Cranberries are small, refreshing red fruits from the mulberry family. Cranberries are widely used in North American cuisine. For several decades, cranberries have been very popular in Europe, but above all for their health benefits. In this article, we will discuss the use of cranberries to fight urinary tract infections.
Briefly
- Cranberries prevent the adhesion of bacteria, especially E. coli, to urothelial cells in the bladder, preventing infection.
- The concentration of proanthocyanidins, an active ingredient in cranberries, is critical to its effectiveness. It is often recommended to consume 300 ml of cranberry juice, which contains 36 mg of proanthocyanidins, daily;
- Cranberry products are as effective as antibiotics in reducing the risk of recurrent urinary tract infections, which may help reduce antibiotic use and thus bacterial resistance.
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Urinary tract infections: definitions
A urinary tract infection is diagnosed when the number of bacteria in the urine exceeds a threshold, usually set at 100,000 bacteria per milliliter. This infection may be cystitis (a bacterial infection of the bladder) or pyelonephritis, which is an infection of the kidneys. We will talk about urethral syndrome when clinical signs of cystitis are present, but without infection.
Cystitis
Bacterial cystitis, also called acute cystitis, can occur in both men and women. Signs and symptoms include painful and frequent urination, cloudy urine, and sometimes even hematuria, which is the presence of blood in the urine. Bacterial cystitis is often associated with pyuria, that is, a level of white blood cells greater than 10,000 per milliliter in the urine.
Pyelonephritis
Pyelonephritis is thought to occur as a result of bladder inflammation, especially when there is transient (episodic) or persistent reflux of urine from the bladder into the ureter or renal pelvis. This phenomenon is known as vesicoureteral reflux. Signs and symptoms of pyelonephritis include flank or back pain, fever, chills with shivers, feeling generally unwell, and symptoms of a lower urinary tract infection. Acute pyelonephritis can be serious in older people, infants, and people with weakened immune systems.
Urinary tract infections are said to be recurrent when they occur on average two to three episodes per year.
Urethral syndrome occurs when a person has symptoms of a lower urinary tract infection without bacterial growth, or with less than 100,000 colony-forming units (CFU)/mL in repeated urine cultures.
Populations at risk of urinary tract infections
Certain groups of people are at increased risk of developing a urinary tract infection. This includes infants, pregnant women, the elderly, people with spinal cord injuries and/or using catheters, patients with diabetes or multiple sclerosis, patients who are immunocompromised or infected with HIV, and patients with Basic urinary tract abnormalities. Furthermore, urinary tract infections are on average more common in women than in men. Likewise, in children, urinary tract infections occur three times more frequently than in girls (in 3 to 7% of girls and 1 to 3% of boys).
Why are women more affected?
Although urinary tract infections can occur in both men and women, they are approximately 50 times more common in adult women than in adult men. This can be explained by the fact that women's urethra is shorter, which allows bacteria to move to the bladder more easily.
It is estimated that symptomatic bladder infections (lower urinary tract infections) affect about 30% of women at some point in their lives. The annual incidence of acute urinary tract infections is 7% among women of all ages, with a first peak in the incidence of these infections between 15 and 24 years of age and a second peak in women over 65 years of age. In addition, up to 25% of women with a UTI are likely to experience a recurrence within six months of infection.
The upward path of infection
Most urinary tract infections are thought to arise from the so-called ascending route of infection. The first stage is colonization of the periurethral tissue by uropathogenic organisms, followed by passage of bacteria through the urethra to the bladder. Urinary tract infections result from bacterial overgrowth in a normally sterile urinary tract.
Cranberries and prevention of urinary tract infections
Cranberries, especially in juice form, have been widely used for decades to prevent and treat urinary tract infections. Cranberries contain about 90% water, but they also contain various organic substances such as fructose, quinic acid, malic acid and citric acid.
Until recently, quinic acid was thought to cause the excretion of large amounts of hippuric acid in the urine, which then acts as an antibacterial agent. However, several studies have shown that the presence of hippuric acid has only a transient effect and current research suggests another way cranberries work.
Remove the adhesion of bacteria to the walls
Research now suggests that cranberry's mode of action is to inhibit the adhesion of bacteria (particularly E. coli) to the urothelial cells that line the bladder wall.(1)(2). Without this adhesion, bacteria cannot infect the mucosal surface of the urinary tract.
In vitro, the anti-adhesive role of bacteria has been shown to be mediated by two components of cranberries: fructose and proanthocyanidins. Bacteria have protein structures called fimbriae on their surface that allow them to adhere to a surface. Fructose has been shown to inhibit type I mannose-specific fimbriae adhesion in Escherichia coli.(3)(4). Furthermore, proanthocyanidins in cranberries have also been shown to inhibit the adhesion of P fimbriae specific to a-galactose-(1-4) in bacteria such as Escherichia coli.(5).
The proanthocyanidins in cranberries contain A- and B-type bonds. Knowing that A-links are only found in proanthocyanidins found in cranberries, the latter have been linked to preventing the adhesion of E. coli.(6).
Proanthocyanidin concentration
Cranberry products come in the form of juice, syrup, capsules, and tablets. The usually recommended amount for preventing urinary tract infections is daily consumption of 300 ml of cranberry juice, which contains 36 mg of proanthocyanidins.(7).
However, processing cranberries into different products such as tablets or capsules may affect the proanthocyanidin composition.(8)This may lead to products containing too little proanthocyanidin, the active ingredient in cranberries.
Furthermore, the complexity of the structures of proanthocyanidins and A-bonds makes it difficult to measure their proanthocyanidin content. Therefore, to ensure the quality of cranberry powders, proanthocyanidin levels must be properly measurable.
The 4-dimethylaminocinnamaldehyde method is currently the most proven standard method for quantifying proanthocyanidins in cranberry powders.(9). A randomized controlled trial evaluating the dose effect of cranberry powder found that to achieve an antibacterial adhesion effect in the urine, 36 mg of cranberry proanthocyanidin equivalents daily was effective, but 72 mg provided better protection. Since the anti-adhesion activity decreases over time, it is recommended to take these cranberry products in the morning and evening.(10).
Cranberry versus placebo
Two studies reported a significant effect of cranberry compared to placebo(11)(12).
Cranberry versus antibiotic prophylaxis
Two studies on women with recurrent urinary tract infections(13)(14) A study in children compared a cranberry product to antibiotic prophylaxis. All three studies used cranberry capsules or syrup. An analysis of two studies in women showed that the cranberry product was as effective as an antibiotic in reducing the risk of recurrent urinary tract infections in women. The study in children also showed that the cranberry product was as effective as antibiotics in reducing the risk of recurrent UTI symptoms.
Cranberry versus complementary therapies
study(15) compared a cranberry product with methenamine hippurate in patients with spinal cord injury and showed similar efficacy between groups. Two studies, one in children(16) The other is in adult women(17)compared cranberry to probiotic treatment and showed a significant reduction in symptomatic urinary tract infections with cranberry compared to probiotics.
What to remember
As a recent meta-analysis concluded(18) : “Doctors should use the results of the current study to recommend cranberry consumption to reduce the incidence of urinary tract infections, especially in people with recurrent UTIs. This would also reduce the use of antibiotics, which is a valuable asset because antibiotics promote the onset of Resistant bacteria around the world.
Cranberries and prevention of urinary tract infections
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