(Time) Strawberries. Your mistake: Slicing them before eating. The fix: Eating them whole. Why it works: Whole strawberries contain 8% to 12% more vitamin C than the cut fruits, according to a 2011 Brazilian study. That’s because vitamin C begins to break down when it’s exposed to light and oxygen. For the biggest C boost, store whole strawberries in the fridge — cool temperature helps retain vitamin C too, finds the same study. Click here to read more on 5 Foods You’re Eating Wrong .