Factor #1: Usage of Sunscreen: In order for the skin to make Calcitriol (Vitamin D), it needs UVB rays from sunshine. Consequently, sunscreens that block UVB radiation also stop your skin from making vitamin D. This is an very important factor to keep in mind, if you’re concerned about your Vitamin D (Calcitriol) levels, especially because sunscreen protects us from the sun’s damaging effects, which can be caused by the very same rays, including premature aging of the skin and skin malignancy.

Factor #2: Skin Melanin content: The degree of skin pigmentation also largely determines how well the dermal tissues can make Calcitriol (Vitamin D) from the sun. The darker the pigmentation of the skin, the more difficult it is for your skin to make Calcitriol. This is because melanin is a natural sunscreen that filters out UVB radiation, which is mandatory for vitamin D manufacturing.

Factor #3: Your Weight: Vitamin D (Calcitriol) is a vitamin soluble in fat and oils, which means it gets tucked away in your fat tissue. The more body fat you possess, the more Vitamin D (Calcitriol) is stored in the body lipids, which means less vitamin D makes its way into your circulation, this is called decreased bioavailability. Vitamin D deficiency is strongly correlated with obesity and many studies have shown that there is reduced bioavailability of vitamin D in obese people.

Factor #4: A Person’s Age: Age also reduces the skin’s natural ability to make vitamin D from sun light. Scientific studies have revealed that a seventy year old person makes approximately 4x less vitamin D from the sun than a twenty year old. Knowing this difference is very very important for the elderly who may spend an insignificant amount of time in the sun, and solely depend on exposure to the sun for their vitamin D needs.

Although our bodies are capable of producing plenty of vitamin D from the sun, the aforementioned factors influence the ability of vitamin D synthesis by our skin. It is important to understand that vitamin D attained through food sources is not influenced by any of these factors. The Food and Drug Administration’s listed daily requirement of vitamin D is only 400IU, however, several studies contest this dosage and seem to indicate a need for a higher daily supplementation. The National Institute of Medicine recommends 2,000IU per day for healthy adults. Due to the lipid-solubility of vitamin D, amounts larger than 10,000IU daily may be toxic unless prescribed by a medical physicianwho has checked your circulating Vitamin D levels.