My familiy's collie needs regular brushing; he's an outside dog so shedding's not really an issue, but if he's not, he quickly develops a distinctly Rastafarian look and has to have his dreads cut out, to his great humiliation
I think sheddings's generally something certain breeds just do
and I can't imagine diet would make much difference.
I've seen many a clipped collie...a heat, rather than shedding thing, but it'd work.
But I think it looks ridiculous, and I'm pretty sure the dogs feel the same!