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  • Writer's pictureJoan Rothchild Hardin

In Response to “Do Probiotics Really Work?” (Scientific American, July 2017)

Source: Time Magazine

An article titled “Do Probiotics Really Work? in the current (July 2017) issue of Scientific American really irked me so I decided to send a Letter to the Editor responding to it. Since the chances my letter will get printed are slim and I think it addresses several important issues, I’m putting it into this post. Ferris Jabr, the author of the article, presents evidence from several sources that lead him to conclude “Although certain bacteria help treat some gut disorders, they have no known benefits for healthy people.”

It’s this conclusion and the outdated but widely held belief that we’re healthy unless we’ve been diagnosed with a disease that bugged me (pun intended). Here are the opening paragraphs of the article:

Do Probiotics Really Work?

Although certain bacteria help treat some gut disorders, they have no known benefits for healthy people

By Ferris Jabr |   Scientific American   July 2017 Issue

Friendly Microbes: Bacteria such as these lactobacilli, which are often added to yogurt and probiotic supplements, help to maintain a healthy environment in the intestine. Credit: Kari Lounatmaa Science Source

Walk into any grocery store, and you will likely find more than a few “probiotic” products brimming with so-called beneficial bacteria that are supposed to treat everything from constipation to obesity to depression. In addition to foods traditionally prepared with live bacterial cultures (such as yogurt and other fermented dairy products), consumers can now purchase probiotic capsules and pills, fruit juices, cereals, sausages, cookies, candy, granola bars and pet food. Indeed, the popularity of probiotics has grown so much in recent years that manufacturers have even added the microorganisms to cosmetics and mattresses.

A closer look at the science underlying microbe-based treatments, however, shows that most of the health claims for probiotics are pure hype. The majority of studies to date have failed to reveal any benefits in individuals who are already healthy. The bacteria seem to help only those people suffering from a few specific intestinal disorders. “There is no evidence to suggest that people with normal gastrointestinal tracts can benefit from taking probiotics,” says Matthew Ciorba, a gastroenterologist at Washington University in St. Louis. “If you’re not in any distress, I would not recommend them.” Emma Allen-Vercoe, a microbiologist at the University of Guelph in Ontario, agrees. For the most part, she says, “the claims that are made are enormously inflated.”

You can read the entire article here. And here’s my Letter to the Editor responding to this article:

In “Do Probiotics Really Work?” (July 2017), Ferris Jabr concludes “Although certain bacteria help treat some gut disorders, they have no known benefits for healthy people.” This conclusion is misleading.


Our nutrient-poor Standard American Diet (SAD), wide consumption of pharmaceuticals and exposure to many other toxins have led to at least 50 million Americans suffering from one or more of the 100 known autoimmune diseases – including acne, allergies, several types of arthritis, asthma, autism, cardiac myopathy, chronic fatigue, diabetes, multiple sclerosis, rheumatic fever, thyroid imbalances and ulcerative colitis.

Autoimmune diseases are the result of chronic inflammation in the body produced by an unhealthy, imbalanced gut microbiome, Since it can take years (even decades) for low level chronic inflammation to develop into a diagnosable disease, it hardly seems correct to regard pre-diagnosed people as ‘healthy’.


The beneficial bacteria in a probiotic supplement need to survive passage through hydrochloric acid in the stomach and acidic bile salts in the small intestine to reach the bacterial ecosystem residing in the large intestine in order to be effective. The bio-availability level of a probiotic supplement refers to the proportion of the live probiotics put into a supplement capsule that survives to reach its target: the colon.

Were the probiotic supplements tested in the studies Jabr cites highly bio-available? If not, it follows that beneficial effects wouldn’t be found. In describing various studies that found scant benefit from taking probiotics, he mentions only one that specifically tested a particular strain of Bifidobacterium longum known to survive in the human intestine.


Two examples:

Researchers are discovering changes in normal gut bacteria that take place before diabetes turns into a diagnosable clinical condition, while the amount of glucose in the blood is above normal but not yet high enough to qualify as diabetes. Pre-diabetic people are at greater risk for heart disease and stroke. And pre-diabetics have been found to have fewer gut bacteria than people with normal glucose blood levels.

Antibiotics, especially broad spectrum ones like Cipro and Amoxicillin, kill good probiotic bacteria along with the pathogenic bacteria they’re targeting, resulting in bacterial imbalance in the gut microbiome. This creates space for harmful bacteria to multiply and crowd out the remaining good microbes. An unhealthy mix of microbes in the gut sets the stage for obesity, diabetes, heart disease and all those other autoimmune conditions and diseases.

Consumers are looking to probiotics to keep them healthy or reverse an already existing autoimmune or metabolic disease because western medicine, with its focus mostly on early detection and alleviation of symptoms once we become ill, has failed them. We now know that 70-80% of the human immune system resides in our guts. A large body of research has clearly shown that the composition of the gut microbiome has a profound effect on the balance between health and disease. The idea that improving our gut microbiomes can actually keep us healthy so we don’t develop most conditions and diseases is a much more sensible and useful paradigm than early detection and treating symptoms.

Absence of diagnosed disease is not the same as health. The knowledge that it usually takes a long time for the body to develop a diagnosable autoimmune or metabolic disease suggests most of us are not actually healthy and would do well to look to improving our gut microbiomes. FUNCTIONAL MEDICINE’S VIEW OF PROBIOTICS’ IMPACT ON HEALTH

Perhaps these remarks from an interview with well-respected Functional Medicine doc Mark Hyman, MD, will clarify whether probiotics are helpful and how they work:

Well – to be frank, our poop and all the bugs that live in there are the great new frontier in medicine. Who knew!? The health of the 100 trillion bugs in your gut (which outnumber you 10 to 1) is one of the biggest things that impacts your health. Is it as simple as just taking a few probiotics or eating some yogurt? Not really – we have to learn how to tend the gut flora of our inner gardens by being selective of what we eat and how we live; feeding the good bugs and avoiding gut-busting drugs and habits– like eating too much sugar and starch, or consuming too much alcohol, or not managing our stress (yes, your gut bacteria are eavesdropping on your thoughts)….

Basically, the microbial ecosystem in the gut has to be healthy for you to be healthy. When your gut bacteria are out of balance, it makes you sick. Among all that gut bacteria, there are good guys, bad guys, and VERY bad guys. When you have too many bad guys, and not enough good guys, this is a problem. That’s where probiotics come in.

– Do Probiotics Really Work? (Hyman, 2016) You can take a look at the entire interview with Dr Hyman for his recommendations on how to tend the garden that is your gut microbiome to stay – or become – well. See  Do Probiotics Really Work?

Mark Hyman MD is the Director of Cleveland Clinic’s Center for Functional Medicine, the Founder of The UltraWellness Center, and a ten-time #1 New York Times Bestselling Author.

Many thanks to Susan Lipson for leaving this issue of Scientific American in my room on a recent visit. REFERENCES

Hyman, M. (2016). Do Probiotics Really Work? See:

Jabr, F. (7/2017). Do Probiotics Really Work? Scientific American. See:

Parth, J.P., Balart, L.A., & Johnson, D.A. (2015). The Influence of the Gut Microbiome on Obesity, Metabolic Syndrome and Gastrointestinal Disease. Clinical and Translational Gastroenterology. See:

Wallis, C. (6/2014). How Gut Bacteria Help Make Us Fat and Thin: Intestinal bacteria may help determine whether we are lean or obese. Scientific American. See: © Copyright 2017. Joan Rothchild Hardin. All Rights Reserved.

DISCLAIMER:  Nothing on this site or blog is intended to provide medical advice, diagnosis or treatment.

Comments submitted prior to 8/25/2021

Good for you for writing this here, Joan. I linked it to uBiome and Scientific American on Twitter. To perhaps draw more attention to your post, and perhaps SA will read it as a result. For your readers, I am off all but two daily meds and take probiotics daily. Thanks to your

wonderful counsel I survived a hospital stay and a 10-day course of Cipro and Flagyl, two very powerfu, scary, gut-busting antibiotics. I drank kefir and ate yogurt and took extra doses of saccharomyces boulardii and broad spectrum probiotics, as you advised. You may have

saved my life! I also posted about my improved health here


In reply to Sonnische


Thanks for the Twitter postings, Sonnische. And how wonderful that probiotics got your gut through the onslaught of those two powerful antibiotics. Good news indeed!

Joan Hardin


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