Vitamin D produced in the skin is less than actually thought
Normally, when a person is diagnosed with vitamin D deficiency, it is thought that their skin is not adequately producing enough vitamin D resulting from the effects of the sun’s rays. New evidence is suggesting that much of the vitamin D that our body uses does not come from the skin alone, but actually diet and other sources as well.
A lot of people believe that the amount of vitamin D ingested through any consumed food is quite minimal, while the majority of vitamin D is obtained by the skin in the summer months while being out in the sun, and that some vitamin D is stored in fat. In the winter, it is thought that our bodies live off of the vitamin D in the fat stores due to the lack of sun exposure during the colder month
A study published in The Journal of Nutrition, patients were given vitamin D supplementation to determine the amount that their vitamin D levels increased over the period of a year. Results showed that season change only really accounts for a small portion for the varying vitamin D levels among individuals. This shows that vitamin D synthesis from the sun is not playing as big of a role in blood vitamin D levels as most people have thought.
The study also showed that vitamin D stored in fat also appears to be low, which means that when vitamin D is ingested, it is used immediately and not stored in high amounts, as previously thought. This means that once vitamin D supplementation is stopped, levels in the blood will fall.