Pros and Cons of Cranberry Supplement


Dear dietician:

It seems to me that I have three or four bladder infections every year. My friend told me to try cranberry supplements. Do they work?

Thank you,


Dear Meredith,

Anyone who has suffered from a urinary tract infection (UTI) knows the discomfort that comes with it. Up to six million people get a urinary tract infection each year; most are healthy women between the ages of 20 and 40. A urinary tract infection occurs when bacteria, such as Escherichia coli (E. Coli), enter any part of the urinary system – the bladder, kidneys, ureters, and urethra.

Some prefer a more natural approach to healing and may choose cranberry juice or tablets to defend against UTIs. Cranberries were once thought to help UTIs by making urine more acidic, making it harder for bacteria to survive. More recent research has found that cranberries contain a nutrient called proanthocyanins (PACs) which changes the surface of E. Coli, making it less likely to stick to the urinary tract.

In a review of randomized controlled trials (RCTs), the gold standard of research, Wang et al. found that cranberry-containing products were associated with preventing UTIs, especially in women with recurrent UTIs (1). Several other studies have shown similar results. It is important to note that cranberry products do not treat UTIs but help prevent them.

Overall, most well-designed studies show that cranberries help prevent recurrent UTIs in healthy middle-aged women. Studies did not produce similar results in older populations.

The next question is: “How many cranberries do you need?” The consensus is that 36 mg CAP equivalents per day are needed for the prevention of urinary tract infections. This amount can be found in one to two cups of cranberry juice cocktail (26% cranberry juice) (2). If you choose a supplement or extract form, check the label for PAC equivalents.

Cranberry products are considered safe, but some have reported upset stomach and diarrhea when using them. Keep in mind that cranberry juice cocktail tends to be high in sugar, although there are low sugar versions. Cranberries, extracts and supplements are high in oxalates. Oxalates bind to calcium and increase the risk of kidney stones. Do not use cranberry products if you are prone to kidney stones.

When choosing a supplement, select one with USP on the label. The United States Pharmacopoeia (USP) is a nonprofit organization that tests the quality, potency, and absorbability of supplements and drugs. USP helps you get the most from your money.

Until next time, be healthy!

Dear dietician

Disclaimer: This column is for educational purposes and is not a substitute for medical care. Talk to your health care provider if you think you have a urinary tract infection and follow their recommendations.


1. Wang CH, Fang CC, Chen NC, Liu SS, Yu PH, Wu TY, Chen WT, Lee CC, Chen SC. Products containing cranberry for the prevention of urinary tract infections in susceptible populations. Arch Intern Med 2012; 172: 988–96.

2. Wight CE, Thornby KA. The evidence to support the use of cranberries to prevent and treat UTIs is limited. The pharmacy today. January 23, 2017 (1): 29.

Leanne McCrate is an award winning dietitian based in Missouri. Its mission is to educate the public about healthy, evidence-based diets. Do you have a nutritional question? Email him at [email protected]

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