Part Two of Here Comes the Sun: The Extraordinary Benefits of Circadian Health
I’m Walking on Sunshine (And Don’t It Feel Good!)
— Katrina and the Waves
The health benefits of real sunlight and the pleasure of dawn
At the heart of circadian health is your internal clock. Light-sensitive proteins in the eye—melanopsin and neuropsin—signal the brain’s master timekeeper, the suprachiasmatic nucleus (SCN), which controls alertness, hunger, energy, immunity, sleep, and indirectly detracts from libido and sociability because of fatigue.
Cortisol, the hormone for preparedness, begins rising at 2–3 a.m. The SCN suppresses melatonin and sleepiness, increases cortisol, and responds to ultraviolet light by helping the brain make serotonin, the daytime “feel-good” hormone. Cortisol peaks in the afternoon. Bright artificial light at night confuses the SCN, flattens cortisol production, and leaves you groggy and out of sync. Blue light from screens worsens this by suppressing dopamine, weakening the brain’s reward system, and making technology more addictive.
Circadian Rhythms and Weight Loss
Timing matters as much as calories. Food burns more efficiently in the morning. In World War II, U.S. Army tests showed troops who ate in the evening gained weight; those who ate in the morning lost weight, despite equal calories.
Incandescent Light vs. Sunlight
Humans evolved under sunlight. Electric light is recent—about 200 years old—and disrupts sleep and waking patterns. It extends the workday into night shifts but does not activate the body’s circadian system as natural dawn does. Incandescent bulbs may lift mood in winter, but artificial blue light at night causes problems.
“Sunrise” Alarm Clocks
Sunrise alarm clocks shift from orange to white over half an hour. They resemble dawn but lack the near-UV and near-infrared light that signals the brain’s clock. They may help you wake up, but they do not reset your internal rhythm.
“Daylight” Bulbs Are Not Daylight
- LEDs and fluorescents block ultraviolet light (except special bulbs).
- LEDs emit little infrared. Incandescent and halogen bulbs release some infrared as heat, but not in the pattern needed for circadian timing.
Blue Light’s Harm
Blue light from screens and lamps suppresses melatonin, delaying sleep and lowering sleep quality. It can shift your circadian rhythm. Modest blue light from a lamp or wood fire is unlikely to disrupt sleep or cause fatigue the next day.
Benefits of a Healthy Circadian Rhythm
Blue light at night also sharply suppresses dopamine, a key motivation hormone. Artificial light disrupts the reward system. The more time spent with screens after dark, the less satisfaction you get from them. Technology stimulates and drains the system—a clever trap.
Chronobiology is the science of how our body’s timing affects health. It studies the rhythms that guide sleep, energy, hunger, and more. Today, chronobiology helps match medications, meals, and activities to your body’s natural clock for better results. For example, taking medicine at the right time can make it work better. Eating in the morning, when your metabolism is most active, helps maintain a healthy weight. Even exercise and sleep routines benefit from being timed to your internal rhythm.
In short, chronobiology recognizes that when you do something can be as important as what you do. By syncing your habits with your body’s clock, you can improve sleep, energy, and overall health.
Lack of Sunlight and Cancer Risk
Modern life disrupts rhythms: we spend days indoors under artificial light and evenings with blue glow from devices. This raises risks for obesity, diabetes, depression, and certain cancers. Low sunlight exposure is linked to shorter lifespan.
Simple Fixes
- Get morning sunlight.
- Dim lights after sunset.
- Keep regular mealtimes and sleep times.
- Avoid screen glare at night.
Experience the Dawn
Every dawn feels like a reset. The sun has been sending these signals for ages, but I only benefit when I stop and notice them. At 6:47 this morning, I stood behind my house and watched the sky open. It looked blue at first glance, yet the soft “rosy fingers” of dawn were still working on my SCN. I even caught the moment on my iPhone. In Boston, the sun rises around 7. I’m outside by 6:30, facing east, no glasses, letting the light do its quiet work. As winter approaches, I can start a little later each day, right up to December 15. The wavelengths will reach me, even if the sky appears blue or mild cloud cover.
Bonus: A Good Warm Winter Breakfast Recipe
A Seasonal Favorite for 20 Years
Dr. Nadelberg and I frequently speak of mixing and matching foods to make balanced dishes, rather than counting calories or trying to stay on restrictive diets. Below is an example of a good winter breakfast that balances carbohydrates and proteins, has beneficial fiber, and can be modified from day to day.
Ingredients:
- oatmeal – uncut, steel cut, or old-fashioned. The less processed the oatmeal, the better it is for you. Highly processed oatmeal can take as little as a minute to cook. What you want is oatmeal that takes 5 minutes to cook. This type of oatmeal is high in fiber, helps digestion, and lowers cholesterol. The quick oatmeal has been highly milled and and while smoother (think “smooth” as in the texture of white bread) is less nutritious.
- To prepare take ½ cup oatmeal, 1 cup water, 1/8 tsp salt, microwave 5 minutes at ½ power. Just keep the same proportions if you want larger or smaller servings.
- This serving of oatmeal contains about 30 grams of carbohydrate. A handful of nuts (cashews and walnuts are my favorites – they are softer than almonds and contain better fats than peanuts) is also about 30 grams of protein. Mix in. Now you have a balanced starting point.
- You can sweeten this with dried fruit, brown sugar, regular sugar, honey, berries, bananas, or fruit preserves and the still have a low glycemic nutritious breakfast. You can also add milled flaxseed which increases fiber and binds cholesterol and other bad lipids.