The Buzz on Caffeine

About 85% of Americans drink at least one caffeinated beverage every day. But is caffeine good for us? Is it helping or harming our health?

How does caffeine work?

Caffeine is a stimulant. Adenosine is a natural sedative that builds up during the hours that we are awake, and the adenosine molecules break down while we are sleeping. Caffeine blocks adenosine receptors in the brain so that adenosine can’t cause drowsiness. So caffeine acts as a stimulant. When a person consumes more caffeine, their brain will make more adenosine receptors. This means that a person would need even more caffeine to block the extra receptors to help keep them alert. As a result, you can build up a tolerance to caffeine.

There are some downsides to consuming caffeine. Caffeine can make you jittery and disturb your sleep. It can raise your blood pressure for several hours after you consume it. Energy drinks have been linked to irregular heart rhythms and increases in heart rate and blood pressure.

How much caffeine is too much? The Food and Drug Administration says that most adults can consume up to 400 mg of caffeine a day. To give you an idea of the amount of caffeine in common food and beverages:

• 20 ounce (Venti) Starbucks Coffee (Pike Place Roast): 410 mg
• 16 ounce (Grande) Starbucks Caffe Latte or Cappuccino: 150 mg
• 10 ounce (Grande) Starbucks Coffee Frappuccino: 95 mg
• 16 ounce (Grande) Starbucks Decaf Coffee (Pike Place Roast): 25 mg
• 1 pod Keurig K-Cup, most varieties: 75-150 mg
• 2 Tbsp Folgers Classic Roast (makes 12 ounces): 120-160 mg
• 16.9 ounce Pure Leaf Unsweetened Black Tea: 77 mg
• 1 bag Lipton Black Tea (brewed): 55 mg
• 12 ounce Mountain Dew (diet or regular): 54 mg
• 12 ounce Dr. Pepper (diet or regular): 41 mg
• 8.4 ounce Red Bull (regular or sugar-free): 80 mg
• 5.3 ounce Dannon Lowfat Coffee Yogurt: 40 mg
• 1.4 ounce Hershey’s Special Dark Chocolate Bar: 20 mg
• 1 packet Swiss Miss Milk Chocolate Hot Cocoa Mix: 1-3 mg

Caffeine’s effects can vary from person to person due to genetic variability in the activity of the enzymes that metabolize caffeine. On average, it talks about 3-5 hours for a person’s body to break down half of the caffeine. So if you drink a cup of coffee containing 400 mg of caffeine at 2:00 PM, about 100 mg of the caffeine could still be in your body between 8 PM and midnight, blocking adenosine receptors. You can generally can tell if your body metabolizes caffeine more slowly based on how wired you feel after consuming caffeine. People who are more affected by caffeine would likely choose to consume less caffeine.

Sleep and Caffeine

Some studies show that when people are given caffeine right before going to bed, they take longer to fall asleep, get less deep sleep, and wake up more often throughout the night. One study looked at people who consumed caffeine regularly and who also had trouble sleeping. The participants gave up caffeine cold turkey but still took the same amount of time to fall asleep and spent about the same amount of time asleep as when they were using caffeine. However, another small study gave the participants (who regularly consume caffeine) either a placebo or 400 mg of caffeine 6 hours, 3 hours or immediately before bedtime on separate days. The participants who received the caffeine slept about an hour less no matter when they received the caffeine compared to those who received the placebo. So the bottom line? If you think caffeine is preventing you from getting a good night’s sleep, either cut back on the amount of caffeine you use or avoid caffeine after mid-day.

Type 2 Diabetes

A number of studies have shown that coffee consumption is consistently associated with a lower risk of developing type 2 diabetes. One analysis of 28 research studies showed that the risk of developing type 2 diabetes was 6-8% lower with each daily cup of coffee (8 ounces) up to 6 cups per day. An important point to keep in mind is that an “association” does not mean that the coffee consumption is what causes the lower risk. In addition, people who drank either regular or decaffeinated coffee both had a decreased risk so a component of coffee other than the caffeine may be responsible for the decreased diabetes risk.

Exercise Performance

In an analysis of 21 studies, when study participants were given between 200 and 400 mg of caffeine, their exercise performance was increased by about 3%. A small research study showed that men who had caffeine on a particular day burned 5% more calories, pedaled 5% harder and pushed their heart rates 5% higher while riding stationary bicycles compared to a day when they received a placebo. What accounts for this boost in performance? Caffeine can reduce feelings of fatigue and decrease the perception of muscle pain which can lead to the feeling that exercise is a little easier. You may be able to push yourself a little harder after consuming some caffeine.

LDL Cholesterol

When 400 mg or less of caffeine is consumed, caffeine doesn’t increase a person’s risk of developing heart disease. However, some methods of brewing coffee (either regular or decaffeinated) can raise LDL cholesterol and lead to heart disease. Drip-filter methods of brewing coffee allow a compound called cafestol to remain in the filter and not get into the coffee you drink. The cafestol is what raises LDL levels. When coffee is made with a French Press or boiled (like Scandinavian or Turkish coffee), the cafestol is not filtered out. One study of 64 adults showed an increase in LDL cholesterol of 16 points in the adults who drank unfiltered coffee compared to the adults that drank filtered coffee. So if you already have elevated LDL levels, it would be a good idea to drink filtered coffee and save the French Press for a special occasion.

Parkinson’s

In Parkinson’s disease, the loss of dopamine causes movement issues. Caffeine improves dopamine signaling in the brain. So could caffeine consumption decrease the risk of Parkinson’s or help slow its progression? In one study that tracked about 138,000 people for up to 32 years, people who consumed the most caffeine (about 600-800 mg/day) had a 38% lower risk of developing Parkinson’s compared to people who consumed the least amount of caffeine. However, like the risk of developing type 2 diabetes, it may not be caffeine that is leading to the decreased risk that was seen. In a study that looked at the use of either 200 mg of caffeine twice a day or a placebo in patients who already have Parkinson’s, there were not any obvious improvements in movement in the patients who received the caffeine. Therefore, caffeine is not currently recommended for management of Parkinson’s symptoms.

Phentermine and Caffeine

By now you may be thinking that the potential benefits outweigh the risks of drinking coffee and/or other caffeinated beverages, and you may also be thinking you definitely should keep drinking coffee and perhaps even increase how much coffee you drink. However, if you are taking phentermine, it is recommended that you limit the amount of caffeine you consume while taking phentermine. Both phentermine and caffeine are stimulants. They both can cause insomnia, increased heart rate and jitteriness. If you use caffeine while taking phentermine it is likely these side effects will be increased.

The bottom line: Consider decreasing the amount of caffeine you consume while you are taking phentermine, especially if you are experiencing some of the side effects mentioned above. Even if you are not taking phentermine, limited your caffeine consumption to 400 mg or less per day is a good idea. If you tend to like to drink coffee beverages or other caffeinated beverages that contain added calories or add cream and sugar to your coffee/tea, you are adding extra fat and calories to your daily intake. Therefore, decreasing the amount of caffeinated beverages you drink could also help with your weight loss efforts.

Information was summarized from “The Best Part of Waking Up? Is Caffeine Helping or Harming Your Health?” in Nutrition Action Healthletter, March 2021.