The Probiotic Formulated Specifically for Runners

You have unique challenges and needs as a runner that generic probiotics just don’t address. MAS Flush contains clinically effective doses of 4 ingredients scientifically shown to…

Practically eliminates gastric distress during & after workouts and races
Increases carbohydrate oxidation when racing so you process gels and other carbs faster
Significantly improves digestion of the foods you need to fuel your training
Reduces ‘leaky gut’ by up to 40%

4.9/5.0 513+ Happy Athletes

The Probiotic Formulated Specifically for Runners

You have unique challenges and needs as a runner that generic probiotics just don’t address. MAS Flush contains clinically effective ingredients scientifically shown to…

Significantly improve digestion of the foods you need to fuel your training
Practically eliminates gastric distress during & after workouts and races
Increases carbohydrate oxidation when racing so you process gels and other carbs faster
Makes bowel movements more consistent so you never start your runs needing to go
Reduces ‘leaky gut’ by up to 40%

Non GMO

Clinically Tested

Vegan

Research-Backed

Non GMO

Clinically Tested

Vegan

Research-Backed

Non GMO

Clinically Tested

Vegan

Research-Backed

Non GMO

Clinically Tested

Vegan

Research-Backed

Non GMO

Clinically Tested

Vegan

Research-Backed

Non GMO

Clinically Tested

Vegan

Research-Backed

Non GMO

Clinically Tested

Vegan

Research-Backed

Non GMO

Clinically Tested

Vegan

Research-Backed

Hundreds Have Experienced Real Relief, Peace of Mind and Results

I honestly can’t believe this product worked so well. Before using flush, I’d be scrambling back home to go to the bathroom at least 3 days per week. It made me scared to go to group runs or even try out new trails for fear of not having a bathroom nearby. I’ve been using for 3 weeks now and not once have I had to go to the bathroom once I started running. This is such a relief!

I tried this product during the beta launch because I really struggled with stomach pain when racing and even after hard workouts. There were times after hard workouts that it would take hours for my stomach to feel normal. MAS Flush changed everything. I’ve been using it for a month and I haven’t had any stomach pain after workouts. I’m so glad I found this.

I’ve tried countless gut products, but this is the one that actually worked. For the first time in years, my digestion feels normal. No more discomfort, bathroom urgency, or unpredictable bloating. It’s been such a relief. This formula actually works.

I honestly thought needing to go to the bathroom within the first few miles of a run were just something all runners needed to deal with. I was given MAS Flush as a gift during a running retreat and I was definitely skeptical, but I didn’t need to go to the bathroom during the 3 runs we did at the retreat, which is unusual, so I kept using. It’s been working every day for the last 3 weeks. I can’t believe I didn’t look into something like this sooner.

I’ve tried countless gut products, but this is the one that actually worked. For the first time in years, my digestion feels normal. No more discomfort, bathroom urgency, or unpredictable bloating. It's been such a relief—this formula actually works. I love how gentle it is but still powerful enough to make a real difference day-to-day.

I honestly thought needing to go to the bathroom within the first few miles of a run were just something all runners needed to deal with. I was given MAS Flush as a gift during a running retreat and I was definitely skeptical but I didn’t need to go to the bathroom during the 3 runs we did at the retreat, which is unusual, so I kept using. It’s been working every day for the last 3 weeks. I can’t believe I didn’t look into something like this sooner.

the end of stomach trouble

here's what MAS Flush Can Do for You

Stop Worrying About Carrying Toilet Paper or Finding Place to Hide

Every runner fears starting a run without nearby bathrooms.

Frequent needs to go to the bathroom early in a run are usually caused by not being able to quickly digest the foods you ate for dinner or when your digestive system isn’t able to keep up and you have inconsistent bathroom times.

MAS Flush contains Psyllium seed husks, which when taken in the evening helps make bowel movements easier and more consistent.

It can also help add bulk to stool, which helps relieve the feeling of needing to go to the bathroom. This is especially helpful due to the jostling that occurs in the digestive tract during running.

Taking just two MAS Flush capsules after dinner will make it easy to go to the bathroom as soon as you wake up so you can virtually eliminate needing to go to the bathroom during your runs.

Eliminate stomach pain during and after races

Put an end to stomach pain and cramping during and after hard workouts that lead to you slowing down and not getting the most from your performance.

Stomach issues during races and hard workouts often happen for two reasons.

First, endotoxins (bacterial toxins) are released during strenuous, long-duration exercise which lead to cytokine release, oxidative stress, and altered gastrointestinal function.

Second, internal and exertional heat stress causes blood to be redistributed away from the digestive system to help with thermal regulation. As a result, lack of blood supply stresses the gut, which results in bathroom and stomach issues.

MAS Flush’s combination of Bifidobacterium Longum and New Zealand Blackcurrant have been shown in research to

Reduce total gastric distress in runners by 73%
Reduce endotoxin unit levels during races
Reduce the duration of GI symptoms post-race

Fix Bloating & Digestive Issues While Absorbing More of the nutrients you consume

Bloating and digestive issues occur more often in endurance athletes because the fuel we need to train and recover often comes from difficult-to-digest foods such as plant fibers, complex carbohydrates, and proteins.

Usually, this is caused by not producing enough of the enzymes that help break down these foods.

Our endurance-focused digestive enzyme blend is specifically designed to help your body naturally digest the foods you need to fuel your training while improving your gut microbiota to create a more favorable environment in your stomach.

The enzymes in MAS Flush have been shown in research to…

Break down food and extract nutrients, making it easier for the body to absorb.
Improve the integrity of the gut lining, which helps prevent the leakage of undigested food particles (often called leaky gut) and enhances nutrient absorption.
Reduce gut inflammation to increase the absorption of micronutrients like calcium and iron.

No more stomach issues taking gels and other carbohydrates during your race

One of the most difficult things about racing half, full and ultra marathons is taking in enough fuel to keep your glycogen levels topped off without causing stomach issues.

All that simple sugar is difficult for your body to process quickly, which is a main contributor to why many runners suffer to fuel properly during races.

The included Bifidobacterium in MAS flush has been shown in research to improve carbohydrate absorption and metabolism during endurance races, potentially sparing muscle glycogen during prolonged exercise.

Additionally, Bifidobacterium may help maintain gut barrier integrity, reduce gastrointestinal distress, and improve nutrient absorption.

Eliminate post workout stomach issues so you can refuel easier

There’s a reason we often refer to hard workouts as “gut-busting”. That’s because they often leave us with stomach discomfort after the workout.

This happens because after a hard training run, blood is still being shifted away from the stomach to aid in muscle recovery.

This leaves fewer enzymes available to break down your meals.

It’s also why you’re often not hungry for hours after hard workouts.

The digestive enzymes in MAS Flush have been shown in research to reduce post-workout stomach discomfort so you can jump start your recovery process with the nutrients your muscles need.

Reduce The Occurrence of Colds and other immune issues

Hard training temporarily weakens your gut lining, allowing inflammatory compounds to leak into your bloodstream and suppress your immune system.

This is why runners tend to catch the cold and flu more when training hard.

The probiotics in MAS Flush help seal these gaps and strengthen the gut lining to prevent these inflammatory compounds from entering the blood stream

It also helps cultivate and prime virus fighting cells so your body is more capable of fending off the pathogens that cause getting sick.

Consistent supplementation has been shown in research to help you spend less time recovering from illness and more time building fitness.

Revolutionary Ingredients Backed by Science

MAS Flush is more than just a probiotic. We’ve carefully chosen the specific strains of bacteria and yeasts proven to help the most for athletes. Then we combined them with cutting-edge ingredients that help improve all the unique aspects of gut health runners and endurance athletes face.

Psyllium Husk Powder [Plantago ovata] (1500mg)

Psyllium, derived from the plants known as ispaghula, is a primarily soluble, bulk-forming fiber supplement shown in research to help improve digestive and metabolic health.

Compared to similar fibers, psyllium is less fermentable in the gut, which means it’s less likely to produce flatulence, stomach pain, and nausea.

Research has demonstrated that psyllium makes bowel movements easier and more consistent which can help alleviate the issue of runner’s trots by ensuring you’re able to go to the bathroom before your run¹.

Psyllium has also been shown in research can help add bulk to stool, which helps relieve the feeling of needing to go to the bathroom. This is especially helpful due to the jostling that occurs in the digestive tract during running.

1. Jalanka J, Major G, Murray K, Singh G, Nowak A, Kurtz C, Silos-Santiago I, Johnston JM, de Vos WM, Spiller R. The Effect of Psyllium Husk on Intestinal Microbiota in Constipated Patients and Healthy Controls. Int J Mol Sci. 2019 Jan 20;20(2):433. doi: 10.3390/ijms20020433. PMID: 30669509; PMCID: PMC6358997.

Bifidobacterium Longum Powder [100B CFU/G] (100mg)

Bifidobacteria are a type of probiotics, which are healthy bacteria found in your intestines that help digest fiber, prevent infections, and produce important compounds, such as B vitamins and healthy fatty acids.

One of the main functions of bifidobacteria is to digest fiber and other complex carbs your body can’t digest on its own, which can lead to bathroom issues.

Specifically, bifidobacteria supplementation has been shown in research to significantly lower the incidence and severity of GI symptoms in marathon runners¹.

Research has also shown that runners who supplemented with bifidobacteria saw a reduction in the severity of GI symptoms during training² as well as a reduction in the duration of GI symptoms post-race³.

1. Kekkonen RA, Vasankari TJ, Vuorimaa T, Haahtela T, Julkunen I, Korpela R. The effect of probiotics on respiratory infections and gastrointestinal symptoms during training in marathon runners. Int J Sport Nutr Exerc Metab. 2007 Aug;17(4):352-63. doi: 10.1123/ijsnem.17.4.352. PMID: 17962710.

2. Roberts JD, Suckling CA, Peedle GY, Murphy JA, Dawkins TG, Roberts MG. An Exploratory Investigation of Endotoxin Levels in Novice Long Distance Triathletes, and the Effects of a Multi-Strain Probiotic/Prebiotic, Antioxidant Intervention. Nutrients. 2016 Nov 17;8(11):733. doi: 10.3390/nu8110733. PMID: 27869661; PMCID: PMC5133117.

3. Pugh JN, Sparks AS, Doran DA, Fleming SC, Langan-Evans C, Kirk B, Fearn R, Morton JP, Close GL. Four weeks of probiotic supplementation reduces GI symptoms during a marathon race. Eur J Appl Physiol. 2019 Jul;119(7):1491-1501. doi: 10.1007/s00421-019-04136-3. Epub 2019 Apr 13. PMID: 30982100; PMCID: PMC6570661.

Black Currant Extract 4:1 [Ribes nigrum] [Berry] (240mg)

One of the most common reasons runners experience bathroom issues later into runs and races is due to internal and exertional heat stress. This is because blood is redistributed away from the digestive system to help with thermal regulation.

As a result, lack of blood supply stresses the gut, which results in bathroom and stomach issues.

Recent research has shown that New Zealand blackcurrant…

Reduces total gastric distress symptoms by 73% in runners¹.
Reduces ‘leaky gut’ by up to 40%²

1. Willems MET, Flood TR, Kuennen MR, Lee BJ. Anthocyanin-rich New Zealand blackcurrant extract reduces treadmill running-induced gastrointestinal symptoms in the heat: pilot observations. Res Sports Med. 2025 Jul-Aug;33(4):440-447. doi: 10.1080/15438627.2025.2471380. Epub 2025 Feb 25. PMID: 39996414.

2. Lee BJ, Flood TR, Hiles AM, Walker EF, Wheeler LEV, Ashdown KM, Willems MET, Costello R, Greisler LD, Romano PA, Hill GW, Kuennen MR. Anthocyanin-Rich Blackcurrant Extract Preserves Gastrointestinal Barrier Permeability and Reduces Enterocyte Damage but Has No Effect on Microbial Translocation and Inflammation After Exertional Heat Stress. Int J Sport Nutr Exerc Metab. 2022 Mar 14;32(4):265-274. doi: 10.1123/ijsnem.2021-0330. PMID: 35287112.

Endurance-Specific Digestive Enzymes

Fueling your training properly means you have to digest and absorb the foods you eat, but this can be difficult for a number of reasons.

First, the foods that fuel our training are often difficult to digest, such as plant fibers, starches, and proteins.

Second, after hard training blood is still being shifted away from the stomach to aid in muscle recovery, which leaves fewer enzymes available to break down your meals. This is why you’re often not hungry for hours after hard workouts.

Our enzyme blend is specifically designed to target the foods endurance athletes need the most and are most difficult to break down.

Protease 500,000 HUT/g – helps break down proteins into absorbable amino acids

Amylase 100,000 DU/g – splits starches into usable glucose

Lipase 15,000 FIP/g – breaks fats into fatty acids for sustained energy

Cellulase 150,000 CU/g – shreds tough plant fibers your body can’t process alone.

The result is faster, more complete digestion that delivers more building blocks to recovering muscles while keeping your gut calm and race-ready.

Lactobacillus Acidophilus [10B CFUs]

Hard running diverts blood away from your gut, loosening the tight seals between intestinal cells and letting bacteria leak into your bloodstream.

Your immune system responds with inflammation, which triggers cramping, bloating, and nausea.

Lactobacillus acidophilus reinforces those cellular seals before they fail.

This specific probiotic strain crowds out harmful bacteria, tightens the gaps in your intestinal lining, and quiets the inflammatory response.

Research shows that supplementing daily for at least four weeks reduces GI symptom severity during long efforts and cuts down on emergency bathroom stops mid-race.

Bifidobacterium animalis [50B CFUs]

Hard training temporarily weakens your gut lining, allowing inflammatory compounds to leak into your bloodstream and suppress your immune system.

This is why runners tend to catch the cold and flu more when training hard.

Bifidobacterium animalis helps seal these gaps and strengthen the gut lining to prevent these inflammatory compounds from entering the blood stream.

It also helps cultivate and prime virus fighting cells so your body is more capable of fending off the pathogens that cause getting sick.

Consistent supplementation helps you spend less time recovering from illness and more time building fitness.

MAS Flush Vs. Generic Probiotics

While almost any probiotic will help improve your gut health, you have unique challenges and needs as a runner that generic probiotics just don’t address.


Helps alleviate needing to go to the bathroom as soon as you start running
Formulated to target endotoxins to eliminate stomach pain during races
Designed to reduce heat stress, a major cause of GI distress when racing and working out hard
Specific ingredients to improve carbohydrate absorption and metabolism while running
Advanced digestive enzymes to naturally digest fiber, complex carbs, and other difficult to digest foods

your questions answered

Experience the benefits of a healthy gut, better digestion and no more bathroom fears

Can I or Should I Take MAS Flush Every Day?

MAS Flush works best if you take it every day.

In addition to alleviating bathroom issues before and during running, the probiotics in MAS Flush help you more efficiently digest foods, absorb nutrients, and create a favorable environment for the growth of “good microflora” in the large intestine.

That said, if you only wanted to use on the days you run for the improvement of bowel movements, it will still work great.

Should I take MAS Flush Before a Race?

Like almost any product, you should definitely use MAS Flush a few times during your training cycle before using it during a race.

The most significant results and changes often occur during the first few uses as your gut and digestive system experience ingredients for the first time.

However, we did specifically formulate the product to help with many of the digestive challenges we face during the race so it should be a significant aid during your most important performances.

Is MAS Flush Safe to Take With Other Probiotics?

Yes, MAS Flush is safe to take with any other probiotic or gut health product you may be taking.

The current medical literature has found that it’s difficult to overdose on probiotics or experience dangerous side effects from a large dose of probiotics.

Will I Experience Any Side Effects?

You should not notice any side effects when taking MAS Flush.

That said, the most significant results and changes often occur during the first few uses as your gut and digestive system experience ingredients for the first time.

This means your bowel movements the first evening and the morning after you’re your first few doses may be more noticeable than they will be as you continue to use the product.

When Is the Best Time to Take MAS Flush?

MAS Flush should be taken in the evening, ideally after your last meal.

That’s because one of the main ingredients, psyllium husks, takes at least a few hours take effect in the bowels.

This means that when you take it in the evening, it should make it easier to go to the bathroom as soon as you wake up. In addition, it helps improve bowel movements so you evacuate more during this first bathroom visit, making sure you don’t need to go as you start your run or during.

I Have X Condition, Is MAS Flush Safe for Me?

Probiotics and the ingredients in MAS Flush are generally considered safe, but if you have any concerns you should definitely contact your healthcare professional first.

Ready to Never Let Stomach and Bathroom Issues Ruin Your Runs Again?

Why You’ll Love It

As we the latest scientific research on gut health continues to evolve, the more we understand just how important a healthy gut it is, not just to our overall health, but our athletic performance.

The problem is that most probiotics don’t address the specific needs of endurance athletes.

For example, if you…

Consistently struggle with needing to use the bathroom soon as you start running or within the first few miles
Suffer from stomach churning, pain and cramps that cause you to slow down when racing
Have trouble taking or absorbing gels and other carbohydrates when racing and either getting an upset stomach or bonking all together
Have trouble taking or absorbing gels and other carbohydrates when racing and either getting an upset stomach or bonking all together
Feel so nauseas after hard workouts or training in the heat that you can’t eat for hours or even the rest of the day

Then MAS Flush is the probiotic specifically designed for you.

Not only does it help you improve your gut health and create a health environment for better digestion like most probiotics do, it also helps with the unique stomach issues you face as a runner.

MAS Flush is more than just a probiotic. It’s the endurance athlete’s probiotic.

Ingredients

Psyllium Husk Powder [Plantago ovata] (1500mg)

Research has demonstrated that psyllium makes bowel movements easier and more consistent and can help add bulk to stool.

This helps ensure you never have to go to the bathroom as soon as you start running ever again.

Bifidobacterium Longum Powder ]100B CFU/G] (100mg)

Helps digest fiber and other complex carbs your body can’t digest on its own

Research has also shown that runners saw a reduction in the severity of GI symptoms during training as well as a reduction in the duration of GI symptoms post-race.