As we approach the winter solstice, the shortest day of the year, it's a reminder that even our bodies operate on a cycle tied to the sun. With less natural sunlight during this time, our circadian rhythms—the internal clock that regulates many bodily functions, including skin cell regeneration—can be disrupted. This can manifest in a variety of ways, from dullness and dryness to increased sensitivity and even premature aging. But by understanding how our skin responds to these changes, we can take steps to support its natural rhythm and maintain a healthy, radiant complexion all year round.

The skin, even more than the eyes, is the soul's mirror and your most honest interface, revealing your overall health and well-being more accurately than most laboratory tests available today. One way to help your skin age well is by understanding your skin's and body's circadian rhythm and making small changes in behavior around it. The totality of exposures to which an individual is subjected to from conception to death is sometimes referred to as the "exposome." Let’s try an exercise to illustrate…

Part One

Close your eyes for a moment and think about how you're feeling today. Are you feeling well-rested, relaxed, stressed, or exhausted? Make a general note of your diet over the past day or so—have you had more or less refined foods and simple sugars, and have you managed to stay well-hydrated? Now, think about if you've had a good level of physical activity.

Now take a look in the mirror. Take a moment to take in the skin on your face and body in a new way. Start by looking at the overall color and notice whether it is even in tone. Notice if the texture is smooth, how visible the pores are, if there are areas of redness, and any other changes that stand out to you. Gently pinch the skin on the back of your hand and notice how long it takes for it to return back to baseline. Observe if a part of your face and body looks younger or healthier than another part.

It is a good idea to take a few notes because after reading this, I want you to repeat this same exercise in just a few days. I am convinced you will quickly be thrilled with the difference just by making a few simple, and free, changes once you better understand your skin's circadian rhythm and learn how to optimize it for beautiful aging.

Part Two

Try making the following adjustments to your routine for a few days, then refer to your notes from Part One and take note of the difference.

• Try to go to bed at the same time every night, make sure your room is as dark as possible, or even better, wear a night mask to block out all light altogether.
• If you wake up to go to the bathroom, have a red light in the bathroom and keep it as dim as possible, without risking your health.
• Try to wake up at the same time every morning even on weekends.
• When you wake up go for a walk and get morning light on your eyes for about 5 minutes. Never look right at the sun, but look in the direction of the sunrise, without sunglasses.
• Generally, for non-athletes looking to stay healthy, if you’re a woman, exercise in the morning, for men the afternoon seems to be better.
• Try to avoid caffeine after 1pm
• Try intermittent fasting for at least 13 hours per day or more, 16-18 hours would be a great goal, even if just on a few days per week (this includes sleep time!) and make sure to not eat for at least 2 hours before bed.
• Avoid alcohol as much as possible and for at least 2-3 hours before bed.
• Try to eat most of your calories earlier in the day (more breakfast, less dinner). This is because the genes that regulate metabolism and those that regulate inflammation (which you can think of as synonymous with aging) work as a see-saw- when one is more active the other recedes.
• In the evening go for a walk as the sun sets, for 5-10 minutes to get the evening setting sun on the eyes.
• After that, avoid bright lights and use blue light filters on computers and phones.

We now know that circadian rhythms are relevant to every cell and organ in our body, including the skin. In fact, nearly half of our genes cycle through a 24-hour rhythm. This means that what you put in your body and on your skin, including medications, may affect you very differently and be more or less effective, or possibly even toxic, at certain times of the day versus others, depending on the phase of the clock in those particular tissues and organs. Also, your circadian rhythm is unique to you; the more you learn to be in tune with it, the greater benefit you will have.

Sun exposure has been the main factor in deciding when to use or avoid products, but we are learning that using the same product during the day may increase UV protective effects and decrease damage from the sun's rays, and side effects like irritation can be reduced by changing the time of day a cream is used. For example, most retinols are used at night due to their sensitivity to light, not because they make your skin more sun sensitive. However, using a stabilized retinol during the day may offer a greater benefit in collagen production in the skin than from using it at night.

Researchers have identified groups of genes that create on-off cycles and discovered that each cycle takes about 24 hours. This is true of all the cells in all our organs, but what each accomplishes as a result of those cycles is very different. In simple terms, the brain is directly connected to the retina of the eye which calibrates signals for day and night. That connection is critical to coordinating the rhythms and is why it is important to consistently get light on your eyes first thing in the morning when you wake up, ideally waking up at the same time each day, even on weekends. It also means it is important to not receive light signals on the retina at night- no TV, phone or computers after dark, or at least have blue light filters to reduce the exposure to the eyes. This understanding and treating the effects of light exposure on the brain and body is part of a new and exciting field of medicine called Circadian Medicine. It focuses on treating conditions such as PTSD, concussions, obesity, diabetes, high blood pressure, Alzheimer’s, even cancer and more by helping patients optimize their circadian rhythms.

The best part of circadian medicine is that there are no medications involved, all you need is a pen and paper and a willingness to make a few simple changes in your life. The difference will feel and look better, almost instantly.

Your circadian clock and regulation of inflammation (aka aging):  Inflammation occurs due to everything from stress to sun exposure to pollution and toxins, and even due to normal activities of cell functioning and repair. Research has shown that this too works according to a circadian clock and in 2015 the Nobel Prize in Medicine was awarded for the discovery that a skin protein that repairs damage from UV exposure operates with a circadian rhythm that is controlled by a clock gene. The award-winning scientists showed that rodents exposed to UV radiation early in the day, when it is usually dark out, were five times more likely to develop deadly skin cancer than those exposed later in the day when it was naturally light out. Now the research is ongoing to better determine the time of day to apply products or to deliver life-saving treatments in order to best work with the body’s circadian rhythm and to live healthier and longer.

Bottom Line:

Adjusting our behavior to match our natural circadian rhythms will help improve overall health and immunity and personalized circadian medicine may be the norm in the future. The timing of each of our clocks is individual and is set by factors including the sun, genetic predisposition, lifestyle choices, indoor lighting, our age and more. Scientists are still working to understand and create easy, individualized methods for telling what phase, or phases, your organs are in.

The good news is that you don’t need to be totally precise in order to improve the coordination and strength of your biological rhythms. Something as simple as being sun-smart: getting as much sunlight as you can as the sun rises (then wearing sun protection when out), making your bedroom dark at night, eating more in the morning and starting your fast earlier in the evening, while maintaining a consistent routine from one day to the next (even on weekends), will go a long way to coordinating your rhythm with your body. For skin care, consider using topical antioxidants like Vitamin C during the day and hydrate your skin well before bed. Your skin will reflect the improvement quickly and the next time you look in the mirror you will like what you see so much better for it. The awesome bonus is you will feel better as well. Ultimately, as a dermatologist and physician, I don’t just want you to look better, I also want you to feel better and live better.