Strong Exterior, Healthy Interior: Part 1 - Glorious Guts

Strong Exterior, Healthy Interior: Part 1 - Glorious Guts

I'll admit straight away that the gastrointestinal tract (GIT) is not exactly the prettiest of topics. When your glance gets captured by the latest cover model on Muscle and Fitness, I'm guessing the first thing that springs to mind is not 'Wow, I bet their bowels are in great shape!' Hardly.

Frankly, talking about faecal composition, bowel movements, eructations (burping), flatulence, diahorrea, constipation and bloating is normally only the realm of Gillian McKeith or Martine McCutcheon trying to sell you expensive yoghurts on the television... But could they affect your sports performance and training?


Definitely. It's almost a certainty that at some point in your life you'll experience what is termed a functional gastrointestinal disorder (FGD); in fact, it's been shown that up to 55% of active individuals will experience a FGD as part of their daily routine (Porter et al. 2011).

The same study attributes up to 62% of those episodes as viral in nature and only 1.2% as specifically bacterial. So, direct exposure to environmental pathogens did not always account for whether an individual developed symptoms of a FGD. Perhaps it's not as clear cut as reaching for the soap and water.

Besides clear GIT issues that prevent training e.g. acute diahorrea, constipation, vomiting or abdominal pain, a functionally 'impaired' GIT through poor dietary and lifestyle management has been shown to lead to increased permeability ('leaky gut') without necessarily any clinical symptoms (Hollander, 1999) such as:

  • Reduced absorption of nutrients from the diet, especially dietary fats and protein.
  • Lowered drug (and supplement) absorption.
  • Delayed recovery time from training sessions.
  • Increased incidence of FGDs in the future.

As it has been shown that there are significant, inherent differences in GIT motility, sensitivity, degree of psychological involvement, food intolerances and gut microflora (good bacteria) between individuals (Jian-Min et al. 2004), that figure could be potentially worse. If those issues above start making you sweat a little, it would make sense to start treating your guts with respect.

Weaker guts = less gains?? Okay, so you're not keeling over from gastroenteritis and training just as hard in the gym, I eat my meals and take a post-training shake... Everything's okay then, right? I'm building muscle and improving performance just as well as everyone else?

Perhaps not. Irritable bowel syndrome (IBS) is one of the most common of all bowel disorders, accounting for up to 20% of all people at any one time (Camilleri, 2008). However, due to the complexities associated with its diagnosis only ~10% of all cases will ever present to their physician with issues (men are particularly reticent).

Much of the research now points IBS toward a strong psychological component. Outside of your diet, chronic stress (including early life stresses such as pre-term birth), fatigue and mental health issues such as depression and anxiety are all strongly correlated with FGDs including those associated with IBS (Barreau et al. 2007, Hertig et al. 2007).

So, without even mentioning your diet, working longer hours, training with excessive volume and sleeping less may all be having knock-on effects on your GIT. As you sip your post-training shake, less and less is being absorbed. In fact, research has shown (Matar et al. 1996) that protein (amino acid) availability with impaired gut health may be as much as 50% LOWER, than a fully functional, healthy gut.

So from your 1 scoop of whey in your post-training shake you may be only absorbing up to 12g of protein... ...and over the course of a year (assuming training 3 times a week), that's nearly 2000g (or a whole tub of protein) of unabsorbed protein, wasted!

So what can you do?

If your symptoms are severe (symptoms weekly or more) your first point of call should be your doctor if you are concerned. This is to rule out conditions such as Lactose Intolerance or Lactase Insufficiency (Inability to digest the natural sugars found in dairy produce) and/or Coeliac Disease (intolerance to gluten, protein component of certain grains).

If these prove inconclusive, a dietitian accessed through your doctor would be able to assess your diet fully. If your symptoms are infrequent (less than once every week) or you have no clinical symptoms, here are some tips for a much healthier GIT. For an everyday healthier GIT:

  • At least 5 portions of fruit and vegetables a day from a variety of sources.
  • Probiotics from a recognised strain (e.g. Lactobacillus Casei), as some strains have no effect on the gut! Taken daily with a prebiotic too.
  • Increase your hours slept at night to enhance recovery. Six-eight hours would be a good start and a natural sleep aid could help greatly with establishing a normal pattern.

For re-occurring symptoms of diahorrea:

  • Try reducing the overall fibre content of your diet, as this can produce more GIT motility and worsen the symptoms. Switch to lower fibre versions of cereal grains (e.g. white bread, pasta and rice, cornflakes, rice krispies), cook vegetables thoroughly and remove the skins of fruit to help ease symptoms.
  • 0.34g/kg bodweight of L-Glutamine taken on an empty stomach prior to your first meal of the day. For a 70kg person, this would be ~23g/day.
  • Lower Caffeine intake through fewer caffeinated beverages and pre-workout drinks, try herbal teas or non-stimulant pre-workouts.

For re-occuring symptoms of constipation:

  • Increase overall fluid intake to at least 2L a day, try to use non-caffeinated beverages.
  • Take probiotics and increase overall fibre intake (with extra fluid)

Hope that all helps! If you liked this piece, please take a look at the following articles: Strong Exterior, Healthy Interior: Part 2 - Caffeine, friend or foe? / The Lowdown on Beta-Alanine / Training Myths Busted

Author: Rick Miller


Barreau, F., Ferrier, L., Fioramonti, J. & Bueno, L. (2007) New Insights in the Etiology and Pathophysiology of Irritable Bowel Syndrome: Contribution of Neonatal Stress Models. Pediatric Research, 62(3), p. 240-245

Camilleri, M. (2008) Challenges To The Therapeutic Pipeline For Irritable Bowel Syndrome: End Points and Regulatory Hurdles. Gastroenterology, 135(6), p.1877-1891

Hertig, V.L., Cain, K.C., Jarrett, M.E., Burr, R.L., Heitkemper, M.M. (2007) Daily Stress and Gastrointestinal Symptoms in Women with Irritable Bowel Syndrome. Nursing Research, 56(6), p. 399-406

Hollander D. (1999) Intestinal Permeability, leaky gut, and intestinal disorders. Current Gastroenterology Reports, 1(5), p.410-416

Jian-Min, S., Ying-Cong, Y., Yu-Jing, F. & Shu-Jie, C. (2004) Intestinal Microecology and Quality of Life In Irritable Bowel Syndrome Patients. World Journal of Gastroenterology, 10(12), p.1802-1805

Porter, C.K., Gormley, R., Tribble, D.R., Cash, B.D. & Riddle, S. (2011) The Incidence and Gastrointestinal Infectious Risk of Functional Gastrointestinal Disorders in a Healthy US Adult Population. The American Journal of Gastroenterology, 106, p.130-138

Matar, C., Amiot, J., Savoie, L. & Goulet, J. (1996) The Effect of Milk Fermentation by Lactobacillus Helveticus on the Release of Peptides During in vitro Digestion. Journal of Dairy Science, 79, p.971-979