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Well you can't eat as much titanium as you can eat calcium so there is that.

LeifCarrotson 9y ago
That's because neither you nor anything in your diet (nor anything in your diet's diet) has titanium teeth and jaws. The Earth's crust is 3.6% calcium, and we get more than enough of that in our diet...it's 5% iron. There's even a lot of titanium - fully 0.6%, much higher than 'rare' elements like carbon! [0] I don't think we'd have any trouble getting it if the metabolic and biological systems that are employed to get us calcium were instead employed to produce titanium. [0]: https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth...
- comicjk 9y ago
  We take in calcium as +2 ions, and use it in the same state when making calcium phosphate for bones. That helps because calcium, like most metals, takes a lot of energy to reduce to its metallic form. Titanium and iron are also naturally found as ions. Getting bulk quantities of the metallic form would be a waste from an evolutionary standpoint, when it could just make a strong mineral-based composite material like bone.
- bsder 9y ago
  > There's even a lot of titanium - fully 0.6%, much higher than 'rare' elements like carbon! [0] Almost all our carbon goes back to the air. This leads to the interesting concept that when you are losing weight, you are actually exhaling most of your weight loss. Edited: Downcommenter is correct. Sorry, glitched. I was thinking about various things and pulled plants into the mix when the article is only about humans.
  - FreeFull 9y ago
    What do you mean by "We don't eat carbon"? All food that humans consume is mostly made out of carbon, hydrogen, oxygen and nitrogen. The carbon is indeed breathed out in the form of carbon dioxide, but no animal is capable of taking carbon from the air and integrating it into their body.
    - chrisdbaldwin 9y ago
      unless you consider plant life some form of animal ;)

That's because neither you nor anything in your diet (nor anything in your diet's diet) has titanium teeth and jaws. The Earth's crust is 3.6% calcium, and we get more than enough of that in our diet...it's 5% iron. There's even a lot of titanium - fully 0.6%, much higher than 'rare' elements like carbon! [0] I don't think we'd have any trouble getting it if the metabolic and biological systems that are employed to get us calcium were instead employed to produce titanium. [0]: https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth...

comicjk 9y ago
We take in calcium as +2 ions, and use it in the same state when making calcium phosphate for bones. That helps because calcium, like most metals, takes a lot of energy to reduce to its metallic form. Titanium and iron are also naturally found as ions. Getting bulk quantities of the metallic form would be a waste from an evolutionary standpoint, when it could just make a strong mineral-based composite material like bone.
bsder 9y ago
> There's even a lot of titanium - fully 0.6%, much higher than 'rare' elements like carbon! [0] Almost all our carbon goes back to the air. This leads to the interesting concept that when you are losing weight, you are actually exhaling most of your weight loss. Edited: Downcommenter is correct. Sorry, glitched. I was thinking about various things and pulled plants into the mix when the article is only about humans.
- FreeFull 9y ago
  What do you mean by "We don't eat carbon"? All food that humans consume is mostly made out of carbon, hydrogen, oxygen and nitrogen. The carbon is indeed breathed out in the form of carbon dioxide, but no animal is capable of taking carbon from the air and integrating it into their body.
  - chrisdbaldwin 9y ago
    unless you consider plant life some form of animal ;)