Could Junk Food Lower Your Child’s Immunity?

Could Junk Food Lower Your Child’s Immunity?

Runny noses, fevers, upset tummies — these are some of the all-too-familiar signs that kids have become infected with viruses or other harmful microbes. Wouldn’t it be nice if you could help them avoid some of these illnesses?

Not every child exposed to germs gets sick. It partly depends on how strong their immune system is. Eating habits can play a big role in this.

The foods kids eat determine whether they get the nutrients their immune system needs. Foods also influence children’s weight and gut health. All of these factors impact whether kids catch the latest cold or stomach bug that’s circulating. (1)

Immunity Hijacked by Junk Food

On average, children in North America get more than 55% of their daily calories from highly processed foods — aka junk food. This includes items like snack chips, breakfast pastries, pizza, ice cream, and sugary drinks. These foods can be pretty tasty (food companies make sure of it), so they’re easy to overeat. (2, 3

Highly processed foods are primarily “empty calories,” offering few essential nutrients and plant compounds needed to support immunity. (Don’t let a few added vitamins touted on the front of the package fool you.) These junk foods tend to squeeze out nutrient-dense, whole foods from kids’ plates. (4, 5, 6, 7)

About 74% of packaged, processed foods in the grocery store contain added sugars. Eating too much refined sugar can decrease phagocytosis. That involves special white blood cells engulfing germs to destroy them. Think of phagocytosis like Pac-Man gobbling up cunning digital ghosts in the popular video game of the 1980s. With excess sugar on board, kids lose at the immunity game. (8, 9)

Connections with Childhood Obesity

Obesity is linked with a greater risk of catching infectious microbes, especially ones that affect the respiratory tract. Kids who eat more junk food and highly processed foods are more likely to pack on extra pounds. That weakens immunity. (4, 10)

Overweight kids have fewer white blood cells to fight infection. The ones they do have don’t work as well. For example, they’re less effective at phagocytosis, needed to tackle invading microbes. (9)

Obesity also increases inflammation. Fat cells release inflammatory substances that may act as “false alarms.” Like the little boy who cried wolf in the Aesop fable, the immune system may dial down its response to these signals over time. Then, when a real infection comes along, the immune system’s response may be slow because the early warning signs were ignored. (9)

Disrupting Kids’ Gut Health

Approximately 80% of immune system cells are housed in the gut. So, helping kids keep their gut health is important for good immunity. (11)

Processed foods are often laced with chemical additives like polysorbate-80, sodium sulfite, and sucralose that can wreak havoc on the gut lining. Such chemicals can also shift the makeup of children’s gut microbes to favor harmful bacteria instead of helpful ones. This community of bacteria and other microbes (good and bad) is called the gut microbiome. (12, 13)

Refined sugars can increase inflammation and disrupt the gut microbiome. Obesity also shifts the makeup of the gut microbiome, enabling harmful bacteria to gain a foothold. (9, 14

On the other hand, probiotic bacteria, such as some strains of Lactobacillus and Bifidobacterium, can help fight back against viruses in several ways, including: (11, 13)

  • Preventing invading viruses from entering the body’s cells
  • Producing compounds (metabolites) that can block the actions of viruses
  • Stimulating immune system cells, including ones outside the gut, to fight invaders
  • Enhancing the production of natural protectants for the gut lining

Keeping kids’ gut microbiomes healthy could result in milder symptoms of some contagious illnesses or possibly avoiding some infections altogether. (13)

Nutrition for Good Immunity

To keep their immune system working at its best, kids need a wide range of nutrients. These include protein, healthy fats, vitamins A, C, D, and E, several B vitamins, and minerals like zinc and selenium. The best sources of these nutrients are whole, minimally processed foods, including vegetables, beans, fruits, whole grains, nuts, eggs, seafood, and grass-fed meat. (15)

Vitamins, minerals, healthy fats, and protein may help bolster immunity by supporting the: (5)

  • Physical barriers that keep germs out, such as in the respiratory tract and gut
  • Formation, activation, and maturation of immune system cells
  • Phagocytic functions of white blood cells (think Pac-Man)
  • Production of antibodies
  • Quieting of inflammation
  • Antioxidant defense systems
  • Healing of damaged tissues

Healthy, plant-based foods also supply phytochemicals that support the immune system. According to some lab studies, many of these plant compounds have direct antiviral properties. For instance, polyphenols, such as those found in berries, pomegranates, and asparagus, may help ward off the flu. (4, 16, 17, 18)

Plant-based foods also provide fiber, some of which “feeds” the good bacteria in the gut. Fermented plant foods, such as pickles and sauerkraut, can supply beneficial bacteria (if the foods aren’t processed by heat) to promote a diverse, healthy microbiome. (11, 19, 20)

Kids could potentially have a powerful army of beneficial microbes and nutrients ready to help defend them against germs. It starts with making savvy choices at the supermarket.



    1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6340979/
    2. https://www.karger.com/Article/FullText/507840
    3. https://pubmed.ncbi.nlm.nih.gov/31689013/
    4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6124954/
    5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7230749/
    6. https://pubmed.ncbi.nlm.nih.gov/26962035/
    7. https://pubmed.ncbi.nlm.nih.gov/27125637/ 
    8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3490437/ 
    9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4074336/
    10. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6109602/
    11. https://www.mdpi.com/2072-6643/13/3/886 
    12. https://pubmed.ncbi.nlm.nih.gov/31965661/
    13. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7827890/
    14. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4338791/ 
    15. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6212925/ 
    16. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5925142/
    17. https://pubmed.ncbi.nlm.nih.gov/26567957/
    18. https://link.springer.com/article/10.1007/s13659-020-00271-z 
    19. https://pubmed.ncbi.nlm.nih.gov/32996638/
    20. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6532841/ 


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