Category: Nutrition


How Late is Too Late for Coffee?

I, like many of you, have often wondered about the notion of drinking a cup of coffee after the evening meal. People often say things like, “I can’t drink coffee after 4PM or I won’t be able to sleep,” and this seems to make sense. Others, like myself, can enjoy a coffee after dinner seemingly without any consequences, as far as sleep is concerned.

To help shed some light on this issue, researchers publishing in the Journal of Clinical Sleep Medicine recently reported the results of study in which individuals consumed 400mg of caffeine 0, 3, or 6 hours prior to their normal bedtime. These folks were compared to a similar group of people who received a placebo. Sleep was measured by self-reporting as well as through the use of a portable sleep monitor.

The results showed that even when caffeine was consumed 6 hours before bedtime, there was a remarkable disruption of sleep. This was found to be associated with an average loss of sleep of 41 minutes as well as doubling the time it took these subjects to fall asleep. 

On the other hand, compared to placebo, caffeine consumption 6 hours prior to bedtime did not seem to affect the amount of wakefulness during the sleep period or the actual quality of sleep. Consuming caffeine 3 hours before bedtime, however, was clearly associated with disruption in the quality of sleep. 

Overall, the researchers of this small study of 12 individuals concluded that caffeine consumption at this dosage, and at these times prior to sleep, is significantly disruptive of this important and restorative bodily function.

My take on this report is that for those of us who might drink a coffee late in the day and don’t think much of it, the research would argue that there may indeed be consequences that are not readily apparent that could be harmful in the long run.

 So maybe decaf will turn out to be the best choice after dinner.

  • Courtney Schmidt

    I can’t have decaf either late in the day or it disrupts my sleep too!! I’ve tried several times! But I could drink a caffeinated soda with dinner with less effects, it seems. Which is weird. I don’t get it. But that’s me!

    • David Perlmutter

      If you know it doesn’t work for you Courtney, then best to avoid! Have to work on the plan that’s right for you and your body.

  • Lynn Dell

    Good to know. I like drinking a product from KeVita, which is their lemon-cayenne probiotic drink. It tastes like fizzy lemonade, and one of the cultures is l.rhamnosis. Good for unwinding, and extremely low in sugar, unlike their other probiotic brews.

  • DeAnn Morgan

    I have other issues with drinking coffee that disrupts my quality of sleep, I used to believe it was caused by caffeine but now believe it is something else. 1 cup of coffee in the morning will cause me to clench my teeth at night while I sleep and if I continue daily drinking coffee (3 days in a row) I develop white spots on my finger nails that my acupuncturist says is calcium deficiency. When I stop drinking coffee and drink CALM in the evening the clenching stops and the white spots fade away on my nails. CALM is a Magnesium supplement developed by Peter Gillham.
    If I drink black tea anytime during the day I don’t experience clenching or white spots on my nails which tells me it is not caffeine that is causing the problem. So now I am researching what is in coffee besides caffeine, something that may be pulling the calcium/magnesium away from the bones or not letting it get absorbed from the diet??? If anyone has any insight please share.

    • solitairecat64

      I recently purchased a cold brew coffee maker to enjoy a smoother cup of coffee. It’s been a few months and at my dentist appointment the other day he asked if I drink coffee and when I said yes he wondered why my teeth don’t have coffee stains like most coffee drinkers. I hadn’t thought about the cold brew coffee being less acidic (over 60% less) than hot brew but it seems that is why it’s not staining my teeth.

      According to this article https://livewell.jillianmichaels.com/magnesium-coffee-5186.html it is both the acidity and caffeine that impact magnesium levels. Another change I’ve noticed drinking cold brew coffee is it doesn’t have the laxative effect like the hot brew, so perhaps it isn’t resulting in as much mineral loss or wearing away at the villi of the small intestine as stated in the article.

      My husband has A-fib which can be caused or triggered by a magnesium deficiency so we’re using the transdermal magnesium gel from the same company you get your CALM. The combination of the less acidic cold brew coffee and magnesium supplementation have resulted in less of the muscle cramps he used to experience which are a symptom of magnesium deficiency. We’re hoping he can stay in remission with these simple changes, in combination with eating gluten free which may be the true cause of A-fib.

  • Megan

    400mg of caffeine? That’s not even remotely comparable to a cup of home brewed coffee which would contain between 80-120mg of caffeine. I’d prefer to see a study more rooted in reality!

    • Bill P

      I agree most definitely!

  • Magoo

    Can I add the prebiotic fiber by Garden of Life to a hot fluid like coffee or tea or will the heat destroy its benefits?

  • Ron M

    There is a gene that determines whether you are a fast or slow metabolizer of caffeine. Presumably fast metabolizers don’t have the same problem with it later in the day that slow metabolizers have.

    • Michelle

      Correct Ron, that same gene detoxes estrogens too. Something to think about for those who are prone to estrogen dominance.

  • I love the taste of coffee, but have found that I cannot drink at after 10am or I will be up all night and have unleashed energy the entire next day.

  • Bill P

    I personally can’t put much credence in the results of this study. Only 12 subjects were used, 6 female & 6 male, aged 19-48. Subjects were selected if they met either of the following criteria: (1) ≥ 3 servings of caffeine in any single day or (2) ≥ 5 caffeinated servings per week. Subjects who consumed > 5 caffeinated beverages per day were excluded from participation.

    The study gave the participants 400 mg of caffeine, yet this does not compare to the amount of caffeine that one cup of home-brewed coffee contains. The study itself states that “if home-brewed coffee was indicated, an 8-oz cup was calculated to be equal to 100 mg of caffeine (1 serving).”

    If I am at a dinner party and have one or two cups of coffee, that equals 200 mg of caffeine. My sleep is not disrupted, but that is my body. This may not hold true for other people. I think that we need to be aware of how caffeine affects our own bodies and not decide what to do based on a study of only 12 people under the age of 50 who are given more caffeine than what some might otherwise drink after dinner.

    • Prof. Elio Verde

      I consider that 400 mg of caffeine is a kind of rat killer

      • AnnieLaurie Burke

        Yes! According to many internet health sources, an average 8-ounce cuppa has under 100 mg of caffeine. So, you’d have to drink a quart of strong coffee to get 400 mg. And if you did, I’d postulate the full bladder would disrupt your sleep more than the caffeine, since the upper end of liquid volume for the average bladder is 600 ml, or about 20 ounces.!

    • AnnieLaurie Burke

      I’m with you, Bill. I used to try a cup of coffee late in the evening if I still had a lot to do and was feeling a little sleepy. It did nothing. I have consumed a cup right before going to bed, and fall asleep as quickly as always and sleep through the night, not even waking up to go tinkle. Usually, if I drink a cup of coffee, I have to get rid of the liquid in fairly short order. I will say, however, that when I was younger, say under 50 (now 72), even a cup of strong tea in the evening would keep me awake, so perhaps it’s an age-related thing. Maybe this experiment should be tried not only with a larger group, but also with some 50-80 year-olds included.

      • Bill P

        Interesting how things have changed for you as you’ve grown older, Annie Laurie. I should think that it would be more common for older people to have difficulty falling asleep due to coffee/caffeine consumption at night. In your situation, this wasn’t the case except when you were younger. As for me, I’ve almost always been able to fall asleep after drinking coffee…and I’m now 65. The only time I can remember having difficulty was once as an undergrad in college when at a Spanish Club gathering, I drank some very strong Colombian coffee at night. Thanks for sharing your thoughts!

        • AnnieLaurie Burke

          If I analyze for what might be different as I’ve gotten older, I think I get more work-related physical activity now. Before I retired (!), I was sitting a lot more at a computer terminal, worrying about deadlines and office/client politics (depending whether I was working directly for a company or consulting). Occasionally, I’d have a problem falling asleep because of some particular work-related concern, even when tired. It was more mental than physical fatigue. Since retiring, I am farming, albeit on a small scale, and running a small private animal shelter. I am not sitting as much, and I am moving more, so there’s more physical fatigue at the end of a day. And, the “job” worries are, at least subjectively, a bit more under my control. So, as science is now finding with so many potential problems, physical “exercise” has its benefits for falling asleep in spite of a little caffeine in the system.

  • frankjenson

    Coffee in the morning is a mild stimulant. Coffee in the afternoon is like a tranquilizer and puts me to sleep. In the evening I drink decaf. I haven’t tried drinking regular coffee right before bed; maybe it wiil help me sleep better!

  • Ermanno

    Make sure decaf coffee is Swiss water decaffinated. Most decaf coffees use chemicals in the decaf processing

  • Opal Misae Giger-Arnold

    As I noticed that there are coffees that keep me awake and others that don’t, I was comparing the beans and their origins and I found out that I myself have reactions to herbicides, fungicides or insecticides used, and their quantum, but not much to the caffein. Otherwise, I have no problem drinking several espressi after dinner if nothing else is added to it. Sugar or milk with coffee is for me detrimental, even if it’s organic beans. I would stick to the Arabica sort in the evening also. I think it’s a conbination af several factors which will determine how a person reacts to it.

  • Gianluca Toselli

    In this study the quantity of caffeine used is 400 mg. In Italy a coffe like espresso contains perhaps 80/90 mg of caffeine. Do you think that even this quantity of caffeine could have detrimental effects on the quality of sleep?

  • Sondra Harcourt

    I’ve always known that I have a very slow metabolism. I have my last coffee at around 3pm. Any later and I’d be tossing in bed for hours. We are all so unique that you often just have to pay attention to what your body tells you.

  • Ron

    The study, as you reported it, is useless because it says nothing about individual responses.

    If there was one person in the study who had no disruption, like you, then it doesn’t matter what the others experienced. The proper study title would then be, Coffee Before Bed Disruptive For Some, Supportive For Others.

    Further, in a sample size of 12, the likelihood there is an appropriate inclusion of all caffeine response types is nearly zero.

    I hate crappy science like that and am surprised you honored it with a stamp of approval by posting about it.

  • george

    Hi everyone,
    Just b4 I started my brain `rejuvenation` following d. Perlmutter `POWER UP YOUR BRAIN` book I been drinking 10 – 15 espressos a day. Waiting for my wife returning from her work around 23.00 we had a last coffee and bed time. No problem with sleeping at all. However as I mentioned when I started the diet and abruptly stopped my caffeine intake I suffered from double vision for couple of days.
    I went through `The Torture`, no alcohol/not a problem/ no caffeine /big challenge/ and cut to average 6 cuppa a day by now and feel like Spring time chicken. I am 67, working app. 10 hours a day in renovation field, only day off when taking my grandson to his BMX races.
    So my take on coffee is: GO FOR IT, IT IS GREAT, FOLKS

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