My body, being old, no longer processed the iron correctly. This was discovered in hospital and confirmed by my GP although blood tests did not show anaemia.
What most people need is heme iron and nowadays it's being called 'gentle iron' in some places as it doesn't cause constipation.
Ask your pharmacist for advice - iron is not expensive and if your husband needs supplements, clearly he's not getting enough from food - in fact we rarely do, especially as we get older.
Foods which can inhibit iron absorbtion are:
wheat, the tannin in tea and coffee, eggs, dairy and rhubarb
But only in excess - I get by in very lively fashion with an occasonal egg and my Iron & Vitamin C supplement and frankly feel bleh if I forget to take it.
I take brands made in NZ so no point in recommending the one that keeps me bouncing - but your chemist/pharmacist will know.