The 7 biggest myths about probiotics

‘Gut mania’ is at an all-time high. Despite the ever-increasing number of ‘probiotic’ supplements, foods, and beverages out there, there’s still a lot of confusion about what probiotics are, how they work, and why we should take them. We’ve clarified the 7 most common myths.

1. Probiotics are only for digestion.

61% of Americans live with gastrointestinal issues. 63 million suffer from chronic constipation. So it’s unsurprising that most people exclusively associate probiotics with digestive health. But this is a common misconception.

Your body is complex and interconnected, and the gastrointestinal system sits at the core of it all. It’s connected to and influences everything from metabolic and gut immune function to cardiovascular, dermatological, and urogenital health. So, while improvements in gut health are often the most immediate, localized, and evident (with digestion often improved in as little as 24-48 hours), probiotics can actually have powerful effects across the entire body, far beyond your digestive tract.

2. Probiotics can be found in fermented foods and beverages like kombucha.

You drank a kombucha on your way to the gym, and this pack of nuts you’re munching on now says it’s probiotic. You’re good, right?

Well, scientifically speaking, many of the products out there that claim to be probiotic, don’t actually qualify as one. Just because something contains live microorganisms, doesn’t mean it satisfies the scientific definition of ‘probiotic’—”live microorganisms that, when administered in adequate amounts, confer a health benefit on the host”, a definition authored by the United Nations – World Health Organization Expert Panel chaired by our Chief Scientist, Dr. Gregor Reid, in 2001.

You might have ingested some bacteria, but do you know which strains? In what quantities? Have they survived the acidic journey through your digestive system and landed in your colon? Have those strains been studied, in those quantities, to actually do something in your body?

This is, of course, not to say that you shouldn’t eat or drink fermented foods and beverages. Many are extremely nutritious, not to mention very tasty, additions to your diet (though we do suggest keeping an eye out for excessive sugar content—as many commercial products like yogurts and beverages are sweetened with added sugars). The distinction is that they are not necessarily reliable sources of beneficial, effective bacteria.

The science of probiotics demands precision, accountability, and efficacy (you are putting live bacteria in your body, after all).

3. Probiotics don’t work unless they colonize your gut.

When it comes to taking probiotics, you may have heard that you need to ‘restore’ your gut or ‘put the good bacteria back’. This is based in a common misconception that probiotics must ‘colonize’ or alter the composition of your microbiome to “work”. It’s not true.

In fact, outside of specific cases like fecal transplants, there is little evidence that probiotics ‘colonize’, or that they need to. Compared to the tens of trillions of microbes already rooted in your gastrointestinal tract, most probiotics don’t contain enough new bacteria to make a significant difference in the composition of your microbiota.

Even if they did, we don’t know enough about the safety of introducing colonizing microbes (especially soil-based microorganisms, which are becoming popular). Large numbers of newcomers moving in and displacing your existing bacteria could alter the unique balance of your ecosystem within and trigger unintended consequences.

What scientists do know is that, as transient microbes, probiotics travel through your GI tract, interacting with your immune cells, dendritic cells, gut cells, dietary nutrients, and existing bacteria to, directly and indirectly, deliver benefits.

Some enhance the gene expressions involved in tight junction signaling, which help protect against intestinal permeability—this means a tight gut barrier. Others trigger neurotransmitters that stimulate muscle contractions for increased motility—think, better, more regular poops. Yet other bacteria produce byproducts like short-chain fatty acids, which have been extensively shown to be beneficial for metabolic and gut immune health.

This is why, if you choose to take a probiotic, continuous daily intake is important.

4. Probiotics need to be refrigerated to work.

Contrary to other perishable food products, refrigeration doesn’t mean ‘freshness’ or superiority. It’s true that bacteria are fragile—they’re sensitive to light, temperature, and moisture. While some probiotics do need to be refrigerated to preserve efficacy (especially in hotter summer months, or during transport), you shouldn’t discount a probiotic that doesn’t require refrigeration. Technological innovations like lyophilization (freeze-drying) can render probiotics ‘dormant’, meaning they remain in an inert, shelf-stable state until they reach the digestive tract and are reactivated.

The more important thing to look for is demonstrated survivability (through improved delivery technologies like our novel delayed-release capsule technology), regardless of the storage conditions.

5. Probiotics with higher CFUs are always better.

Not necessarily—especially if it contains billions and billions of bacteria never tested in humans.

You’ve probably seen the term CFU on a probiotic label. That refers to colony-forming units, which basically tells you how many bacteria in the sample are capable of dividing and forming colonies. First, a bigger number on the bottle does not always mean better results. The best dose, per strain, is one that has been shown to deliver clinically-validated, positive outcomes in humans.

Second, CFU has become a marketing tool. Many probiotics today proclaim outrageously enormous CFU counts, but are unable to survive the trip from manufacture to store shelf, much less the journey from your mouth, through your acidic digestive process, to your gut. Oftentimes, to get around this, the number on the box will refer to ‘time of manufacture’, when really, it should tell you what amount will still remain viable near the expiration date.

More interestingly, a new form of measurement has emerged—AFU. AFU stands for Active Fluorescent Units. It’s measured with flow cytometry, a process where probiotic cells are tagged with fluorescent ‘markers’ and counted by a laser as they pass through a tube. Through AFU, we are able to calculate a more precise measurement of all viable cells, including ones that are efficacious but not necessarily culturable (and therefore would not be counted in a traditional plated CFU measurement).

6. Probiotics are all the same.

You’ve heard of Lactobacillus acidophilus, right? Let’s break down the name: Lactobacillus is what’s called a genus, that is, a ‘group’. Think back to taxonomy mnemonics from middle school biology (King Phillip came over for good soup) and recall that genus is followed by species. Within the Lactobacillus genus, we have species like Lactobacillus acidophilus or Lactobacillus rhamnosus.

There’s more. Within each species of bacteria, there can also be hundreds or thousands of strains. And just like a golden retriever and a french bulldog (both categorized as Canis lupus familiaris species) are incredibly different, these strains of bacteria can also be night and day. This is referred to as ‘strain specificity’. Here’s why it’s important:

  1. Escherichia coli Nissle 1917 is a non-pathogenic bacterial strain of the infamous E. coli family that has actually been extensively studied for its probiotic effects on gastrointestinal disorders. Meanwhile, E. coli O157:H7 is responsible for romaine lettuce recalls. And for good reason, it can cause hemorrhagic diarrhea, abdominal cramps, and even kidney failure.
  2. Of the thousands of Lactobacillus plantarum strains studied, Lactobacillus plantarum SD-LDL400-UK in our Daily Synbiotic was the only one with a demonstrable effect of lowering LDL cholesterol in the body.

When it comes to probiotics, benefits are clinically-assessed on the strain level, and cannot simply be extrapolated across the entire genus. So when someone tells you you need more Bifidobacterium or to increase your intake of Lactobacillus acidophilus, your response should be, ‘Which strains?’.

7. Probiotics need to be “personalized”.

In 2007, the National Institute of Health spearheaded a $173 million Human Microbiome Project with the goal of characterizing the human microbiome and to determine if changes in microbiome composition could be correlated with health and disease. The project encompassed five years of research and over 200 scientists and concluded in 2012 that there is no universally healthy microbiome.

Their findings also revealed that the metabolic function of our microbiome is much more important than what microbial species present. That means, it’s much more important what your bacteria are doing, rather than who they are. So, while we wish it were as simple as ‘find out what’s missing and put the good stuff back’, that’s unfortunately not how a complex ecosystem like the human body works.

We do think diagnostics may be insightful for specific endpoints like bacterial vaginosis, or how our bodies metabolize glucose, but most of the ones available today (though fun to do and satiate our curiosity for data) are unable to give us scientifically-substantiated, actionable advice. Beyond the technical limitations of at-home sampling and whether or not the shipped sample even represents the full spectrum of bacteria present in the gut microbiota (swabbing your post-number-2 toilet paper is different from dissecting and taking a sample from the middle of your stool), correlating actionability with composition is challenging given what science knows today.

Scientifically-validated probiotics today take a different approach, looking at specific strains of beneficial bacteria which have a health benefit in humans independent of someone’s starting microbiome.

As our mindset shifts from sick care to self care, we’ve become more intentional about our diet, nutrition, exercise, and lifestyle. But we now also know that probiotics are complementary tools to preventively and proactively care for our whole selves (not just our human parts). The key to choosing the right probiotic? Just ask these two important questions:

  1. What are the strains (not just species) present? In what quantities?
    (Our answer: a proprietary formulation comprised of strains characterized at academic institutions and research partners in Italy, Spain, Belgium, US, and Japan. Our full list of strains and quantities can be found here.)
  2. What is the clinical and scientific data behind these strains (in these quantities)?
    (Our answer: clinically-studied in 16 strain-specific, double-blind, placebo-controlled, published human studies, as well as 13 in vitro/ex vivo mechanistic studies.)