If you avoid the sun, avoid milk products or are vegan then you are possibly at risk for vitamin D deficiency.
Human skin can make vitamin D when large areas of skin are exposed to ultraviolet B light.
Vitamin D is essential for strong bones, because it helps the body use calcium from the diet.
Although not explicitly proven, Vitamin D deficiency has been linked with autism, autoimmune disease, cancer, chronic pain, depression, diabetes, heart disease, high blood pressure, flu, neuromuscular diseases, and osteoporosis.
The only proven benefit of vitamin D is its role in helping calcium build strong bones. But that's far from the whole story. Vitamin D helps regulate the immune and the neuromuscular system. Vitamin D also plays major roles in the life cycle of human cells.
We can acquire vitamin D through sunlight and diet i.e. by eating fatty fish etc. but the amount we consume pales in comparison to how much we can make by exposure to sunlight.
10 minutes in the midday summer sun with your arms and legs exposed (we don't need to be naked. We aren't savages) is enough to make 50 times the vitamin D you need in a day.
Now, your location and time of the year is important. We require UVB rays (invisible on the human spectrum) and at higher latitudes and in the winter months the angle means that UV-B rays cannot penetrate the atmosphere as well. This means a reduction in vitamin D.
Luckily for cultures like the Innuit, they are able to obtain a good amount of Vitamin D as their diet is rich in fatty fish.
What is vitamin D?
Vitamin D is possibly the oldest hormone found in nature (750 million years) and was produced by plankton in the ocean.
As life evolved in the ocean almost all animals use vitamin D.
Our ability to produce vitamin D is like a human version of photosynthesis but rather than using the suns energy for food, as in plants, we use it to create vitamin D.
Evolutionary pressure gradually forced humans to lose body hair thus exposing our skin to the sun. This loss of body hair allowed us to sweat all over our body, a key advantage in hot climates that allowed us to “persistence hunt” other animals and forage for food for long periods of time under the hot sun without brain damage due to overheating. this gave us an evolutionary advantage over other species
The loss of hair also demands the need for better protection from the sun.
For about 1.5 million years up to around 100,000 years our ancestors had dark skin. Climactic changes drove early humans into arid, open landscapes. Such conditions likely caused excess UV-B radiation.
This favored the emergence of skin pigmentation in order to protect from folate depletion due to the increased exposure to sunlight.
Migration, whether forced or not took us into colder climates and with the colder climates came the use of clothing which, in turn, reduced the evolutionary pressure working against the survival of lighter-skinned gene variants. This was due to less photodestruction of folate. As lighter skin is able to produce more vitamin D it would be advantageous in low sunlight conditions.
That was a long time ago and things have changed. In our hectic lives we barely spend any time outside anymore. Pressures of work, family commitments etc leave no time for play and exposure to the sun.
There were times in the winter when I would wake up in the dark at 6:30. head to the metro and arrive at work just before the sun rose. I'd stay indoors most of the day, eating lunch in work and leave at 4 when it was just going dark! I'm sure this is a common daily routine for a lot of people with 9-5 indoor jobs. Talk about lack of exposure to the sun.
Even when we think about getting out in sun, we're warned that we are going to get skin cancer if you so much as look at the sun so more of us are being put off being out in it for too long, even if we have adequate sun protection cream on. Experts inform us that you can spend 10 to 20 minutes in the sun without protection depending on the colour of your skin. Naturally darker skin has more protection.
The great news is that we can still get adequate protection from the sun if we use sunscreen. An SPF 15 sunscreen filters out 93 percent of UVB rays, SPF 30 keeps out 97 percent, and SPF 50 filters out 98 percent. This leaves anywhere from 2 to 7 percent of solar UVB reaching your skin, even with high-SPF sunscreens.
The take home message here is that we should get out and play)!
If we stay active we reduce body fat, mobilize joints and bones. Workout muscles and increase bone density. We stimulate our visual system which keeps out brain active. Not only that but we get a nice healthy dose of vitamin D.