To B or Not to B: Ultraviolet B Waves for Better Sleep!

With Spring upon us bringing longer days, and since daylight is essential for getting restorative, nocturnal sleep, it’s the perfect time to address which hours of the day deliver the most sleep-influencing sunrays.

Before jumping in, let’s quickly review how sunlight is helpful to sleep in the first place. Light signals to your brain to wake up and stay up. It provides a morning foundation for your master clock to support a healthy and natural 24-hour rhythm. In fact, light at night is problematic since it misleads the brain into thinking it’s daytime and, consequently, the evening release of melatonin, the sleep hormone, is delayed.

Natural, outdoor sunlight also helps you to sleep by supporting the body to manufacture vitamin D

While vitamin D influences weight loss, improved mood, maintaining strong bones, and decreasing colon cancer risks, studies have also found that low vitamin D levels are associated with less sleep as well as with more disrupted sleep.

Here’s the kicker...not all sunlight helps to produce vitamin D! For the purpose of this discussion, I’m going to focus on ultraviolet A, and particularly UV-B waves. While both can cause sunburn, (which you should avoid at all costs due to possible skin damage including cancer), only UV-B waves help to make vitamin D. And, ultraviolet B waves are by far the best way to maintain healthy vitamin D levels.

Vitamin D supplementation, which is great in the winter, as well as eating foods like wild salmon, mackerel, sardines, beef liver, eggs, cod liver oil and mushrooms also augment vitamin D.  While supplementation can be quite effective, maintaining appropriate D levels through diet is difficult since you would need to consume the specific foods listed above on a daily basis.

How can you get UV-B exposure to heighten your vitamin D while limiting the risk for melanoma?

UV-B is not readily available during the winter. In fact, if you live in the States north of Atlanta, it’s virtually impossible to produce vitamin D from the sun since it doesn’t get high enough in the sky for ultraviolet B waves to penetrate the atmosphere.

In New York City, ultraviolet B is absent for 6 months of the year between the Autumnal and Spring Equinoxes. To track the exact days and times when ultraviolet B is present where you live, check out the United States Naval Observatory site at:

USNO Sun or Moon Altitude/Azimuth Table

Once on the USNO site, enter your specific location and the date, then click Compute Table. A table will appear with three columns. Go to the center Altitude column and look down for any and all numbers 50.00 or greater. (Fifty or higher indicates that ultraviolet B is present.) To the left of this column are the corresponding times of day.

Have a look below at the sample Sun Altitude Table for New York City, April 1st, 2019:

Astronomical Applications Dept.                                              

U.S. Naval Observatory                                                       

Washington, DC 20392-5420

NEW YORK, NEW YORK                                                                                         

Altitude and Azimuth of the Sun                                               

Apr 1, 2019                                                           

Eastern Daylight Time                                                  

h m        Altitude    Azimuth                                                                                                                      10:20       39.2       124.4

10:30       40.7       127.0

10:40       42.2       129.7

10:50       43.6       132.5

11:00       45.0       135.4

11:10       46.3       138.4

11:20       47.5       141.6

11:30       48.7       144.9

11:40       49.7       148.4


11:50       50.6       152.0

12:00       51.5       155.7

12:10       52.2       159.6

12:20       52.8       163.5

12:30       53.3       167.6

12:40       53.6       171.8

12:50       53.8       176.0

13:00       53.9       180.2

13:10       53.8       184.4

13:20       53.6       188.6

13:30       53.3       192.7

13:40       52.8       196.8

13:50       52.2       200.8

14:00       51.4       204.6

14:10       50.6       208.4


14:20       49.7       212.0

14:30       48.6       215.4

14:40       47.5       218.7

As you can see, UV-B is out on 4/1/19 in New York City between 11:50 am and 2:10pm. In order to get ultraviolet B exposure on this day, you would need to be outside during this specific time frame only. No other hours/minutes will do.

Moreover, the presence of ultraviolet B is dependent upon sunshine. Ultimately, the best way to maintain a sound level of vitamin D is to get outside midday on a sunny day for no more than fifteen minutes approximately three times per week. And, remember, overcast and rainy days don’t cut it.

In short, vitamin D absolutely assists in getting a good night’s sleep. You can try to increase your body’s supply by eating certain foods but that can be overly cumbersome for many. On the other hand, careful ultraviolet B exposure, (avoiding sun burn), as well as wintertime vitamin D supplementation are your two best bets to establish and maintain healthy levels of this powerful and very important hormone.


If you enjoyed this article, please pass it on to anyone you think may benefit. Also, I welcome any comments or questions you may have.

Susan D’Addario, Author, Certified Sleep Science Coach, and Founder of Back-To-Sleep, helps people struggling to get a good night’s sleep so they can finally sleep soundly again and feel rested and ready to take on the world.



Susan D'AddarioComment