513+ Happy Runners

The #1 Doctor & Dietician Reviewed Probiotic for Runners

Gastroenterologist, dieticians, coaches and health experts recommend MAS Flush for it’s unique approach to gut health and the unique GI issues endurance athletes face when training and racing.
GET MINE NOW

513+ Happy Runners

The #1 Doctor & Dietician Reviewed Probiotic for Runners

Gastroenterologist, dieticians, coaches and health experts recommend MAS Flush for it’s unique approach to gut health and the unique GI issues endurance athletes face when training and racing.

GET MINE NOW
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

Independent Doctor & Dietician Reviews

Clinicians and dieticians receive product samples, but are never compensated for their reviews

Dr. Michael Torres, MD

  • Gastroenterologist
Formulated for Endurance

What impressed me about MAS Flush is the inclusion of blackcurrant, which is not something general probiotics include and shows how dialed in this formula is for endurance athletes. If you're an endurance athlete looking to improve gut health, there's no better option suited to your needs.

Highlights

  • Formulated for endurance
  • Cutting-edge formula

Maria Santos

  • RRCA Certified
Simple improvement

For newer runners, GI issues can be the thing that makes them quit the sport entirely. I've had athletes tell me they mapped every public bathroom within a 5-mile radius of their house. That's no way to enjoy running. What I like about MAS Flush is how straightforward the protocol is. It's not asking athletes to overhaul their diet or try complicated timing strategies. For the average runner who just wants to enjoy a Saturday morning group run without fear, this kind of simple solution can be transformative

Highlights

  • Easy to add to your routine
  • Prevents bathroom issues

Dr. Sarah Chen, MD

  • Gastroenterologist
Reduces GI Issues

Many of my running patients come to me frustrated by unpredictable bowel patterns that interfere with training. The inclusion of psyllium husk at a clinically meaningful dose helps reduce these issues significantly. The fact that MAS Flush builds this into its probiotic shows they understand the physiology behind the issues runners face.

Highlights

  • Prevents runners trots
  • Efficacious dose

James Whitfield, RD, LD

  • Clinical Dietitian
Digestive Enzyme Blend

Endurance athletes have paradoxically high caloric needs but often struggle with digestion. The digestive enzyme blend in MAS Flush is thoughtfully formulated to target the specific macronutrients that cause the most digestive burden for endurance athletes. My only suggestion would be to take it consistently, as enzyme support works best when the gut environment is primed.

Highlights

  • Improves digestion
  • Take consistently

Rachel Nguyen MS, RD

  • Sports Dietitian
Helps With Fueling

One of the biggest challenges I see with marathon and ultra athletes is the inability to absorb adequate carbohydrates during racing. For athletes who've resigned themselves to reduced fueling because 'my stomach just can't handle it,' this could be help a lot. I'd recommend starting supplementation 4-6 weeks before a goal race to allow the gut microbiome to adapt.

Highlights

  • Unique formula
  • Useful in training & racing

And it’s not just recommended by doctors and professionals

Real Runners Love MAS Flush Too

Carlos H.

⭐⭐⭐⭐⭐

I’ve had some of my best races ruined when I took a gel in the middle of the race and couldn’t seem to keep it down. I wasn’t sure how a probiotic could really help with that, but I gave this a shot anyway. My last two races I haven’t had any issues even though my last race was pretty warm. Feels good to have the confidence I might have kicked this issue.

Olivia H.

⭐⭐⭐⭐⭐

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!

Teddy Adler

⭐⭐⭐⭐⭐

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.

Melissa Johnson

⭐⭐⭐⭐⭐

No matter what products I tried, I just couldn’t seem to deal with all that sugar. They all tasted okay and seemed to go down okay, but my stomach would always be on the edge of throwing up 20 minutes after. I found MAS Flush from a podcast I listen to and thought maybe it would help. It worked almost right away, I was a little surprised. I’m still cautious, but this seems to have done the trick.

Marko V.

⭐⭐⭐⭐⭐

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.

Jenna Reardon

⭐⭐⭐⭐⭐

Gels gave me horrible stomach cramps on three different occasions so I was desperate to try anything. I used Flush on every long run for my build up for Chicago and had no issues. Race day was the first marathon I had where my stomach wasn’t churning in the final miles. Really happy I found this!

Olivia H.
Olivia H.⭐⭐⭐⭐⭐
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!
Melissa J
Melissa J⭐⭐⭐⭐⭐
No matter what products I tried, I just couldn’t seem to deal with all that sugar. They all tasted okay and seemed to go down okay, but my stomach would always be on the edge of throwing up 20 minutes after. I found MAS Flush from a podcast I listen to and thought maybe it would help. It worked almost right away, I was a little surprised. I’m still cautious, but this seems to have done the trick.
Marko V.
Marko V.⭐⭐⭐⭐⭐
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.
Jenna R.
Jenna R.⭐⭐⭐⭐⭐
Gels gave me horrible stomach cramps on three different occasions so I was desperate to try anything. I used Flush on every long run for my build up for Chicago and had no issues. Race day was the first marathon I had where my stomach wasn’t churning in the final miles. Really happy I found this!
Teddy Adler
Teddy Adler⭐⭐⭐⭐⭐
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.
Carlos H.
Carlos H.⭐⭐⭐⭐⭐
I’ve had some of my best races ruined when I took a gel in the middle of the race and couldn’t seem to keep it down. I wasn’t sure how a probiotic could really help with that, but I gave this a shot anyway. My last two races I haven’t had any issues even though my last race was pretty warm. Feels good to have the confidence I might have kicked this issue.
Emma M.
Emma M.⭐⭐⭐⭐⭐
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.
Close