Drinking 2 to 4 cups of green juice a day (alternatively 16 to 32 ounces) of green juice is the optimal amount. It doesn't have to be a single serving; you can alternate between morning and night. The Institute of Medicine recommends a daily intake of 25 grams for women and 38 grams for men. While vegetable juice is nothing new, since products such as V8 and carrot juice have been circulating for years, green juices use large quantities of leafy and brassic vegetables, such as kale, spinach, chard and broccoli.
The other main difference between green juice (fresh) and traditional vegetable drinks is the technique: cold pressed, in which the juice is extracted through a method of crushing and pressing. Traditional centrifugal juicers, the type normally sold in Great Britain, use fast-spinning blades that heat up when turning and, therefore, say the cold-pressed converts, oxidize and thus destroy some of the nutrients in the juice. Clare Neill, co-founder of the juice company Radiance Cleanse, says that juice from a centrifugal machine oxidizes faster because a large amount of air has passed through the juice while it is being made. You can drink juices as often as you want, depending on your health goals.
You can drink juices daily and incorporate them into your current diet. Drink it right away, instead of storing it in the fridge, and keep in mind that they're not as good at squeezing leafy greens, so you'll have to squeeze more to get the same volume. The most inveterate drinkers of green juice prefer freshly made juice at home, but you can also buy it in cafeterias that specialize in juice.