Doctor's Note

Check out these videos for more on sleep:
Kiwifruit for Insomnia
Tart Cherries for Insomnia

And check out the prequel: Sleep & Immunity

Also see my associated blog post, Eating To Extend Our Lifespan.

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  • Michael Greger M.D.

    Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. And check out the prequel, “Sleep & Immunity.” Also, there are 1,449 other subjects covered in the rest of my videos–please feel free to explore them as well!

  • amylee83

    Hi Dr. Greger!
    I recently had a sleep study done and was diagnosed with mild sleep apnea and severe periodic limb movement disorder. I am 28, of normal weight, and do not want to sleep with a CPAP machine for the rest of my life, so I was wondering if you knew of any nutrition based or alternative treatments for these disorders. I do know that anemia is connected with periodic limb movement and right now my ferritin is 37 (started at 12). I’ve heard that ferritin levels between 70 and 90 are optimal. Do you know anything about this?


  • Thatsleepguy

    Hello Dr. Greger. I am a sleep therapist and have a question. Did this study cited in the video test subjects at differnt ages. We currently teach different total hours of sleep needed depending on age. HGH in children is better utilized and produced during Delta sleep. (conitued research has shown me I know nothing*gulp*)

    • veganguy

      Hey I have recently been wondering if sleeping for 90 mins 4 times a day increases HGH levels at all. What benefits are there to breaking up sleep cycles?

  • ranchita

    I wonder about the age variable to!

  • Matthew Ciuccio

    This is great information. That give me 17 hours a day to other great stuff. Thanks Doctor!

  • iVegan, CPT

    This is very helpful. Recently up to 12 hours of sleep can be beneficial. Thank you for clearing that up!

  • iVegan, CPT

    Dr. G. I have a question about optimal duration for people who do rigorous exercise. If one eats vegan drinks enough water and does everything they are supposed to do nutritionally how much does the variable of intense rigorous exercise and sort about 5 times a week affect the equation. Is 7 hours still the magic number?

  • I just can’t “buy it” – unless there is a nap involved. There has to be a lot of factors involved including quality of sleep, time of the year, etc.

  • greyjaybee

    As someone who wakes up around every 2 or three hours at night, does this mean I’m doomed ?

  • LizB

    How do we know that the sleep duration causes morbidity rather than that it is simply associated with it? Could it be that people who are unwell already, though without knowing it, sleep longer?

    • As you mentioned there are many variables and the study just provides correlational data so you have to be careful when attributing a causal relationship. Based on the article and others cited it appears that regular sleep of 7 – 8 hours duration is best when studying populations. However, I’m sure there are variations between individuals and their individual situations.

  • Renee

    So, 8 hours in bed, then, allowing for pee breaks and going to sleep/waking up and Other Stuff. Possibly up to 9 hours, just to make sure there’s plenty of time… I think we need to schedule in more than 7 hours, yes? To make sure we get the requisite amount.

    And after being sleep-deprived for some time (children) I was sleeping 8-9 hours for a few months. That + catch-up nights are not going to kill us earlier, right? We modern humans are a tad inconsistent… On that note: does having children and having our sleep messed up mean we’ll live longer or shorter lives? All the centenarians I’ve met have had children, but that’s a small sample size… and I’m going off on a tangent here…

  • Gayle Delaney

    Since the psychology of dreams is my specialty, I have experimented with various sleep patterns and lengths.

    My favorite is sleeping 5 hours at night and 2-3 in the afternoon. Over a year of this, my desired sleep was reduced from 8 to 7 hours per 24 hours. Best of all, I felt I got to live a double life. For example, at my annual ski weeks in Zermatt, When sleeping in two “sleeps” I could ski with the serious skiers from 8 am to 4pm, take my nap, missing the group apres-ski drink then dinner and dancing till 1am with the snow bunnies. Before that I had to choose between my delights.

    However this pattern is so unlike the dominant one in the US that I have let it go and now sleep in one stretch. This way, I usually need a full 8 hours to feel happy and energetic.

    Steve Allen, Host of the original “Tonight” show, author of 40 books and many, many songs, and creator of “The Meeting of Minds” PBS shows wrote me that he absolutely needed 10 hours of sleep. No one can say he was not creative and productive. However, I do not know any of the details of his health and cause of death. AH but what a life he lived!

  • Elizabeth Kenney

    Have you ever heard of anyone being sensitive to omega 3’s . . . in that they cause insomnia. . . not sure if that is a slow metabolizing problem . . .
    or what? Thanks so much! I just found out about you today!

    • Thea

      Elizabeth: I don’t personally have an answer to your question, but I wanted to welcome you to It really is a great resource. I encourage you to check out all the amazing videos on this site. Most of the videos are very short, single-topic focused. However, you might also want to check out Dr. Greger’s two hour-long presentations that summarize some of the latest info. They are great talks that blew me away!:

      Hopefully someone else will have an answer to your question about omega 3s. Though please keep in mind that a great many of the questions that people ask on this site have an a answer of, “we don’t know yet” and often do not get answered.

      Good luck.

    • Toxins

      How do you mean that? Is there a specific food that is causing you trouble? Omega 3 is essential to survive.

  • Mark Welch

    Dr. G or NF Team,
    For years I have heard the early-to-bed, early-to-rise folks claim that the hours of sleep before midnight are worth twice as much as the hours after 12am. So, for example, if I’m up till midnight but my schedule allows me to sleep in to 8am (12-8), I’m not getting the same “quantity” as someone who hits the sack at 10pm and gets up at 6am. Or maybe what they really mean is that the hours before midnight are worth more – that the quality of that sleep is somehow higher. You thoughts?

    • Toxins

      Perhaps the quality of sleep may be higher when sleeping earlier, but it sounds more subjective to me. Based on personal experience, the quality of sleep is poorer the later I sleep. Perhaps too the later we sleep, the less hours we have before light creeps through the window blinds. Of course, this is all my personal hypothesis.

      • Mark Welch

        I was hoping there might be some sleep research that would speak to the assertion that the hours before midnight are worth twice as much as the hours after.

  • Dale

    I hypothesise that sleep duration is affected by health, and diet can impact on this. So if your diet has inadequate intake of antioxidants, then your body may sleep longer for enhanced recovery. Melatonin is a powerful antioxidant after all! A study looking at diet and sleep duration would be useful.

  • Rebecca

    Do you have any nutrition based suggestions for treating borderline narcolepsy? My mom was on Provigil for years but stopped taking it because it was causing her to have chest pain. She is having trouble staying awake at work despite drinking caffinated beverages throughout the day.

  • vincent richard

    I was wondering is 7-8 hours was enough for athletes? thank you