewed coffee — about 85 (range: 65 to 120) mg of caffeine.

• Instant coffee — about 75 (range: 60 to 85) mg of caffeine.

• Decaf — about 2 to 4 mg of caffeine (decaffeinated coffee must be at least 97.5% caffeine-free).

Generally, the longer coffee is brewed, the more caffeine it contains.

“Brewing methods like french press coffee and the newer trends like cold press require longer brew times. Cold press coffee requires 10 hours or more,” Czerwony says. “These methods of brewing result in much higher amounts of caffeine, so you should pay specific attention to minimizing your intake of these kinds of coffee.”

Tea — A typical 8-ounce cup of tea contains a variable amount of caffeine. How much depends on how long you steep it and whether you prefer black, green or white:

• Black tea — about 40 (range: 20 to 90) mg of caffeine.

• Black tea decaf — about 2 to 10 mg of caffeine.

• Green tea — about 20 mg of caffeine.

• White tea — about 15 mg of caffeine.

• Herb tea contains 0 caffeine! (Most, but not all, herbal teas are caffeine-free and labeled as such on the box).

“To reduce caffeine levels further for tea, steep for five minutes, throw out the liquid and re-steep the tea bag in fresh water,” Czerwony says. “This should remove almost all caffeine.”

Soft drinks — 12-ounce sodas contain lots of calories and varying amounts of caffeine, from 54 mg in Mountain Dew to 34 mg in Coke to 0 mg in 7-Up. Even root beer and cream soda contain caffeine (though they also vary by product).

Energy drinks — Energy drinks are loaded with both caffeine and sugar. The caffeine content ranges from about 80 mg in an 8-ounce can of Red Bull to 320 mg in some of the newer 32-ounce energy drink brands. You should consume these carefully due to the high amount of caffeine in one can.

Chocolate — Dark chocolate may be good for your heart, but it can get it racing, too. Just one ounce contains 20 mg of caffeine, while the same amount of milk chocolate contains about 6 mg of caffeine. And parents: While an 8-ounce carton of chocolate milk allows your kids to get calcium, they’ll also get a hefty dose of sugar and caffeine (typically about 4 mg). And be sure to pay attention to the caffeine in all chocolate desserts too.

Coffee-flavored desserts — If you’re going to indulge in 8 ounces of your favorite coffee frozen yogurt or similar products, do it early in the day. These may be made with real coffee — and with an average of 85 mg of caffeine, it’s like drinking it. And that’s not something you want right before bedtime.

In general, remember that caffeine can be included in a healthy diet. But if you can’t drink coffee for any specific medical reasons or it doesn’t seem to agree with you, you should really look for decaf or low-caf options.

If you experience symptoms other than the occasional jitters, it’s suggested you seek medical care.