By Perry Holman, Executive Director, Vitamin D Society

Summer is the best time to take advantage of our bright sun to start building up your depleted vitamin D levels.

But how? What is the best way to sensibly use the power of the sun for vitamin D and health benefits?

Simply go outside when the UV index is above 3 and your shadow is shorter than your height and expose your skin making sure you don’t burn!

Cancer Research UK and six other organizations including two dermatology groups in the UK developed a Consensus Vitamin D Position Statement which recommends:  “Enjoy the sun safely while taking care not to burn, can help provide the benefits of vitamin D without unduly raising the risk of skin cancer.”

Here is how it works:

Vitamin D is made naturally in your body when the UVB rays from the sun reach your skin and convert a cholesterol to pre-vitamin D3. UVB rays are a short ray and need to be directly overhead to penetrate the atmosphere. When the sun is on an angle or low in the sky as it is in winter or in early morning or late afternoon and evening, the UVB rays do not get through the atmosphere so you cannot make vitamin D in your skin.

That is why the best time to make vitamin D in your skin in Canada is between the months of May and October, at midday, between 10am and 2pm, when the UV index is above 3 and the sun is directly above you, high in the sky. You can tell if it’s the right time if you look for your shadow. If your shadow is shorter than your height you’re good. If it is longer, the sun would be on an angle, the UVB would be mostly absorbed in the atmosphere and vitamin D production will be diminished.

Sunscreen if applied properly, prevents UVB from penetrating your skin, and will reduce your production of vitamin D by 95%.

How long should you be out in the sun to make adequate vitamin D through your  skin? Its complicated. The problem is everybody is different and it is hard to give one time estimate that works for everyone and in all the different situations.

Latitude, altitude, cloud cover, pollution, time of day, and the UV index all affect how much UVB reaches the ground. We do know that full body sun exposure at non-burning levels can create between 10,000-25,000 IU of vitamin D in your skin.

Skin pigmentation (colour) and age are also key factors. Darker skin will require significantly more exposure time in the sun than lighter skin colour up to approximately 10 times. And older people will need 3 times longer in the sun than younger folks as the capacity to generate vitamin D through the skin decreases with age.

Think of your body as a giant solar receptor. The more skin you have exposed, the more vitamin D you will make with less time and less chance of overexposure.

Body angle is also a key factor. Standing up vertically while in a t-shirt and shorts just lets the sun hit your head and shoulders. But laying down horizontally would allow the sun to reach your bare arms and legs. This would provide much more available skin area to make vitamin D.

It is important to gradually increase your time spent out in the sun. Your skin needs time to acclimatize itself to the sun. Exposing for too long early in the summer season will overpower your skin and may cause burning.

If you are planning to be out in the sun for a longer period of time make sure you protect yourself after your vitamin D session with clothing, a hat, shade or sunscreen to ensure you do not burn.

The key is to know your skin and skin type. Don’t burn. And never overexpose yourself.

If you like phone apps check out Dminder. It will help you determine when you can make vitamin D from the sun in your area.

Have a sunny vitamin D summer everyone!

 (To learn more about some of the points discussed above please read the paper - Sunlight and Vitamin D: A global perspective for health, by Matthias Wacker and Michael F. Holick.)