While fruit juices have a healthy reputation, I don't believe they're as healthy as their image suggests.
One key property of fruit juices is that they tend to be very sugary indeed. Many fruit juices have a sugar concentration similar to sugary soft drinks. And some juices (such as grape juice) contain considerably more sugar.
Now, if I had to drink fruit juice or a sugary soft drink I'd choose the former—the fruit juice wins hands down in terms of its ability to deliver some nourishment to the body. However, the intensely sugary nature of fruit juices make them far from an ideal beverage for those seeking to optimize their health.
With this in mind, I was interested to read the results of a recently published study in which the relationship between the consumption of green vegetables, whole fruit, and fruit juice and risk of diabetes was assessed in more than 73,000 women over a period of 18 years [1]. The results of this study showed the following:
An increase in whole fruit consumption of three servings a day was associated with an 18 percent reduced risk of diabetes.
An increase in green vegetable consumption of one serving a day was associated with a 9 percent reduced risk of diabetes.
An increase in fruit juice consumption of one serving a day was associated with an 18 percent INCREASED risk of diabetes.
Epidemiological studies of this nature may show that drinking fruit juice is associated with diabetes risk, but they cannot prove that fruit juices can cause diabetes. However, the high-sugar nature of fruit juices means that they may indeed have a genuine diabetes-inducing effect.
It is sometimes said that the fruit sugar (fructose) found in high levels in fruit juice is relatively harmless because it does not tend to raise blood sugar levels. However, fructose is anything but safe, and its consumption has been found to induce something known as insulin resistance, which is a precursor of diabetes.
Personally, I don't think it's any major surprise that the drinking of fruit juice has been implicated in the development of diabetes. My advice remains the same: Give fruit juice a wide berth.
Reference:
1. Bazzano LA, et al. Intake of Fruit, Vegetables, and Fruit Juices and Risk of Diabetes in Women. Diabetes Care [Epub 4 April 2008]
Dr. John Briffa is a London-based doctor and author with an interest in nutrition and natural medicine.
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