A friend is over and asked me a question about sunlight and it’s properties after going through glass.
Mainly the two biggest questions are:
How much vitamin D is absorbed when sitting front of a window as opposed to being outside in direct sunlight? I realize there’s a factor of the type of glass and any tinting, but let’s stick with your everyday pane glass found in most homes.
Sub-question. Does the body absord vitamin D from sunlight, or does sunlight somehow help us process the vitamin D already in us?
Can you still get a suntan if sitting in front of a window?
The first question is the big one we hope to have answered. It can up as a result of a friend of ours who gave birth to a very sick baby. The doctors adviced her, based on jaundice, to have the baby in front of a window for a certain period everyday for the vitamin D factor.
Any help on this would be greatly appreciated. Thanks
Window glass typically has a UV cutoff (i.e. wavelength below which little light gets through) at around 320 to 350 nm, although that varies depending on the type of glass.
So you won’t make much vitamin D by sitting in front of a closed window.
Phototherapy for neonatal jaundice has nothing to do with vitamin D metabolism.
In infants, hyperbilirubinemia arises from a number of causes, but basically boils down to an inability of the liver to adequately dispose of the breakdown products of hemoglobin. Insoluble bilirubin builds up in the body tissues, leading to the characteristic yellow-brown color change of jaundice. Bilirubin breakdown products are normally excreted into the bile and thence into the gut, where they contribute to most of the brown color of poop.
Glossing over the details of diagnosis, prognosis, etc., neonatal jaundice is often treated with phototherapy, in which blue light , not UV light, of a wavelength of around 450 nm is used. The effective wavelength range, from 425-475 nm, passes easily through plate glass. The blue light causes the bilirubin in the skin to break down into a water-soluble form which is then eventually excreted by the kidneys. Hospitals use fiberoptic blankets with controlled light sources that look deep blue, like a Wood’s lamp, to maximize the effect, but UV is not used. Regular sunlight is effective to a lesser degree, and if a child has recovered from the cause of the jaundice but is still slow to clear the pigment, then sunlight alone will hasten the breakdown.
Note: IF YOUR BABY IS JAUNDICED, SEEK MEDICAL ATTENTION! SEVERE NEONATAL JAUNDICE CAN CAUSE BRAIN DAMAGE OR DEATH!