Virtually all commercial and automobile glass blocks UVB rays. As a result, you will not be able to increase your vitamin D levels by sitting in front of a sunny window, though much of the UVA radiation will penetrate the glass and may be harmful.
Here's Why: Can you get vitamin D through a window when sunlight streams in? The answer, in general, is “no.” It might seem like glass lets all the sun's UV rays get through to you, but that's just an illusion: glass – as well as plexiglass and plastic – absorbs all UVB radiation.
Shade. While it might seem counterintuitive, you can still get your daily dose of vitamin D without being in direct sunlight. When you sit in the shade, your skin is exposed to scattered UVB rays.
Abstract. To get an optimal vitamin D supplement from the sun at a minimal risk of getting cutaneous malignant melanoma (CMM), the best time of sun exposure is noon.
You need to have some skin exposed, for example, your forearms, hands and lower legs. But you can still make vitamin D even if you sit in the shade. Sitting inside by a sunny window doesn't count because glass filters out the UVB rays – the type of light that is needed to make vitamin D.
In summer, exposure is best at mid morning or mid afternoon (outside peak UV times). In winter, longer exposure times are needed, preferably around midday. It is important to balance the need for sun exposure to produce adequate vitamin D, at the same time avoiding the risk of skin damage from too much exposure.
Therefore, conditions that affect the gut and digestion, like celiac disease, chronic pancreatitis, Crohn's disease, and cystic fibrosis, can reduce vitamin D absorption.
According to the national Institutes of Health, between five and 30 minutes of sun exposure to your unprotected face, arms, legs or back between the hours of 10 a.m. and 3 p.m. two to three times every week is enough for your body to produce all of the D3 it needs.
A common misconception is that you can get vitamin D from the sun through clothing. This is not true, as the only way to trigger the chemical reaction that results in vitamin D production is for sunlight to reach your skin directly.
In summer and spring, with 22% of uncovered skin, 1000 IU vitamin D doses are synthesized in 10-15 min of sun exposure for adults.
The skin produces more vitamin D when in the sun during the middle of the day, the time it is at its highest point in the sky. When spending prolonged time in the hot sun, wear sunscreen, and stay hydrated. Amount of skin exposed. The more skin a person exposes, the more vitamin D the body will make.
Q. Am I still getting vitamin D when I'm outside on a gray, cloudy day? A. Just as it is possible to get a sunburn on an overcast day, it is possible to get the ultraviolet-B radiation needed for the skin to synthesize vitamin D even when skies are cloudy and gray.
The best sources are the flesh of fatty fish and fish liver oils. Smaller amounts are found in egg yolks, cheese, and beef liver. Certain mushrooms contain some vitamin D2; in addition some commercially sold mushrooms contain higher amounts of D2 due to intentionally being exposed to high amounts of ultraviolet light.
Vitamin D is lipophilic (fat-soluble) in nature, and can be absorbed through the skin, whether you acquire it from sunlight or topical use.
The best time to soak yourself in the sun to get the maximum vitamin D is between 10 am to 3 pm. At this time, the UVB rays are intense and it is also said that the body is more efficient in making vitamin D at this time.
Can vitamin D be harmful? Yes, getting too much vitamin D can be harmful. Very high levels of vitamin D in your blood (greater than 375 nmol/L or 150 ng/mL) can cause nausea, vomiting, muscle weakness, confusion, pain, loss of appetite, dehydration, excessive urination and thirst, and kidney stones.
According to Yale Medicine, vitamin D derived from sunlight is no better than the Vitamin D we get from supplements. They are functionally the same and can both boost vitamin D levels to a healthy range. The body can use supplemental and sunlight derived vitamin D in exactly the same way.
"Adequate levels of magnesium in the body are essential for the absorption and metabolism not only of vitamin D but of calcium as well," Dean states. "Magnesium converts vitamin D into its active form so that it can help calcium absorption.
Vitamin D deficiency is most commonly caused by a lack of exposure to sunlight. Some disorders can also cause the deficiency. The most common cause is lack of exposure to sunlight, usually when the diet is deficient in vitamin D, but certain disorders can also cause the deficiency.
Both forms are well absorbed in the small intestine. Absorption occurs by simple passive diffusion and by a mechanism that involves intestinal membrane carrier proteins [4]. The concurrent presence of fat in the gut enhances vitamin D absorption, but some vitamin D is absorbed even without dietary fat.
Symptoms of vitamin D deficiency may include:
Fatigue. Not sleeping well. Bone pain or achiness. Depression or feelings of sadness.
It can take anywhere from 1-6 months to raise vitamin D levels with supplements.
Recent findings: Low vitamin D levels are associated with increased symptoms of depression and anxiety. For this reason, vitamin D screening should be performed in the prevention and treatment planning of these mood disorders.