the problem is that most bulbs that are reported to produce UVB may not actually produce UV in the correct wavelengths (280-315 nm). These results may be due to utilizing the incorrect photometer when measuring the wavelength (some recent data shows that using a broad range photometer can result in inconsistant results) and even narrow bands can provide the wrong data unless they are calibrated against a known standard.

In general, UVB supplementation should be utilized as a backup method for D3 supplementation (this is because photoconversion will only occur if there is insufficient D3 in the body).

Ed