There's more good news about cranberry juice: Based on human studies, 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 researchers 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 until now. Their findings, the first long-term study of the effect of cranberry juice on cholesterol levels, were described today at the 225th national meeting of the American Chemical Society, the world's largest scientific society.
"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," says Joe Vinson, Ph.D., the study's lead author and a professor of chemistry at the University of Scranton in Scranton, Penn.
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.
In the current study, Vinson measured cholesterol levels in nineteen 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 percent pure cranberry juice by volume, like the common supermarket variety.
Each subject was fed 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, the researcher says.
While there were no changes in overall cholesterol levels, good cholesterol (high density lipoprotein, or HDL) appeared to significantly increase by an average of 10 percent after three servings of juice per day. Based on known epidemiological data on heart disease, this increase corresponds to an approximate 40 percent reduction in heart disease risk, says Vinson.
Plasma antioxidant capacity, a measure of the total amount of antioxidants available for the body, was significantly increased — by as much as 121 percent — after 2 or 3 servings of juice per day, he says. Like elevated levels of good cholesterol, increased antioxidant levels are also associated with a decreased risk of heart disease.
The mechanism by which cranberry juice changes cholesterol levels has not been clearly established. Vinson suspects that the effect may have to do with the fruit's high levels of polyphenols, a type of potent antioxidant. Previous studies by the researcher have shown that cranberries have among the highest levels of phenols in comparison to 20 of the most commonly consumed fruits.
Eventually, Vinson plans to test the effect of cranberry juice consumption on subjects with normal cholesterol levels. To get the most health benefit from the juice, the researcher recommends drinking a low sugar version that contains an artificial sweetener.
If you don't like cranberry juice, there are other heart-healthy alternatives. A recent study by another researcher showed that drinking three cups of orange juice per day similarly increased levels of good cholesterol. Unlike cranberry juice, however, it did not appear to increase plasma antioxidant capacity, says Vinson.
As both juices are healthy, he suggests that people may want to include both types as part of their daily diet.
Grape juice, another breakfast favorite, increases plasma antioxidant capacity but appears to lower the level of good cholesterol, according to another study by Vinson.
There are many other types of juice whose effect on cholesterol levels is not known, he adds. But don't forget exercise: Studies have shown that vigorous aerobic exercise has also been linked to increases in good cholesterol, says Vinson.
The current study underscores government health recommendations that people should eat more fruits and vegetables to help maintain a healthy diet and lifestyle.