My supermarkets sell like one or two brands, with three or four boring flavors in total, of fake (non-Asiatic) and tasteless instant noodles.
Actually my small Asiatic market I go to has the cheapest price on eggs, bread, soy milk, vegetables, many meats, etc. ... and yeah I always end up going there, because of that considerably lower price, and since there's overall quality in their products too.
It's smelly, it's crammed, they sell weird mushrooms, fishes and other animal parts, I can't read the labels (some times I absolutely no idea of what is contained in that tin can), but it's clean, the people are nice and polite... and they have one full alley of instant noodles!
Scurvy? oh yeah, Vitamin C, exactly like the one you find in a Ramen! I surely never had such a deficiency/sickness!
As long as you eat fruits and vegetables in between whatever unhealthy food you like, I think you're safe.
No joke I must have survived almost one full week (more like 5 days) only on white rice once, at the end of the finals, and it didn't feel bad.