Could cranberries combat superbugs?

Analysis by Dr. Joseph Mercola Fact Checked

could cranberries combat superbugs

Story at-a-glance -

  • Antibiotics in many forms have been used over millennia; herbs, honey and moldy bread poultices were the forerunners of more sophisticated antibiotics such as sulfa drugs and a traditional Chinese medicine called qinghaosu
  • With the advent of penicillin, which was discovered in 1929 and mass produced in 1945, antibacterial resistance emerged to offset earlier successes in disease control, creating superbug infections both inside and outside of hospital settings
  • Researchers recently found that cranberry extract makes bacteria more sensitive to antibiotics, and stands up against some of the most notorious and virulent pathogenic bacterial strains
  • When the scientists treated such bacteria with a combination of an antibiotic along with a cranberry extract, they were surprised to be able to report that “no resistance developed”
  • Due to specific compounds in cranberries, a number of serious diseases were found diminished, including obesity, cardiovascular disease and certain types of malignant tumors

Finding a drug to either kill harmful bacteria or slow their growth has been a priority for medical practitioners for thousands of years. Not all antibiotics have been effective or even safe, although herbs, honey and moldy bread poultices used in ancient Greece, Rome, China and Egypt were used with some success.1

Needless to say, as scientists experimented with treatment possibilities and resorted to things like animal feces, heavy metals like mercury, bismuth and arsenic to eradicate sexually transmitted diseases such as gonorrhea and syphilis via specially designed syringes, the "administration and side effects often proved worse than the disease."2

The Journal of Antimicrobial Chemotherapy references many attempts over centuries to nail down a definitive antibiotic, and several showed great promise, such as Pyocyanase, derived from a green bacteria isolated from injured peoples' bandages, which slowed the growth of other microbes. "They grew the organism (Pseudomonas aeruginosa) in batches and used the supernatant as a medicine, with mixed success."3

Sulfa drugs such as a prominent one called Prontosil, first tested in 1935, also showed promise.4 At times, catastrophic illnesses made the search more desperate, as when an herb called qinghaosu (artemisinin) used for millennia in traditional Chinese medicine (TCM), was tried and found to be a potent treatment for malaria as late as the 1970s.5

But since the discovery of penicillin in 1929 and its mass production and distribution in 1945,6 not only the study of medicine has changed, but the world.

Frontiers in Microbiology suggests that antimicrobials could be called the most successful chemotherapy agents since the study of medicine began, noting, "It is not necessary to reiterate here how many lives they have saved and how significantly they have contributed to the control of infectious diseases."7

'Germs will always look for ways to survive'

However, overuse has created a dire situation: The successes have been "marred by the emergence of hard-to-treat multiple antibiotic-resistant infections."8 In fact, as the U.S. Centers for Disease Control and Prevention observes, "Germs will always look for ways to survive and resist new drugs."9

According to researchers at McGill University, antibiotic resistance is undermining decades of progress in fighting bacterial infections. Antibiotics are used not only in medicine but in agriculture. In fact, methicillin-resistant Staphylococcus aureus (MRSA) and other superbug infections have been spreading rapidly among people both inside and outside of hospital settings.10 McGill scientists asserted:

"We are on the cusp of returning to a pre-antibiotic era in which minor infections can once again become deadly. Therefore, countering the fall in antibiotic efficacy by improving the effectiveness of currently available antibiotics is a crucial goal."11

But in May 2019, a familiar plant-based product was found to make bacteria more sensitive to antibiotics and prevent resistance. Testing the popular belief that cranberries, even more than the juice, might be effective agents against painful and often debilitating urinary tract infections (UTIs),12 the researchers wanted to see how its compounds would stand up against some of the most virulent strains.

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Cranberries are tapped to help fight pathogenic bacteria

The journal Advanced Science13 reports that cranberries — or more specifically, the proanthocyanidins in cranberries — are very effective in the fight against pathogenic bacteria. EurekAlert explains results from the study:

"Countering the fall in antibiotic efficacy by improving the effectiveness of currently available antibiotics is a crucial goal … When treated with molecules derived from cranberries, pathogenic bacteria become more sensitive to lower doses of antibiotics. What's more, the bacteria don't develop resistance to the antibiotics.

Given the popular belief that drinking cranberry juice is helpful against urinary tract infections, the researchers sought to find out more about the berry's molecular properties by treating various bacteria with a cranberry extract. The bacteria selected for study were those responsible for urinary tract infections, pneumonia, and gastro-enteritis (Proteus mirabilis, Pseudomonas aeruginosa, and Escherichia coli)."14

According to Nathalie Tufenkji, McGill chemical engineering professor and the study's lead author, "Normally when we treat bacteria with an antibiotic in the lab, the bacteria eventually acquire resistance over time." But when her team treated these bacteria with a combination of an antibiotic along with a cranberry extract, they were surprised to be able to report that "no resistance developed."15

The researchers wrote that cranberry proanthocyanidins, which they called CPAC, prevent not only the "evolution of resistance" to tetracycline in Escherichia coli and Pseudomonas aeruginosa, but "rescues antibiotic efficacy" when posed against cells exposed to antibiotics and, further, inhibited biofilm formation.

Further study revealed the resistance happened two ways: First, the cranberry extract made the bacterial cell wall more permeable so the antibiotic could reach it, and second, it rendered the bacteria less able to get rid of it. As such, the antibiotic was more effective at lower doses. In addition:

"After confirming the activity of the cranberry molecules on bacterial culture, the researchers tested to determine whether the pattern persisted in a preliminary animal model: infected insects. Since the synergistic effect of the extract and the antibiotic was also observed in the insects, further experiments will be conducted to clearly identify the active molecules."16

What are cranberries good for? Researchers weigh in

There's been some controversy regarding the efficacy of cranberries for bladder infections, but increasingly, the positive research on cranberries begins to make more sense when you find how many diseases and disorders the small, tart red fruit can benefit. Here are a few important ones:

Cardiovascular disease — The impacts of cranberries on not just the cardiovascular system but every component of metabolic syndrome was explored in a 2017 review. It listed several areas impacted, including reduced obesity markers (body weight, body mass index and waist circumference), blood pressure and balanced blood sugar levels.17

Cancer — A 2016 review on what compounds in cranberries can do for cancer noted that 17 different types, including cancers of the colon, bladder, prostate, esophagus and stomach, as well as glioblastoma and lymphoma, were inhibited by cranberries or cranberry-derived constituents.

Cranberries may fight cancer, in part, due to apoptosis, necrosis and autophagy due to "reduction of cellular proliferation; alterations in reactive oxygen species; and modification of cytokine and signal transduction pathways."18

Oral health — Proanthocyanidins in cranberries may help prevent bacteria from binding to teeth and prevent gum disease, one study notes. "Clearly, cranberry (proanthocyanidins) show promise for the development of novel alternative or adjunctive anticaries chemotherapy."19

Ironically, cranberry juice was a popular remedy recommended by doctors for many years for UTIs, but more recent research suggests that the placebo effect might have accounted for the successes the use of cranberry juice elicited more than solid science,20 especially since its active ingredient is likely "long gone before it reaches your bladder,"21 one researcher explains.

What problems can antibiotics cause?

Research in 201822 showed that, particularly for children, antibiotic use can cause short-term problems, but they also can trigger a permanent change in your gut microbiome, which accounts for nearly 80 percent of your immune system function, so it is important to use antibiotics only when absolutely necessary.

They've also been found to cause mitochondrial dysfunction and overproduction of reactive oxygen species (ROS) in human cells, DNA and vital organs.23 But that doesn't stop doctors from prescribing them — often unnecessarily. The CDC notes:

"In 2015 alone, approximately 269 million antibiotic prescriptions were dispensed from outpatient pharmacies in the United States, enough for five out of every six people to receive one antibiotic prescription each year. At least 30 percent of these antibiotic prescriptions were unnecessary."24

As if that weren't enough, besides ruptured tendons, kidney stones and/or failure, retinal detachment and blindness, and ruptured aorta (the main artery supplying oxygenated blood to your circulatory system), research emerged that antibiotics can also raise the risk of mental disorders, such as schizophrenia, autism and numerous personality and behavior disorders.25

Fluoroquinolones are a type of antibiotic often prescribed for upper respiratory and urinary tract infections. However, because of the damage they've been known to cause, from acute kidney failure to psychotic reactions to "fatal events,"26 antibiotics — and fluoroquinolones in particular — should be used only as a last resort.

More on the dangers of overusing antibiotics

The U.S. Food & Drug Administration (FDA) issued a warning in 2017 about an increased risk of ruptures or tears in the aorta due to the use of fluoroquinolones in certain patients.27 In 2018, the journal Nature mentioned the commonly prescribed drug causes "rare but disabling" side effects, noting that in 2015, doctors prescribed them 32 million times, making them the fourth-most popular antibiotic in the U.S. Further:

"Fluoroquinolones are valuable antibiotics, and safe for most people. Yet they are so widely prescribed that their side effects might have harmed hundreds of thousands of people in the United States alone, say scientists who are working with patients to unpick FQAD's causes.

Fluoroquinolone toxicity, they say, provides a compelling example of an emerging understanding that antibiotics don't just harm microbes — they can severely damage human cells, too."28

Antibiotic use for two months or longer by women aged 60 and older has been shown to lead to a 32% increased risk of developing cardiovascular disease, including heart attack and stroke. It's important to note the likely reason: Antibiotics have the power to not only alter your gut, but "wipe out" your microbiome.29 Interestingly, the study concludes:

"The intestinal microbiome appears to play an important role in atherosclerosis. These findings raise the possibility of novel approaches to treatment of atherosclerosis such as fecal transplantation and probiotics."30

One of the best and least expensive ways to optimize your gut microbiome is to eat traditionally fermented and fiber-rich foods. But there's also spore-based probiotics, aka sporebiotics, which make use of the microbe Bacillus to dramatically increase your immune tolerance.

If you must take antibiotics, I recommend taking the beneficial yeast Saccharomyces boulardii after you've finished to prevent secondary complications of antibiotic treatment, such as diarrhea.