Vitamin D is all the rage now because of COVID-19. Yet, as Dr. Rhonda Patrick and others have promoted the ability of Vitamin D to protect against virus-initiated lung injury, they’ve failed to mention how a strong dose of the “sunlight nutrient” also protects against sleep disorders.

The link between vitamin D deficiencies and poor sleep is no longer arguable. Researchers in Italy, China, and Texas have all reached the same conclusion. The Texans even called it a “global epidemic.” Considering how over half the world suffers from vitamin D deficiency, including approximately 36% of otherwise healthy Americans (and 57% of medical patients), we can’t argue.

Though the mechanisms at work remain unclear, what is clear is that people who maintain optimal serum vitamin D levels enjoy better sleep than those who don’t.

Let’s examine the science and see if we can determine how to optimize our own vitamin D levels to achieve healthier sleep and immunity.

What is Vitamin D?

According to Wikipedia, vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and multiple other biological effects. Our primary natural source of the vitamin is a chemical reaction in the skin dependent on sun exposure.

Basically, the more sunlight you receive, the more vitamin D your body produces naturally.

A few foods do provide significant amounts of vitamin D, namely the skin of fatty fish such as salmon, tuna, herring and sardines. This amount, however, pales in comparison to the quantities our bodies convert from sunlight.

After its conversion into metabolites, vitamin D circulates in the blood as a hormone. There it helps promote bone growth and repair, assists in cell growth, reduces inflammation, and modulates certain neuromuscular and immune functions.

Vitamin D was first discovered when doctors went searching to find a nutritional culprit behind rickets, that terrible condition that gives children soft bones, bowed legs, and stunted growth (and not to mention sleep disorders). Even today, vitamin D supplements are used to treat this condition.

How Does Vitamin D Affect Sleep?

No one knows for certain, we’re sorry to say. Studies with hamsters (yes, hamsters) have discovered vitamin D receptors in regions of the brain responsible for sleep. Similar receptors have been found in humans, as well as vitamin D target neurons, but it will likely be another few years before their role in sleep is made clear. Human brains, after all, are slightly more complicated than hamster brains. (Though some of the guys we see at the gym might prove otherwise.)

Even so, the link between vitamin D deficiency and sleep disorders is deadly clear. As mentioned earlier, clinical studies have repeatedly found low vitamin D levels in people who suffer from abnormal sleep. Insomniacs. Sleep apnea patients. Raccoon-eyed old men plodding around the nursing home at 3AM. They all have low vitamin D levels.

Most interesting, however, is a 2018 study which showed substantial sleep improvements after giving patients a nuclear dose of vitamin D (50,000 IU) once every two weeks:

Conclusion: This study shows that the use of vitamin D supplement improves sleep quality, reduces sleep latency, raises sleep duration and improves subjective sleep quality in people 20-50 years-old with sleep disorder.

So, though we’re still trying to understand HOW vitamin D regulates sleep, we are certain that’s involved in a very big way. People with low vitamin D levels just don’t sleep like healthy humans should.

How to Maintain Healthy Vitamin D Levels?

As always, the best way to maintain your nutrient hormone levels is through natural sources. But eating enough fatty fish and getting enough sunlight isn’t always easy.

The UK National Health Service claims that it’s “not known exactly how much time is needed in the sun to make enough vitamin D to meet the body's requirements.”

The amount of time is different, in fact, depending on the color of your skin and the strength of the sun during various seasons. People with dark skin, such as those of African or South Asian descent, need more time in the sun to produce as much vitamin D as pale gents from Ireland and Norway. The only major concern is avoiding sunburn (which may cause skin cancers).

But don’t count time when you’re wearing sunscreen. The ultraviolet B (UVB) rays blocked by sunscreen are necessary for generating natural vitamin D.

How about time sitting next to a sunny window? Nope. Glass blocks UVB rays extremely well.

“These many factors explain why vitamin D deficiencies are shockingly common in the United States,” says the Harvard Men’s Health Watch.

Thus, the balance is somewhere in between having a healthy tan, and avoiding burned skin. But what do you do in the middle of a cloudy winter? And what about those who work in an office all day?

Luckily, the body doesn’t seem to discriminate between vitamin D synthesized from the sun and that from dietary or oral supplements. “The body can use each perfectly fine,” says Yale Medicine endocrinologist Karl Insogna.

Fantastic. In that case, the only question is…

How Much Vitamin D Should You Take?

In the United States, the recommended daily allowance (RDA) of vitamin D is 600 IU for adults between the ages of 19 and 70. But is that enough for someone who lifts weights, runs hill sprints, and spends weekends rolling on the jujitsu mats?

Not at all. It’s not even close. And it might not even be enough for sedentary people either.

A 2018 Saudi Arabian study examined 135 men and women suffering from vitamin D deficiency. They found that a standard treatment of 50,000 IU weekly for 3 months rectified the deficiency. However, when the patients went on a maintenance dose of 2,000 IU for the following 3 months, they found blood serum levels dropping again. In their own words: “Our study indicates that the maintenance dose of 2,000 IU of vitamin D is not enough for patients to keep the 25(OH)D levels above 30 ng/mL.”

It’s worth noting that 30 ng/mL is the borderline for vitamin D deficiency, a condition seen in 42% of African American women aged 15 to 49, in 41% of non-hospitalized patients aged 49 to 83, in up to 57% of hospitalized patients, and in more than a third of Americans between the ages of 18 and 29.

So when it comes to vitamin D, is more better?

Maybe.

4,000 IU is a safe daily upper limit according to the National Institute of Health. It’s also the dose included in Hibernate. But that’s not why.

In 2013, English researchers studying both professional and non-elite athletes measured an increase in sprint performance and vertical leap after eight weeks of supplementing 5,000 IU/day of vitamin D.

In the same year, researchers in Utah made a group of athletes take 4,000 IU of vitamin D for 5 weeks. On the fourth week, they made them do an absolutely brutal workout of 10 sets of 10 single-leg squat jumps with resistance at 75% of bodyweight. Their goal? “To induce muscle damage.” (Science. Gotta love it.) The results? Compared to athletes who didn’t take vitamin D, those who did saw enhanced recovery in peak isometric force after the “damaging event.” They also saw drastically lower biomarkers representative of muscle damage, “without ameliorating muscle soreness.”

Good grief. Remind us never to train with those guys.

But do remind us to take our daily dose of 4,000 IU of vitamin D. Better sleep. Increases in athletic performance and enhanced recovery from training. These are all things we love.

Conclusion

While we might not understand the exact mechanisms that link vitamin D to sleep, it does make perfect sense. We were born to live in the sun. By staying cooped up indoors all day, we modern humans deprive ourselves of the natural light that regulates so many biochemical reactions within our bodies. We already know how electric light can ruin our circadian rhythms. Thus, it doesn’t take a great logical leap to imagine how sun deprivation leads to low vitamin D levels, and inhibits our ability to sleep the way nature intended.

Luckily, oral vitamin D supplements seem to do a fantastic job of improving our sleep and recovery abilities. Regular doses greater than 2,000 IU per day seem to improve sleep length and quality, while boosting athletic performance and limiting muscle damage after training.

This is why Hibernate includes a hefty dose of meticulously sourced vitamin D.

We love the sun. We love getting jacked and tan as much as anyone else. But knowing that oral vitamin D works so well, we’d be crazy to not take advantage.

Fight the worldwide insomnia epidemic. Take a strong dose of the sunlight nutrient and sleep the way nature intended.