Be mindful of these foods that decrease immunity

By Naveed Saleh, MD, MS
Published July 19, 2021

Key Takeaways

Over the past 200 years, there’s been a sea change in the causes of death globally. In the late 19th century, 50% of mortality traced back to infection, whereas today that number has dropped to 15%, according to an analysis for the Global Burden of Disease Study. This decrease in infection-related deaths is due to better sanitation, vaccines, and antibiotics.

However, just because infectious disease doesn’t kill as many people as it once did, it’s still important to maintain a healthy immune system. Specifically, inflammation secondary to high-calorie foods can disrupt the immune system.

Here is a list of four groups of foods that can wear down the immune system.  

Western diet

Humans and other vertebrates have evolved two types of immune systems: innate and adaptive. The innate immune system (also called the “trained” immune system) facilitates non-antigen-specific protective responses versus pathogens, whereas adaptive immunity triggers antigen-specific memory formation after encountering a pathogen. The innate immune system is controlled by epigenetic and metabolic reprogramming, the effects of which can be long-lasting.

The innate immune system likely prepares the body for onslaught by secondary infections. It activates innate immune-signaling receptors, including toll-like receptors (TLRs) and the nucleotide-binding oligomerization (NOD)-like receptors (NLRs). Experts hypothesize that “sterile” inflammatory signals such as diet can induce innate immunity.

According to the results of a study published in Cell, researchers found that in mouse models, a Western diet (WD) vs chow diet (CD) exerted negative repercussions on immunity and tapped innate immunity. 

“We show that WD-induced systemic inflammation subsided after shifting mice to chow diet (CD),” noted the authors. “Furthermore, WD triggered a proliferative hematopoietic cell expansion associated with functionally reprogrammed granulocyte monocyte precursor cells (GMPs). These responses were maintained over prolonged times after reversing the diet from WD to CD indicating that WD can induce trained immunity. Mechanistically, we identified the NLRP3 inflammasome as the central receptor, which mediates WD-induced systemic inflammation and myeloid precursor reprogramming."

The researchers hope their findings will open the door to therapeutic possibilities that can interfere with WD-associated pathologies.

Fast food

Fast-food diets are dangerous because they contain high levels of saturated fatty acids, refined carbohydrates, and sugars, as well as low levels of fiber, unsaturated fats and antioxidants. They also contribute to diabetes and obesity, which decrease immunity. In an article published in the International Journal of Food Properties, Iranian researchers noted that decreased immunity due to fast-food diets was linked to the increased morbidity and mortality of COVID-19.

“Fast food consumption activates the intrinsic immune system and impairs adaptive immunity, leading to chronic inflammation and impaired host defense against viruses,” they wrote. “Furthermore, inflammatory responses caused by COVID-19 may have long-term costs in [surviving] individuals, leading to chronic disorders such as dementia and neurodegenerative disease through neuroinflammatory mechanisms that are related to an unhealthy diet.”

The authors concluded that broader access to healthy foods should be a priority and that individuals should engage in healthy eating habits to reduce COVID-19 complications. 

Read The 10 worst foods for your heart to learn more about the negative health effects of eating fast foods, on MDLinx

Chronic heavy drinking

Drinking too much alcohol comes with various heightened risks, including organ damage, respiratory disease, liver damage, heart disease, and cancer. It also heightens susceptibility to tuberculosis, HIV, and pneumonia. Another potential harm is slower recovery from infection or trauma.  

In a study published in Nature, researchers noted that “chronic alcohol drinking, regardless of dose, alters resting transcriptomes of PBMC [peripheral blood mononuclear cells], with the largest impact seen in innate immune cells.”

The authors added, “These transcriptional changes are partially explained by alterations in microRNA profiles. Additionally, chronic alcohol drinking is associated with a dose-dependent heightened inflammatory profile[s] at resting and following LPS [lipopolysaccharide] stimulation. Moreover, we observed a dose-dependent shift in the kinetics of transcriptional responses to LPS. These findings may explain the dichotomy in clinical and immunological outcomes observed with moderate versus heavy alcohol drinking.”

Learn more about how alcohol use, especially heavy intake, weakens the immune system and potentially leads to a greater susceptibility to pneumonia (a severe complication of COVID-19), on MDLinx.

Processed foods

Certain substances present in processed foods can decrease immunity, according to the results of a study published in the International Journal of Environmental Research and Public Health.  Among them are the preservative tert-butylhydroquinone (TBHQ), found in Kellogg’s Pop-Tarts, Cheez-Its, and hundreds of other foods, as well as per- and polyfluoroalkyl substances (PFAS)—which refer to a group of chemicals that can seep into food from packaging. Of note, the authors performed toxicological tests and high thoroughput screening when testing these substances.

“From the public policy perspective, the discovery of impacts on human health of substances that have long been used in consumer products and food products suggests that the pre-market safety evaluation of these substances was inadequate,” the authors concluded. “We recommend that immunotoxicity testing should be prioritized in order to protect public health, and immunotoxicity analysis should be, in our estimate, an integral part of chemical safety assessment.”

On a related topic, check out The 7 most surprising causes of death in the US, on MDLinx.  

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