Iron in iron tablets is in the Fe 2+ oxidation state, which is the most "bioavailable" i.e. accessible to the human body.
Some iron-rich foodstuffs - like spinach - are paradoxically low in bioavailable iron because it's all bound up in an unusable oxidation state.
Not surprisingly the best sources of dietary iron are red meat and black puddings - because the iron in these is already in a bioavailable state.
Furthermore, consuming some ascorbic acid (vitamin C) alongside something iron-rich is a good way to boost iron uptake because it can competitively prevent iron oxidation (being the anti-oxidant that it is).
Chris
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