Side Effects of Probiotics

June 8, 2017 / Research
Side Effects of Probiotics

Probiotics are all the rage right now, thanks to the blogging and medical community’s focus on the microbiome – the ecosystem of bacteria that live inside your gut. A healthy microbiome is associated with better blood sugar control, lower rates of colorectal cancer, better all-around energy levels and fewer symptoms of depression. In fact, the science on the benefits of a healthy gut is so overwhelming that the medical community has experienced something of a paradigm shift. No longer is the human body viewed as a single organism but rather a synergistic ecosystem, where the health of all the species of bacteria living in the gut has a direct effect on the health of the entire body. That being said, there are many questions about the side effects of probiotics. In this article, we’ll review which ones are real and which ones are myth.

With the renewed interest in gut flora, the supplement industry now offers a broad range of probiotics – supplements which contain live bacteria, designed to bolster the number of “good” bacteria in your gut. But because probiotics are so new, consumers and patients have a lot of questions. As a community, we’re still trying to wrap our heads around probiotics and want to know whether they’re as good for us as they’re cracked up to be.

This post is designed to answer some of the most common questions about probiotics, helping you make a decision on whether or not to include probiotics in your regime. You may also want to read the following two posts we have provided on the subject:

Lactobacillus Acidophilus Benefits

Digestive Enzymes VS Probiotics

Can you take too many probiotics?

When it comes to pills, we’re used to the idea that we can “overdose.” Take too many aspirin or Lipitor, and you can end up seriously hurting yourself. But when it comes to probiotics, it’s difficult to overdose, if not impossible.

The reason for this has to do with numbers. Remember that ecosystem we discussed in the intro – all those bacteria living in your gut? It turns out that there are more than 100 trillion of them – that’s 100 followed by twelve zeroes. In fact, there are many times more bacteria living in your gut that there are human cells in your entire body. The reason they all fit down there is because they are so small.

These enormous numbers make it difficult to overdose on probiotics. The average probiotic pill contains between 1.2 billion and 50 billion bacteria. Even if you took 20 probiotic pills each containing 50 billion live bacteria, you’d only get around 1 trillion bacteria, just 1 percent of the total number already living in your gut.

Furthermore, the type of bacteria contained in these probiotics is the beneficial kind: the kind that you probably don’t have enough of already. Displacing harmful bacteria and replacing them with a healthy type of bacteria will probably do you some good.

The number of viable bacteria in your gut also depends on what you feed them. Certain bacteria eat certain types of food and fiber that pass through your gut. If you don’t feed probiotics food that they eat, their numbers will fall, and you’ll end up with only a trace population living in your gut, no matter how many pills you consume.

Are Probiotics Safe?

Unfortunately, there hasn’t been a significant amount of research investigating whether probiotics are safe or not. Though there doesn’t seem to be any immediate need for concern, some researchers hypothesize that probiotics could impact our bodies in ways not yet fully investigated by science.

For instance, because probiotics introduce new bacteria into the body, there is concern that they could have an adverse impact on at-risk populations of people, including infants, the elderly and those with compromised immune systems. There is also concern that probiotics might lead to excessive stimulation of the immune system in some patients, as well as harmful gene transfer in others.

It is important to stress that none of these possible dangers have yet been quantified in a scientifically rigorous way, meaning that if they are an issue, then they likely affect only a small proportion of the total population.

Side effects of Probiotics

Can Probiotics Cause Diarrhea?

Diarrhea is not a frequent side effect of taking probiotics. In fact, probiotics may actually be beneficial in countering diarrhea.

The reason is rather simple. Most of the bulk of your stool isn’t food particles or fiber; it’s actually bacteria which have eaten your food. The more healthy bacteria you have in your gut, the larger your stools will be and the easier it will be to go to the toilet.

The world-famous Cochrane Institute recently conducted a meta-analysis of more than 63 studies investigating the link between diarrhea and probiotics. By pooling all the of data from the studies, they found that probiotics significantly reduced the incidence of diarrhea across more than 8000 study participants. The bottom line, probiotics fight, not encourage, diarrhea.

Can Probiotics Cause Constipation?

Another fear is that taking probiotics will lead to constipation – a painful condition in which stools are unable to progress through the bowel. There are all kinds of causes of constipation, including not eating enough, becoming dehydrated, failing to eat sufficient fiber and so on. However, medical professionals and research scientists are yet to produce any evidence linking the consumption of probiotics to constipation. This does not mean that probiotics could not conceivably cause constipation in some people, just that there is, as yet, no evidence to suggest that they do.

One could speculate the probiotics causing constipation is unlikely. The reason for this is that, because they contain live bacteria, they are likely to lead to increased stool weight which has been shown in many studies to result in improved bowel motility. Intestinal transit in populations with large stools is often twice as fast as those with small stools, so the bigger, the better.

Do Probiotics Make You Gassy?

Although probiotics rarely have serious side effects, one of the more unpleasant consequences can be flatulence in some people. Because probiotics contain live cultures which need to metabolize, they often let off waste products in the form of gas. The good news is that flatulence rarely lasts more than a couple of weeks. Over time, the balance of gut bacteria in your intestines adapts and settles into a more stable population.

“Should I Take Probiotics?”

Whether or not you should take probiotics is a personal choice, but one supported by the evidence. Given the numerous health benefits of fostering healthy gut flora unearthed by science, and the few side effects of probiotics, it would appear prudent for everybody to find ways of supporting their gut health.

Traditionally, populations consumed foods containing live cultures, like kefir and yogurt, to bolster their good gut bacteria. But science has since discovered that eating these foods may be ineffective since the bacteria they contain are routinely destroyed when they come into contact with stomach acid.

Researchers, including Dr. Shekhar Challa, the author of Probiotics for Dummies, say that it may be better to take probiotics in pill form because of the added protection the pill provides bacteria while traveling through your stomach. Bacteria need to be able to reach the small intestines alive to be beneficial.

How Long Does It Take Probiotics To Work?

The length of time it takes for probiotics to work depends on a broad range of factors.

The first factor is what scientists call “the substrate.” To survive, thrive and reproduce, the bacteria in probiotics need to be able to feed once they get down to your gut. If your gut is rich in nutrients like amino acids and ascorbic acid, then the bacteria are likely to grow quickly. If however, your gut does not provide an adequate source of nutrition, these bacteria will not thrive and fall back to trace levels over time.

The second important factor is the type of bacteria that you ingest. Probiotics come in all sorts of different forms, including live cells, heat-inactivated cells or parts of cells contained in powder. Live cells will reproduce whereas dead cells will not, meaning that live bacteria are usually able to exert an influence far more rapidly.

Depending on these factors, probiotics can begin working in just a few hours or take weeks and months to have an effect. It all depends on the conditions in your body and the type of probiotic you consume.

What Are The Best Foods For Probiotics?

As discussed, some foods are also probiotics. Just like live supplements, they contain live cultures which can live in your gut, providing a whole host of benefits.

Yogurt contains many billions of bacteria, including lactobacillus and acidophilus. What’s more, the yogurt itself contains amino acids necessary for the survival of the bacteria it contains, making it an excellent way to add probiotics to your diet.

Kefir is a fermented dairy product made of goat’s milk and fermented kefir grains. Like regular yogurt, it contains a broad range of beneficial bacteria designed to support gut health.

Many other foods are great probiotics too. These include sauerkraut – the German pickled cabbage rich in vitamins A, B, C and K – dark chocolate, which is a great carrier of bacteria into the gut, miso soup made from fermented soy beans, and pickled vegetables.

What Is The Difference Between A Probiotic And A Prebiotic?

If you do a search for probiotics and prebiotics, you’ll often see them used interchangeably. But it is important to note that they are not the same things. Probiotics are foods or supplements which contain live cultures designed to bolster the number of bacteria in your gut, whereas prebiotics are foods which lay the groundwork, providing an environment in which bacteria can thrive. Excellent prebiotics include practically all fiber-containing foods since bacteria can eat the fiber in these foods and use it to increase their population.

What Are The Benefits Of Probiotics?

Probiotics have been shown by researchers to have a whole range of effects…


  • Lower Cholesterol. Elevated cholesterol is a serious cardiovascular risk factor and often a precursor to strokes and heart attacks. But recently, scientists at the American Heart Association found that probiotics in some animal foods can help to lower cholesterol. One of the ways that cholesterol gets into the body is that it is reabsorbed by the intestines after being released by the liver in the form of bile. Scientists found that particular strains of bacteria were able to break down these bile salts, preventing the cholesterol they contained from being reabsorbed through the intestines.


  • Less Tooth Decay. Tooth decay is a serious global epidemic right now. More than 90 percent of people have some form of oral tooth decay by the time they reach 40, thanks to diet and lifestyle factors. The good news, however, is that a healthy gut flora might help prevent tooth decay. Studies have demonstrated that certain strains of gut bacteria, Lactobacillus reuteri, kills the bacteria which cause tooth decay, helping to keep your mouth beautiful and cavity-free.


  • Reduced Eczema. Eczema is an unpleasant and annoying condition which can ruin your quality of life. Walking around with constantly itching skin is enough to drive anybody mad. It turns out, however, that probiotics might help alleviate some of the symptoms. Researchers writing in the Journal of Allergy and Clinical Immunology found that infants who were at heightened risk of developing eczema benefited when their mothers drank probiotic products. The infants of mothers given probiotics saw reduced levels of skin inflammation at different intervals during the first two months of life.


  • Fewer respiratory infections. Are you one of those people who always gets sick in the winter no matter what? It could be the result of a compromised immune system. It turns out that the bacteria in your gut are the first line of defense in your immune response to infection. If the gut bacteria aren’t healthy, or if they are of the wrong variety, then your immune system could be weakened, and you could be more susceptible to infection. Researchers at the Cochrane Library concluded that probiotics seemed to help prevent respiratory tract infections better than placebo, indicating their importance to whole body health.

For more details see this post mentioned above: Lactobacillus Acidophilus Benefits


Concluding Remarks

The evidence is pretty clear: rarely are there serious side effects of probiotics, and they tend to be beneficial, thanks to the fact that they support a healthy microbiome, the lynchpin of a robust immune system. Loving your gut has many health effects which

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