do vitamin d supplements work without sunlight?

Do Vitamin D Supplements Work Without Sunlight?

When the Sun’s rays penetrate your skin, they can do far more than warm your body.

I’m sure you’ve heard it many times:


​You need to get out in the Sun, or you’ll become deficient in vitamin D.

That’s true, but…

What if you’d take a vitamin D supplement instead?

Would you still be required to sunbathe to activate it?

The answer is no. Even though the vitamin D you take still needs to be activated, this process is performed by your liver and kidneys – not by the Sun.

That’s right: a quality vitamin D supplement will provide you with the exact same compound you would get from sunbathing. This chemical is known as cholecalciferol and it’s the inactive form of vitamin D.

Cholecalciferol is always an inactive substance. You can think of it as a metal key that almost fits in the lock, but not quite.

How does cholecalciferol get activated?

In ideal circumstances, when you sunbathe in the midday Sun, you are receiving solar radiation that’s rich in ultraviolet B rays. These rays will penetrate your skin and transform some of the molecules inside you.

One of these molecules is called 7-dehydrocholesterol. This substance is manufactured by your body and, when the ultraviolet B rays from the Sun come into contact with it, they convert it into cholecalciferol – vitamin D.

Then, from these outer layers of your skin, it’ll find its way into your blood.

In contrast, when you supplement into a capsule containing vitamin D3, you are ingesting a fully assembled molecule of cholecalciferol. In this case, it’ll find its way into your blood through your digestive tract.

This is the only difference between the Sun-derived cholecalciferol and the one found in supplements: the way they get to the blood.

However you got it into your bloodstream, though, this metal key isn’t ready to open any locks yet. It’ll still need to travel through the workshops of at least two different locksmiths: the liver and the kidneys.

Why the liver?

Because your liver is like a miniature laboratory, performing countless chemical conversions. One of these is the transformation of cholecalciferol into 25-hydroxyvitamin D.

Why the kidneys?

Thanks to the work performed by your liver, the shape of the key has gotten closer to what you need. Now, there’s just one other small change that’s required.

You’ll need a specialized locksmith for that, though: a kidney.

The kidney files the key precisely, in a way only he knows how to do, and 25-hydroxyvitamin D becomes 1,25-dihydroxycholecalciferol.

1,25-dihydroxycholecalciferol is the activated form of vitamin D. You don’t need to memorize this long name though, as it’s also known as calcitriol.

Calcitriol is the key that can open the hidden locks, and it has been carefully crafted from cholecalciferol.

As you can see, it doesn’t matter whether you got the raw material – the cholecalciferol – from either your skin or from your gut. As long as you get the metal through the hands of your skilled locksmiths, you’ll get calcitriol.

Does this mean that you can skip the Sun altogether and still avoid becoming vitamin D deficient?

If you supplement, the answer is yes.

Does this mean that you should skip the Sun as long as you keep supplementing?

No. Not at all.


what does the sun do for humans?

Helping your skin to produce vitamin D isn’t the only benefit you get from the Sun.

To understand that, we need to take a closer look at one specific skin cell: the melanocyte.

As its name implies, a melanocyte produces melanin, the dark pigment responsible for skin tone.

How helpful is melanin?

You can think of it as the body’s own shield against the harmful effects of long-term Sun exposure. The more melanin you have, the longer the time you can safely spend on the Sun. Also, and as a bonus, all this extra melanin will give you a tanner look.

These are certainly benefits, but did you know the Sun’s rays also stimulate melanocytes to produce other helpful substances besides melanin?

These include “cytokines, melanocortin peptides, catecholamines, serotonin, and nitric oxide.”(1)

Or, in other words, our skin was designed to depend on the Sun’s radiation to function properly.

This means that, even if you were to supplement with a large amount of vitamin D, you’d still need a daily dose of sunlight to make sure your skin cells were functioning optimally.

But these substances can do more than help in keeping your skin working fine.

Nitric oxide, for example, has been shown to have an important role in cardiovascular health. (2)

What are other benefits of sun exposure?

As researchers from Oslo, Norway point out:

Ultraviolet radiation from the Sun can help in reducing the symptoms of multiple sclerosis. This has been shown to be an outcome that’s independent of vitamin D production.(3)

This means that, even if you are taking high doses of vitamin D, and these large doses are keeping your multiple sclerosis under control, you’d still benefit from exposing your skin to pure sunlight.

There’s even a type of depression, ​seasonal affective disorder (SAD), that responds well to sunlight.

The reason why this happens may have to do, at least in part, with serotonin and how sunlight stimulates its production.

Even though researchers aren’t yet sure on how exactly it happens, it has been observed that the exposure to the bright sunlight increases the levels of serotonin in your brain. (4, 5)

This is one of the reasons why seasonal affective disorder has been linked to insufficient sun exposure.

As a final example, Sun exposure helps to regulate your circadian rhythms – the way your body decides what to do next depending on whether it believes its either night or day. (6)

If you spend all your day indoors, the lack of sun exposure leaves your organism feeling confused. Should it be producing the kind of chemicals that help you go to sleep, already?

By extension, when you get proper Sun exposure, you’ll have an easier time falling asleep because your brain will have a better understanding of when to start producing melatonin, the sleep hormone. (7)

It’s as if the Sun were responsible for keeping your biological clocks on time.

But isn’t the Sun’s radiation dangerous?

Only if in excess.

For example, even though Sun exposure stimulates your skin to become better at protecting you from sunburns, too much Sunlight will harm you.

Fortunately, you have a built-in warning system: your sense of temperature.

For example, imagine it’s a sunny Summer Sunday noon and you’ve overslept.

When you finally get out of the house and out into the welcoming sunlight, how would you describe your experience?

Enjoyable, pleasant. It lightens you up, both figuratively and literally.

The warmth feels cozy and inviting.

But... after a few minutes under the burning midday Summer Sun, how do you begin to feel?

Your eyes are hurting from all the squinting and your skin is crying for a shade. You are sweating, as your organism attempts to lower your temperature.

Are you in danger yet? Not if you listen to these warning signs and look for a shade.

After a few minutes hiding from the Sun, however, you’re ready for yet another pleasant incursion through the burning heat.

In contrast, if you were to ignore these warning signs and would force yourself to stay under the burning Sun, you’d risk harming your skin.

How to enjoy the benefits of sunlight without harming yourself

Provided that you don’t suffer from a serious health condition that disturbs your body’s ability to deal with sunlight – such as albinism or skin cancer – you can safely stay under the Sun until your skin begins to look pinkish.

This rosy color is an indication that your thermostat is turning on. Your skin blood vessels are beginning to dilate as your body floods your skin with blood in an attempt to transfer the heat away from your skin.

How long does this take to happen?

It depends on the strength of the Sun’s radiation hitting your skin and on how much melanin is on your skin, shielding you from that very radiation.

To give you an example, when the weather is mostly cloudy and the Sun can hardly be seen behind the clouds, you’ll endure much longer outside, even it’s noon and the Sun is at its peak.

This is one of those situations in which a little common sense goes a long way.

​Do vitamin d supplements work without sunlight?

In conclusion, even though your skin isn’t like a solar panel, where the more sunlight the merrier, its cells are designed to make of sensible amounts of sunlight in several different ways.

Fortunately, activating vitamin D isn’t one of those.

This is good news because it means you can obtain the benefits of either the Coimbra Protocol or low-dose vitamin D supplementation even if you live far away from the equator or spend most of your time indoors.

Did you find this information enlightening?

Be sure to consider sharing it with at least one person who you believe could benefit from it.

Tiago Henriques

With more than 10 years of experience as a Public Speaker, Tiago Henriques has done hundreds of public talks. He was born in 1987, in Portugal, and is the Author of 3 books — and counting — and the creator and editor of the Portuguese Science Project, "Ciência Desenhada," where complicated science is explained in a simple way, using whiteboard animation techniques. Tiago developed his own practical and down-to-earth teaching method inspired by his experiences with the Portuguese Deaf Community and their use of highly visual, descriptive and easy-to-understand language.

  • Alise says:

    You are the most marvelous teacher on earth! So grateful for publishing this. I am reading your book.

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