Blastocystis Hominis

Understanding Blastocystis Hominis: A Comprehensive Guide

Blastocystis hominis is a common parasite found in the gastrointestinal tract of humans and animals. Despite being one of the most frequently detected gut parasites globally, its role in health and disease is still debated. Some consider it a harmless commensal organism, while others link it to various gastrointestinal symptoms. This blog explores what we know about Blastocystis hominis, its potential health effects, whether treatment is necessary, and natural approaches to managing it.

What is Blastocystis Hominis?

Blastocystis hominis is a single-celled protozoan parasite that resides in the large intestine.

Despite its classification as a parasite, Blastocystis has characteristics that resemble commensal gut microbes. It is highly diverse, existing in various genetic subtypes, with humans most commonly infected by subtypes 1–4 (source, source, source). Blastocystis subtype 1 is one of the most commonly found subtypes in humans worldwide (source).

There are thought to be at least 17 different subtypes (source)

How Do You Get Blastocystis Hominis?

You can acquire Blastocystis hominis through the fecal-oral route, meaning ingestion of contaminated food, water, or surfaces containing the parasite’s cyst form. Poor hygiene practices, such as inadequate handwashing after using the restroom or handling animals, increase the risk of transmission. Consuming unwashed fruits and vegetables, drinking untreated or contaminated water, and traveling to areas with poor sanitation can also lead to infection.

The parasite spreads easily in crowded environments, including daycares and households with shared facilities.

Blastocystis Hominis Symptoms

Many people infected with Blastocystis hominis are asymptomatic. However, in some individuals, especially those with other health conditions or compromised immune systems, the presence of Blastocystis may be linked to (source, source, source):

Gastrointestinal symptoms:

• Diarrhoea or loose stools.
• Abdominal pain or cramping.
• Gas and bloating.
• Nausea.
• Vomiting.
• Constipation.

Systemic symptoms:

• Fatigue.
• Skin rashes (in some cases, possibly linked to hypersensitivity reactions).
• Intense itching.
• Iron deficiency anaemia.
• Anorexia.

One study (source) revealed a higher prevalence (but not significant) of Blastocystis hominis infection among patients with urticaria than healthy individuals. In fact researchers have discussed Blastocystis infection as a neglected cause of urticaria and skin disorders (source).

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Blastocystis Hominis And The Gut-Brain Axis

The gut and brain are constantly communicating, and this connection is called the gut-brain axis. This two-way interaction happens through several systems, including the nervous system, immune system, endocrine (hormone) system, and gut bacteria metabolites. Keeping this balance is essential for overall health.

While research has explored how parasites affect the nervous system in insects, there are fewer studies on how parasites interact with the human brain. However, a growing field called neuro-parasitology is uncovering how parasites can influence brain function, immune response, and even mood and behaviour.

Studies suggest Blastocystis may influence the gut-brain axis. Research on rats infected with Blastocystis found links to colonic hypersensitivity (gut sensitivity), anxiety, and depressive-like behaviours. Another study in mice found that transplantation of human Blastocystis strains led to changes in brain function and gene expression in the prefrontal cortex. Interestingly, in a group of university students, a specific Blastocystis subtype (ST4) was associated with better stress resilience and a more diverse gut microbiome. Some researchers suggest Blastocystis may affect mood and behaviour through the tryptophan metabolism pathway, a key process involved in neurotransmitter production (source).

Given that Blastocystis can synthesize tryptophan, researchers hypothesise that infection with these parasites may have the ability to influence behaviour and mood within the host. There is a small but growing body of research exploring roles Blastocystis might play in this context (source, source).

Is Blastocystis Hominis Good or Bad?

As already mentioned the reputation of Blastocystis hominis as a “good” or “bad” organism is still unclear and may depend on the following factors:

As a pathogen: Some studies link Blastocystis to irritable bowel syndrome (IBS)-like symptoms and inflammatory bowel diseases (IBD) (source). For instance, a higher prevalence of Blastocystis has been observed in patients with IBS.

As a commensal organism: In healthy individuals, Blastocystis may coexist without causing harm and could even play a beneficial role in the gut microbiome. Research suggests Blastocystis may promote microbial diversity, a key marker of gut health. Perhaps Blastocystis is more common in healthy people because it helps maintain a healthy mucus layer in the intestine, either directly or through interactions with beneficial bacteria or the immune system (source).

In a paper published in 2024 Blastocystis hominis was detected in 15.38% of IBS patients and 9.2% of the healthy group (source).

Blastocystis Hominis And ColoRectal Cancer

A systematic review and meta-analysis published in 2022 concluded: “Given the significant prevalence of both parasites in colorectal cancer patients and their statistically significant association, there is a need to pay more attention to these two intestinal parasites in under treatment patients.” (source)

Discussed within this review is lab studies (conducted in test tubes) that have shown certain proteins from Blastocystis hominis can cause harmful effects on human colon cancer cells. These effects include damage to the cells and changes in the immune response. The research suggests that an infection with B. hominis might make colon cancer cells grow faster, spread more easily, and become more aggressive.

Should We Treat Blastocystis Hominis?

The decision to treat Blastocystis hominis depends on the individual’s symptoms and health status:

When to treat: Treatment may be warranted in symptomatic individuals where other causes of gastrointestinal symptoms have been ruled out, and Blastocystis is suspected as the culprit. In one study (source) concluded that chronic abdominal pain in children has different causes; but, it is appropriate to provide antimicrobial treatment for patients with Blastocystis hominis and chronic abdominal pain.

When not to treat: Asymptomatic carriers typically do not require treatment. Eradicating Blastocystis in healthy individuals may disrupt gut microbial balance and inadvertently cause harm.

A careful assessment by a healthcare professional is essential to determine whether treatment is appropriate.

Blastocystis And Inflammatory Bowel Disease

Natural Approaches to Managing Blastocystis Hominis

If treatment is needed or desired, several natural approaches can support gut health and potentially reduce Blastocystis levels (source). While these methods may not completely eliminate the organism, they can improve overall gut function and reduce symptoms.

Diet Modification

• Eliminate processed foods: Processed foods and sugars may fuel pathogenic gut microbes, including Blastocystis.
• Anti-parasitic foods: Incorporate garlic, oregano, pumpkin seeds, and turmeric, which have natural anti-parasitic properties.
• Fiber-rich foods: Support a healthy gut microbiome with fiber-rich foods like fruits, vegetables, and whole grains.

What Foods Should I Avoid For Blastocystis?

When dealing with a Blastocystis hominis infection, there’s no universally prescribed diet to eliminate the parasite. However, certain dietary adjustments can help support your gut health, reduce symptoms like bloating, diarrhea, and fatigue, and possibly make the environment less favorable for the parasite.

🚫 Foods to Avoid with Blastocystis hominis

Sugary Foods

Why: Parasites, including Blastocystis, can thrive on refined sugars. High sugar intake may fuel their growth and worsen symptoms.

Examples to Avoid:

• Sweets, candy, chocolate
• Sugary drinks (soda, energy drinks, fruit juices)
• Pastries, cakes, cookies

Refined Carbohydrates

Why: White bread, pasta, and processed grains quickly convert to sugar in the body, feeding the parasite.

Examples to Avoid:

• White bread, white rice, regular pasta
• Processed cereals and crackers

Dairy Products

Why: Some people with Blastocystis experience temporary lactose intolerance due to gut inflammation, leading to bloating and diarrhea.

Examples to Avoid (if symptomatic):

• Milk, cheese, ice cream, yogurt (opt for lactose-free if tolerated)

Gluten-Containing Foods (Optional)

Why: In some individuals, gluten can cause gut inflammation, especially if there’s underlying sensitivity. While not required for everyone, a trial of a gluten-free diet may help if symptoms persist.

Examples to Avoid:

• Wheat, barley, rye, regular pasta, bread

Alcohol

Why: Alcohol can irritate the gut lining, weaken the immune response, and disrupt healthy gut bacteria, which are important for fighting off the infection.

Examples to Avoid:

• Beer, wine, spirits, cocktails

Processed and Junk Foods

Why: Foods with preservatives, additives, and unhealthy fats can disrupt the gut microbiome and increase inflammation.

Examples to Avoid:

• Fast food, chips, frozen dinners, packaged snacks

Fermentable Foods (High-FODMAPs) (If Bloating is Severe)

Why: Some fermentable carbohydrates can worsen bloating and gas. A low-FODMAP diet may provide symptom relief, though it’s not necessary for everyone.

Examples to Limit:

• Onions, garlic, beans, lentils, cauliflower, apples

✅ Foods to Include for Gut Support

While avoiding certain foods, it’s equally important to focus on a gut-friendly diet that supports recovery:

• High-Fiber Vegetables: Broccoli, spinach, zucchini, carrots
• Lean Proteins: Chicken, turkey, eggs, fish
• Healthy Fats: Olive oil, avocados, nuts, seeds
• Low-Sugar Fruits: Berries, kiwi, citrus (in moderation)
• Probiotic-Rich Foods: Sauerkraut, kimchi, kefir, plain yogurt (if dairy is tolerated)
• Anti-Inflammatory Foods: Turmeric, ginger, green tea

Probiotics

Probiotics are beneficial bacteria that help keep your gut healthy. They work in several ways to protect against harmful microbes (source):

1. Boost Good Bacteria: Probiotics help increase the number of healthy bacteria in your gut.
2. Create an Unfriendly Environment for Harmful Germs: They change the gut environment, making it harder for bad bacteria to survive.
3. Compete with Harmful Bacteria: Probiotics fight for the same food and space that harmful bacteria need, which helps stop them from growing.
4. Release Protective Substances: They produce natural compounds like bacteriocins, lactic acid, and hydrogen peroxide that can kill or weaken harmful bacteria.
5. Block Toxins: Probiotics can prevent harmful bacteria from releasing toxins that cause illness.
6. Increase Mucus Production: They help your gut produce more mucus, which acts as a barrier to block harmful germs.
7. Strengthen the Immune System: Probiotics support your gut’s immune defenses, helping your body respond more effectively to infections.

In short, probiotics help maintain a healthy balance in your gut, making it harder for pathogens to cause problems.

While research on probiotics specifically targeting Blastocystis is limited, some studies suggest that beneficial bacteria, such as Lactobacillus and Bifidobacterium species, can help reduce gut inflammation and compete with pathogenic microbes. Blastocystis is more likely to cause symptoms in individuals with gut dysbiosis, and restoring microbial diversity through pre- and probiotics may help mitigate its potential pathogenic effects.

Although probiotics alone may not completely eradicate Blastocystis hominis, they can be a useful adjunct therapy, particularly in individuals experiencing IBS-like symptoms associated with the parasite. More research is needed to determine the most effective probiotic strains and dosages for managing Blastocystis infections.

Recommend Product: Saccharomyces Boulardii. In a placebo-controlled study, it was found to be more effective against Blastocystis when compared to metronidazole (source).

Herbal Remedies

• Garlic: Contains a wide range of the thiosulfinates (e.g., allicin), which are responsible for the antibacterial activity related to the inhibition of enzymes, including thiol in microorganisms. Moreover, allicin in the garlic acts by totally inhibiting RNA synthesis and partially inhibiting DNA and protein synthesis of the parasites (source).
• Ginger: hexahydrocurcumin, a constituent isolated from ginger, might be effective in killing the parasites (source) but research is mixed here. One study found that ginger has the greatest effect on Blastocystis clinical isolates, but another study found that it was not effective against subtypes 1 and 3 (source).
• Oregano Oil: Supplementation with 600 mg emulsified oil of oregano daily lead to the complete disappearance of Blastocystis (source).

Turmeric extracts have potent antimicrobial activity against Blastocystis ST3 and ST7 (source).

Maintain Good Hygiene

Prevent reinfection by practicing strict hygiene:

• Wash hands thoroughly before meals and after using the restroom.
• Avoid drinking untreated water.

Manage Stress

Psychological and emotional stress can influence Blastocystis hominis infection by weakening the immune system and disrupting gut health, creating an environment that may favour the parasite’s persistence. Chronic stress triggers the hypothalamic-pituitary-adrenal (HPA) axis, leading to increased cortisol production, which can impair immune responses and reduce the body’s ability to eliminate pathogens like Blastocystis. Additionally, stress alters the gut microbiome by promoting dysbiosis (an imbalance of gut bacteria), increasing intestinal permeability (“leaky gut”), and affecting digestive processes, all of which may contribute to the parasite’s survival and potential pathogenicity.

Some studies suggest that individuals with Blastocystis and chronic gastrointestinal symptoms, such as IBS, may experience heightened stress responses, possibly exacerbating symptoms. While Blastocystis does not always cause illness, stress-induced immune suppression and gut dysfunction may increase susceptibility to infection or worsen its effects. Managing stress through relaxation techniques, meditation, and gut-supportive practices may help improve resilience against infections and restore microbial balance.

Conventional Treatment Options

In symptomatic cases where natural methods are insufficient, conventional treatments include anti-parasitic or antibiotic medications like metronidazole, nitazoxanide, or trimethoprim-sulfamethoxazole (source). These drugs may help eliminate Blastocystis but can also disrupt beneficial gut microbes, necessitating careful post-treatment gut health restoration.

But these drugs are not always effective. Most probably, it depends on the Blastocystis subtypes. One study in 2015, reported that STs 1, 3, and 5 are susceptible to metronidazole, but resistant to ketoconazole, even when high doses were administrated (source).

Key Points to Remember

• Not always harmful: Many people live with Blastocystis hominis without symptoms or complications.
• Holistic view required: Symptoms should not be automatically attributed to Blastocystis without ruling out other causes.
• Gut health matters: A healthy diet and lifestyle can significantly impact symptoms and gut microbial balance, whether or not treatment is pursued.

Future Research

Ongoing studies aim to better understand the role of Blastocystis in human health, with a focus on its interaction with the gut microbiome. Future insights may enable personalised approaches to managing Blastocystis and other gut microorganisms, enhancing our ability to promote gut health naturally.

Conclusion

Blastocystis hominis remains a complex and often misunderstood organism. While it may cause symptoms in some individuals, many coexist with it without issues. Whether treatment is necessary depends on individual symptoms and overall health. Focusing on gut health through natural methods, such as diet, probiotics, and lifestyle changes, is a safe and effective way to manage Blastocystis and support digestive well-being.