Feeding and Nutrition :: Vitamin D3 and Calcium

[Deon]

Well, the site wasn't too clear and i think i read something different on another site so i wanted to clarify: (i've been wondering for a while now)

What does the turtle actually need to grow strong bones and shell - the calcium or vitamin d3?

I know that sunlight allows the turtle to create Vitamin D3 but (not sure about this ->) is the vitamin is needed to absorb the calcium? Or is the vitamin absorbed as well?

This is because i gave my turtle a calcium block once, and i was wondering if there was no UVB (and therefore no vitamin d3), would the calcium block have any effect?

One other thing - i read somewhere that the vitamin d3 will allow vitamin A to turn into calcium, is that true?

Thanks a lot!

[Kemul]

Well, from what I understand after reading about Vitamin D in wikipedia, Vitamin D
is regulating the absorption of Calcium. Without Vitamin D, Calcium cannot or not
optimally absorbed.

I think the calcium block has little to no effect without Vitamin D.

Vitamins are organic molecules, very different from single element like Calcium.
I don't think Vitamin A can simply turn into Calcium. Besides, looking at the
chemical structure, there isn't any Calcium (Ca) to make up Vitamin A.

Perhaps others can clarify? JAX (TheComputerGremlin) is the resident
chemistry expert here

[TheComputerGremlin]

Heehee, here I am to save the day! Thanks Kemul!

So, calcium is absorbed into the bones, making them stronger. This is for all species. Now in humans at least, vitamin D3 regulates calcium absorption by keeping the calcium in the bones put and using the calcium that is freely around, rather than the body depleting its calcium stores from the bones. I would guess that a similar mechanism is involved in turtles.

Vitamin D3 is made by exposure to UVB, causing a precursor to form into vitamin D3.

As I understand it, turtles need the calcium and the sunlight for strong bones. One without the other will cause some bone decay. But since vitamin D3 is formed naturally and calcium has to be taken in, calcium is crucial to the diet of turtles and humans. So definitely keep feeding your turtle cuttlebone, these are white blocks found in the bird section of the pet store. If you see a turtle-shaped white block, that's a conditioner and not meant to be eaten.

As for calcium being made out of vitamin A, there is no calcium in that molecule, so I would say that is false. Calcium, being an element, is at the lowest form that it can have. The only way to "make" calcium is to free it up from an existing chemical bond, but vitamin A doesn't contain any calcium.

If you need anything else clarified, I am happy to help! I'm a little absent-minded these days, so sometimes I feel like I'm rambling instead of giving a straight answer!