Beyond Vitamin D Production — How Sensible Sun Exposure Supports Overall Health

• There’s more to sun exposure than just vitamin D production — His work has demonstrated that sun exposure not only generates vitamin D but also triggers the production of other beneficial compounds that support immune function, cardiovascular health and even mental well-being.

• Sun-derived vitamin D is processed differently — Through his extensive research, Holick has shown that the body processes vitamin D from sunlight differently than it does from supplements, leading to longer-lasting effects and additional health benefits that cannot be replicated with a pill.¹

“When you make vitamin D in your skin what happens is that you actually don’t make vitamin D … It’s the precursor of cholesterol known as 7-Dehydrocholesterol. It absorbs the ultraviolet radiation or light from sunlight. It opens up that cholesterol molecule into pre-vitamin D,” he explains.

“[A]s soon as pre-vitamin D is made, it’s absorbing ultraviolet light and it’s being converted to other photo products called lumisterol and tachysterol. We, and Dr. Slominski and others, are beginning to show now that these photo products may have some unique biologic properties.”

• Your body uses all the vitamin D you get from sunlight — When you ingest a supplement, only about 60% of the vitamin D binds to your body’s transport proteins, while the rest is quickly excreted.

In contrast, vitamin D made from sun exposure is bound at nearly 100%, making it far more efficient and useful.² This means that a single session of moderate sun exposure provides a much more stable and sustained supply of vitamin D than taking a daily supplement.

• Vitamin D from the sun has a self-regulating process — Unlike supplements, which can lead to dangerously high vitamin D levels when taken in excess, sun-derived vitamin D undergoes a self-regulating process. Your body regulates how much vitamin D it produces naturally, preventing toxic buildup, something that is not possible with high-dose supplementation.³

• There’s no danger of overdosing — This mechanism ensures that your body only produces the amount of vitamin D it needs, making sunlight the safest and most efficient way to maintain optimal levels without the risk of overdose. Holick explains:

“Why don’t you become toxic when you’re exposed to sunlight? … Mother Nature is really clever. When you’re exposed to sunlight you’re making pre-vitamin D, which then converts to vitamin D, which is slowly entering into your bloodstream. But also, it’s now being exposed to sunlight and to ultraviolet-B and ultraviolet-A radiation.

By doing so, pre-vitamin D gets converted to lumisterol and tachysterol. Vitamin D gets incorporated and is absorbing that ultraviolet radiation and is converted to 5,6-trans super sterols.

And so, we think that all of these different photo products are being made and no longer are you making vitamin D … We showed many years ago, if you expose human skin constantly, you can only convert about maximum 15% of the pre-vitamin D ultimately to vitamin D.

So, as a result, Mother Nature designed us that even if you were crazy enough to go outside for the entire day, you will not become toxic because sunlight will destroy any excess.”

• Sunlight boosts nitric oxide production — This is released into the bloodstream during sun exposure, helping to lower blood pressure and improve circulation. This explains why people often feel more relaxed after spending time in the sun — nitric oxide acts as a natural vasodilator, widening blood vessels and enhancing blood flow.⁵

“[W]hen you’re exposed to sunlight, you immediately release nitric oxide in your skin cells and that causes vasodilation. I.e., it’s a medication that could be used for decreasing blood pressure. Also, it stimulates then the enzyme to actually make more nitric oxide.

So, you have two processes going on simultaneously. One is you’re instantly releasing nitric oxide making you feel more relaxed, and secondly it will stimulate now the production of nitric oxide so that this effect lasts for a longer period of time,” he explains.

• Sunlight also stimulates the release of beta-endorphins — These are your body’s natural painkillers and mood enhancers. Beta-endorphins contribute to the feeling of well-being that many people experience after being outdoors.⁶ This natural mood-boosting effect is one reason why sun exposure has been linked to reduced rates of depression and seasonal affective disorder (SAD).⁷

• Avoiding the sun affects your longevity — One study he references found that people who avoid the sun have the same reduced life expectancy as smokers, indicating that sun exposure plays a major role in overall longevity.⁸ According to the authors of that study:

“Nonsmokers who avoided sun exposure had a life expectancy similar to smokers in the highest sun exposure group, indicating that avoidance of sun exposure is a risk factor for death of a similar magnitude as smoking.”⁹

• Optimal sun exposure helps you live longer and healthier — Additionally, research from Sweden has shown that individuals with the lightest skin, who receive the most sun exposure, tend to live longer and experience fewer chronic illnesses compared to those who avoid the sun.^10,11

• The benefits extend to cardiovascular health — Sun exposure has been linked to a lower risk of high blood pressure, heart disease, and stroke. The release of nitric oxide not only helps regulate blood pressure but also reduces arterial stiffness, a key factor in preventing heart disease. By spending time outdoors regularly, individuals could improve their cardiovascular function in a way that cannot be replicated by supplements alone.¹²

“When you’re exposed to sunlight, you increase DNA repair enzymes. And so, yes, you initially damage your DNA, no question about it. But Mother Nature designed us so that you would repair those, and as a result, no long-lasting effect. And so, in my opinion, there is really minimal risk for being exposed to sensible sun exposure, but there’s a lot of upside in improving your overall health and well-being,” Holick says.

• Vitamin D helps moderate inflammation — Studies show that individuals living at higher latitudes, where sunlight is scarce, have a much higher prevalence of these conditions. This is because vitamin D plays a key role in controlling inflammation and supporting the body’s defense against infections.¹³

• Vitamin D helps reduce your risk of cancer — Holick illustrates this by sharing the results of one of the studies they conducted:

“[W]e gave 600, 4,000 or 10,000 units a day to healthy, vitamin D deficient, insufficient adults and got their blood level at the beginning and at the end. [We] looked at their white blood cells and looked at what genes are being expressed.

What was really remarkable, on 600 units a day, a little over 150 genes were actually being affected. So even a tiny amount of vitamin D is having an effect. 4,000 units a day, about 300 genes. On 10,000 units a day, more than 1,200 genes were being affected.

And these genes control apoptosis, which plays a role in reducing risk for cancer, effects on your immune system, on DNA repair, and on a variety of other metabolic processes. So, we do believe that vitamin D has a very important role to play on your immune system.”

• Melatonin is the hormone responsible for signaling that it’s time to sleep — People who get regular morning sunlight exposure tend to have healthier sleep patterns, falling asleep more easily and experiencing deeper, more restorative sleep.¹⁶

• Blue light helps balance your sleep-wake cycle — This type of light you get from the sun during the day helps to keep the body’s sleep-wake cycle in balance, while excessive exposure to artificial blue light from screens at night interferes with melatonin production. This is why experts recommend spending time outside during the day and minimizing screen exposure in the evening to maintain a healthy circadian rhythm.¹⁷

• Using sunscreen daily hampers your vitamin D production — A sunscreen with an SPF of just 30 blocks about 97.5% of UVB radiation, effectively shutting down your body’s ability to make vitamin D. Studies of outdoor workers, such as farmers who regularly apply sunscreen, show that many remain vitamin D deficient despite being outdoors for long hours.¹⁸

• This does not mean sunscreen should be avoided entirely — Rather, Holick recommends using it strategically. “What I always recommend for my own self and also my family members is, you could wear some protection on your face or a hat, and on the top of your hands and ears. Those are the areas that are always constantly sun exposed,” he said.

1. Get morning sunlight to regulate your body’s internal clock — If you struggle with poor sleep, low energy, or mood swings, your circadian rhythm might be out of sync. The easiest fix is to step outside within the first hour of waking up, as morning sunlight helps regulate melatonin production, keeping your sleep-wake cycle balanced.

Even 10 to 15 minutes of direct morning light on your skin and eyes (without sunglasses) can make a noticeable difference in your energy and sleep quality.

2. Expose large areas of skin to midday sun without burning — Vitamin D production happens when your skin absorbs UVB rays, which are strongest around midday. To maximize your vitamin D levels safely, aim to expose at least 30% to 40% of your body (arms, legs, and back) for about 10 to 30 minutes, depending on your skin type.

If you have darker skin, you will need a bit more time. If you burn easily, start with short sessions and gradually build up your tolerance. Never stay out long enough to burn — redness means damage, not health.

All of that said, I recommend avoiding high-intensity midday sun exposure until you’ve been off vegetable oils for at least six months, as polyunsaturated fats like linoleic acid, which are extremely prone to oxidation, get incorporated into your skin cells. When exposed to sunlight, these oils oxidize, forming harmful compounds that raise your risk of sunburn and skin damage.

3. Reduce sunscreen use on non-burn-prone areas — Sunscreen blocks nearly all UVB rays, making it almost impossible for your body to produce vitamin D. As Holick recommends, use sunscreen strategically; only apply it on areas prone to sun damage instead of covering every inch of your skin. If you plan to be outside for long periods, wear protective clothing or seek shade after getting your necessary sun exposure.

4. Avoid the common mistake of over-supplementing — While vitamin D supplements are helpful in certain situations, they do not provide the same benefits as sun-derived vitamin D. When you take high-dose supplements, you risk accumulating too much vitamin D, which leads to calcium imbalances and kidney stress. If you are getting regular sun exposure, there is little need for excessive supplementation.

5. Support your skin’s natural protection — Your diet plays a major role in how your skin responds to sunlight. As mentioned, if you consume a diet high in vegetable oils and processed foods, your skin is more prone to oxidative stress and damage. In this case, temporarily limit midday sun exposure while drastically reducing your vegetable oil intake. After around four to six months, you can resume getting midday sunlight.

To help protect your skin from sun damage while reducing seed oil intake, consider supplementing with astaxanthin, one of the most powerful carotenoids. A daily dose of 12 mg provides potent antioxidant support and may extend the time it takes for your skin to burn from sun exposure.²⁰ Research also suggests it could play a role in minimizing skin photoaging and lowering the risk of skin cancer.²¹

Another beneficial nutrient is niacinamide, which supports skin health and may help protect against photoaging and skin cancer.²² While some recommend applying it topically,²³ taking 50 mg orally will also work.

Additionally, taking a low-dose aspirin (81 mg) about 30 to 60 minutes before sun exposure could help reduce the risk of skin cancer. This may work by preventing LA in your skin from being converted into oxidized linoleic acid metabolites (OXLAMs), which are strongly linked to skin and other cancers.²⁴

In addition, prioritize saturated fats from sources like grass fed butter, ghee and tallow, which help maintain strong, resilient skin. Antioxidant-rich foods like berries, carrots and dark leafy greens also provide nutrients that protect against UV damage from the inside out.