Old Wives’ Tales and Garlic as an Antibiotic: Are Microbial Myths Fact or Fiction?

July 19, 2019

Can you feed a cold or starve a fever? Does eating chocolate cause acne? Will earwax help prevent cold sores? These were some of the microbial myths addressed in the video, “Microbial Myths II.”
 

Dr. Michael Schmidt and I began the discussion with a gross question about earwax, after which Schmidt explained the facts on treating fevers and addressed other questions in depth. We followed this with a lightning round for short answers on some big questions, and the session wrapped with Dr. Schmidt on the spot as he accepted questions from the live audience at ASM Microbe 2019 in San Francisco, CA.
 
In this second video edition of “Microbial Myths,” Dr. Schmidt notes that the women who ran households were the first scientists, and we discuss how “old wives’ tales” might deserve more respect than they’re often given. In this follow-up, I’ll describe the history of “old wives” and how they supported their communities against disease and infection. I'll also examine the history and the literature of garlic as a cure-all against infections.

Old Wives Tales are Just Superstitions

Verdict: FALSE
 
Women (many of them wives, some of them old) may be the source of some food and water safety practices used long ago in the Indian subcontinent. The ancient medical texts called the Ayurveda date to India in the 6th century BCE. These texts were largely focused on the healing properties of various metals such as lead, mercury, and copper. For instance, the Ayurveda suggested purifying water by storing it in copper and silver pots. According to Dr. Schmidt, this custom was adopted 8,000 years ago when women water-gathers observed that drinking water from copper pots was less likely to result in diarrhea. Storage of drinking water in copper pots has since been validated by modern research to kill bacterial strains that cause diarrhea.
 
This is an example of how women pioneered the use of empirical evidence to inform their decisions. But it isn’t the only example.
 
Women, not men, were the first medical practitioners, though men are often given the credit. In almost every medical textbook, the Greek Hippocrates is lauded as “the Great Physician" or “the Father of [Western] Medicine.” Sometimes the history goes further back, to the seemingly first man appointed as court physician in Egypt, Imhotep. Imhotep was later deified by the Egyptians and considered equivalent to the Greek demi-god of healing, Asclepius. But before Imhotep, every Egyptian court physician was a woman.
  
Merit-Ptah (the first recorded scientist) and her husband. “Merit-Ptah is not only the first female doctor known by name, but the first woman mentioned in the study of science.”

In Egypt and other North African and Mediterranean cultures (e.g., Assyria, Sumer), religion and medicine were both deeply intertwined and considered to be the purview of women as priestesses. In Egypt and Sumer, priestesses were learned women, rigorously trained in botany and minerals. Their prayers and incantations cared for the emotional state of their patients, while their poultices and tinctures worked to heal the physical ailment.
 
Over time, coinciding with the Indo-European invasion of the Middle East and North Africa, men claimed the prestige and and medical standing women once held. Simultaneously, medicine was slowly untangled from religion with women’s medical knowledge relegated to superstition.
 
Despite its designation as superstition, women’s medical knowledge was irreplaceable for many communities throughout history. Professional medical care requires formal payment, making it inaccessible to the poorer members of a society who have had to turn to “the old wives.” Within this niche, medical knowledge was passed from generation to generation in the informal “old wives” network. 
 
These were the women in a community called upon when the head of a poor household fell ill, or a woman began childbirth. Unlike doctors and other medical professionals, the expertise from these women was rarely compensated. The “old wives” tradition and expertise in herbalism, botany, minerals, and the human body has been passed down and maintained through the early 1900’s and even today, in areas where modern governments and medicine have not yet ventured.
 
The historical association of women’s medical knowledge with religion, and its more recent decline have turned the formerly trusted “old wife” into the ultimate term of derision, “that’s an old wives’ tale.”
 
As our series on microbial myths has shown, much of the old wives’ knowledge was actually based on empirical evidence. Evidence that I hope we can refine and pass to the next generation of “old wives.”
 

Garlic is an Antimicrobial 

Verdict: TRUE
 
Since written records have existed, garlic has been used medicinally.
 
Allium sativum (garlic), from “Medical botany” circa 1793.

In Traditional Chinese Medicine (~2000 BC), garlic was used as a treatment for respiratory and digestive issues, particularly diarrhea and parasite infections. Five hundred years later, the Egyptians recorded their use of garlic for circulation issues, parasite infections, and “abnormal growths,” which were possibly abscesses. Additionally, garlic-like bulbs were used in teas to treat flu-like symptoms by indigenous North Americans.
 
Notably, these practices were in place long before the birth of the modern university and the associated Western medicine standards. These independent discoveries of garlic-based treatments are prime examples of robust scientific research that were reproduced by multiple cultures across the globe. The scientific literature today, however, adds important resolution to the discovery made by anonymous scientists millennia ago. For instance, how does garlic work as an antimicrobial?
 
Garlic has many active antimicrobial components, but allicin is the most researched. Allicin originates from the sulfur-containing amino acid alliin in a conversion facilitated by the enzyme alliinase. Alliin and alliinase are contained in separate compartments of the garlic clove. When garlic is crushed, the 2 ingredients come together to generate allicin, a highly volatile compound that provides the lovely smell of fresh garlic.
 
Allicin contains sulfur amino acid groups that enable it to target thiol-containing enzymes, particularly those in non-mammalian cells. Thiol is another term for sulfhydryl groups (SH), and if 2 of them are close enough when a protein is folded, they become deprotonated and form disulfide bonds. Allicin interferes with thiols by forming disulfide bonds with protonated sulfhydryl groups, a temporary and reversible reaction that inactivates the proteins in key microbial processes such as RNA synthesis and acetyl-CoA formation.
 
Mammalian cells are less affected by allicin because they contain much more glutathione, a sulfhydryl antioxidant, than microbial cells. The large amounts of glutathione presumably rapidly re-protonate the affected sulfhydryl groups, putting the proteins back in action and drastically reducing allicin toxicity for mammalian cells. 
 
As an antimicrobial, allicin is active against all types of pathogens and their toxins. For instance, allicin inhibits gram-positive bacteria, gram-negative bacteria, and even Mycobacterium tuberculosis when used in combination therapies. Allicin can also deactivate viruses such as influenza B, herpes simplex viruses 1 and 2, rhinovirus, and human cytomegalovirus, plus inhibit growth of a broad range of parasites. Allicin has antifungal activity against Cryptococcus neoformans, Candida (yeast), and inhibits the formation of mycotoxins, such as the highly-carcinogenic aflatoxin from Aspergillus parasiticus. Allicin can also prevent the formation of Staphylococcus enterotoxins A, B, and C1, though not all bacterial toxins are negatively affected by allicin (e.g., Clostridium botulinum toxins). The only bacteria that seem to be protected from allicin are those that produce mucoid layers or capsules, like some Pseudomonas aeruginosa strains.
 
All members of the Allium genus (e.g., onions, leeks, chives, and garlic) contain alliin and alliinase. At least 10% of the total protein in garlic bulbs, however, is alliinase, an abnormally high amount for the Allium genus. This likely increases the amount and speed with which allicin is produced by garlic compared to other members of the genus, potentially explaining why garlic is so potent among these plants against infectious disease.
 
For all of the historical and modern evidence of garlic as an antimicrobial, it hasn’t been developed into a mass-produced therapeutic - at least not yet. With the increased attention to antibiotic use in agriculture, some farms may turn to garlic. There are reports that adding garlic to pig feed has similar health and growth outcomes compared to antimicrobials. Who knows, maybe this cheap alternative to antibiotics could result in healthier livestock and tastier bacon.

Further Reading:   

Microbial Myths II: True or False?

Do you want to skip ahead to your favorite myth or most burning question? Jump to the following timestamps in the video to hear the verdict on the following myths:
  • Earwax can treat and/or prevent cold sores? 00:31
  • Fevers: Do you “sweat it out” or try to “break the fever”? 02:19
  • “Feed a cold, sta(r)ve a fever.” 02:43
  • Drinking from the hot tap makes you sick. 06:00
  • Watching TV when you have the measles can make you go blind. 10:20
  • Drinking milk (or eating meat) with fish discolors your skin. 13:45
  • Women were often the first scientists 18:18
  • Soda helps an upset stomach. 20:21
  • Eating cheese before bed hurts your sleep. 21:56
  • “You’ll catch a cold if you go out in winter without a coat.” 22:15
  • Toothpaste can send spots packing. 22:45
  • “An apple a day keeps the doctor away.” 23:35
  • A bulb of garlic a day keeps the doctor away. 23:54
  • Eating chocolate causes acne. 24:23
  • Sleeping with a raw potato over your eye helps pinkeye. 24:35
  • Put chewing tobacco juice on bee stings. 24:52
  • Vinegar can reduce bruising/swelling. 25:07
  • Fever weed (Feverfew, Tanacetum parthenium) tea can help with fevers/headaches. 25:37
  • Baking soda can be used to whiten your teeth 26:28
  • Picking your nose and eating it is good for your immune system 27:10
  • Frequent bathing can lead to increased skin infections 27:10

Author: Ada Hagan

Ada Hagan
Senior Contributor Dr. Ada Hagan works with the ASM Journals Chair Dr. Pat Schloss in the Department of Microbiology and Immunology at the University of Michigan. Her postdoctoral research focuses on representation and bias in scientific publishing, focusing on the field of microbiology. In addition to diversity, equity and inclusion, Ada is an advocate for science communication and research trainees. You can follow her on Twitter @adahagan.