Originally published 2017-03-04.
Can stevia kill the bacteria that cause Lyme disease? In a laboratory dish, a whole-leaf stevia extract did damage Borrelia burgdorferi, including the tough, slow-growing forms that resist some antibiotics. That is what a 2015 study from the University of New Haven found. What it did not show is that stevia, or the sweetener sold in shops, treats Lyme disease in people. No patients were involved, and no later clinical trial has shown stevia to be a substitute for antibiotics.
The study is real and interesting, but online headlines claiming that stevia "beats antibiotics" stretched it far beyond what the researchers tested. Here is what the experiment actually did, what it found, and what anyone worried about Lyme disease should know.
Lyme disease in brief
Lyme disease is a bacterial infection spread by the bite of infected blacklegged ticks (Ixodes species). In North America the main culprit is Borrelia burgdorferi, a corkscrew-shaped bacterium known as a spirochete. Most infections come from tiny nymph-stage ticks, and transmission usually needs the tick to stay attached for at least a day.
The classic early sign is a slowly expanding red rash called erythema migrans, which appears in roughly 70 to 80% of infected people, often with fever, fatigue and aches. If untreated, the infection can spread to joints, nerves and the heart.
It is common. US states report more than 80,000 cases a year to the Centers for Disease Control and Prevention (CDC), but because many cases go unreported the CDC estimates, from insurance records, that about 476,000 Americans are diagnosed and treated each year. The agency itself notes that this figure is probably an overestimate of true infections. Cases are concentrated in the Northeast, the mid-Atlantic and the upper Midwest.
How Lyme disease is treated today
Standard treatment is a short course of antibiotics, most often doxycycline, with amoxicillin or cefuroxime as alternatives and intravenous drugs for some serious cases. Courses usually last from one to four weeks depending on the stage. Most people recover fully, especially when treated early.
A minority, estimated at roughly 5 to 20%, have lingering fatigue, pain or difficulty concentrating after treatment. Doctors call this post-treatment Lyme disease syndrome. Its cause is not understood. Some scientists suspect surviving bacteria or bacterial debris, others an immune reaction, but placebo-controlled trials have found that long extra courses of antibiotics do not help and carry real risks. Most people with these symptoms improve slowly over months.
This uncertainty is exactly why the idea of "persister" bacteria and biofilms attracts attention, and why a plant extract that seemed to reach them made headlines.
What the stevia study did
The research was led by Eva Sapi, a microbiologist at the University of New Haven in Connecticut, with Priyanka Theophilus as first author. It was published in 2015 in the European Journal of Microbiology and Immunology under the title "Effectiveness of Stevia Rebaudiana Whole Leaf Extract Against the Various Morphological Forms of Borrelia Burgdorferi in Vitro."
"In vitro" means in glass: the work was done on bacterial cultures, not animals or people. The team grew B. burgdorferi in three forms that matter in the debate about persistent infection:
- Spirochetes, the active, corkscrew form;
- Persister cells, including rounded dormant forms that tolerate antibiotics;
- Biofilms, communities of bacteria wrapped in a protective slime that can shield them from drugs.
They exposed these to several whole-leaf stevia extracts and compared them with three antibiotics, doxycycline, cefoperazone and daptomycin, alone and in combination. The researchers then re-grew treated samples for 7 and 14 days to see whether any bacteria survived and could recover.
What it found
The extracts reportedly performed differently, possibly because of how the plants were grown and processed, and the most potent one was studied in detail. It sharply reduced spirochetes and persister cells. When the treated cultures were re-grown, stevia-treated samples showed no viable bacteria after 7 days and about 10% viable cells after 14 days. The extract also significantly reduced bacteria in attached biofilms.
The authors suggested that stevia leaf extract could be considered an effective agent against B. burgdorferi and that it deserved further study. Popular coverage also stressed that some single antibiotics appeared to leave biofilm forms intact, or even enlarged, in culture. Even taken at face value, that is a laboratory observation and has not been shown to predict what happens in patients.
Importantly, the active ingredients were not identified. The researchers used a whole-leaf extract rich in many plant compounds, not the purified steviol glycosides that make stevia sweeteners taste sweet.
Why a lab result is not a cure
Many substances kill bacteria in a dish: bleach, alcohol and countless plant extracts among them. The hard part is reaching the bacteria inside the body, at a safe dose, without harming the patient. A lab experiment cannot tell us how much of an extract would be absorbed, whether it would reach joints or nerve tissue, how long it would last in the blood, or what side effects it might cause.
That is why medicines go through animal studies and then clinical trials in people. For stevia and Lyme disease, those steps have not produced evidence that it works as a treatment. Dosing yourself with a sweetener or an herbal tincture instead of prescribed antibiotics could allow an infection to spread.
Claims that went too far
Several popular claims about this study do not hold up:
- "Stevia kills Lyme better than antibiotics." It outperformed some antibiotics against certain forms in a dish. That is a narrow lab comparison, not a verdict on human treatment.
- "Antibiotics rarely cure Lyme." Most people treated with standard antibiotics recover, particularly when treated early.
- "10 to 20% of patients develop chronic Lyme." Up to about one in five may have lingering symptoms, but whether ongoing infection is involved is unproven, and many people labelled with "chronic Lyme" show no evidence of infection at all.
- "The study showed stevia lowers blood pressure and blood sugar." It did not. It tested only bacteria in the laboratory.
What to do if you are worried about Lyme
Prevention is still the best protection. In tick country, wear long sleeves and trousers, use a repellent containing DEET or picaridin, check your skin and your children's after being outdoors, and remove any attached tick promptly with fine-tipped tweezers.
If you develop an expanding rash, fever or unexplained joint pain after a possible tick bite, or if you still feel unwell after treatment, talk to a doctor. Stevia remains a useful low-calorie sweetener and an intriguing subject for further research, but it is not a proven treatment for Lyme disease.
Sources: Theophilus, Sapi et al., European Journal of Microbiology and Immunology 5(4), 2015; PubMed record 26716015; CDC: Lyme disease data and statistics; Wikipedia: Lyme disease; originally reported by Collective Evolution.
COMMENTS