Would you be prepared to share how much do you spend, for how many people, and what are your standards when food shopping? If you want to share how much of a stretch it is for you too, that would be interesting, but obviously most people probably don't like sharing that
We, for instance, are really only feeding 2 proper people, plus DS (only 8.5 months, eats a reasonable amount). We eat only organic meat, almost all seasonal veg (occaisonal lapse, and we have bananas and oranges most of the year), organic veg where possible, but choose british over organic if necessary.
We spend on average £35 a week at the moment, and could probably cut a bit more if necessary, by eating less meat, being less precious about organic veg and embracing lentils and pulses a bit more.
As a percentage of entire income it's not a huge percentage (DP isn't anywhere near being a higher rate taxpayer, I am not earning anything at the moment), but it probably accounts for a good percentage of our spare income after rent and debt repayments from DP's misspent youth - we do not have holidays abroad, meals out etc, at all.