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Sunlight and Vitamin D – How much do you need?

Michael Jus

Michael Jus

We’ve talked about the importance of sunlight for our sleep and circadian rhythm before. But what about Vitamin D? How much Sun do you need to produce enough and what are the risks?

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How dangerous is sunlight actually?

When it comes to our health, the Sun often gets a bad rep for being very dangerous. Sunburns, heat strokes and skin damage are certainly no joke, on the other hand we need sunlight for some of the most basic functions in our body.

To put these risks in perspective, we can consult a Global Burden of Disease report on solar ultraviolet radiation that contrasts the risks of excessive solar UVR exposure with a lack thereof, including vitamin D deficiency. This is measured in disability-adjusted life years (DALYs), which you can think of as lost years of full health.

Globally in 2000, excessive solar UVR exposure caused the loss of around 1.5 million DALYs (0.1% of the total global burden of disease), whereas a massive loss of 3.3 billion DALYs was attributed to a lack of UVR exposure and vitamin D deficiency.

This is a 2200-fold difference or as one scientist puts it: “The results indicate a relatively modest burden of disease from ultraviolet radiation, but highlight the important benefits from having adequate UVR to maintain vitamin D levels”. The global prevalence of vitamin D deficiency further emphasizes this assessment.

How much Sun exposure do you need?

Before we get enlightened about the effects of vitamin D, let’s first clarify how much Sun exposure is necessary to fill up our tanks. This comes down to a combination of duration, skin area and skin type, as well as season and location.

Darker or tanned skin offers more protection against UV light via melanin pigments – a factor that reduces vitamin D synthesis in turn. Also, the further away from the equator you are, the more likely you won’t have enough UV light for production in winter or even longer.

A simple rule of thumb to estimate this is to look at your shadow on the ground: if it is as long as your height or shorter, the Sun should provide enough UV light. Check your situation and consider supplementing vitamin D, if you need. More on that later.

Keeping all that in mind, 30 minutes of midday Sun with half of your skin exposed should give you all the vitamin D you need. Lighter skin types might need less time. This is a daily recommended minimum, but you don’t have to overdo it either. Don’t wait for a sunburn to get back in the shade or to put on protection after your sunbath.

What is vitamin D important for?

We can already see that the Sun seems to be a guiding light for our health, if used sensibly. But what is so important about the Sun vitamin?

Vitamin D is a key player in our calcium, magnesium and phosphorus metabolism. There are several chemical forms, depending on which it can be defined as a nutrient or (pre-)hormone and is crucial to our bone health and cardiovascular health.

Moreover, sufficient D levels have been linked to increased resistance and recovery for many health conditions that involve inflammation, infection and even cancers. Last but not least, the Sun hormone helps us to stay mentally fit and might be a promising remedy for seasonal affective disorder, with ongoing research.

Vitamin D capsules in a bottle from top view
Recommendations for vitamin D supplementation vary widely.

Should you take vitamin D supplements?

The easiest answer for this would be given by a simple blood test. If you score below 30 ng/ml or 75 nmol/L (serum 25(OH)D) of vitamin D, you are commonly considered deficient and supplementation would be advisable. Conservative estimates set the bar far lower, while others suggest higher minimum thresholds.

Deficiency is not unusual In our modern lifestyles of indoor desk jobs in big cities – many don’t get the essential Sun exposure they would need. In other words: Even if you live in Ecuador you can get a deficiency, if you spend no time in the Sun.

What is a good vitamin D level?

Now not being deficient isn’t exactly the pinnacle of health. To find out what vitamin D level can be considered normal or healthy, we can look at traditional African populations that spend a good part of their day outdoors in the Sun – with no supplements. Their serum-D-levels are consistently above 40 ng/ml or 100 nmol/L.

Depending on the definition of an optimal vitamin D level, clearly the daily recommended dose varies greatly. Also as a fat-soluble nutrient, its metabolism is dependent on body fat and other factors, including your starting level and goal. A combination with vitamin K2 supplementation is often advised.

If you haven’t done any lab work or consultation yet, you can start with the daily intake recommendation from Harvard ranging from 600 IU to 4000 IU as upper limit. However, to fill up deficient individuals or to reach higher levels of D up to 10,000 IU daily might be required.

For a precise recommendation according to your situation, please consult an expert on this topic.

As you can see, It can get quite complicated, but we hope that you got the basic message – get sensible Sun exposure everyday if you can and supplement if necessary, stay safe and healthy!


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