Fruit juices are a source of fructose, which goes by the more common name "fruit sugar." The fructose in fruit juice may be naturally occurring, or it may be added in one of two different forms. Depending upon the type of fruit juice and the source of the fructose present, juices may or may not be a particularly healthy component of diet.
Fructose
Fructose shares some similarities with the more common and familiar sugars sucrose -- the chemical name for table sugar -- and glucose. All three are sweet to varying degrees, and all three occur naturally in fruit. They also all contain calories and have the ability to provide your cells with the energy they need to engage in various processes. Compared with sucrose, fructose is about 40 percent sweeter, according to Elmhurst University. Compared with glucose, fructose is twice as sweet.
Natural Fructose in Juice
Two natural sources of fructose are in fruit juice. All natural fruit juice -- that is, juice made from fruit rather than from sugar syrup and flavoring agents -- contains fructose from the fruit itself. Plants synthesize fructose using the sun's light through the process of photosynthesis, explain Doctors Reginald Garrett and Charles Grisham in their book "Biochemistry," and store much of the fructose in the fruit of the plant. Natural fruit juices also contain sucrose, which is made up of fructose chemically bonded to glucose.
Added Fructose in Juice
Juices may also contain added sugar -- this is particularly true of juices made from sour fruits, such as grapefruit and cranberry. Added sugar typically comes in one of two forms: sucrose or high fructose corn syrup -- both of which contain fructose. Adding additional sugar to fruit juice increases the caloric content of the juice, as well as the potential of the juice to raise blood sugar, which can lead to obesity.
Health Value
In general, fruit juices aren't as healthy as whole fruit, regardless of whether they contain added fructose. This is because whole fruit contains fiber and makes you feel more full for a longer period of time than do juices. However, juices without added sugar are healthier than juices with added sugar, because they're lower in calories. Furthermore, juices with added sucrose are healthier than juices with added high fructose corn syrup. Studies, such as a 2004 publication in the "American Journal of Clinical Nutrition," suggest that high fructose corn syrup consumption increases your risk of obesity.
References
- Elmhurst University (Illinois): Relative Sweetness
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
- "American Journal of Clinical Nutrition"; Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity; George Bray et al; April 2004
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