Circadian Rhythms

Entraining circadian rhythms is one of the pillars of the Perfect Health lifestyle. The five key circadian rhythm time-givers are:

  • Light
  • Physical activity. (For equipment supporting physical activity, see our Shop Exercise Equipment page.)
  • Food
  • Social interactions
  • Ambient temperature

Creating a good sleep environment is a sixth way to improve circadian rhythms.

Light Environment Supports

These products can help you optimize the light environment in your home or workplace.

Phillips Hue lighting system
  • App-controlled LED bulbs can adjust color
  • Use white light in day and yellow/orange at night
  • Currently not good for daytime, but excellent at night

Light boxes
  • Place within the field of view of your eyes during daylight hours
  • We no longer recommend blue only light boxes; use white light boxes

Natural white light bulbs
  • For indoor daytime lighting
  • Day: bright white lighting with a color temperature >5000K
  • Night: dim amber lighting with a color temperature <3000K

Amber bulbs
  • Use these in the evening and night to avoid disrupting night time rhythms
  • Left to right: 60 watt & 25 watt incandescent, 13 watt compact fluorescent

Amber glasses
  • Wear these when watching TV at night or when using the computer if you haven’t installed f.lux
  • An alternative to installing amber bulbs

Amber glasses
  • More choices. The yellow Solar Shield is the most popular at the Retreats

Wake up light
  • We don’t recommend alarm clocks, but if you need one, this is the best

Terrarium (UV) lamps
  • A low wattage source of indoor UVB to generate vitamin D and other sun-factors in the winter
  • 10.0 — high UVB; 5.0 — medium UVB
  • intended for skin not eye exposure

Floor lamp
  • To have separate daytime and night-time lighting, you may need more lamps

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  1. Hi Paul,

    links not working yet?

    • which ones? You may have an adblocker on that is preventing you from seeing them.

      • All of them actually 😀
        but you are right – it was the adblocker. Now it is working!

        Question: I am not from the US and regarding the amber glasses what do I have to watch out for. The most in my country say something like: UVA is reduced by 100% and UVB by 80%.
        Are these glasses sufficient?

        • Hi Mark, yes, that’s fine. The point of the glasses is not so much to block UV in the daytime as to block blue in the night, which they do quite well.

          I don’t know what Mumbo Amber means but I don’t think it matters.

      • and in addition: does it matter if the description says something like “Mumbo Amber” instead of “Amber”?

  2. Hi there – Why don’t you recommend blue light only light boxes?

  3. You mention the importance of ambient temperature on circadian rhythms a few times on the website (including this page) but don’t (as far as I could find) explain what that is or how to optimize. I understand that it is likely that we should go to bed in cooler room and then warm up upon awakening, but is there anything more to say about it than that?

    ps. delayed congratulations on your new(ish) baby!

  4. Hi Paul- In terms of degrees Kelvin, how low do you think nighttime light bulbs need to be? Supposedly firelight, candles, etc., are right around 1,800K, and morning sunrise begins at 2,000K. Would it be advantageous, then, to only use nighttime bulbs <2,000K? And if so, can you verify that the amber bulbs you've linked to have a color temperature below 2,000K? Thanks!

    • Hi David,

      I think the best thing to do is to get red or orange bulbs that filter the light to block all green, blue, and ultraviolet wavelengths. That way you can get decent brightness in the red-yellow without any blue. Such bulbs cannot be described by a single color temperature.

      Best, Paul

  5. Is there such thing as a dual switch light (with perhaps 4 or 6 lightbulbs) so one can have half of them orange to use for evenings and half of them white/blue to use in the mornings etc…
    Our house is dark so do need lights on during the day.

    • an alternate option would be the philips hue system listed by Paul above. but that could get expensive.

      there are cheaper variable color LED bulbs available with remote controls (infra red remotes i think) that could work out cheaper.
      here’s a link to the first one that popped up on Amazon,

      these are usually known as RGB or RGB (red green blue white) LED bulbs & you can vary the color of the bulb using the remote. i think there are about 15 or 16 color variations.

      i have not looked in to any of this myself (yet).
      have a read of the reviews on the amazon page linked, they may help give you an idea if these bulbs may be a fit for you.

  6. Episode 12: Circadian Rhythms with Paul Jaminet | Phoenix Helix - pingback on February 14, 2015 at 11:00 pm
  7. Hi guys,

    I am from Amsterdam. Does anyone have some tips on ordering some of those light bulbs for someone in Europe? I tried to order some on and, but i had some problems with that (especially with shipping and payment options).

    To give you guys an example, i tried to order this ones:

    And if you order them, do they need to have a special coating for blocking ‘the blue end of the spectrum’? Or is any ‘amber light bulb’ on amazon (for example) sufficient?

    Thanks in advance!

  8. does not eating breakfast make sleep worse…
    a few posts over here;
    seem to conclude Yes. ie. skipping breakfast is not a good idea.

    As a ‘breakfast skipper’ myself it was good to see a post with another point of view over here;

    Comments anyone…
    …&/or links to similar posts/articles/studies etc.

    Thanks All

  9. Paul, would it be a good wake-up-light hack to pair a programmable outlet timer with a lamp equipped with a Terrarium UV bulb rather than spending $200 on the Philips light alarm for those of us whom are on the frugal end of the spectrum?

  10. so, what is the best time of day to exercise? Does it depend on the type of exercise? If one is intermittent fasting, not eating the first meal until noon, when would be the ideal time to fit in exercise? I’ve always been an early morning exerciser but I get pretty hungry if I exercise early and need to wait until noon to eat. Some advise in this area would be greatly appreciated.

    • Hi Laura,

      The best time is late morning to late afternoon / early evening. At our retreats we have two exercise classes, one in late morning (10-11 am) and one late afternoon (4-5 pm). Either way they should come just before meals.

      Intense activity in the early morning is too stressful. Light activity, like yoga sun salutations or walking, is good.

  11. How do you recommend using the UVB lights? Are they low wattage for risk mitigation?

    Also, I don’t see any high wattage incandescents on here, but you seem to recommend red light therapy elsewhere.

  12. OPP 018: Paul Jaminet and The Perfect Health Diet - pingback on November 16, 2015 at 5:27 pm
  13. Do you have any advice for people living above the Arctic Circle, particularly for the Summer months when we have 24-hour daylight?

  14. Frustrating that popular yellow Solar Shield is not prime and, thus, there is a charge of $8.99 for shipping. 😥

  15. Hi Paul,
    We’re finally at the stage of trying to improve our lighting at home due to upgrading so I want to take this opportunity to get the best options. You talk about using white lights in the day but I’m not to clear about what that means. In the UK our LED lights that we use are called warm white. I see there are options of natural or pure white too:
    Which would be best?
    I’m thinking that the pure or natural white is best for daytime but if we can’t do orange light for evening perhaps I stick to warm white which would be less damaging to use in the evenings?
    My husband is not keen on doing orange lighting.
    Many thanks.

    • Hi Claire, for daytime you want a 5500K color temperature so that would be “Pure” lighting from that vendor.

      You do need a different type of bulb for night. Warm white is the worst of all worlds, bad for daytime and night time.

      Your husband should give orange bulbs a try in at least one room, most people find it very relaxing and pleasant.

      Best, Paul

      • Thanks Paul. Much appreciated. I’m passing the info on to my husband who is selecting lights.
        He also wants to get an LED strip to add to our kitchen over the worktops. He wanted warm white again but there is a RGB option which I am persuading him to get, since that will have an orange option. Would an orange RGB LED system be adequate to use as the orange lighting in the evenings for the kitchen atleast? Sorry to ask but I see it’s not one of your options listed but was hoping it will fulfil the criteria.

        At the moment most of our rooms have a dimer switch for our warm white lights. I have been using the dim function for the evenings hoping that would be enough. Is that helpful or not worth doing? He wasn’t keen on buying extra lamps and didn’t want to change the bulb of the one lamp we do have.

        But I’m hoping to atleast perfect the kitchen as I spend a lot of time in there.

        • Hi Claire,

          The key thing is to keep out green and blue from your night lighting. Anything from yellow to red is fine. The advantage of painted bulbs is that they filter the green and blue out, giving much better discrimination. LEDs can achieve this too but the common commercial red-only LEDs give a dim light which is hard to use for reading or many other functions, unless you have a very large number of LEDs; so RGB bulbs like the Philips Hue system tend to add some low-level green and blue which is circadian disruptive.

          I really hope the quality of offerings improves here, I think there is a big commercial opportunity for quality circadian-friendly lighting.

          • Thanks so much Paul! You stopped me from the mistake of buying the RGB LED lights to use as orange.

            We are now looking to change our old natural white lights for new pure white 5000K ones. Thank you so much for this information. It has been so helpful.

            It just occurred to me that perhaps it is my poor low level lighting(natural white at home and black out blinds at night, and not much outdoors in the winter months) that caused me to have very high melatonin levels last year in my adrenal test? I couldn’t figure out any other explanation. I never supplemented with it. You did once mention a link to excess seratonin but at the time I was unable to test for that. I’ve read that symptoms of too much seratonin can include “spontaneous trembling of your group muscles”. I did experience this several times. Each time it started just after lying down in bed to sleep. Suddenly my body would start shaking. This all started afeter a course of antibiotics called Trimethoprim (for UTI which I later found was due to Klebsiella p. gut infection). All my strange symptoms started over a year ago with that UTI and course of antibiotics. I just deteriorated after then…. I have since identified that klebsiella infection and some adrenal fatigue and high melatonin. I also found out that people with MTHFR defects (I’ve never tested for this) react badly to Trimethoprim. I wonder if there is a connection with MAO to dispose of seratonin (and I read it also helps dispose of norepinephrine and dopamine).
            I also had a miscarriage a week before the UTI. I know that the immune system shift post pregnancy can potentially cause health problems too.

            Been trying to put al the pieces of the puzzle together for why my health deteriorated. so much

            Am so happy that you helped me figure out that my day lighting was wrong. That will be a new piece to the puzzle to improve my health, for which I am very grateful.

      • Hi Paul. It seems to be impossible to find 5000K LED lights for our home. My husband wants LEDs. What would be better? 6000K LED lights or 2800K and use a light box in the house?

  16. If one works at a computer all day would there be any benefit to wearing blue light blocking glasses during work hours?


    • No. You want blue light during the day. There are some people who wear amber goggles or glasses beginning in the early evening though. Check

  17. Thanks Peter. I didn’t know if the blue light from the computer screen is bad for the eyes or not. I do wear my glasses at night.

  18. Paul,

    Would it be detrimental to go to sleep at 1am every night and wake up at 9 am as long as a normal sleep/wake schedule was maintained?

    You always hear about an hour of sleep before midnight being worth 2 hours after midnight. Is there any truth to this?


  19. Hi Paul,
    I’m getting very confused here.
    Just heard a talk by Dr Mercola on the Truth About Cancer Symposium this weekend. He said to avoid LEDs and fluorescent lighting in the home as they are the highest in blue light which is damaging to the eyes. He believes there will be an epidemic in eye sight problems due to the move to LEDs away from incadescent.

    Now, we were planning to replace all our bulbs with LEDs as they are more energy efficient so cheaper. But now I am worried. Are all LEDs high in blue light? We did buy one which is meant to be warm white (the standard in UK) but it does seem more blueish compared to our existing warm white spotlights.

    Is Dr Mercola right about the LEDs being high in blue light? All of them?! He showed graphs of various bulbs showing this. Or is he perhaps unaware that there are LEDs with less blue light? Or do all LEDs have blue light no matter where on the spectrum they are on…..

    I am really struggeling with this lighting issue, balancing having enough light at home and not too much blue light too.

  20. I spend a lot of time on my computer in the evening. I have installed f.lux. Can I wear orange goggles on top of that? I need to use textbooks too.
    I can’t replace the lightbulbs in my flat as I rent it (and the bulbs are the 3-pin bayonet BC3 variety!).
    Would going for a walk before turning in for the night be any help? The streets are quite dark around where I live, the city council is trying to save energy, and there are fields and meadows which are unlit (I go there to watch the stars!).

    • Hi Helen,

      You can purchase cheap floor lamps with regular bulb sockets and install orange lightbulbs in them. You can also cover your computer screen with a sheet of rubylith; that will be much more effective than f.lux (which still lets through a significant amount of blue light).

      Unless you do both of these, I would wear a good pair of orange or red glasses at night time. Glasses plus f.lux or glasses only is fine, either way; if you have a good pair of glasses, you shouldn’t be able to tell whether your computer is running f.lux or not.

      The UVEX glasses linked above are quite good, but I actually prefer this brand of red glasses:

      They don’t let through any green light either (which can also be disruptive to circadian rhythm), unlike the orange options which transmit wavelengths longer than 540 nm (which includes a significant portion of the green spectrum). The one downside is they don’t fit quite as snugly to the face as the UVEX ones, but that can easily be fixed with a bit of tape (foil tape works great since it blocks all light).


      • Hi Eric,
        Thank you very much for your detailed answer. Am placing the order for the red goggles, will look to get rubylith sheet next month. Have been thinking about floor lamps, but balking at the thought of schlepping them from the shop (bad back and not here during the day to wait for delivery of bulky items).
        I already struggle a little with the Uvex glasses as I have to wear them over my reading glasses (I am very far sighted). I wish someone would come up with comfortable goggles, or even a helmet like the ones used for welding!
        Best wishes.

  21. We’ve needed to keep some nightlight around the house since we have young kiddos. We’ve bought this pack of night light bulbs and just used Dollar Tree nightlight. This set has lasted us 3+ years:

  22. All pictures and links are broken :(?

  23. What is your opinion on sleep trackers?

  24. What about night shift work? As a police officer, I work nights on a two week schedule of two days on two days off three days in three days off. How do I incorporate the PHD into this – including fasting?

  25. Hello Paul,
    There’s a study which suggests that “Afternoon naps halve risk of fatal heart attack.”

    What do you think about this? Wouldn’t an afternoon nap disrupt circadian rhythms?


    • Hi Jayme,

      Sleep itself is not disruptive of circadian rhythms, but failing to get light, exercise, and food in the daytime is. So a few hours nap is no problem but a sleep that displaces light exposure, exposure, or food would be.

      Best, Paul

  26. Hi Paul,
    Dr. Mercola writes about the health dangers of LED lights:

    Don’t you think this is problematic in terms of your recommendation of Philips Hue lighting system?

    Best, Erik

  27. Hi Paul,

    is it a no-go when painted bulbs have 1-2mm blank (not covered in paint) space around the bulb socket?

    Thank you and all the best!

    • Hi Mark, Common sense can be your guide. If you are worried about it, wrap a strip of black electrician’s tape around the unpainted part of the bulb. Best, Paul

  28. Hi Paul,

    So are all LEDs bad news for health even if they were custom built with the correct frequencies/spectrum? For example (in reference to Eric’s comment above), is the Phillips Hue lighting system not ideal because it uses LED bulbs or because the spectrum of those LEDs is off?

    Do you have any papers that immediately come to mind or sources where we could find more info on this?

    Thank you! Nikki

    • Hi Nikki, it’s because of the spectrum. LEDs would be just fine if they emitted the right frequencies. We need lighting makers to focus more on health.

      Best, Paul

    • Hi Nikki,
      Additionally you want to look into something called flicker which has to do with the way LEDs produce light and incandescent bulbs don’t have. Flicker is really bad for you.

  29. Peter Sullivan

    Dear Paul,
    For the last 15 years I’ve suffered from stuffy nose that has turned me into a mouth breather and it affects the quality of my sleep and overall life. Do you know of anything that I can do to solve this?

    • Hi Peter,

      Try getting extra vitamin A, along with vitamin D optimization.

      Best, Paul

    • Hi Peter, you may want to try systemic enzymes: serrapeptase and nattokinase. I use the Natto-serra supplement which combines both, and have seen some improvements. Make sure you take them on an empty stomach and at least 30-45 min before any food, otherwise they will be used for digestion instead of being absorbed into the body.

  30. For those of us who work indoors with inadequate lighting, can we use a light box continuously during the day to simulate sunlight? Or is it best only to use it for 30 – 60 minutes in the early morning?

    • Oh, never mind. Bright white light with color temperature >5000K, got it. I should be able to find a desk lamp that fits that criteria for my work station.

  31. Why can I not see the recommended yellow light bulbs? I do not have an ad blocker and am needing to replace bulbs. Years ago I purchased a good supply but the store no longer stocks them. What do you suggest? When I look on Amazon, all I see are “bug lights.” Please advise. 🙂

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