UVB

The first key insight is that ambient UVB emerges as a critical predictor of vitamin D status, even in a place like the UK, which receives relatively little sunlight.

For example, as BMI and age increase, the amount of vitamin D produced in response to UVB decreases.

UV light includes UVA, UVB and UVC light.

UV light is categorized into three different regions -- UVA, UVB and UVC -- based on different wavelength ranges.

Longer-wavelength UVA rays penetrate deeper into the skin than shorter-wavelength UVB rays, although both types are known to cause skin cancer.