They determined that this is equivalent to taking 15,000 to 20,000 IUs of vitamin D. As a general recommendation, Dr. Holick suggests starting your sun exposure in the spring, going out for about one-third to one-half of the time it typically takes for you to turn a slightly darker shade in the middle of the summer.
The app, dminder.info, that Dr. Holick helped develop, provides guidance for sensible sun exposure.
So for example, if you normally get red after 30 minutes of exposure at noontime in June, then start out by exposing your arms, legs, abdomen, and back, for 10 to 15 minutes per day. After that, put on some protective clothing to prevent excess exposure.
Each day, add a couple of more minutes to build up a tan. Keep in mind that the pigmentation of your skin will influence how much sun you can tolerate.
The skin pigment melanin is a natural sunscreen, absorbing UV light coming into your skin. As a result, it markedly reduces the efficiency of your skin to produce vitamin D. As a result, dark-skinned individuals need more sun exposure than light-skinned individuals to produce the same amount of vitamin D.
What's the Ideal Vitamin D Level?
What do you want your blood level to be? A study done in Africa on Maasai warriors, who are outside every day, showed they had a blood level of 25-hydroxyvitamin D averaging around 48 ng/ml. At present, a vitamin D (25-hydroxyvitamin D) level between 40 and 60 ng/ml is thought to be ideal for optimal health and disease prevention.
"The Endocrine Society Clinical Practice Guidelines Committee that makes the recommendations to physicians for how to treat or prevent vitamin D deficiency [say that] your level should be at least 30 ng/ml. Forty to 60 ng/ml is a good range, and we know up to 100 ng/ml is perfectly safe," Dr. Holick says, adding that: "It's estimated that improving vitamin D status worldwide could reduce healthcare cost across the board by about 25 percent."