A Functional Medicine approach to Giardia

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So you’ve had a stool test and it looks like you have a Giardia infection.

Giardia is a parasitic infection that can bring about a host of disruptive symptoms, affecting both digestive and overall health, yet it is rarely discussed and often overlooked as a possible cause of chronic digestive symptoms. This article aims to shine a spotlight on this overlooked infection, delving into the intricacies of giardia from the perspective of functional medicine.

A Functional Medicine Approach to Giardia

Functional medicine takes a holistic, patient-centred approach to health, focusing on identifying the root causes of disease rather than simply treating symptoms. For those grappling with giardia, this approach offers a multi-dimensional strategy for diagnosis, treatment, and recovery.

We will explore the various symptoms of acute and chronic giardia infections, effective testing methodologies, and pertinent nutritional considerations that can facilitate recovery. Additionally, we will investigate the role of natural therapies in conjunction with conventional treatments, offering a comprehensive view of managing giardia.

Whether you are a healthcare practitioner, a patient enduring the symptoms of giardia, or simply someone looking to expand their knowledge on digestive health, this article aims to be a valuable resource. Let’s embark on this journey of understanding and treating giardia through the lens of functional medicine.


What is Giardia?

Giardia is a common human parasite that was first described back in 1681. It can cause significant morbidity; however, natural medicine has great potential to influence the course of Giardia infection, particularly those that are chronic in nature.

It is a microscopic protozoan parasite that is considered to be the most common cause of diarrheal disease worldwide. Humans infected with Giardia may have diarrhea, vitamin and mineral deficiencies, weight loss and failure to thrive.

Giardia has a teardrop shape. It has four thin filaments protruding from its body. These structures are known as flagella and they help Giardia to move. Giardia also has a disc that allows it to attach to the lining of the small intestine.

In chronic cases of Giardia, a blend of nutrition intervention with specific plant based therapeutics should be the first line of therapy and antibiotics saved for more acute or stubborn cases because of the known potential side effects of antibiotic therapy.


Giardia Lifecycle

Unlike some other parasites, Giardia’s lifecycle is very simple. There are only two forms of the organism, active trophozoites and inactive cysts.

The cysts are passed out in the stool and are picked up by humans or animals that eat or drink from contaminated sources.

When Giardia cysts are ingested, the cysts are exposed to stomach acid and digestive enzymes. This process is called excystation and results in Giardia becoming the active trophozoite form.

Most common causes of a Giardia infection

Giardia is usually transmitted through contaminated water by ingesting the parasitic cysts.  Here are some of the most common transmission routes:

Water: Ingesting water from rivers, lakes, ponds etc can lead to giardia infections. Thus, recreational swimming in contaminated pools, rivers etc, increases the risk or transmission.

Person-to person: Close contact, poor hygiene practices can be a major cause of transmission. Nurseries and nursing homes can be a higher risk environment to pick up an infection, however anywhere that someone is not taking proper hygiene precautions after being exposed to faecal matter can increase risk. Transmission through sexual practices that expose a person to faecal matter is also another avenue of person-to-person transmission.

Food: Consuming raw or uncooked food that has been washed in contaminated water or cross contamination during food preparation.

Pets and Livestock: Infected animals can pass the cysts through their faeces, contaminating soil and water.

Travel: Giardia may be more prevalent in certain countries. Therefore, travel to those countries may increase the risk of transmission. These are typically countries that have less developed sanitation infrastructure, reduced access to clean drinking water and lower hygiene standards.

Immuno-compromised individuals: As is often the case with the gut microbiome and our immune systems. The host and their health are often just as important as the infection itself. If one is more compromised from an immune perspective, this may leave you more open to infection or a higher risk of that infection becoming chronic.

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The most common symptoms of Giardia

Giardia gained notoriety because of its ability to cause diarrhoea, but it can also cause many other symptoms. Because the organisms attach to the intestinal lining, they can cause a blanketing effect where large areas of intestine are covered. This leads to the inability to digest and absorb food properly, inevitably leading to malnutrition, even in people who are eating a healthy diet.

Some of the most common symptoms include diarrhea, fatigue, gas and bloating, abdominal cramping, nausea, weight loss, fever, constipation, and general irritable bowel syndrome type symptoms. In some cases, it has also been linked with urticarial and reactive arthritis (Hill, 2001).

Notice how Giardia can cause general symptoms of malaise, as well as seemingly unrelated symptoms such as nausea, urticaria (a skin condition), arthritis and anorexia. In our experience, any unwanted visitor to our digestive system – be it a pathogenic parasite, fungus or bacteria – has the ability to cause pretty much any symptom you can think of because of how the gut influences all other systems in the body.


Acute Symptoms

 Acute symptoms usually appear 1 to 3 weeks after exposure and may include:

  • Diarrhoea: Often the most prominent symptom, diarrhoea can be watery and sometimes foul-smelling.
  • Abdominal Cramps: Intermittent or constant pain may occur, often in the lower abdomen.
  • Nausea and Vomiting: These symptoms can contribute to dehydration.
  • Gas and Bloating: Excessive gas is common, leading to bloating and discomfort.
  • Fatigue: General feelings of tiredness and malaise are often reported.
  • Loss of Appetite: A reduced desire to eat is common and can lead to weight loss.


Chronic Symptoms

If untreated or not fully eradicated, giardia can lead to chronic symptoms:

  • Persistent Diarrhoea: This can lead to malabsorption and nutritional deficiencies.
  • Weight Loss: Ongoing poor absorption of nutrients can result in significant weight loss over time.
  • Lactose Intolerance: Temporary lactose intolerance can develop due to damage to the intestinal lining.
  • General Weakness: Ongoing fatigue and malaise can affect daily activities.
  • Malabsorption: The inability to properly absorb fats and other nutrients can lead to deficiencies and associated symptoms, like skin issues or anaemia.


Because Giardia attaches to the wall of the intestine, it can cause damage to the delicate structures that help in the digestion and absorption of nutrients, known as the villi. This can make it hard for the digestive system to absorb fat, vitamins such as A, D, E, K and B12, protein, iron and lactose.

A person who has vitamin A, B12, fat, protein and iron deficiency may develop symptoms consistent with those deficiencies. So even if there are only very mild digestive symptoms, fatigue, skin problems, neural problems and other symptoms can quickly develop simply because the Giardia prevents adequate nutrition reaching the body.


Asymptomatic Cases

It’s worth noting that some individuals carry the parasite but do not exhibit classic symptoms, making them “asymptomatic” carriers.

However, whilst they might not have the classic symptoms, they may be dealing with other symptoms that you would not normally associate with giardia. This not only makes them a public health risk, it also means they are never tested for Giardia.

This is why I am a strong believer in annual assessments of blood, urine, stool etc, irrespective of symptoms. Not only is this a good way to set health optimisation goals, but you can also often pick up on stealth infections or imbalances that might leave someone more vulnerable to infection.


Testing for Giardia

Testing is critical to determine if you have a giardia infection or not. Before undergoing any treatment that is going to disrupt the microbiome, whether conventional or alternative, knowing what you are targeting is critical.

We use a variety of labs when it comes to stool testing. Our Digestive Health Advanced test includes Giardia as part of the parasitology screen. However, if you prefer to speak with one of or Functional Medicine digestive health experts first about the best testing for you, feel free to complete our CLIENT ENQUIRY FORM.

Giardia Nutrition Considerations

The main aims of dietary modification in giardiasis should be to reduce the acute symptomatology, promote immune function, and inhibit growth and replication of Giardia. These aims can be achieved by consuming a whole-food, high fibre, low simple-carbohydrate and lower-fat diet along with some targeted supplementation.

Consuming foods low in simple carbohydrates limits the amount of sugar available in the intestinal lumen, which may lessen the osmotic draw of water into the intestinal lumen, and reduce diarrhea if that is a symptom.

Reducing the intake of fat might reduce nausea and diarrhea symptoms. Dietary fat stimulates the release of bile acids, something giardia depends upon for their survival in the small intestine.

As well as the above changes utilising functional pre and probiotic foods and wheat germ in some individuals appears to be beneficial in giardia clearance.

Dairy Removal

Studies have shown Giardia infection, whether symptomatic or asymptomatic, can reduce the production of lactase in the small intestine, resulting in lactose malabsorption and its resultant diarrhea.

Dr. David R. Hill recommends that:

“All patients should be instructed to avoid lactose-containing products, so that any recurrent diarrhea will not be confused with relapse of infection”.

Prebiotic Foods

Prebiotics are the compounds and fibers in foods that feed beneficial bacteria. In terms of giardia, prebiotics can increase short chain fatty acids which helps support the integrity of the intestinal lining and increase mucin production which can assist in giardia clearing.

In some instances bloating, pain and flatulence can increase, thus start low and take it slow when introducing in prebiotic foods, especially if other digestive imbalances are present.

You can learn more in my article – What are the best prebiotic and priobiotic foods.

Some specific dietary recommendations

Functional foods include:

  • Probiotic foods minus the dairy based probiotic food options, in particular sauerkraut and Kimchee because of their good content of the probiotic strain L.plantarum. This particular strain has been shown to have specific giardia inhibition qualities.
  • 2tbsp of wheatgerm 3 x per day may be beneficial in those who are gluten tolerant, although it has to be said many people with such an infection often have issues with gluten that have developed.
  • Choose lean proteins and minimise the amount of fat added to meals to help reduce bile acid production.
  • Avoid the consumption of refined sugar and grains.
  • If tolerated, consume some whole grain, beans and lentils as your carbohydrate foods.
  • Emphasis on good quality protein and limit added fats to meals to the options on the food list provided and only one portion added per meal maximum.

Specialist support

As well as nutritional adjustments, specialist support is often required. As mentioned there are natural therapies that have been shown to be useful against Giardia. These should be implemented under the eye of a professional to ensure it is the right therapy at the right time.

We have found broad-spectrum antimicrobial herbal blends alongside high dose oregano oil to be particularly useful and research has indicated that oregano oil especially can have anti-giardia effects. We would also typically recommend some level of intestinal barrier support.

Animal studies have indicated that cinnamon and ginger appear to have suppressive effects on Giardia.

 If you follow the 5R approach to gastrointestinal health, emphasis on the removal and repair followed by or alongside repopulation (pro & prebiotic therapy) is typically very supportive.

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You can also check out our Digestive Health Specialist page for more information about how we work with digestive imbalances specifically