Author | Hu Rong
Source｜Medical World Obstetrics and Gynecology Channel
Cranberry health products are a hot commodity, supporting a large number of overseas resellers. These products are advertised as treating urinary tract infections, vaginitis, pelvic inflammatory disease, uterine fibroids, and ovarian cysts—practically a miracle cure for all gynecological ailments. In gynecology clinics, we often encounter patients like this: "Doctor, I've been taking cranberry health products, so why am I still getting gynecological problems?" Today, let's delve into whether cranberries really have any magical effects.
What exactly is a cranberry?
Cranberries, also known as cranberries or small red berries, are fruits of the genus Vaccinium. They mainly grow in acidic peat soils in cool regions of the Northern Hemisphere and are considered one of the three traditional fruits of North America, along with Concord grapes and blueberries [1]. Cranberries are oval berries that are 2-5 cm long. When ripe, both the skin and flesh are bright red. They are very sour and difficult to eat on their own, so they need to be paired with other foods.
Research on the components of cranberries has revealed that they contain many bioactive substances, such as proanthocyanidins, flavonols, phenolic acids, and anthocyanins. Most of these substances have antioxidant effects, which can counteract lipid peroxidation of unsaturated fatty acids in biological membranes, protect the structure and function of biological membranes, and prevent various degenerative diseases such as aging and tumors [2]. However, it is inappropriate to discuss the efficacy of any effective ingredient without considering the dosage. Cranberries are a good choice as a food, but it is not realistic to use them as a medicine.
Are cranberries really that effective?
Current research on cranberries mainly focuses on the prevention and treatment of urinary tract infections. Laboratory studies have confirmed that cranberry juice can inhibit the adhesion of urinary tract pathogens to urothelial cells. The mediators of this anti-adhesion effect may be fructose and proanthocyanidins. The former can interfere with the adhesion of Escherichia coli type 1 to urothelial cells, while the latter can inhibit the adhesion of Escherichia coli type P[3].
In a study involving 176 women, the number of urinary P. coli strains in the cranberry juice group was reduced (but not statistically significant) [4]. Previous studies have shown that cranberry products can reduce the incidence of urinary tract infections, but the validity of the results is limited due to poor study design, such as insufficient efficacy, non-blinding or other design flaws, and inconsistencies with the results [5-7]. To date, clinical studies have not definitively confirmed that taking cranberries can effectively prevent urinary tract infections.
A 2012 updated Cochrane meta-analysis showed that cranberry products did not reduce the incidence of urinary tract infections compared to placebo, water, or other treatments. Furthermore, cranberry products did not show effectiveness even in specific populations, such as the elderly, pregnant women, women prone to urinary tract infections, children, and cancer patients.
A 2016 JAMA article compared elderly women who took cranberry capsules (each containing 36 mg of the active ingredient proanthocyanidins, two capsules daily) for one year with a placebo. The study found no significant difference in the effects of cranberry capsules on bacteriuria and pyuria between the two groups, and cranberry capsules did not reduce the proportion of patients with bacteriuria or pyuria [8]. Further searches in databases for cranberry and gynecological-related diseases yielded zero relevant studies. Furthermore, other "health benefits" of cranberry, such as lowering blood sugar and anti-cancer properties, also lacked sufficient evidence to support them.
How should we view cranberries correctly?
The potentially effective components in cranberries are also abundant in fruits and vegetables such as purple sweet potatoes, grapes, blueberries, and cabbage. This is not a unique feature of cranberries. It is not recommended to use cranberry products (juice, tablets, or capsules) to reduce the incidence of urinary tract infections in daily life. In addition, as anyone who has eaten cranberries knows, fresh cranberries are too sour and usually need to be made into drinks or jams with sugar to taste good, which leads to additional sugar intake. Long-term consumption of cranberry juice will increase calorie and glucose intake. Some studies have shown that cranberry juice may also increase the possibility of causing gastrointestinal side effects (such as heartburn)[4].
Cranberries are mostly imported into China, which makes them relatively expensive. If you really enjoy their tart flavor, it's fine to eat them as a fruit snack, but relying on cranberries or cranberry capsules to treat illnesses is not advisable. It's better to save your money and exercise more regularly.
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