Coffee, coffee everywhere--but how much can I drink?

coffeeStroll along almost any street with small retail shops and you're likely to come to a coffee shop.  What?  You don't like the taste of coffee?  That doesn't matter.  It can be doctored with any number of high-calorie sweet flavorings to give you a beverage you'll adore.  But the big question is this: considering both the benefits and the unpleasant and sometimes unhealthful side effects, how much of the caffeinated version should you allow yourself to consume each day? 


In recent years, much has been made of the beneficial effects, along with a rather long list of problems associated with this ubiquitous beverage.  As most of us have noticed, coffee can perk us up, make us more alert, cheerful, and energetic. Beyond all that, if we've been contemplating suicide, it may help to drive away that depressing thought. According to the Tufts University Health and Nutrition Letter, "Coffee consumption has been associated with a reduced risk of some cardiovascular diseases, age-related cognitive decline and dementia, Parkinson's disease, stroke, and type 2 diabetes." These benefits are attributed to many different chemicals present in coffee, including caffeine. 


However, lest we forget, some folks may find that coffee also causes restlessness, insomnia, acid reflux, heart palpitations, and other undesirable reactions. Furthermore, Consumer Reports says that consuming two to three 8-ounce cups of brewed coffee daily "appears to increase bone loss that can lead to osteoporosis in postmenopausal women."  For this site's past discussion of the pros and cons of drinking caffeinated coffee, go to "Cheer Up! Have a Cup of Coffee."


Now let's pursue the answer to the question in the title and then check out some other interesting coffee facts.


What is the upper limit of safe coffee-drinking for adults and children, according to the EFSA?


The European Food Safety Authority (EFSA) published its draft scientific opinion on the safety of caffeine for adults and children early this year.  To translate the findings into cups of coffee is not simple.  The amount of caffeine in a cup depends upon the size of the cup, the way the coffee was made, and other factors. Consumer Reports says 400 milligrams (the EFSA study's recommended daily limit for healthy adults) would be the amount in 2-4 cups of coffee.  Food scientist Dr. Karin Allen says a cup of coffee has 65-150 milligrams of caffeine, with 100 milligrams being the average.  Also note that the EFSA draft tells us what amounts are safe, not what amounts are harmful.  Between safe and harmful, there could be a gray area such as "unknown" or "unsafe for certain people with certain conditions." Another matter to consider is what other sources of caffeine (besides coffee) a person may be consuming--for example, from energy drinks, tea, chocolate, or medications.


Now, here are the main conclusions from this EFSA draft:


  • A single dose of 200 mg of caffeine is safe for adults (ages 18-65) even less than 2 hours prior to intense exercise. "Caffeine intakes from all sources up to 400 mg per day do not raise safety concerns for the general adult population," the EFSA draft also says.  The only exception is for pregnant women.
  • For pregnant women, 200 mg a day is considered safe for the fetus.  For women who are nursing a baby, a single dose of up to 200 mg and a total daily dose of 400 mg are considered safe.
  • For children, the amount of caffeine considered safe depends upon body weight. Daily intakes of 3 mg per kilogram of body weight are considered safe.  (A kilogram equals approximately 2.2 pounds, which means 1.4 milligrams per pound.) This formula can be used for children ages 3-18.
  • A single dose of 100 mg of caffeine can increase the time it takes to fall asleep.   It can also shorten sleeping time if drunk just before bedtime.

 Dr. Allen has safety tips regarding caffeine and exercise: "Caffeine raises the heart rate and blood pressure.  Don't guzzle coffee or an energy drink as fast as you can. Sip it; consume it slowly.  The body is better able to handle gradual consumption of caffeine. Also, after drinking a caffeinated beverage, don't go straight to the gym and get involved in intense physical activity that is going to raise your heart rate even more."


Food scientist Dr. Catherine Cutter points this out: "How coffee affects a person depends, to some extent, on genetic make-up and how one metabolizes it." Yes! I've noticed that. My husband can drink a cup of coffee at the conclusion of a late-night dinner and have no trouble falling asleep a few hours later. But, if I did that, I'd be wide awake until at least 3 a.m.


Are the EFSA guidelines reasonable?


Here's the analysis of food scientist Dr. Clair Hicks:


"For an adult, the guidelines mean that one could drink 7.4 twelve-ounce cans of Mountain Dew (54 mg/can) each day or two 44-ounce Mountain Dews from a Speedway each day. This level would keep one's kidneys flushed and probably keep the person wide-eyed most of the day.  For the average two-year-old at 25 - 30 pounds, the guidelines say he/she could drink about 3/4 of a can of Mountain Dew and still be within the limit of 3 mg/kg.  In my opinion, these recommendations are probably higher than most consumers consume.  I have known people that consumed larger amounts of caffeine over prolonged periods, which led to nervous disorders (shaking) and heart issues, but this is probably not very common."


What should parents and adolescents know about caffeine's effect upon children?


Food scientist Dr. Joe Regenstein mentions hyperactivity as one effect coffee consumption can have on children.


Food process engineer Dr. Timothy Bowser offers this warning: "For children, excessive caffeine can be problematic, especially when combined with nascent judgment and popular drugs. Alcohol is a depressant and a very popular drug among teens. When caffeine is combined with alcohol, the effects of the alcohol may be masked, leading to excessive consumption of alcohol."


MedlinePlus (a U.S. National Library of Medicine, National Institutes of Health website) says this: "Caffeine may harm a child's nutrition if drinks with caffeine replace healthy drinks such as milk.  Caffeine cuts down on appetite, so a child who consumes caffeine may eat less."  However, Dr. Allen says, if kids drink soda rather than coffee, the acidity (the phosphoric acid) can have a negative effect on their bone density, and that may be worse than an occasional small cup of coffee.


How much caffeine is in various coffee drinks, energy drinks, expresso, and cola?


If you want to find out how much caffeine is in various beverages, here is a link that can lead you to the answers: "Caffeine Content of Drinks."


If you want to figure out how much caffeine you (or your children) should consume, go the Caffeine Calculator. It allows you to enter a person's weight (in pounds or kilograms), the type of coffee (or other caffeinated beverage) the person drinks, and find out that person's safe caffeine limit.  It told me that I could drink 5.5 cups (8 oz sizes) of instant coffee a day before my coffee consumption might kill me. It also said I can drink 126 cups of decaffeinated instant coffee per day and survive.  I don't think I'll try it. Note: The site's disclaimer says its goal is to provide entertainment not medical advice.  Still, it warns readers that very high doses of coffee can be "toxic and even lethal."


What else has been learned about the benefits of coffee?


In addition to the benefits mentioned in the second paragraph, here are some more:


Coffee & Health (from the Institute for Scientific Information on Coffee, a trade association): "Taken overall, the research indicates that caffeinated coffee consumed in moderation (typically 3-5 cups per day) has positive effects on both mental performance and endurance performance."  This publication also mentions that coffee has been shown to be beneficial for treating a number of diseases of the liver.


Findings published in the Journal of the National Cancer Institute: Recent research suggests that coffee drinking may be protective against melanoma (a dangerous skin cancer), according to a study conducted by the U.S. National Institutes of Health and AARP. The conclusions were based upon responses (from almost 450,000 white seniors in the U.S.) to a questionnaire asking about their coffee-drinking habits.  The responders were then followed for ten years.  Four or more cups of coffee per day was associated with a 20% reduced risk of melanoma, the Lincolnwood Review (a suburban newspaper that is part of the Chicago Tribune media group) reported. Previous research has indicated that coffee-drinking decreases the risk of other skin cancers.


Dr. Bowser: "I think the health benefits that have been associated with coffee and chocolate are because of the antioxidant content rather than caffeine."


Why doesn't the product label tell users how much caffeine is in an edible item?


The FDA says that the Nutrition Facts panel on food labels is required to include recommended dietary information for nutrients.  However, caffeine is not a nutrient.


Dr. Allen (our Board expert on all matters concerning food labels) also explains this: If caffeine is in a food naturally--that is, it is not added to it--then caffeine doesn't need to be on the label.  This is the case with coffee, tea, and chocolate. However, if caffeine is added (as in energy drinks), then the ingredients statement must include caffeine. 


Will caffeine help counteract the effects of alcohol?


According to the website MedlinePlus, "Coffee stimulates, or excites, the brain and nervous system.  It will not reduce the effects of alcohol, although many people still believe a cup of coffee will help a person 'sober-up.'"


Want to know more about coffee?  Click on the following link to reach information about the shelf life of various types of coffee and a list of Q/As on coffee:




Shelf Life Advice Advisory Board scientists:

Karin E. Allen, Ph.D., Utah State University, Dept. of Nutrition, Dietetics, and Food Sciences

Timothy J. Bowser, Ph.D., Oklahoma State University, Dept. of Biosystems and Agricultural Engineering

Catherine Nettles Cutter, Ph.D., Pennsylvania State University, Department of Food Science

Clair L. Hicks, Ph.D., University of Kentucky, Dept. of Animal and Food Sciences

Joe Regenstein, Ph.D., Cornell University, Dept. of Food Science "Cheer Up! Have a Cup of Coffee" have-cup-coffee


Tufts University Health and Nutrition Letter, "Ask Tufts Experts:  BMI math...Rx for coffee,..." November 2014. "Draft Scientific Opinion: Scientific Opinion on the safety of caffeine"


coffee &  "Caffeine: ISIC welcomes EFSA draft opinion on safety of caffeine" "Caffeine Content of Drinks" "Coffee Calculator"


Consumer Reports "The New Rules for Coffee and Wine Drinkers," December 2014.


medlineplus/ency "Caffeine in the diet" "Why isn't the amount of caffeine a product contains required on a food label?"



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