Juices won't take the place of your five-a-day, because the roughage in whole fruit and veg is crucial. But they can take the place of one or two and bump consumption up to seven or eight.
Because they are essentially concentrated vegetables and fruit, juices pack plenty of antioxidants such as vitamins A and C, which neutralise free radicals. We can't avoid free radicals – unstable molecules in our system which damage healthy cells, causing cancer, and age-related diseases like macular degeneration and arthritis – but we can mop them up with antioxidant-rich foods.
Juice has countless other beneficial nutrients, such as potassium (particularly high in bananas), which is good for balancing sodium and keeping blood pressure low, and magnesium, which is abundant in leafy green vegetables and is important for bone density and muscles.
Of course, there are plenty of tablets on the market, but the evidence suggests that the complex blends of vitamins and minerals in food work synergistically, boosting each other's effect. So, get your nutrients from a balanced diet, not a soulless supplement. And juices taste so much better.