The True Relationship Between Vitamin D and Sun

Vitamins are a critical part of our everyday health – yet there are some that we simply do not get enough of.

In most cases, we have to get vitamins into our body through food or through supplements, because in most cases the human body simply can’t make them. Vitamin D is one exception to this rule.

We can make vitamin D. But only in sunlight.

So, how much sun do you need to make vitamin D?

The question seems like a pretty simple one. However, the topic is actually much more complicated than it first appears.

Because we can make vitamin D, people often assume that it isn’t something to be concerned about. This might be why vitamin D has been ignored for so long.

Yet, vitamin D offers significant health benefits.

More importantly, deficiency in vitamin D is associated with a number of negative impacts on health – and that deficiency is much more common than most people realize (1).

After all, our society has become increasingly indoor focused. I mean, just look at all the time people spend on computers and gaming systems. At the same time, many people are working extended hours to pay their bills. All of these things certainly don’t leave much time for being outside and in the sun.

Even when we are outside, people tend to wear sunscreen or cover up, to help protect themselves from skin cancer.

Those are important practices, but at the same time, they dramatically reduce a person’s ability to produce vitamin D.

To really know how much sun you need, there are a lot of factors we have to consider.

How Much Sun Do You Need to Make Vitamin D?

Because sun exposure is critical for making vitamin D, there is always a question of how much exposure you actually need.

After all, many people don’t like the idea of taking supplements if there is an alternative, more natural, approach for getting that vitamin.

Vitamin D is a challenging case in this respect and there isn’t a simple answer.

How Much Vitamin D Do You Need?

Ultimately, the amount of sun exposure that you want is going to depend on the vitamin D levels that you are trying to reach.

But, there is no consensus on how much vitamin D we actually need.

For example, official reports focus on dietary intakes of 600 IU daily for most people and 800 IU for people above 70 years of age (2).

However, some research points to much higher numbers, such as 1,000 IU (3), 2,000 IU (4) or even as much as 10,000 IU (5).

Indeed, many physicians already regularly prescribe patients vitamin D supplements, often with values of 1,000 to 2,000 IU per day.

Likewise, very high levels of vitamin D are used in some cases. One example of this is 50,000 IU, which is often used once per week, especially in the elderly or people who are vulnerable to vitamin D deficiency. That level of supplement is also sometimes used for people who are very low in vitamin D levels, as a way to quickly bring those levels back up.

This pattern is used because there is limited evidence of any upper limit in vitamin D consumption.

For example, the main study that highlighted on any level of vitamin D toxicity did so at 484 nmol/L (6). That level is much higher than most recommendations and it is unlikely that people would be taking it. In fact, the patient in this case had been mistakenly taking 50,000 IU per day instead of the 1,000 IU that she was prescribed.

Certainly research has indicated that upwards of 4,000 IU per day may be safe and 4,000 IU per day is an official recommended upper intake (7).

If you are going to take high doses of vitamin D supplements, it’s best to talk to a professional and have your blood levels monitored. There are also tests that you can buy yourself to monitor your vitamin D levels, such as one from the Vitamin D Council.

However, that’s beyond the scope of what we’re talking about here.

Overall, the wide range of recommendations makes it pretty hard to work out what vitamin D levels you actually need.

It Depends on Time and Location

The creation of vitamin D is all about sun exposure, and that varies throughout the world. It also varies seasonally.

For example, the Scientific Advisory Committee on Nutrition in the United Kingdom recommends that all people take the equivalent of 400 IU of vitamin D every day (8,9). This argument is based on how unreliable sunshine is in the United Kingdom.

The time of year is also significant.

In particular, it is much more difficult to get vitamin D from the sun in the winter, especially because the sun tends to be too low and there are inversions that act to block some of the sun’s rays (10).

It doesn’t help that it is often too cold to be outside for long in the winter – and if you are outside, most of your skin is going to be covered up.

It Depends on Who You Are

There are also some key differences in how much vitamin D individuals synthesize.

In particular, some groups of people will make less vitamin D from the same amount of sunlight. These groups are much more likely to be vitamin D deficient.

Seniors are one example, as the ability to synthesize vitamin D decreases with age. At the same time, these people are likely to spend less time outside in the sun (11).

Dark skinned individuals also receive less vitamin D from sunlight (12).

Some health conditions can also affect ability to synthesize vitamin D or the ability for the synthesized vitamin D to be released. Often this occurs when the ability to absorb fat is decreased, such as in obesity or inflammatory bowel disease (13,14).

At the same time, your level of vitamin D is going to play a role.

If you are severely deficient in vitamin D, it would be very difficult (if not impossible) to get enough sun exposure to bring your vitamin D levels into normal range.

Often supplements will be needed to bring up your vitamin D levels to the point where getting vitamin D from the sun is realistic.

Recommendations

Common recommendations focus on the idea of getting a certain amount of sun exposure every day.

For example, one recommendation focuses on going out in the sun every day between 10am and 3pm, with at least 10% of your skin exposed. The recommendation suggests staying out there long enough to synthesize vitamin D, but not long enough to get burned (15).

It’s not a particularly helpful recommendation because it doesn’t give you an idea of how long you are supposed to be out there.

Another recommendation suggests sunbathing (in a bathing suit) for a few minutes at noon if you are fair skinned, and 15-20 minutes if you are tanned or have a darker skin tone (16).

Yet another recommendation suggests 10 to 15 minutes of exposure two or three times a week (17).

These recommendations are useful (although they contradict each other), but they are also limited.

For one thing, the authors don’t really talk about what level of vitamin D they are talking about, so it’s hard to know how optimal the strategies are.

Another issue is that these are very general recommendations.

They don’t take into account other factors, like your skin tone, what season it is or where in the world you are located.

For example, if you were to sunbathe all day on an overcast day in winter, you probably still wouldn’t get enough sun to make sufficient vitamin D (you’d also get pretty cold).

The recommendations are also a bit unrealistic, especially those that suggest going out into the sun every day.

Yes, we should all be outside more often – just like the site Little Things highlights.

However, getting outside between 10am and 3pm (which really is the best time for sun exposure) is an impossibility for many people on weekdays. Some people may have the option of going outside on a lunch break, but this isn’t viable for everyone.

Additionally, if you did go outside on a lunch break, you are likely to be in clothes that don’t allow for all that much sun exposure.

Using an App or Tool

One interesting approach to answering the question of how much sun do you need to make vitamin D, is to actually figure out recommendations that are tailored towards your location.

There are a few different tools out there that do this, and it’s likely that more are going to be developed over time.

One example is dminder, which is an app for both Apple and Android devices. The app allows you to take into account a range of factors, including age, skin tone and how much skin you have exposed.

It also provides IU estimates of how much vitamin D you have gained from your exposure.

It’s hard to know how effective this type of app is because there has been little research into using apps for this purpose.

However, it might be a useful tool for people trying to avoid supplements.

Dminder is the most significant example of an app that does this, but I imagine that we are going to see more apps focused on vitamin D tracking in the future.

Monitoring Vitamin D

At the end of the day, the best way to work out how much sun exposure you need for vitamin D is to keep an eye on your own vitamin D levels.

There are various options when it comes to checking your vitamin D levels.

One main option is that you can request that your physician does a vitamin D test. Another option is using an at-home vitamin D kit. This approach typically involves a finger prick and sending in a sample through the mail. Your result is sent back to you through the mail.

By taking this approach, you have the ability to see how different behaviors change your vitamin D levels.

This should give you at least a rough idea of whether you are doing enough to get vitamin D or if you need to do more.

I favor going through Life Extensions, as they have a vitamin D testing service where they email you a lab script. You then print this out and take it to your local lab. The cost of the test is close to $50.00.

Getting a physician to test your vitamin D levels does tend to be a less expensive option, but it does have its disadvantages.

One issue with relying on medical professionals for testing vitamin D is that they may not test it as often as you would like. Additionally, some medical professionals will just tell you whether your levels are okay or not, without ever telling you the actual levels or what standards they are using.

The downside is that these tests can be expensive, especially if you are paying for them out of pocket.

However, if you can afford to take this approach, it certainly has its merits.

After all, not getting enough vitamin D can be quite detrimental for health.

Supplementing

The simplest alternative to sun exposure is supplements, especially as there are few dietary sources of vitamin D.

Now, you can get vitamin D through some products that have been fortified with it, such as milk and orange juice. However, this fortification is the D2 form of vitamin D, which is not powerful. Additionally, it is simply not enough vitamin D to help combat deficiency.

The negative outcomes of vitamin D deficiency make it important to find ways of increasing your level of vitamin D – whether you do this through sun exposure or through supplements.

However, even those of us that do get outside enough to get vitamin D that way, turning to supplements may still be an important approach in the winter months when our ability to get enough sunlight is severely compromised.

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