I doubt that would put them out of business completely, and it might actually encourage people to look at what they eat a little more than they do currently.
I'm pretty much for abolishing all tax "breaks" - they're too easily manipulated. If you earn it, it counts as income, you pay a tax on it. Something like 30%*(total income - avg. cost of living in region - maybe by county?). That's open to being gamed as well, but less so than the current system.