The Buzz on Caffeine

Caffeine: Most of us can't get through the day without it. Whether brewing a fresh pot of coffee in the morning, enjoying lunch with a refreshing can of cola, or recharging in the afternoon with an energy drink, we have many routines and food rituals revolving around this energizing substance. Found naturally in the leaves, seeds and fruits of more than 60 plants (including cocoa beans, kola nuts, guarana, yerba mate, green tea extract and tea leaves) and added to many other foods and beverages, caffeine is the world's most popular stimulant. In the US alone, more than 80% of adults consume it. 
Like many commonly enjoyed foods and ingredients, we get mixed information about caffeine. Sometimes we hear it does a body good. Other times, we hear it's bad for us. Keep reading to uncover the truth about caffeine: how it works—and how it affects your health.
Why Caffeine Keeps You Charged
The brain produces a natural sedative called adenosine, which binds to the appropriate receptor sites in the brain, resulting in a drowsy feeling. Adenosine levels rise during daytime/waking hours, encouraging sleep in the evening. While sleeping, adenosine levels drop, so you awaken refreshed and raring to go.  
Caffeine is similar in structure to adenosine. It temporarily binds to adenosine receptor sites in the brain.  This prevents adenosine from attaching itself to the sites and thus, wards off fatigue. If you regularly consume caffeine, you might also discover that you build up a tolerance because the brain makes more receptor sites as a result. Therefore, you need more caffeine to attach to these new sites and get the same results.

While caffeine is one of the most studied ingredients in food supply, there is still great confusion regarding its effects on health. For years caffeine has been included on the U.S. Food and Drug Administration's list of substances that are "generally recognized as safe" (GRAS) list. Extensive research has been conducted on numerous health aspects of caffeine consumption. Here is a synopsis of the findings regarding caffeine and health.
5 Health Benefits of Caffeine
  • Dementia Risk: While it is too soon to tell about caffeine's role in the prevention of dementia in humans, there are some preliminary animal studies showing that it might help to protect against dementia. 
  • Headache Treatment: The blood vessels in the brain dilate (enlarge) during a headache. Caffeine constricts the blood vessels, which lessens the pain. It is also a mild pain reliever. This is why caffeine is found in headache medications like Excedrin Migraine (130 mg per 2 tablets), Midol Complete (120 mg per 2 tablets) and Anacin (64 mg per 2 tablets).
  • Mental Stimulation and Problem Solving: Caffeine has been shown to speed up reaction time and improve processing skills, such as paying attention, solving arithmetic problems, typing and proofreading.
  • Parkinson's Disease: Several preliminary studies have shown that higher caffeine intake can reduce one's risk for developing Parkinson's Disease. In fact, caffeine might help improve tremors and motor skills in people who already have the disease. However, the benefits could lessen as a person develops a tolerance to caffeine. 
  • Physical Performance: Low to moderate doses of caffeine (200-300 mg) have been shown to improve athletic performance in well-trained athletes, especially in endurance events like running. However, in sports that require short bursts of movement like weight lifting or sprints, caffeine is less effective. Caffeine might help with the burning of fat for energy after exhausting the carbohydrates stored in the muscles. Caffeine also helps reduce the feeling of muscle pain and tiredness, so one feels better while exercising.
4 Health Risks of Caffeine Consumption
  • Complex Tasks: Caffeine can worsen performance on complicated tasks, and with caffeine usage over time, the mental boost one gains from caffeine is reduced.
  • Fertility and Pregnancy: The March of Dimes recommends that women who are pregnant or trying to get pregnant consume no more than 200 milligrams of caffeine per day due to possible adverse effects on fertility, miscarriage and fetal growth.
  • Fibrocystic Breast Disease: While it does not cause this condition, caffeine can aggravate the symptoms in some women who already have the disease. 
  • Sleep: Consumed later in the day, caffeine can interfere with the onset of sleep and especially rapid eye movement (REM) sleep. Most people report difficulty falling asleep when consuming caffeine within six hours before going to bed. Your sensitivity will vary based on how quickly your body metabolizes caffeine, the amount you ingest and your regular consumption amount.  
6 Things Caffeine Has NO Affect On
  • Cancer: Current research does not show a link between caffeine intake and cancer in humans. 
  • Dehydration: Caffeine is a mild diuretic that can increase the frequency of urination. However, the fluid you consume in the caffeinated beverage tends to offset the fluid loss when you urinate. Studies have shown that caffeinated beverages do not cause dehydration. 
  • Heart Disease or High Blood Pressure: Caffeine has not been shown to increase the risk for cardiac arrhythmias, coronary heart disease, stroke or the development of chronic hypertension. It has not been shown to increase cholesterol levels or alter lipid profile.
  • Osteoporosis: Caffeine has not been shown to be a risk factor in the development of osteoporosis, especially in adults with adequate daily calcium intake. It does not alter calcium absorption or excretion significantly.
  • Reduced Intoxication: When intoxicated from too much alcohol intake, caffeine does not "sober you up" faster.
  • Weight Loss: Because caffeine is a stimulant, it does speed up metabolism, but the effect is only minimal and very short term. Clinical research does not show a significant weight loss with the use of caffeine-containing supplements. Therefore, save your money and leave those supplements (which can contain up to 300 mg of caffeine per dose) on the store shelf.  
How Much Caffeine Are You Consuming?
While a moderate caffeine intake up to 400 milligrams a day is considered safe for a healthy adult, it is not mandatory for the amount of caffeine to be listed on the label of foods, beverages or supplements.  Therefore, determining your daily intake can be difficult. The chart below shows estimated caffeine contents in commonly used foods, beverages and pills. The amount will vary based on ingredients used, brewing method, brewing time and a company's formula.

Other nutritional supplements, such as weight-loss supplements, vitamin-mineral supplements, and sport-enhancing supplements might also contain caffeine in varying amounts. To determine if a supplement contains caffeine, look for plant names that contain caffeine on the ingredient list such as guarana, yerba mate, kola nut and green tea extract. Since products and formulas change, contact the company to see if the exact caffeine amount is available.  

Product Caffeine (mg) 
Brewed coffee, 8 oz 80-160
Instant coffee, 8 oz 50-90
Decaf coffee, 8 oz 3-8
Alertness medication, pill 100-200
Appetite suppressants, pill 100-200
Headache medication, pill 65
Brewed black tea, 8 oz 30-90
Yerba mate, 8 oz 85
Instant tea, 8 oz 25-50
Iced tea, 8 oz 10-50
Green tea, 8 oz 25
Herbal tea, 8 oz 0
Flavored Milks:  
Chocolate milk, 8 oz 2-7
Chocolate soy milk, 8 oz 4-5
Soft Drinks:  
Mountain Dew, 12 oz 54
Cola, 12 oz 35-50
Root beer, 12 oz 0-25
Energy Drinks:  
Energy shots, 1.9 oz 200
Energy drinks, 8 oz 80-100
Energy vitamin water, 20 oz 50
Energy gum, per piece 35-100
Coffee ice cream, 4 oz 20-50
Dark chocolate, 1.5 oz 10-50
Milk chocolate, 1.5 oz 5-20
Hot chocolate, 8 oz 13
Chocolate flavored syrup, 1 oz   4-5
Chocolate ice cream, 4 oz Less than 1

Cutting Back on Caffeine:  If you decide it's time to cut back on your caffeine intake, there are two basic approaches you can try:
  • Go Cold Turkey: Consider all of the typical sources of caffeine that you might consume, then remove some or all of them at once to reach your desired upper limit of caffeine per day. You will probably experience caffeine withdrawal symptoms such as headaches, drowsiness and tiredness. These discomforts usually subside in 4-7 days.
  • Cut Back Slowly: Determine your typical daily caffeine intake and sources of caffeine. Remove about 50 milligrams of caffeine from your diet to start. Stay at this amount for several days to allow your body to adjust. Then cut back another 50 milligrams. Continue with this process until you reach your desired level of caffeine consumption.  
The Final Scoop 
In moderation, caffeine can increase alertness, performance, productivity and may have some health benefits. Too much, however, can ove-stimulate the nervous system and bring about restlessness, irritability, and insomnia. Based on current evidence, the U.S. Beverage Guidance Panel suggests that moderate caffeine intake up to 400 milligrams a day is safe for healthy adults and is not associated with increased risk of heart disease, hypertension, osteoporosis or high cholesterol. Discuss your daily caffeine intake plan with your doctor as it relates to your medical conditions and tolerance. 
Note:  This article was specifically researched and written regarding caffeine intake and the adult population. Refer to the American Academy of Pediatrics for information on caffeine intake for children and adolescents. 
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Center for Science in the Public Interest, "Caffeine Content of Food and Drugs,", accessed on October 21, 2013.
EnergyFiend, "Caffeine Amounts,", accessed on October 21, 2013.
Eskelinen MH, Kivipelto M. "Caffeine as a protective factor in dementia and Alzheimer's disease." J Alzheimers Dis. 2010;20 Suppl 1:S167-74.
Hodgson AB, Randell RK, Jeukendrup AE. "The metabolic and performance effects of caffeine compared to coffee during endurance exercise." PLoS One. 2013;8(4).
Hursel R, Viechtbauer W, Westerterp-Plantenga MS. "The effects of green tea on weight loss and weight maintenance: a meta-analysis." Int J Obes (Lond). 2009 Sep;33(9):956-61.
Lieberman JA, Sylvester L, Paik S. "Excessive sleepiness and self-reported shift work disorder: An internet survey of shift workers." Postgrad Med. 2013 May;125(3):162-71.
March of Dimes, "Caffeine in Pregnancy,", accessed on October 21, 2013.
Nawrot P, Jordan S, Eastwood J, Rotstein J, Hugenholtz A, Feeley M.
"Effects of caffeine on human health." Food Addit Contam. 2003 Jan;20(1):1-30.
Palacios N, Gao X, McCullough ML, Schwarzschild MA, Shah R, Gapstur S, Ascherio A. "Caffeine and risk of Parkinson's disease in a large cohort of men and women." Mov Disord. 2012 Sep 1;27(10):1276-82.
Rosalie Marion Bliss, ARS. "Caffeine-Containing Botanicals in Dietary Supplements," Agricultural Research, April 2009.
Sengpiel V, Elind E, Bacelis J, Nilsson S, Grove J, Myhre R, Haugen M, Meltzer HM, Alexander J, Jacobsson B, Brantsaeter AL. "Maternal caffeine intake during pregnancy is associated with birth weight but not with gestational length: results from a large prospective observational cohort study." BMC Med. 2013 Feb 19;11:42.
Snel J, Lorist MM. "Effects of caffeine on sleep and cognition." Prog Brain Res. 2011;190:105-17.
The Nutrition Transition, "Tea, Coffee, Unsweetened,", accessed on October 21, 2013.
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Member Comments

ďDon't judge each day by the harvest you reap but by the seeds that you plant.Ē ? Robert Louis Stevenson ~ 1/10/18 Report
thanks. Report
Very informative! Report
Great info. I like the caffeine chart. Report
Great information! Report
Finally! Something I am actually doing well in! hoorah! Report
great information Report
Excellent article, good need-to-know information. Report
coffee a major source of caffeine and anti-oxidants has been found to be beneficial for the liver
cheers Report
For me, 2 cups of coffee, a cup of tea and a piece of dark chocolate will work out just fine. Report
Interesting Report
Please note that they amount of caffeine in a cup of coffee or tea depends on the brand, brew-strength, and even the species of plant used. Report
Caffeine didn't used to bother me as much as it does now. Even diet Pepsi or Coke will affect my sleep. Sometimes it is will be 2-3 in the morning. Report
For me, itís not caffeine at all, itís taste. I brew decaf or regular, cheap, etc. Iíve been drinking watered down coffee since age 5, because a cold glass of milk always made me sick, first thing in the morning. So I got used to it. I never drink any of those popular flavored drinks, canít stand the sweetness. Black coffee is it . Tried tea, tea does something bad to my kidneys, makes me have to pee right away. I stick to coffee, iced in summer and hot in winter. Iím in my 70ís. Plain water makes me sick! Report
Coffee is a great treat to enjoy. I think in moderation it can be beneficial. I usually drink tea as well which is calming. Report

About The Author

Becky Hand
Becky Hand
Becky is a registered and licensed dietitian with almost 20 years of experience. A certified health coach through the Cooper Institute with a master's degree in health education, she makes nutrition principles practical, easy-to-apply and fun. See all of Becky's articles.
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