Increase of the Cutaneous Vitamin D3 Synthesis for a Person Wearing UV Transparent Clothes: A Model Study

Humans should avoid prolonged exposure to the Sun during the warm subperiod of the year with naturally high solar UV level. One of the known recommendations to reduce excessive UV radiation is to wear clothes with UV protection additives. The level of the UV protection by clothing fabrics is measured as the Ultraviolet Protection Factor (UPF) which is usually calculated from spectral measurements of UV radiation transmittance through a selected fabric. Thus UPF is obtained as the ratio between UV intensity before and after passing through the fabric. The European Standard for sun-protective clothing (EN13758) states that fabrics with UPF larger than 40 could be labeled as UV-protective. However there is an important question: how to get adequate solar UV doses to keep a healthy status of vitamin D without overexposure risks?

Experiments with the artificial (emitted by fluorescent tubes) and solar radiation passing through various garments show that some kind of 100% cotton knitted fabric, used as normal daily clothing, has UPF~10. Model studies using UV exposure data typical for central Poland show that a garment made of this fabric allows larger synthesis of vitamin D3 in human body without the skin redness. Thus the adequate level of vitamin D could be attained safely by a person exposing only small part of his body (face, palms) during the warm sub-period (May-August) of the year with naturally high intensity of solar radiation. Wearing UV transparent garments is an option to keep adequate vitamin D level for persons with traditional way of clothing covering almost the whole body.