I agree, three cans a day is quite a lot to have on a daily basis. would you consider other forms of protein such as eggs? nuts can be cheap enough too if you get own brand. Or if you are really watching calories, there are other choices such as kidney beans that are also very cheap too, i get mine from aldi and if you have little tuppawares they make a portable snack, a full tin is 16 g protein so not as much as the tuna. turkey mince is also great and you can prepare it ahead in batches, in 300 g of turkey mince there is 100 g of protein (an average sized carton) so if you were to split this five ways and maybe prepare ahead with some veg or something you would get five mini meals from that and prob the same price as your cans of tuna with 20 g protein per meal, also really low cal too, i think in the full carton of mince its 450 cal (taken from the colins book of calories). so you would be looking at less than 100 g per mini meal. Hope thats of help! I think the guidelines for fish are still three times a week so I wouldnt go too mad on it!