When does the good cancel the bad

When you combine good food and bad food do you come out even, backwards or forwards. This is a question I often think about. There is no simple answers, however the questions I have are like:

• I've just made a small amount of garlic bread for supper. Took 1/3 of french stick (white bread/white death) then made garlic butter, lashings of garlic, fistful of fresh parley (Italian), wholesome butter. Hmmm yummy. Does the health benefits of garlic, parsley and butter out weigh the bad of the white bread?
• When you sprinkle sugar on your stewed plums (in the middle of winter cause we freeze them free flow in summer) do you make it nutritionally neutral. Plums are nearly always to sour/tart to eat by themselves, but when you put white sugar on them - was does this do to the nutrition. (we often get around this by putting a few plums at a time in stewed apple / apple crumble thus adding color, flavor and nutrition without any extra sugar as the apples have enough. 

These are the things that keep we wondering about lifestyle choices we make.