Mediterranean diet increases potentially beneficial bacterial species in firefighters

Key takeaways:

• Bacteroides ovatus was more prevalent at 6 months vs. baseline among firefighters on a low-calorie Mediterranean diet.
• Lower BMI was linked to more Bacteroides ovatus.

HONOLULU — World Trade Center firefighters with lung disease showed increases in Bacteroides ovatus after 6 months on a low-calorie Mediterranean diet, according to a presentation at the CHEST Annual Meeting.

This specific bacterial species may have a positive impact on metabolic and lung health by decreasing inflammation, according to researchers.

Anna Nolan

“Diet and overall health are very important for clinicians to discuss with their patients,” Anna Nolan, MD, FCCP, professor in the department of medicine at NYU Langone Health, told Healio. “It is also important to clearly define goals for patients and to provide them with targets for weight loss and healthy eating. These goals and targets need to be tailored to your patient population. They should also be realistic about the goals they set for their patients and provide frequent follow-up.”

In the Food Intake REstriction for Health OUtcome Support and Education (FIREHOUSE) randomized clinical trial, Nolan and colleagues evaluated stool (OMNIgene-GUT, DNA Genotek) from firefighters exposed to World Trade Center (WTC) particulate matter with lung disease at baseline and 6 months after eating a Mediterranean-type diet to determine the impact of the diet on the microbiome, specifically whether it leads to better metabolic health, improved lung function and less inflammation.

Researchers compared a low-calorie Mediterranean (LoCalMed) diet to usual care in a pilot cohort (n = 5 LoCalMed; n = 5 usual care) and a validation cohort (n = 15 LoCalMed; n = 16 usual care).

Researchers used a multidisciplinary approach, including cloud-based self-monitoring, social cognitive theory-based behavioral counseling and standardized education, to both monitor and educate the study cohort.

Two tools allowed for analysis of microbiome: sequencing (BoosterShot Shotgun, Diversigen) and alignment of sequences to a bacterial database (Diversigen).

Researchers noted their cohort was primarily white, and the diet groups appeared comparable for characteristics including mean age, WTC exposure and years of service.

Researchers found no differences between the LoCalMed and usual care arms when assessing Shannon diversity and microbial community composition at baseline and at 6 months. Both arms had similar microbial community composition from baseline to 6 months, whereas Shannon diversity declined between these two periods (pilot cohort, P = .02; validation cohort, P < .0001).

In the pilot cohort, only one microbial taxon —Bilophila wadsworthia — differed over time, and this difference was only found within the usual care group with an elevated relative abundance of B. wadsworthia at 6 months vs. baseline. Researchers wrote that previous literature has noted a link between this species and high-fat diets, as well as inflammation.

Researchers also observed a link between lower BMI and a larger quantity of B. ovatus after factoring in health measures and joining both arms together.

During the microbiome analysis of the validation cohort, researchers found significant decreases in several microbial taxa at 6 months vs. baseline in the usual care arm: order Veillonellales (P = .032); genus Anaeromassilibacillus (P = .012), Johnsonella (P = .042) and Subdoligranulum (P = .019); and species Bacteroides massiliensis (P = .027), Alistipes ihumii (P = .034) and Clostridium asparagiforme (P = .018).

Notably, researchers only found a reduction in the family Ruminococcaceae at 6 months vs. baseline (P = .015) among those on the LoCalMed diet. Further, B. ovatus was higher at 6 months vs. baseline (P = .03) in this group, which may be beneficial to an individual’s health as indicated by a murine model that found fewer negative health effects with high-fat diets that have increases in this specific bacterial species. This model revealed a link between higher B. ovatus and reduced BMI and decreased serum LDL cholesterol and triglyceride levels, according to the presentation.

Compared with baseline, individuals in the LoCalMed arm also had a significant increase in the species Alistipes shahii (P = .038) at 6 months.

“Surprisingly, even though our study was small and focused on a homogeneous population of WTC-exposed firefighters, we were able to find a microbiome signature that we continue to explore in this patient population,” Nolan told Healio.

“Future studies will need to be validated in other populations with environmental particulate exposure that have metabolic risk factors such as elevated BMIs,” she added. “This is a crucial step because without validation in other cohorts our finding will be less generalizable.”

Even though this research focuses on a specific patient population, it deepens knowledge of particulate matter, Nolan told Healio.

"Longitudinal assessment [of] WTC FDNY first responders has already provided and will continue to provide significant observations that not only impacts clinical care but also fosters mechanistic understanding of the devastating toxic effects of particulates,” Nolan said.

Reference:

• Diet and the microbiome in firefighters with lung disease exposed to WTC-particulate matter. Published Oct. 2, 2023. Accessed Oct. 2, 2023.