‘Parasite’ Found in Healthy People: Study

While Blastocystis can be harmful in individuals with compromised immune systems, such as those with HIV, it is also found in asymptomatic individuals who are considered carriers of the parasite. This has led to a debate among scientists about whether Blastocystis is harmful or neutral to humans.

Recent large-scale studies have revealed that Blastocystis may have some beneficial effects. It has been found in the stool samples of healthy individuals and is associated with positive cardiovascular and cardiometabolic markers, as well as whole-food diets.

The gut microbiome consists of trillions of microscopic organisms, including bacteria, fungi, viruses, and parasites. These microbes play a crucial role in physiological functions and immune protection, creating a largely symbiotic community.

Francesco Asnicar, a professor at the University of Trento and corresponding author of the study, emphasized the importance of research to determine whether Blastocystis is harmful or not.

“We were surprised by a few findings. Research can be exciting, and sometimes we discover interesting stories to tell,” Asnicar said. “It might be time to start looking at Blastocystis from a different perspective.”

Blastocystis is intriguing because it is a common member of the microbiome, present in over 5 percent of the population in developed countries and between 30 percent and 60 percent in developing countries.

The absence of Blastocystis was associated with obesity in the Cell study. Conversely, individuals with Blastocystis in their microbiomes had lower visceral fat, reduced weight, and better glucose regulation. Higher levels of Blastocystis were linked to more favorable blood sugar and lipid profiles.

Blastocystis was also correlated with diets high in fiber and minimally processed foods.

“Our findings provide a better understanding of the complex interactions between the human gut microbiome, diet, and cardiometabolic diseases involving the often overlooked Blastocystis species,” the authors noted.

They added, “In the future, personalized nutrition interventions aimed at altering gut ecology could serve as a viable strategy for disease prevention, and our study suggests that underappreciated non-bacterial taxa can have significant roles in maintaining and enhancing human health.”

While it remains unclear whether Blastocystis directly improves health, its presence is associated with better gut health.

According to Asnicar, the study suggests that individuals with healthier lifestyles, diets, or stronger immune systems do not seem to have negative reactions to Blastocystis.

Infectious Nature of Blastocystis

Blastocystis has traditionally been linked to infections that cause symptoms such as diarrhea, abdominal pain, weight loss, constipation, excess gas, and anal itching, according to the U.S. Centers for Disease Control and Prevention (CDC).

The infection is often observed in international travelers who have been exposed to Blastocystis in other countries or who have come into contact with someone who recently traveled, according to Ken Boorom, director of the Blastocystis Research Foundation. The foundation was established in 2006 by patients and their families to promote research on the parasitic infection and educate healthcare providers about antimicrobial treatments.

“Some individuals may acquire and clear Blastocystis infection spontaneously without experiencing any symptoms, while others may suffer from persistent illness following exposure,” Boorom explained via email. He added that genetic susceptibility could also play a role in determining an individual’s response to the infection.

“Some researchers have suggested that Blastocystis directly causes gastrointestinal disorders and is responsible for a specific type of persistent diarrhea, abdominal pain, and vomiting. In immunocompetent individuals, the presence of Blastocystis is not necessarily linked to gastrointestinal symptoms,” the researchers explained. “However, immunocompromised individuals (such as those with cancer or HIV) appear to be more susceptible to the parasite.”

“It’s not a transient microbe passing through the gastrointestinal tract,” Asnicar noted, speculating that specific foods or gut conditions could facilitate the colonization of Blastocystis in the microbiome. These hypotheses could be explored in future studies.

The study also found that diet can influence the presence and abundance of Blastocystis.

In a subsequent phase of the research, 1,124 individuals participated in a personalized diet program to observe the effects on Blastocystis levels in their microbiomes before and after significant dietary improvements.

Asnicar likened the situation to that of Escherichia coli (E. coli), a bacterium known for causing diseases. While some E. coli strains can be pathogenic, many are commensal and beneficial to the gastrointestinal tract.

“We cannot rule out the possibility that Blastocystis is present and influencing the microbial community, but under certain conditions, it could trigger an inflammatory response. This concept also applies to bacteria,” Asnicar explained. “To understand why this happens, we need to determine whether there are subtypes of Blastocystis that may trigger inflammation in some individuals but not in others. There is still much to uncover.”

Although the study focused on eight Blastocystis subtypes with complete genomic sequences for profiling, there are other subtypes that have not been categorized or studied. Asnicar noted that subtypes can encompass various species, and even within a species, there can be different strains.

Another explanation for the mechanism of Blastocystis could be that another microbe, rather than Blastocystis itself, is responsible for causing infection, he added.

“In cases where individuals experience symptoms like diarrhea, abdominal pain, or other issues associated with Blastocystis, approximately one out of five individuals will test positive for the parasite,” Asnicar stated.

“We do not have conclusive evidence from mechanistic studies linking the disease directly to Blastocystis. Blastocystis cannot be cultured in isolation; it always requires the presence of bacteria, making it challenging to study in a laboratory setting,” he continued.

Proceeding with Caution

Despite the potential benefits associated with Blastocystis, the study cautioned against intentionally acquiring the parasite.

“Direct administration of Blastocystis for therapeutic purposes has not been attempted and carries potential clinical risks, particularly for immunocompromised individuals. However, pilot studies in animal models could help establish a causal relationship between Blastocystis and host health,” the authors advised.

Boorom warned against intentionally consuming Blastocystis to improve health, highlighting the risks associated with such a strategy.

“It is unclear whether an observational study can definitively prove the benefits of intentionally consuming Blastocystis, especially considering that Blastocystis consumption is linked to vegetable intake,” he explained, noting that contaminated vegetables have been identified as a source of infection.

“Other studies have shown that children infected with Giardia, another parasite causing gastrointestinal symptoms, may exhibit better health outcomes. However, exposing populations to Giardia can lead to illness in some individuals, with debilitating effects in certain cases,” he elaborated.