UVB light or not?

Question
i wonder why lizard need UVB light to produce vitamin D3.one of my sister have raise one red ear slider for years without any expose to natural sunlight or UVB light.it doesnt seems to develope any signs of MBD.can somebody explain why?she only feed it with turtle pellet.  

Answer
Hello Kew,

I cannot explain why your sister's red ear slider has done so well, genetics perhaps.  Unfortunately turtles can go for years sometimes without showing external signs but then appear to all of the sudden start declining in health.  Soft shell is very common & if your sister is not aware of what that causes, she will need to do some research on that.  It will eventually cause pyramiding of the shell as well as overall lack of appetite, etc.  She only feeds her pellets, but no greens, veggies or insects?  I am very surprised that her turtle is not showing any poor health yet, because eventually, it probably will.  They can only go so long without proper UVB & calcium.  Honestly, that is not a very healthy environment for the turtle to go without UVB.  
Lizards are a little different but still need full spectrum lighting.  They cannot properly absorb their calcium & vitamins or synthesize D3 without UVB exposure.  So, it is not advisable to raise reptiles without UVB, otherwise eventually you will encounter health problems on down the road which cost more than purchasing UVB's on a regular basis.

Tracie