Jean-Louis:

>PHYTIC ACID is a well-known ligand, present in cereals, which form insoluble
>complexes with metals such as Zn.

>OXALIC ACID binds with Ca (calcium), and an excess of oxalic acid (which is
>present in spinach) can create a calcium deficiency.

Do these effects only occur when the mineral is present in the same meal as
the ligand, or can the ligand bind with minerals that have already been
processed by the body, or indeed 'hang around' and interfere with
absorption of minerals eaten at later meals?

While on this topic - is it better to eat hulled or unhulled sesame seeds?
I understand that they contain a lot more calcium when the hulls are left
on, but that the hulls also contain phytic acid, which is problematic. (I
have read that phytic acid interferes with calcium absorption, but did not
know about the zinc.) FWIW, I think I prefer the taste of sesame seeds when
the hulls have been removed.

Regards,
Barbara