What's missing in fruit juice.
Whole fruit provides you with a whole lot more nutrition that fruit juice. Focusing upon two components of fruit - the skin and the pulp - will help to clarify why there is such a difference between the two.
The benefits of fruit skins
The edible skins of many of the World's Healthiest Fruits - including apples, apricots, blueberries, figs, grapes, pears, plums, prunes, raisins, raspberries, and strawberries - are all sites of important biological activity in the life of the fruit. The skin is one of the places where the fruit interacts with sunlight, and forms a variety of colored pigments that absorb different wavelengths of light. These pigments, including carotenoids and flavonoids, are well researched as nutrients that protect our health and nourishment. The skins of whole fruits like grapes have actually been studied for their ability to help lower risk of cancer and help provide protection from ultraviolet light.
Unfortunately, when fruits are juiced, we don't always get to enjoy the fruit's skin. That is because many juicing processes remove the skin, and do not allow for its full benefits to get into the juice.
The benefits of the fruit pulp
In addition to the skin, which is an important source of fiber in most fruits, the pulpy part of the fruit is also a source of fiber (and other nutrients). Orange juice makes a good example of the health difference when you focus on the issue of its pulp. The white pulpy part of the orange is the primary source of its flavonoids. The juicy orange-colored sections of the orange contain most of its vitamin C. In the body, flavonoids and vitamin C often work together, and support health through their interaction. When the pulpy white part of the orange is removed in the processing of orange juice, the flavonoids in the orange are lost in the process. This loss of flavonoids is one of the many reasons for eating the orange in its whole food form (even if you only end up eating a little bit of the white pulpy part). Although many commercial products will say "pulp added" on their labels, the "pulp added" many not even be the original pulp found in the whole fruit, and it is highly unlikely to be added back in the amount removed.
Juicing reduces the fiber content
How much fiber is lost in the conversion from whole fruit to fruit juice? Let's use apples and apple juice as an example.
A cup of apple juice that you can see straight through (pulp removed) contains no measurable amount of fiber. To create this 8-ounce glass of juice, approximately 3-4 apples are needed (depending, of course, on the size and density of the apples). Each of these 3-4 apples contains about 3.75 grams of dietary fiber, for a total of about 12-15 grams of dietary fiber. Virtually all of these 12-15 grams are lost in the production of clear apple juice! These 12-15 grams of lost fiber, if added back into the juice, would fully double our average daily fiber intake!
Is fruit juice unhealthy?
The answer to this question depends on how it's consumed, and what foods it replaces. Fruit juice that has been robbed of its fiber and broad range of nutrients is basically just a concentrated source of sugar that lacks the supportive nutrients to help it digest and metabolize. Fruit juice elevates blood sugar more quickly than whole fruit, and the level of sugar that can be obtained from fruit juice is higher than the level found in whole fruit. For example, 120 calories' worth of whole apples contains about 24 grams of sugar, while 120 calories' worth of apple juice contains about 30 grams.
Additionally, many fruit juices that are sold in supermarkets contain only a small percentage of real fruit juice, and contain added sweeteners (sucrose or high fructose corn syrup). As a result, it is easy to consume a large amount of calories without getting any actual nutrition when you consume these beverages. Make sure you read fruit juice labels carefully! Turn over on the back of the jar or bottle, and look over the ingredient list - you may be surprised to see exactly where the fruit itself fits in!