written by: 

By Stefan Ianev

Gut health is a hot topic these days. Although this is a complicated area and it is beyond the scope of a personal trainer or fitness professional to diagnose or treat clients with serious digestive or gut issues, it is still important to understand the basics of how the digestive system works, and how to optimize digestion through good nutrition and basic supplementation.    

Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body. The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion such as the pancreas, liver, and gallbladder. 

Figure 1. From start to end the gastrointestinal tract is about 25 feet in length

The stomach is the first major stage of digestion and will be the focus of part 1 of this article. The stomach secretes hydrochloric acid (HCL) which serves several important functions.

Firstly, hydrochloric acid kills off and prevents harmful bacteria from entering the small intestine. We are going to talk more about how this compromises gut health in part 2 of this article. 

Secondly, hydrochloric acid also activates pepsin, a proteolytic enzyme which breaks down proteins into smaller amino acid chains called polypeptides. Therefore, protein digestion is initiated in the stomach. Hydrochloric acid also stimulates the release of pancreatic enzymes and bile into the small intestine which is required for the digestion of carbohydrates and fats. 

Lastly, hydrochloric acid is required for the absorption of several vitamins and minerals including iron, zinc, calcium carbonate, beta-carotene, folate, vitamin B12, and vitamin C (1-11). 

Low stomach acid secretion, called hypochlorhydria has been linked to numerous metabolic and health conditions including:

  • Gallbladder disease (13)
  • Alcoholism (14)
  • Skin diseases (10,32)
  • Arthritis (15,16)
  • Osteoporosis (17,18)
  • Diabetes (219-22)
  • Asthma (23,24)
  • Hypo or Hyperthyroidism (25,26)
  • Anemia (19)
  • Bacterial overgrowth an infection (7,9,12,19,27,28,29,30)
  • Stomach cancer (30)
  • Depression (31)

Many of these conditions have been shown to be reversed or drastically improved when hydrochloric acid levels were normalized following hydrochloric acid supplementation (18,10,11,12,19,23,30,32).  

Numerous studies have shown that hydrochloric acid secretion declines with age (30,33,34,35). In fact, it is estimated that 30-40% of adults over 50 years of age suffer from achlorhydria, which is the complete absence of stomach acid secretion.

Other causes of hypochlorhydria include vitamin B deficiency, H. pylori infection, chronic overeating, hypoadrenalism, chronic stress, excess intake of processed foods and carbohydrates, caffeine, alcohol, hypoglycaemia, and undereating (14,36,37,38,39,40).

A variety of signs and symptoms can suggest decreased stomach acid secretion including:

  • Bloating or prolonged fullness after meals (23,30)
  • Diarrhea or constipation (19,23,30)  
  • Flatulence after eating (23,30)
  • Heartburn and indigestion (23,30)
  • Food allergies (5)
  • Nausea after taking supplements (23,30)
  • Soreness, burning, and dryness of the mouth (30)
  • Glossitis – inflammation of the tongue (30)
  • Undigested food in stools (23)
  • Weak, pealing and cracked fingernails (23)
  • Hair loss in women (23)

Notice that many of the symptoms above are related to Gastroesophageal Reflux Disease (GERD). GERD, or acid reflux, occurs when the lower oesophageal sphincter does not close properly, allowing stomach acid to pass back up into the oesophagus.

The most common treatment for GERD is proton-pump inhibitors (PPIs), a class of drugs which suppress stomach acid secretion. While these drugs are effective at masking the symptoms related to GERD, they do not address the underlying cause, and long term they can end up exacerbating the problem if used too frequently or for too long. 

That is because the tightness of the lower oesophageal sphincter is in part regulated by the acidity of the stomach. When the acidity in the stomach increases, the lower oesophageal sphincter responds by contracting more tightly (41-43). 

Therefore, a high amount of hydrochloric acid in the stomach, which is a normal and healthy part of digestion, actually prevents GERD or acid reflux by stimulating the lower oesophageal sphincter to close tightly, preventing stomach acid from passing back up into the oesophagus.  

PPI medications have been linked to increased risk of many health conditions including vitamin and mineral deficiencies, gut infections, pneumonia, osteoporosis and hip fractures, small intestinal bacterial overgrowth, gastric tumours and cancer, infections outside the GI tract, dementia, and chronic kidney disease (44-50). 

There are functional approaches for diagnosing hypochloridria. One such test that we have used for years at CHFI is the HCL challenge test. The HCL challenge test involves taking an escalating dose of betaine HCL capsules immediately after meals until a mild burning sensation in the stomach is felt, or a maximum dosage is reached (51,52).

Instruction for the HCL challenge test are as follows:

  1. Immediately after a meal when your normal digestive processes have started take a 200mg tablet or capsule of betaine HCL. 
  2. If no burning sensation in the stomach is felt 10 to 15 minutes after the meal, then proceed to take two HCL capsules at your next meal.
  3. If no burning sensation is felt again then proceed to take three HCL capsules at your next meal.
  4. Continue this process until you feel a mild burning sensation in your stomach, or you reach a maximum of seven capsules.

If you felt the mild burning sensation after only one cap, then most likely you are producing enough hydrochloric acid on your own. If the burning sensation is too uncomfortable just drink a glass of water with a table tablespoon of baking soda. Baking soda is a mild base and will neutralize the hydrochloric acid. 

If you felt the burning sensation after two to four caps, then you may have a mild hydrochloric acid deficiency, and if you if felt the burning sensation after five to seven caps or not at all, that is considered a sign on hypochloridria. In that case consider taking a supplemental dose of HCL with each meal one capsule below the dose at which you felt the burning sensation. 

If you need to take more than three capsules as a supplemental dose, then considering purchasing 500 to 600mg capsules to avoid having to swallow so many pills at once. HCL supplementation is generally more effective when taken in conjunction with pepsin and gentian. Gentian is a herb which acts on taste bud receptors to stimulate the secretion of saliva in the mouth and hydrochloric acid in the stomach (53).

Hopefully, you can now appreciate the importance of hydrochloric acid in good digestive health. Hypochloridria should always be considered in clients presenting with digestive issues or any of the symptoms listed above as the first line of intervention against poor gut health. 

Want to learn how to design scientifically grounded nutrition and diet programs safely and effectively to help you maximize client results again and again, with a trialled and tested system that actually works?
Register for the Performance Nutrition Coach Certification Bundle, which includes the Level 1&2 online courses!


  1. Bezwoda W, Charlton R, Bothwell T, et al. The importance of gastric hydrochloric acid in the absorption of nonheme food iron. J Lab Clin Med 1978;92:108-116.
  2. Sturniolo GC, Montino MC, Rossetto L, et al. Inhibition of gastric acid secretion reduces zinc absorption in man. J Amer Col Nutr 1991; 10:372-375.
  3. Henderson LM, Brewer GJ, Dressman JB, et al. Effect of intragastric pH on the absorption of oral zinc acetate and zinc oxide in young healthy volunteers. JPEN 1995;19:393-397. 25. Sandstrom B, Abrahamsson H. Zinc absorption and achlorhydria. Eur J Clin Nutr 1989; 43:877-879.
  4. Sandstrom B, Abrahamsson H. Zinc absorption and achlorhydria. Eur J Clin Nutr 1989; 43:877-879.
  5. Hunt JN, Johnson C. Relation between gastric secretion of acid and urinary excretion of calcium after oral supplements of calcium. Dig Dis Sci 1983;28:417-421.
  6. Recker RR. Calcium absorption and achlorhydria. N Engl J Med 1985;313:70-73.
  7. Tang G, Serfaty-Lacrosniere C, Camilo ME, et al. Gastric acidity influences the blood response to a B-carotene dose in humans. Am J Clin Nutr 1996;64:622-626.
  8. Russell RM, Krasinski SD, Samloff IM. Correction of impaired folic acid (PteGlu) absorption by orally administered HCl in subjects with gastric atrophy. Am J Clin Nutr 1984;39:656.
  9. Saltzman JR, Kemp JA, Golner BB, et al. Effect of hypochlorhydria due to omeprazole treatment or atrophic gastritis on protein bound vitamin B12 absorption. J Amer Coll Nutr 1994;13:584-591.
  10. Allison JR. The relation of hydrochloric acid and vitamin B complex deficiency in certain skin diseases. South Med J 1945;38:235-241
  11. O’Connor HJ, Schorah CJ, Habibzedah N, et al. Vitamin C in the human stomach: relation to gastric pH, gastroduodenal disease, and possible sources. Gut 1989;30:436-442.
  12. Brummer P, Kasanen A. The effect of hydrochloric acid on the indican metabolism in achlorhydria. Acta Medica Scan 1956;155:1114.
  13. Capper WM, Butler TJ, Kilby JO, et al. Gallstones, gastric secretion, and flatulent dyspepsia. Lancet 1967;1:413-415.
  14. Joffe PM, Jolliffe N. The gastric acidity in alcohol addicts. With observations of the relation of the B vitamins to achlorhydria. Amer J Med Sci 1937:501-511.
  15. De Witte TJ, Geerdink PJ, Lamers CB. Hypochlorhydria and hypergastrinaemeia in rheumatoid arthritis. Ann Rheum Dis 1979; 38:14-17.
  16. Hartung EF, Steinbrocker O. Gastric acidity in chronic arthritis. Ann Intern Med 1935;9:252257.
  17. Persson P, Gagnemo-Persson R, Chen D, et al. Gastrectomy causes bone loss in the rat: is lack of gastric acid responsible? Scand J Gastroenterol 1993;28:301-306.
  18. Brechner J, Armstrong WD. Relation of gastric acidity to alveolar bone resorption. Proc Soc Exp Biol Med 1941;48:98-100.
  19. Rabinowitch IM. Achlorhydria and its clinical significance in diabetes mellitus. Am J Dig Dis 1949;16:322-332.
  20. Dotevall G. Gastric secretion of acid in diabetes mellitus during basal conditions and after maximal histamine stimulation. Acta Med Scan 1961;170:59-69. 43. 
  21. Shay H, Gershon-Cohen J. Glucose tolerance in anacidity. Amer J Dig Dis 1938-39;5:4-8. 44. 
  22. Richardson CT, Ramsey EJ, Feldman M, et al. Diabetics have reduced acid secretion and delayed digestion. Am Family Physician 1978;June:143.
  23. Wright JV. Treatment of childhood asthma with parenteral vitamin B12, gastric reacidification, and attention to food allergy, magnesium and pyridoxine. Three case reports with background and an integrated hypothesis. J Nutr Med 1990;1:277-282.
  24. Bray GW. The hypochlorhydria of asthma of childhood. Quart J Med 1931;24:181-197.
  25. Dotevall G, Walan A. Gastric secretion of acid and intrinsic factor in patients with hyper- and hypothyroidism. Acta Med Scand 1969;186: 529-533.
  26. Williams MJ, Blair DW. Gastric secretion in hyperthyroidism. Brit Med J 1964;1:940-944.
  27. Giannella RA, Broitman SA, Zamcheck N. Influence of gastric acidity on bacterial and parasitic enteric infections. Ann Int Med 1973;78:271-276.
  28. Boero M, Pera A, Andriulli A, et al. Candida overgrowth in gastric juice of peptic ulcer subjects on short and long-term treatment with H2-receptor antagonists. Digestion 1983;28: 158-163. 47. 
  29. Bolivar R, Bosley GP. Candidiasis of the gastrointestinal tract. In Bodey GP, Fainstein V. Eds. Candidiasis. New York, Raven Press 1985.
  30. Sharp GS, Fister HW. The diagnosis and treatment of achlorhydria: ten-year study. J Amer Ger Soc 1967;15:786-791.
  31. Keuter EJW. Deficiency of vitamin B complex, presenting itself psychiatrically as an atypical, endogenous depression. Nutr Abs Rev 1959;29:273.
  32. Ayers S. Gastric secretion in psoriasis, eczema, and dermatitis herpetiformis. Arch Dermatol Syph 1929;20:854-857.
  33. Young DG. A stain for demonstrating Helicobacter pylori in gastric biopsies. Biotech Histochem 2001 Jan;76(1):31-4.
  34. Krasinski SD, Russell RM, Samloff IM, Jacob RA, Dallal GE, McGandy RB, Hartz SC. Fundic atrophic gastritis in an elderly population. Effect on hemoglobin and several serum nutritional indicators. J Am Geriatr Soc. 1986 Nov;34(11):800-6.
  35. Grossman MI, Kirsner JB, Gillespie IE. Basal and histalog-stimulated gastric secretion in control subjects and in patients with peptic ulcer or gastric cancer. Gastroenterology 1963;45:15-26.
  36. Schubert ML, Peura DA. Control of gastric acid secretion in health and disease. Gastroenterology. 2008;134(7):1842-1860.
  37. Weatherby D. In-Office Lab Testing: Functional Terrain Analysis. Ashland, OR: Bear Mountain Publishing; 2007.
  38. Loud FB, Holst JJ, Rehfeld JF, Christiansen J. Inhibition of gastric acid secretion in humans by glucagon during euglycemia, hyperglycemia, and hypoglycemia. Dig Dis Sci. 1988 May;33(5):530-4.
  39. Guyton AC, Hall JE. Textbook of Medical Physiology (11th ed.). Philadelphia, PA: Elsevier (2006) p.796
  40. Guyton AC, Hall JE. Textbook of Medical Physiology (11th ed.). Philadelphia, PA: Elsevier (2006) p.971
  41. Kaye MD. On the relationship between gastric pH and pressure in the normal human lower oesophageal sphincter. Gut. 1979;20(1):59–63. doi:10.1136/gut.20.1.59
  42. Sandler AD, Schlegel JF, Maher JW, Olinde AJ, McGuigan JE. The mechanism of acid-induced increases in canine lower esophageal sphincter pressure. Surgery. 1989 Apr;105(4):529-34.
  43. Sengupta JN. Esophageal sensory physiology. GI Motility online (2006) doi:10.1038/gimo16
  44. Anderson WD, Strayer SM, Mull SR. Common questions about the management of gastroesophageal reflux disease. Am Fam Physician. 2015 May 15;91(10):692-7.
  45. Vinnakota RD, Brett AS. Iron Deficiency Anemia Associated With Acid-Modifying Medications: Two Cases and Literature Review. Am J Med Sci. 2019 Feb;357(2):160-163. doi: 10.1016/j.amjms.2018.10.014. Epub 2018 Nov 1.
  46. Lodato F, Azzaroli F, Turco L, Mazzella N, Buonfiglioli F, Zoli M, Mazzella G. Adverse effects of proton pump inhibitors. Best Pract Res Clin Gastroenterol. 2010 Apr;24(2):193-201. doi: 10.1016/j.bpg.2009.11.004.
  47. Su T, Lai Sm, Lee A, He X, Chen S. Meta-analysis: proton pump inhibitors moderately increase the risk of small intestinal bacterial overgrowth. J Gastroenterol. 2018 Jan;53(1):27-36. doi: 10.1007/s00535-017-1371-9. Epub 2017 Aug 2.
  48. Gomm W, von Holt K, Thomé F, et al. Association of Proton Pump Inhibitors With Risk of Dementia: A Pharmacoepidemiological Claims Data Analysis. JAMA Neurol. 2016;73(4):410–416. 
  49. Lazarus B, Chen Y, Wilson FP, et al. Proton Pump Inhibitor Use and the Risk of Chronic Kidney Disease. JAMA Intern Med. 2016;176(2):238–246.
  50. Kaye MD. On the relationship between gastric pH and pressure in the normal
  51. Pizzorno JE, Murray MT, eds. Textbook of Natural Medicine. St Louis, MO: Elsevier/Saunders; 2012.
  52. Yarnell E. Natural Approach to Gastroenterology. East Wenatchee, WA: Healing Mountain Publishing, Inc; 2011.

Share to: 

You May Also Like

Top 15 Business Tips for Trainers

The Top 15 PT Business Tips FREE guide, was designed to give you evidence based, yet practical tools you can use to optimise your fitness business across the following categories: