There's more good news about cranberry juice: researchers have found that drinking three glasses a day significantly raises levels of 'good cholesterol' in the blood and increases plasma antioxidant levels, reducing the risk of heart disease.
Although the researchers say they have long suspected, based on laboratory tests, that the antioxidant-rich juice may help lower risk factors for heart disease, no human studies had established such a link before now. Their findings, from a small long-term study funded by the Cranberry Institute in the US, were described this week at the 225th national meeting of the American Chemical Society.
Following three months of a daily intake of cranberry juice, reaching a maximum of three glasses per day, the researchers found significant increases in the amount of good cholesterol - high density lipoprotein (HDL) - and of plasma antioxidant capacity which in turn both correspond to a decrease in the risk of heart disease.
Joe Vinson, the study's lead author and a professor of chemistry at the University of Scranton in Pennsylvania, in the US, measured cholesterol levels in 19 subjects with high cholesterol after a fasting, baseline blood sampling, followed by monthly samplings. Ten of the subjects were given cranberry juice with artificial sweetener but without high fructose corn syrup, while the other subjects drank cranberry juice with no added sugars. The drinks tested all contained approximately 27 per cent pure cranberry juice by volume, like the common supermarket variety.
Each subject drank one glass (8 ounces) of juice a day for the first month, then two glasses a day for the next month, and three glasses a day during the third month of the study. Subjects were not monitored with respect to exercise, diet and alcohol consumption.
While there were no changes in overall cholesterol levels, the researchers reported a significant increase of good cholesterol by an average of 10 per cent after three servings of juice per day. Based on known epidemiological data on heart disease, this increase corresponds to an approximate 40 per cent reduction in heart disease risk, according to Vinson.
Similarly, plasma antioxidant capacity, a measure of the total amount of antioxidants available for the body, was significantly increased - at times by as much as 121 per cent - after two or three servings of juice per day, noted Vinson. As with good cholesterol, increased antioxidant levels are also said to be associated with a decreased risk of heart disease.
The mechanism by which cranberry juice changes cholesterol levels has not been clearly established. Vinson said he suspects that the effect may have to do with the fruit's high levels of polyphenols, a type of potent antioxidant. Previous studies have shown that cranberries have among the highest levels of phenols of commonly consumed fruits. Vinson says he eventually plans to test the effect of cranberry juice consumption on subjects with normal cholesterol levels.
Vinson added that other juices have shown similar properties - a recent study by another researcher showed that drinking three cups of orange juice per day also increased levels of good cholesterol. But unlike cranberry juice, it does not appear to increase plasma antioxidant capacitySimilarly, another of Vinson's studies revealed that grape juice also increases plasma antioxidant capacity but unfortunately appears to lower the level of good cholesterol.
"This study gives consumers another reason to consider drinking cranberry juice, which has more health benefits than previously believed. People should consider drinking it with their meals, perhaps as an alternative to soda," said Vinson. Besides heart benefits, previous studies have shown that cranberries can help prevent urinary tract infections and may reduce the risk of gum disease, stomach ulcers and cancer.
The current study underscores the growing body of evidence showing the health benefits of fruit and vegetables .