Posted on: October 7, 2025
Giardiasis, caused by the protozoan parasite Giardia lamblia, is the most common protozoal infection in humans. Occurring in both developing and industrialized countries, transmission occurs after ingestion of Giardia cysts in water or food. This often occurs during travel. Symptoms occur within 1 to 2 weeks of ingestion. The cysts easily survive the acidic environment of the stomach and rapidly turn to trophozoites in the duodenum.
Symptoms of Giardia infestation include abdominal pain, nausea, anorexia, diarrhea, vomiting, flatulence, eructation and fatigue. Patients often report weight loss, abdominal distension, watery stools, malodorous flatulence, and nutrient malabsorption such as frothy, foul-smelling stools. Fever, chills, headaches, skin rashes, itching and joint pain are also possible. In some, the infection causes no or few symptoms and goes away quickly, whereas in others it can be chronic and debilitating.
Giardiasis is diagnosed by signs and symptoms, as well as the presence of Giardia cysts and trophozoites in the stool. However, stool tests are unreliable as organisms can be extorted at irregular intervals, frequently causing false negative results.
The Giardia trophozoites attach to the microvilli of the duodenum and jejunum (the upper part of the small intestine). This attachment damages the microvilli, which causes inflammation and interferes with nutrient absorption. This leads to enterocyte damage, villus atrophy, crypt hyperplasia, intestinal hypermermeability and brush border damage. This opens the intestines to further damage by food lectins and proteins.
We chose to write about giardiasis in this blog, because we frequently see patients who had diarrhea after travelling to sun destinations and have not been well since. A detailed history and physical examination during the naturopathic initial visit often reveals many of the signs and symptoms listed above. A history of the patient’s concerns reveals signs of inflammation such as food intolerance, fatigue, mental fogginess/cloudiness, diarrhea, constipation, arthritis, poor memory, skin itching and rashes, and many other signs of digestive inflammation. Patients come to see us for these concerns, but a thorough examination reveals that the underlying cause is the Giardia or other pathogenic causes of digestive irritation.
These micro-organisms can be effectively treated naturopathically, by addressing the digestive inflammation and effectively removing the underlying infection.
References:
For health professionals: Giardia infection. https://www.canada.ca/en/public-health/services/diseases/giardia-infection/health-professionals.html
Giardiasis: pathophysiology and management.
Hawrelak J.Altern Med Rev. 2003 May;8(2):129-42.