A Cranberry a Day to Keep the Doctor Away?

Author : Keli Perino, MS, RD, LD

Cranberries have been used for centuries in traditional medicine to treat urinary tract infections (UTIs), and recent research has investigated their potential for reducing risk of kidney disease. However, the scientific evidence supporting the use of cranberry products for both UTIs and kidney disease is limited and inconsistent. It is also important to remember that the added sugars in cranberry products can contribute to weight gain and a variety of other health issues such as diabetes.

Cranberries contain compounds called proanthocyanidins, which are thought to prevent bacteria that cause UTIs from attaching to the walls of the urinary tract. While there have been some studies showing cranberry products may help prevent recurrent UTIs in healthy women, the overall scientific evidence is not strong enough to support a health claim by the U.S. Food and Drug Administration. You may have seen products like Ocean Spray making qualified health claims such as “consuming one serving per day of cranberry juice cocktail may reduce the risk of recurrent UTIs in healthy women.” Qualified health claims are held to a much lower standard of evidence by the FDA than an official health claim, so buyer beware.

Similarly, the evidence supporting potential benefits of cranberry products for kidney disease is mixed. Some studies have suggested that cranberry juice may lower levels of a protein called cystatin C, which is a marker of kidney function. Other studies have shown that cranberry supplements improved kidney function in people with early-stage kidney disease. However, a review of 12 studies found no significant evidence to support the use of any cranberry product for the prevention or treatment of kidney disease.

One likely reason the results are mixed is the variation in type and dosage of cranberry products used in studies. Cranberries come in several forms (fresh, juice, dried, capsules) and the active ingredient varies depending on the type of cranberry and processing methods. Because of this, we are unable to say which type of cranberry product would be most or least beneficial.

So, should we eat more cranberry products? There is a possibility that cranberry products may offer some benefits for preventing UTIs and improving kidney health, but the evidence supporting this is inconclusive. We must also consider the risk of sugar content, knowing that excessive sugar intake can lead to additional health issues. And if risk outweighs possible benefits, we need to take caution.

Ultimately, more research is needed, and people with kidney disease should always consult with their doctor or dietitian before starting new supplements or making changes to their diet to ensure they are following evidence-based recommendations for their health.

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