The benefits from regular exercise — from reducing your risks to catastrophic conditions like cancer, type 2 diabetes and cardiovascular disease to improving your brain — are many and varied. In fact, a very popular Lancet study argued the lack of regular exercise could be as deadly to your health as smoking.

But, what happens when you take exercise to the opposite extreme? Overdoing anything often reverses much of the benefits you might’ve achieved in moderation, and exercise is no exception.

Based on a 2015 study published in the Journal of the American College of Cardiology, people who exercised more than four hours a week had virtually the same risk of dying as sedentary folks who rarely exercised.

A pair of very recent scientific reports have also tied excessive exercise to serious health problems that may promote leaky gut, a disorder in which a breakdown in the intestinal wall allows unintended substances — undigested food, toxic waste products, bacteria and viruses — to seep through the intestinal barrier and into the bloodstream.

Extreme exercise may harm your gut after 2 hours

Exercising for two hours at 60 percent of the maximum volume of oxygen an athlete can use (VO2 max) along with stress felt from excess heat pushed patients into an unhealthy state, based on a review of studies featured in Alimentary Pharmacology and Therapeutics.

How does that happen? If a patient’s gut loses a lot of blood during exercise, medical experts speculate the resulting inflammation can leave its protective lining damaged. In this vulnerable state, an ideal environment is created for leaky gut.

This review also determined that low to moderate exercise may be beneficial for patients suffering from irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD).

Lengthy military training may harm the gut too

Prolonged exercise was a trigger for leaky gut in a second study appearing in the American Journal of Physiology — Gastrointestinal and Liver Physiology.

In this study, military scientists from Norway, the U.S. Army and the Geneva Foundation as well as the Frederick National Laboratory for Cancer Research tracked the health of 73 Norwegian Army soldiers training in cross country skiing for four days. During that time, soldiers skied 31 miles while carrying 99-pound backpacks.

Researchers collected blood and fecal samples before and after the exercise. Before giving urine samples on the first and third days of training, soldiers drank a mix of water and sucralose and mannitol (an artificial sugar and a sugar alcohol, respectively) to detect signs of leaky gut.

By the end of the training period, the collective gut health of these soldiers as well as the composition of substances in blood and stool samples taken from them changed significantly and for worse. The excretion of sucralose rose greatly too, indicating an increase in leaky gut.

Multi-species probiotics do make an impact

Despite the good probiotics do, some scientists believe they may not do much to protect gut permeability. However, a 2012 report from the Journal of the International Society of Sports Nutrition that tracked the health of 22 trained athletes taking multi-species probiotics proved otherwise.

The key takeaway: The production of zonulin — an inflammatory protein that regulates leakiness in the gut — decreased slightly from levels slightly above normal to normal ranges, then dropped significantly after 14 weeks of supplementation with multi-species probiotics.

There are times when the leakiness triggered by zonulin protects your body in healthy ways, experts say, when you eat foods contaminated with harmful bacteria. When that happens, zonulin reacts by triggering diarrhea to get rid of the bad bugs.

Not only is taking a probiotic with multiple strains of beneficial bacteria like EndoMune Advanced Probiotic an ideal way to shorten the duration of diarrhea, this non-drug treatment gives your body a much needed boost to its natural defenses and may offer some protection from leaky gut too.