Processed food diet linked to stronger vaccine fevers, Science study says
Adults who consume diets high in fat and processed food additives exhibit gut microbiome characteristics linked to stronger fever symptoms following mRNA vaccination against COVID-19, according to a study published in the journal Science, as reported by FoodNavigator.com.
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Key Clinical Takeaways:
- Researchers tracked 171 healthy young adults receiving mRNA COVID-19 vaccinations and found that elevated levels of the bacterial protein flagellin correlated with post-vaccination fever.
- Diets characterized by high fat and processed food additives promoted an inflammatory gut microbiome, whereas vegetarian diets correlated with microbiome features linked to reduced fever.
- Dietary patterns and pre-existing inflammation altered side-effect severity without compromising antibody responses or overall vaccine-induced immunity.
Microbiome Flagellin Expression Drives Vaccine-Induced Fever
The research team, led by investigators at the Max Planck Institute for Biology Tübingen in Germany, examined why individuals experience different side effects following immunizations. While most people report mild or no symptoms after receiving a seasonal influenza or COVID-19 vaccine, others experience flu-like reactions that often contribute to vaccine hesitancy. To uncover the biological mechanism behind this variation, Kelsey Huus and colleagues profiled the fecal microbiomes, blood-based immune markers, and oral temperatures of 171 healthy young adults before and after they received mRNA vaccinations. Participants recorded their temperatures three times daily to quantify fever.
The investigation revealed that specific gut bacteria, most notably members of the Lachnospiraceae family, produce flagellin. This protein is utilized by bacteria to build flagella, the whip-like tails that enable movement. Participants with higher pre-vaccination intestinal inflammation or elevated flagellin expression genes activated in the gut were more likely to develop a fever after receiving the vaccine. Ruth Ley, director of the Department of Microbiome Science at the Max Planck Institute, noted in a Max Planck Society release that microbial flagellin acts as a contributor to baseline immune priming.
Contrasting Diets and the Clean Label Food Shift
Dietary habits influence gut microbial ecology, establishing a link between what individuals eat and how their immune systems react to immunizations. The study identified dietary correlations with inflammatory microbiome profiles. Diets featuring greater levels of fat and processed food additives, alongside lower consumption of whole plant foods, correlated with the inflammatory microbiome linked to post-vaccination fevers. Conversely, vegetarian diets correlated with microbiome features associated with fewer fever symptoms.
These findings provide additional momentum to the clean label food movement. While causality requires confirmation through future studies, the association between food additives and inflammatory gut bacteria offers another rationale for dietary modification. Bali Pulendran, an immunologist from Stanford University, observed in a published perspective reacting to the study that microbial ecology and metabolic states are not immutable, suggesting people might one day prepare for vaccination as deliberately as vaccines are formulated.
Experimental Evidence from Mouse Models and Immune Pathways
To confirm whether gut microbes influence post-vaccination inflammation, researchers transferred gut bacteria into mouse models. Experiments demonstrated that after a second vaccine dose, acquired immunity rapidly boosted the response of monocytes—white blood cells—leading to a stronger reaction to the vaccine. Medical Daily reported that while mouse experiments established biological plausibility regarding diet and inflammation, human dietary intervention trials have not been done.
Parallel research highlighted by Medical News Today further emphasizes the complexity of individual vaccine reactions. That research pointed to an interferon-related antiviral defense system as a mechanism explaining divergent side-effect severity across individuals.
Preserving Immunity While Managing Side Effects
A vital finding across the investigations is that neither gut inflammation, flagellin expression, nor dietary patterns impaired antibody production. The microbiome-driven inflammation increased short-term side effects without compromising the primary immune protection conferred by the vaccines. General practitioners like Clare Thompson, a physician at the Cadogan Clinic in London who was not involved in the research, emphasize that individuals should not skip recommended immunizations or alter diets based on this study. Patients with concerns regarding vaccine ingredients or severe reactions should consult qualified healthcare providers before receiving seasonal inoculations.
Disclaimer: The information provided in this article is for educational and scientific communication purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider regarding any medical condition, diagnosis, or treatment plan.