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Occasional High-Fat Feasts Temporarily Suppress Immunity
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Scientists Discover that Occasional High-Fat Feasts Temporarily Suppress Immunity, Increasing Susceptibility to Pathogens.
Not to mention humans, any omnivorous creature can hardly resist the temptation of high-fat, high-calorie delicacies.
Some one is not claiming to prefer vegetables over meat with a yin-yang comparison, but from an evolutionary perspective, seizing the opportunity for a calorically rich meal is indeed a top choice.
Of course, indulging in hotpot, fried chicken, and ice cream every day and night is certainly not advisable, but on special occasions, enjoying a few days of good food shouldn’t be a problem, right?
This week, an intriguing study was published in the journal “Nature Immunology.” A German scientific team found that the impact of a “feast” on the immune system is significant.
Short-term consumption of high-energy-dense foods can induce temporary suppression of mucosal and systemic immunity, increasing susceptibility to pathogens.
The experiment observed T-cell dysfunction and reduced cytokine production due to decreased dietary fiber intake.
The good news is that this effect is not permanent; reintroducing dietary fiber can quickly restore normal immune function. These findings were also validated in human volunteers.
Title Image of the Paper
We know that changes in diet can rapidly manifest in the gut microbiota. Variations in different nutritional components can quickly disturb the composition of microbial communities, some bacteria rejoicing while others fretting. The resulting changes in metabolites can transmit the impact of food to other biological systems.
Including the immune system.
In the experiment, researchers designed two diet patterns: a regular diet (RD) and an energy-dense diet rich in animal fats but lacking fiber (FD), which were alternated every 3 days for mice.
With each dietary switch, the mice’s weight, serum cholesterol, core temperature, and energy expenditure would cyclically change. Furthermore, the diversity of the mice’s gut bacteria would also shift.
Gene set enrichment analysis (GSEA) revealed notable changes in the transcription of genes involved in immune responses, with the highest normalized enrichment scores (NES) seen in T-cell receptors, Janus kinase signaling, and transcriptional activators.
The researchers also discovered that after the initial switch to the energy-dense diet, the expression of type III cytokines, IL1a, IL17f, and IL17, significantly decreased. These cytokines play crucial roles in maintaining gut homeostasis and immunity against pathogenic infections.
It’s not just talk; the researchers infected mice with Salmonella Typhimurium.
When comparing mice on the energy-dense diet with those on the standard diet, the former lost more weight and had more colony-forming units (CFUs) in their small intestines.
Mice on the energy-dense diet were also unable to effectively clear infections from Listeria monocytogenes, indicating an impact on systemic immunity.
Additionally, using ovalbumin (OVA) to induce classic delayed-type hypersensitivity reactions, mice on the energy-dense diet no longer exhibited paw pad swelling.
These results suggest that short-term energy-dense diets suppress both mucosal and systemic immunity, diminishing the immune response of antigen-specific CD4+ T-cells.
Energy-dense diet reduces immunity
Further analysis revealed that short-term dietary changes altered the immune landscape of the gut, suppressing CD4+ T-cell function and the expression of type III cytokines such as IL17a, IL17f, and IL22. Isolating CD4+ T-cells from mice showed significant downregulation of oxidative phosphorylation, mammalian target of rapamycin (mTOR), and glycolytic pathways during the energy-dense diet period.
These effects weren’t solely due to caloric changes. When altering the proportions of calories, fats, and sugars in the mice’s diets, the researchers found that short-term dietary changes weren’t dependent on fats nor limited to specific energy-dense diets. Instead, they applied to all diets lacking dietary fiber.
This immediately brings the gut microbiota to mind. Gut bacteria can metabolize dietary fiber into short-chain fatty acids, which in turn mediate immune homeostasis.
Experimental results showed significantly lower concentrations of acetate and butyrate, products of fiber fermentation, in the colons of mice on the energy-dense diet, accompanied by downregulated synthesis pathways.
Reverting energy-dense diet mice back to a standard diet or supplementing with short-chain fatty acids effectively restored immunity.
The researchers also recruited human volunteers for testing. These healthy volunteers consumed a fiber-rich diet (FRD) for 5 days, followed by a fiber-deficient diet (FPD) for another 5 days.
The lack of fiber significantly altered the volunteers’ gut microbiota composition, leading to a reduction in major fiber-fermenting bacteria such as Bacteroides and certain Ruminococcus species. Concurrently, the volunteers’ peripheral blood showed a significant decrease in TH17 and TH1 cells co-expressing IL7a and TNF-α.
Human volunteers’ gut microbiota changes
From this, it’s clear that while calories might be favored by the body, skimping on dietary fiber just won’t cut it! So, the next time you enjoy several consecutive days of indulgent eating, don’t forget to add some vegetables to your plate!
 Siracusa, F., Schaltenberg, N., Kumar, Y. et al. Short-term dietary changes can result in mucosal and systemic immune depression. Nat Immunol (2023). https://doi.org/10.1038/s41590-023-01587-x
Scientists Discover that Occasional High-Fat Feasts Temporarily Suppress Immunity, Increasing Susceptibility to Pathogens
(source:internet, reference only)