Even with glances of explanations down here I admit I'm still not sure why 'olika' and not 'olik' (if olik is indeed degree zero of the adj) : it mat here simply considered as a plural ? Or is it basically the way it works for uncountable concepts in Swedish ?
I'm no expert, but it seems that 'mat' is being construed as plural. The Swedish 'mat' seems to be like the English 'food' in that you can use it as either a count or a non-count noun. So the Duo translation could also read 'We eat different foods', I would say.