Coach’s Corner: Is Sunlight Your New Supplement?

Jeni O'Neill

April 19, 2022

Sunlight in reflecting in the woods

How much sunlight have you seen today? If you would like to improve your sleep, mood, immune function, or regulate your appetite, this post is for you.
Have you ever thought about sunlight as a necessary element for good health? We all intuitively know that sunlight is energizing and mood-lifting and Dr. Hartman has stressed the importance of sunlight to allow our bodies to make vitamin D. Current research is also revealing other ways in which sunlight brings us health and vitality.
In today’s world, we can easily spend our entire day inside and never see the sun, which can disrupt our bodies natural rhythms. Even when we are driving, we are insulated from the sun’s rays with UV-limiting glass.
When these rhythms are disrupted, we see:

  • Reduced immune function
  • Altered metabolism
  • Mood issues
  • Sleep disruptions

Sunlight sends information to our bodies through specific cells in our eyes, providing metabolic, hormonal, and immune-boosting benefits.


Sunlight resets our circadian rhythm and regulates sleep.

Is it possible that our insulation from daily sunlight can be contributing to our insomnia epidemic?

Getting outside in natural light soon after waking helps to set your biological clock. Even on a cloudy day or under shade, we are exposed to enough photons to activate the light-sensing neurons in our eyes. Artificial lights and sunlight viewed through a window do not seem to have the same effect.
We’re meant to be exposed to moderate amounts of sunlight during the day – on our skin and in our eyes – and we are not designed to be exposed to bright lights at night. Light is our primary time-giver, setting our circadian clock.
Melanopsin receptor cells in the bottom part of our eyes actually send messages to all of our cells setting our “time” and letting our bodies know when to produce cortisol or melatonin. When we don’t get these messages from sunlight, our bodies can get out of sync and produce these hormones at inappropriate times, making us alert when we should be sleeping or vice versa.
Fascinating new research is finding that our eyes even measure the angle of light in the morning and evening – giving further cues to our bodies about the sleep/wake rhythm as well as cortisol and melatonin levels.

Getting sunlight during the day may also improve mood.

The science of how exactly this happens is still emerging. But it is not news to anyone that being outside and feeling the sun improves the mood. I’ve seen Dr. Hartman use this quote here before, and it bears repeating:

If you’re in a bad mood, go for a walk. If you’re still in a bad mood, go for another walk. – Hippocrates



Sunlight exposure to the eyes can help regulate appetite

Have you ever noticed that you feel less hungry on days that you spend more time outside? This is not simply because of your distance from the refrigerator.
When our eyes are exposed to UV light, we actually make melanocyte-stimulating hormone (MSH) which affects our appetite. The increase in MSH also leads to a reduced appetite in the summer months. Getting outside during the day can help us keep our appetite in a healthy range.

Sunlight can boost your immune system

Dr. Hartman has talked a lot about the immune-boosting effects of vitamin D here on the blog. We know that exposing our skin to natural sunlight (in moderation) helps our bodies make vitamin D and can reduce our risk of infections, insulin resistance, type 2 diabetes, cardiovascular disease, cancer, and more. Even beyond the effects of vitamin D, new research is finding that our bodies respond to sunlight by making our infection-fighting T cells more active.


Sunlight sends important information that:

  • Sets circadian rhythms
  • Improves mood
  • Regulates appetite
  • Improves immune function

These benefits are even in addition to the health-promoting effect of vitamin D and the stress-reducing (and cortisol-lowering) effects of simply being outside in nature.
Grandma didn’t need to know that the light-sensing neurons in our eyes help control mood, hunger, sleep, immunity, and metabolism. She didn’t need to understand the role of her vitamin D levels or T cell mechanisms. She just intuitively knew that fresh air and sunshine were health-promoting. And she was right, of course! We intuitively know it too, but sometimes it is motivating to be able to answer our inner three-year-old’s question: Why?
So, if it helps you to think about your T cells, or your circadian clock when you’re deciding to sit at your desk at lunch or go outside and get some fresh air and sunlight, now you have a few more reasons to opt for that walk. Exposure to natural light, sprinkled throughout your day, is definitely good medicine. It doesn’t take long – just 15 minutes in the morning, 10 minutes around mid-day, and 10 minutes in the evening on a regular basis can make a big difference in how you’re sleeping, your immune function, how hungry you feel, and in your mood.
There’s a reason that it feels so good to step outside and feel the sun on your face. It’s delightful when something that feels indulgent is so great for our health. So, go drink up a little sunshine today.
Since 2010, Richmond Integrative and Functional Medicine has been helping people to restore their health and hope with an integrative approach to conventional and alternative medicine that’s entirely science-backed. We at RIFM believe everyone is made for health. We offer a comprehensive, in-person patient membership program to ensure you get access to the care you need to thrive.


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