Can Cranberry Juice Control Blood Sugar and Lower Blood Pressure?
A new study found that drinking cranberry juice reduces some key risk factors for cardiovascular disease and diabetes. The study, published in the Journal of Nutrition, adds compelling evidence to the growing body of research on the benefits of berries on the heart.
Cranberries are rich in a number of polyphenols, chemicals that have been associated with a reduced risk of cardiovascular disease. They include procyanidins, quercetin, myricitrin, and anthocyanins. Quercetin, for example, has been shown to reduce blood pressure, while procyanidins have reduced C-reactive protein (CRP) in animal studies. Anthocyanins have lowered triglycerides in animal studies as well as inflammatory markers in people.
In this study, researchers randomized patients into two groups, one that drank two 8-ounce glasses of low-calorie cranberry juice each day for eight weeks. The juice was sweetened with sucralose and had about 40 calories in each serving. The control group drank a similarly tasting drink that did not contain cranberry juice. Both drinks were supplied by Ocean Spray Cranberries, which partially funded the study, but was not involved in the analysis of the results. Both groups also followed a fully controlled diet to reduce other dietary variables. The study was double blind, so neither subjects nor researchers knew which people drank the juice versus the placebo.
The group that drank low-calorie cranberry juice had lower levels of triglycerides (fatty acids) compared to the controls, and those with the highest level of triglycerides at the onset of the study saw the greatest decrease in the fatty acids. The juice drinkers also had lower diastolic blood pressure and lower levels of CRP, an inflammatory marker for cardiovascular disease. They had a 44% lower level of CRP than those drinking the placebo.
Lastly, the juice drinkers had significantly lower fasting glucose levels than the control group. Those with higher levels of insulin resistance at the study’s outset had greater improvements in insulin sensitivity. Both of these results suggest that cranberry juice may help reduce risk factors for diabetes. The study did not test regularly sweetened cranberry juice.
The level of improvements seen after drinking cranberry juice were significant and in some cases equal to those obtained by recommended dietary modifications. The reductions in blood pressure were similar to those obtained by following the Dietary Approaches to stop Hypertension diet (DASH) or a low sodium diet, wrote the authors. “The magnitude of the change observed in the current study could be associated with a 15% decrease in risk of stroke and a 10% decrease in risk of coronary heart disease,” the authors wrote.
Similarly, the reduction in triglycerides and CRP equaled the benefits of a Mediterranean style diet, including eliminating trans fats, lowering carbohydrates and eating more plant-based fats and polyunsaturated fats.
"For those with diabetes who wish to incorporate cranberry juice into their eating plan, it is important that they include the low-calorie cranberry juice as part of their meal, not an addition, since the extra carbohydrate may cause a rise in their blood glucose levels," advises Amy Hess-Fischl, MS, RD, LDN, BC-ADM, CDE, an advanced practice dietitian at the University of Chicago Kovler Diabetes Center and a member of Diabetic Lifestyle's medical advisory board.