The first day of summer arrives in a few short days! Warm weather, sunshine, beach days, barbecues and every outdoor activity you can imagine is officially in full swing during this short season. With all of the time we spend outdoors and mounds of conflicting information on sunscreen, Vitamin D and sunlight, how do we know how much sun exposure is safe and beneficial for us before it causes harm? I may have some insight from the research I've done on this topic.
Why is Vitamin D important?
Vitamin D deficiency is linked to bone fractures, decreased immune function, rickets, osteoporosis, Multiple Sclerosis, cancers, etc. the list goes on! There are also countless benefits of optimal Vitamin D levels since Vitamin D is used in numerous metabolic processes.
What is Vitamin D?
Vitamin D is a steroid hormone that is derived from cholesterol and converted by a chemical reaction in our skin when exposed to the solar radiation from the sun. There are 5 different D vitamins that exist and from what we know about them, Vitamin D2 (found in plants) & D3 (found in animals) are the two important one’s involved in human metabolism. As a result of working indoors most people in North America do not make enough Vitamin D to sustain body processes at an optimal level and there is a strong correlation with Vitamin D deficiency and latitude.
How is Vitamin D made from the sun?
In our bodies, we produce the precursor of Vitamin D from cholesterol (called dehydrocholesterol or 7DHC), which gets secreted on our skin by our sebaceous glands (i.e. our sweat glands). Essentially, our sweat glands release the precursors we need to make active Vitamin D.
So, how exactly does this work?
When our skin is exposed to UV radiation, the dehydrocholesterol that was released from our sweat glands can react with the sun and get converted into pre-Vitamin D3. Then over a period of time (roughly 2-3 days), the pre-Vitamin D3 on our skin will get converted into inactive Vitamin D3 (called cholecalciferol). After all of these reactions take place, the inactive Vitamin D3 on our skin will get absorbed into our bodies then transported to the liver and kidney's to undergo two more reactions to become active Vitamin D3, so that we can use it for countless metabolic processes.
Based on this explanation of Vitamin D, why are so many people in North America Vitamin D deficient even if they spend hours in the sun?
Because we wash our skin way too much and plaster it with all kinds of creams, lotions, make-up, sprays, sunscreen and fragrance! We cannot make the Vitamin D our body needs if we are covering up our skin with all kinds of personal care products. On top of all of this, if you take a daily shower, go swimming or excessively wash your body, you are washing off all of the components your body made and needs to form active Vitamin D. Remember, it takes 2-3 days for the pre-Vitamin D on our skin to get converted into the active Vitamin D that our body can utilize. So if you’re washing your skin after sun exposure or washing yourself on a regular basis then the chances are that you are washing away all of those important components your body made to make Vitamin D.
Let’s add another layer to this equation. Let’s assume that perhaps you don’t shower and never cover your skin with any products. How much time in the sun would you need to get enough Vitamin D?
It has been suggested that 30 minutes of full body naked exposure to the sun will produce 10,000-20,000 IU of Vitamin D3. Other sources have suggested that 15 minutes of full naked body exposure may get you 5,000 IU of Vitamin D3. But the caveat with these values is that it must be FULL-NUDE sun exposure.
Let’s make things a little more tangible considering the following 6 factors that influence Vitamin D production:
2) Latitude (above 35 degrees latitude is where Vitamin D levels start to drop)
3) Time of day (best during 10-3pm)
4) Degree of skin pigmentation (the darker your skin, the more sun exposure you can tolerate)
5) Age (as we age, our organ function starts to drop so we have less of an ability to convert Vitamin D into its active form)
6) Geographic location (urban areas with high buildings tend to block sunlight)
To make 1000IU of Vitamin D (which is the equivalent of most Vitamin D supplements), it takes 5-15 minutes of sun exposure in fair skinned middle-aged individuals between the hours of 10-3pm. This value takes into consideration if you are wearing a t-shirt and shorts with no hat. Since everyone has a different skin pigmentation, age, and geography, as a general rule, once your skin turns a little pink or feels warm to touch, this is when the Vitamin D production cycle is shut off and you are now exposing yourself to harmful sun exposure. Using this rule and considering your own personal health history (weighing your risks of skin cancer, etc.), you can consider applying sunscreen 5-15 minutes after you go outside.
What about Vitamin D supplements?
Consuming Vitamin D from supplements or food sources (like mushrooms, liver or oily fish) requires that our body must break it down through our digestive processes. Although this absorption is greatly improved if we consume fat in our diet (absorption of Vitamin D is 10X higher when consumed with fat), on average only 50% of the Vitamin D from supplements actually gets absorbed in our body. This isn’t to say that Vitamin D supplements are not beneficial; it just means that we must consider tailoring our Vitamin requirements to meet our own specific needs. Speak with a licensed naturopathic doctor to figure out which dosage is right for you.
Since I spend as much time as I can outdoors in the summer, I try to balance out safe sun exposure with protection. When I know I will be outdoors for prolonged periods, I personally always protect my skin using hats, clothing or sunscreen. If you use sunscreen, I suggest looking into safe sunscreen options. The chemicals found in many sunscreens on the market are awful so choosing a brand that you can trust is essential.
The Environmental Working Group also put together a list of sunscreen options that you can consider. The EWG does a great job at comparing different sunscreen brands that you can find at a store near you!
Please note that there are several other complex steps involved in the metabolism of Vitamin D, but I wanted to simplify the process to the best of my ability. If you would like to learn more details, please feel free to contact me and I can point you in the direction of a few key resources.
Happy summer everyone! Enjoy the sunshine!