can probiotics cause brain fog

Can Probiotics Cause Brain Fog or Help Foggy Brain?

Many people report feeling brain fog after taking probiotics. But is there any science to back up this claim? And if so, what might be causing it? This post is all about what I’ve known and also discovered so far.

Have you just lost focus and are facing difficulty in making decisions? It is indeed wise that you are questioning your supplement’s role in your altered brain function.

Because yes, brain fog after taking probiotics is very common and can occur when certain bacteria grow out of balance than others.

Therefore, in this article, I will explain how and why probiotics cause brain fog if it is related to neurological disorders, and what probiotics may be better options to promote brain function.

Let’s get to it!

Why Do Probiotics Cause Brain Fog?

The gut-brain axis may allow your intestinal bacteria to mess with focus and thinking. Therefore, when probiotics excessively colonize the gut, it may cause you to lose focus.

brain-gut connection

In this context, 2018 research performed at Augusta University substantiates this theory because it identified a link between probiotics and brain fogginess.

In the study, 22 of the 30 healthy participants who took probiotics reported excessive gassiness, bloating, confusion, and difficulty concentrating. Upon further investigation, researchers found that small intestinal bacterial overgrowth (SIBO) and D-lactic acidosis were more common in patients that reported these symptoms.

Another confirmation was that the mental cloudiness resolved in 85% of the affected participants after stopping the probiotic intake and starting an antibiotic course. It was later found that 68% of the total sufferers had a bacterial overgrowth in their bowel (SIBO).

Hence, too many bacteria, especially Lactobacillus, were fermenting the sugars in the gut that generated methane, hydrogen gas, and D-lactic acid, which caused bloating and D-lactic acidosis.

Correspondingly 77% of the total affected participants had two to three times the normal levels of D-lactic acid in their blood.

This D-Lactic acid is temporarily toxic to the brain cells and may affect cognition, thinking process, and attentiveness.

This is why participants reported that their brain fogginess lasts for a half hour to many hours after probiotic intake.

Can probiotics cause neurological problems?


No, although probiotics do have an impact on the Central Nervous System (CNS), this may have a positive outcome on your neurological health rather than a negative one.

You don’t need to bother too much about the brain fog that may occur from probiotics because it is a short-term side effect and will not lead to long-term neurological problems.

For instance, a review of 25 animal and 15 human studies also concluded that probiotic strains, namely B. longumB. breveB. infantisL. helveticusL. rhamnosusL. plantarum, and L. casei improve CNS function, mood, psychiatric problems, and memory.

In these trials, the most effective dosage regime in human trials involved the intake of 109 and 1010 CFU of these probiotics for four weeks.

Below is some further evidence that proves that probiotics may be good for neurological problems.

Probiotics and Mental Conditions

Multiple studies have found the benefit of probiotic supplementation in relieving psychiatric disorders such as anxiety, depression, obsessive-compulsive disorder (OCD), attention-deficit-hyperactivity disorder (ADHD), and autism. 

For instance, a 2019 randomized control trial conducted on 40 healthy volunteers showed that the B. longum 1714 strain might communicate with the brain and alter its neural oscillations or cortisol levels (stress hormone).

Therefore, it helped the participants to better manage negative emotions, reduced mental fatigue, and enhanced their cognition.

Many other animal and human studies reveal the anxiolytic and stress-reducing potential of the Lactobacillus, Bifidobacterium, and Bacteroidetes probiotic species as well.

Correspondingly, a randomized control trial showed that oral administration of L. helveticus R0052 and B. longum R0175 strains for a month significantly reduced the psychological distress and cortisol levels in the study subjects.

Furthermore, studies on L. plantaraum and L. helveticus found that they may increase serotonin and dopamine levels (happy hormones) to improve mood.

Probiotics and Neurological diseases

There’s a whole lot of scientific evidence that supports the fact that neurological diseases may develop due to microbiome dysbiosis. For this reason, probiotics may improve their symptoms.

Moreover, they may even promote neurological development in children.

In fact, a new category of probiotics that is referred to as ‘psychobiotic’ has been proposed that includes strains that combat neuronal diseases and help with behavior. 

Preliminary research suggests that probiotics may counter age-related cognitive decline and temporary or severe brain damage such as hepatic encephalopathy or cerebral ischemia caused due to different reasons.

They may also ameliorate traumatic brain injury, CNS diseases such as multiple sclerosis, or neurodegenerative disorders such as Parkinson’s disease (PD).

For example, in one clinical trial, patients suffering from hepatic encephalopathy were fed 10 billion CFU of a probiotic combination daily, which improved their cognitive function over time.

Here the probiotic combination had a total of nine species. Four of them were from the Lactobacillus genus (L acidophilusL rhamnosusL plantarumL casei).

The other four were from the Bifidobacterium genus (B longumB infantisB breve), one was a yeast strain (Saccharomyces boulardii), and there was a strain of Streptococcus thermophiles as well.

In case you keep wondering, in hepatic encephalopathy, liver failure in the patient causes a subsequent loss of brain function due to the accumulation of toxins in the blood.

Probiotics Brain Fog – Reddit Forum Stories

After skimming through the scientific studies, I looked for some user experience and found that it is also consistent with my initial stance on probiotics and brain fogginess.

So, let’s look into some Reddit stories.

Reddit story 1

u/RecoveringIdahoan shared her detailed experience in this Reddit story, which elucidates a link between probiotics, antibiotics, and SIBO.

reddit story 1 about brain fog and probiotics

She writes that she had symptoms of severe brain fog for over four years but didn’t know the reason.

Until, one day, she was diagnosed with chronic fatigue syndrome (CFS) and dosed up on probiotics to treat it after reading it somewhere. This instead worsened her condition even more, but it also made her realize that probiotics may be the culprit.

Therefore, she cut down on all fermented and probiotic foods, which cleared her mind in just two days.

However, even on days she accidentally took something remotely probiotic, she would end up suffering from the same brain fog again.

Even though quitting probiotics made her feel great, it came at the expense of smelly vaginal discharge and ‘early satiety,’ which was due to a weak digestion process. But after six months, she was incidentally put on an antibiotic course that improved her condition even more as she could now chug in alcohol and hot chocolate without any consequences.

However, after the antibiotic course ended, she fell into an endless pit of suffering as every food she ate kept causing diarrhea or constipation, and neither the probiotics nor the antibiotics seemed to work for her anymore.

Nonetheless, her SIBO test showed mild/moderate methane SIBO, and now she may start taking treatment for it, but she does know for sure that for her, ‘the gut runs the show.’

Reddit story 2

In another Reddit story, u/cheetopuff2525 shared that after the very first day that he took B. coagulans, B. indicus, B. subtilis, and S. Boulardii probiotics, he started getting brain fog and became anxious and depressed. 

reddit story 2

He further suspected yeast sensitivity to be the reason but wasn’t too sure.

To this, a replier shared that he suffered from similar symptoms, and his doctor told him that the S. boulardii inhibits the overgrowth of Candida albicans that releases acetaldehyde after dying, which is toxic to brain cells and may cause brain fog. 

For that, taking molybdenum, which neutralizes acetaldehyde, worked for him.

Related: Can Probiotics Cause Headaches?

Probiotics For Brain Fog

The clinical trial I referred to in the first section of this article was performed on individuals with no history of impaired renal or hepatic function or short bowel syndrome. 

Hence, this indicates that brain fog due to SIBO or D-Lactic acidosis may occur in people who already have a balanced microbiome that may get disturbed with probiotic intake.

In the Reddit stories as well, some of the people specified the underlying health condition while others were perfectly healthy.

Therefore, the outcome of probiotic intake cannot be generalized for everyone, as for many users, probiotics improve focus as well.

In any case, gut dysbiosis is linked to brain fog, and you may use probiotics to restore the microbiome balance and redeem your mental clarity. So, here are some products that are based on clinically acclaimed probiotic strains that improve brain function in case you want to try them.

But note that you must always talk to your doctor before using probiotic supplements and never use them as a treatment without professional advice.

1. Biotics 8 probiotics

Bauer Nutrition Biotics 8

The Biotics 8 probiotics deliver multiple probiotic species that may modulate brain function via the gut-brain axis. These include the L. casei, L. paracasei, L. plantarum, B. longum, and B. breve that alter the gut microflora to uplift mood and optimize brain function.

Whereas the remaining strains have a greater benefit in improving gut health.

Consequently, the prebiotics in the form of chicory root fiber and inulin aids the proliferation of good bacteria in the gut that promotes regularity.

Another digestive aid is the enzymes that enable complete digestion of the macronutrients, which prevents bloating.


  • Its one-month supply of 90 capsules is available for $74.99 and is delivered free of cost.


  • It improves digestion, immune function, and mood and causes weight loss.
  • It improves men’s health.
  • It offers 20 billion CFU per serving.
  • It has digestive enzymes.
  • It has ten probiotic strains.
  • It offers a 60-day money-back guarantee.
  • It is free from gluten, dairy, and soy allergens.
  • It is GMP certified.
  • It can be stored at room temperature.
  • It has prebiotics.
  • It doesn’t have preservatives.


  • Only for men
  • It can only be bought from the official website.
  • Its optimum concentration is delivered in three capsules.

2. YourBiology probiotics 

yourbiology gut +

The Your Biology probiotics ensure that the probiotic strains reach the gut alive and improve overall health along with mood and mental performance.

They contain the L. plantarum and L. paracasei probiotics that improve brain health and psychological disorders such as anxiety and depression.

These species are encapsulated with MAKtrek technology which increases their viability and absorption by 250 times.

Moreover, it also contains the prebiotic fructooligosaccharide, which helps healthy gut bacteria to flourish.


  • Its 60 tables cost $74.99, and the delivery is free.


  • It promotes weight loss and regularity, strengthens immunity, and improves brain fog.
  • It also promotes both men’s and women’s health.
  • It has eight probiotic strains.
  • It contains 40 billion CFU of probiotics per two capsules.
  • It has a 60-day money-back guarantee.
  • It does not require refrigeration.
  • It is preservative-free.
  • It is gluten, dairy, and soy free.
  • It contains prebiotics.
  • It is GMP certified.


  • It is not available in physical stores.
  • It has maltodextrin.
  • The optimum dose is delivered in two capsules.

3. Bio-Kult Mind Probiotics

The Bio-Kult probiotics are formulated with ingredients that have a cognition-enhancing and neuroprotective effect. It has just one probiotic strain, Bacillus subtilis PXN 21, and that too in limited concentration.

You can adjust the dose by taking either one or two capsules per day, which reduces the risk of gut bacterial overgrowth in susceptible individuals.

Preliminary research on animal models shows that B. subtilis may prevent brain aging and neuronal deterioration, which are the major risk factors of Alzheimer’s disease. 

Hence, it may also promote brain function in healthy individuals.

Other ingredients like zinc and flavonoids contributed by grape and wild blueberry extracts may reduce neuroinflammation and oxidative stress that prevent cognitive decline.


  • One bottle contains 60 capsules that you can buy for just $29.50 without any shipping costs on standard delivery.


  • It is targeted to improve cognitive and immune function.
  • It offers 1 billion CFU of probiotics per capsule.
  • It can be stored at room temperature.
  • It has a vegan-friendly formula.
  • Its capsule can be pulled apart to consume the powder content in food or drinks.
  • It doesn’t have artificial sugars, colors, or flavors.
  • It is gluten-free.
  • It is free from fillers.
  • It has a 30-day money-back guarantee.
  • It is available on the official website as well as online and in physical stores.


  • It contains allergens (dairy, soy).
  • It is recommended for those over 12 years of age.

4. Clear Probiotics


The Clear probiotics help to restore normal brain functioning and will put you back in the mood with filler-free formula. It is based on just two probiotic strains, B. longum and L. brevis, that reduce oxidative stress, counter cognitive decline, and promote brain cell growth.

Furthermore, It has ginkgo biloba, which has proven beneficial in enhancing cognitive performance in 18-20-year-olds.

Then the last ingredient, the lion’s mane, may help in regenerating neurons and improve memory processing, focus, and emotional responses.


You need to spend $108 to secure a one-month supply (60 capsules) of this product. Moreover, the manufacturers offer free shipping in the U.S. only.


  • It clears brain fog, improves mental abilities, and elevates mood.
  • It offers 20 billion CFUs per serving.
  • It has no artificial flavors or preservatives.
  • It is vegan.
  • It is soy and gluten-free.
  • It is a non-GMO product.
  • It is developed with delayed-release technology to ensure the delivery of viable bacteria.
  • It has a one-year money-back guarantee.
  • It is available on both the official website and online stores.
  • It is manufactured in FDA-approved cGMP facilities.


  • The recommended dose is two capsules.
  • It is expensive.

5. Bio-Heal 5-in-1 probiotic

bio heal probiotic

The Bio-Heal probiotic has an intelligent strategy to target every condition that may alter brain function, such as inflammation, leaky gut, or neurotransmitter imbalance. Moreover, it offers a dosage recommendation based on body weight and suggests that you start with half of the recommended dose.

Therefore, you have the freedom to personalize your probiotic intake, which may prevent overdosing and side effects.

In it, the gut-focused ingredients include the Lactobacillus, Bifidobacterium, and yeast probiotics, as well as digestive enzymes which aid digestion and reduce bloating.

Furthermore, the brain boosters include S. boulardii, L. plantarum, B. breve, and B. longum species, along with phosphatidylcholine and zinc that boost memory, mood, and focus and restore proper brain activity.


  • A single container is enough to last 4-months and costs $59.99, but standard delivery charges may apply to a one-time purchase. 


  • It promotes gut, immunity, and brain function.
  • It is available in capsules, powder, and flavor sticks.
  • It has 12 probiotic strains.
  • It has 13 billion CFUs per serving (3 capsules or one scoop).
  • It has prebiotics.
  • It doesn’t have artificial sugars.
  • It has non-GMO ingredients.
  • It is free from major allergens like dairy, nuts, soy, and gluten.
  • It has a 90-day money-back guarantee.
  • It doesn’t have filler stuff.
  • It doesn’t contain allergens like gluten, dairy, or nuts.
  • It is available at both the official website and online stores.
  • It has a vegetable-based formula.
  • It is a non-GMO product.


  • It has soy lecithin, which may trigger allergies.
  • It doesn’t have a one-month supply.
  • It might be hard to consume higher recommended doses (up to 6 pills per day). 
  • It has maltodextrin.
  • It has a proprietary blend of probiotics.


Will brain fog from probiotics go away?

Yes, brain fog from probiotics may subside in a few weeks after you discontinue their use and take doctor-recommended antibiotics.

How can probiotics cause d-lactic acidosis and brain fogginess?

Consuming probiotics may cause an overgrowth of Lactobacillus bacteria in your bowel. These bacteria feed on the sugar you eat and generate D-lactic acid as a by-product. 

This D-lactic acid affects brain cells and may consequently cause brain fogginess.

Can probiotics cause confusion?

Yes, D-lactic acidosis and SIBO may cause confusion as it is also a symptom of brain fogginess.

Can gut bacteria cause brain fog? 

Yes, dysbiosis in the gut microbiome may cause brain fog. However, it is temporary and will clear up after the restoration of a balanced and normal gut microbiome.


To conclude, although probiotics may cause brain fog but gladly, it is only short-term and may not lead to long-term neurological problems. The reason behind this is that consuming live bacteria in the form of probiotics allows their colonization in the intestines, which may set off the natural microbial balance there.

Consequently, the gut may turn into a fermentation hub where the bacteria will rush to feed the sugar you consume. This will generate gases that may be toxic to the brain and decrease attentiveness, reduce mental clarity, and cause loss of time sense and short-term memory loss.

As opposed to this, some probiotics are instead effective in improving neurological issues and diseases like anxiety or hepatic encephalopathy.

So, always consult your doctor to determine if you should opt for a probiotic and which supplement would best suit you.

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