We all remember biology class in elementary school. We learned about the body in terms of different systems - the nervous system, digestive system, reproductive system, cardiovascular system, immune system, lymphatic system, skeletal system, and so on. Although we may have been taught these systems individually, they are definitely not independent systems. Their interdependency comes to light more and more as scientific research progresses. In fact, it goes beyond interdependency. They can impact each others health and function, for better or worse.
So, when it comes to what we eat (and digest and absorb), yes, there is definitely an influence on our immune system. Food can weaken or strengthen our immune system. Most are aware that the typical highly processed Western diet - high in saturated fats, omega-6 fats, salt, refined sugar and low in omega-3 fats - when overdone, can harm the heart and the waistline and significantly so. 1 Scientific research is making it clear that this diet can also damage the immune system. Of course, other factors that surround the Western diet also play a role. This includes higher exposure to pollution, increased stress, and other factors that can contribute to a weakened immunity. Still, the diet has its contribution and much of it has to do with one specific factor - inflammation!
Is Processed Food Really Inflammatory?
Let's consider several food additives used in many processed foods, the number of which has been increasing through the years in the food industry. While most of these have been studied in animal models, dosages used in studies are meant to mimic what levels they would be in humans. 2 What are some food additives and how do they influence inflammation in the consumer?
- Carboxymethylcellulose: intestinal inflammation, colitis, metabolic syndrome (seen in mice) 2
- Polysorbate 80 : intestinal inflammation, obesity, liver dysfunction (seen in mice) 2
- Sucralose: increased pro-inflammatory chemicals (seen in mice) 2
- Saccharin: liver inflammation (seen in mice) 2
The food industry adds ingredients called emulsifiers to process low-fat foods. This helps compensate for loss of some sensory properties when the dietary fat is removed. Note what animal studies have revealed regarding common emulsifiers that are used in these low-fat foods:
- 2% carboxymethylcellulose (CMC) in mice is linked with intestinal inflammation. The study concluded that these results make CMC a suspect to be blamed for the increase in inflammatory bowel disease in our time period. 3
- Low-dose glycerol monolaurate (GML) consumption promoted metabolic syndrome, reduced diversity of healthy gut bacteria, and chronic inflammation. The study concluded that these results call for an urgent reassessment of the widespread use of GML in food products. 7
Inflammation's False Alarm
Researchers are still trying to pinpoint the exact mechanisms by which inflammation weakens the immune system. One probable way, however, has been observed in animals and has yet to be confirmed in human studies. It can be illustrated with an analogy to a fire alarm, as one study explained. 1
As we know, a heavily processed diet can lead to excessive body fat (obesity). These fat cells release inflammatory chemicals (with complicated names such as interleukin 1, interleukin 6 and tumor necrosis factor).
In animals, these chemicals act as false alarms. After all, there is no urgent injury or infection. It is simply an increase in fat cells. In time, the continuous false alarms produced by these inflammatory chemicals cause the entire alarm system to "dial down" on its response. As the study "Fast food fever: reviewing the impacts of the Western diet on immunity" put it, it is as if someone took out the battery from a pesky smoke detector that kept ringing when there was no fire. 1 Now that the immune system has dialed down, when an actual injury or infection occurs, the response may be slower.
Regardless of the mechanism, however, there is strong evidence that obesity weakens the immune system in many ways. Researchers have seen obesity linked with higher rates of vaccine failure, more complications from infection (including respiratory infections), skewed numbers and altered function of different white blood cell and immune cell counts, and many other complications. 4,5
Food Culprits
What are some common culprits?
White bread is an obvious one. But don't forget all the different foods made with white flour - cookies, cakes, rolls, pies, etc.
Pop is an obvious one. Don't forget sweetened teas and fruit juices also tend to be high in added sugars. Candy is an obvious one. Don't forget, however, that some breakfast cereals and instant oatmeal packets are so high in sugar and so low in fiber they might as well can be called candy. Interestingly, a study in the American Journal of Clinical Nutrition found that feeding humans 100 gram portions of sugar was linked to reduced phagocyte function. Phagocytes are immune cells that engulf bacteria in an infection. Their number was not affected but their ability to perform their job was and the effects lasted for up to 5 hours! 8
Excessive salt is often associated with high blood pressure. Research shows excessive salt can also contribute to inflammation. 6 In fact, it appears to be worsening autoimmune diseases, such as rheumatoid arthritis. 6 You'll find heavy amounts of salt in canned foods, chips, and microwaveable foods or meals.
Steer clear of immune-weakening foods and focus on the many immune boosting ones we have highlighted in past articles!
References
1. Myles I. A. (2014). Fast food fever: reviewing the impacts of the Western diet on immunity. Nutrition journal, 13, 61.
https://doi.org/10.1186/1475-2891-13-612
2. Zinöcker, M. K., & Lindseth, I. A. (2018). The Western Diet-Microbiome-Host Interaction and Its Role in Metabolic Disease. Nutrients,
10(3), 365. https://doi.org/10.3390/nu10030365
3. Swidsinski, A., Ung, V., Sydora, B. C., Loening-Baucke, V., Doerffel, Y., Verstraelen, H., & Fedorak, R. N. (2009). Bacterial overgrowth
and inflammation of small intestine after carboxymethylcellulose ingestion in genetically susceptible mice. Inflammatory bowel diseases, 15(3), 359–364. https://doi.org/10.1002/ibd.20763
4. Ghanemi, A., Yoshioka, M., & St-Amand, J. (2021). Coronavirus Disease 2019 (COVID-19) Crisis: Losing Our Immunity When We Need It the Most. Biology, 10(6), 545. https://doi.org/10.3390/biology10060545
5. Andersen, C. J., Murphy, K. E., & Fernandez, M. L. (2016). Impact of Obesity and Metabolic Syndrome on Immunity. Advances in nutrition (Bethesda, Md.), 7(1), 66–75. https://doi.org/10.3945/an.115.010207
6. Sigaux, J., Semerano, L., Favre, G., Bessis, N., & Boissier, M. C. (2018). Salt, inflammatory joint disease, and autoimmunity. Joint bone spine, 85(4), 411–416. https://doi.org/10.1016/j.jbspin.2017.06.003
7. Jiang, Z., Zhao, M., Zhang, H., Li, Y., Liu, M., & Feng, F. (2018). Antimicrobial Emulsifier-Glycerol Monolaurate Induces Metabolic Syndrome, Gut Microbiota Dysbiosis, and Systemic Low-Grade Inflammation in Low-Fat Diet Fed Mice. Molecular nutrition & food research, 62(3), 10.1002/mnfr.201700547. https://doi.org/10.1002/mnfr.201700547
8. Albert Sanchez, J. L. Reeser, H. S. Lau, P. Y. Yahiku, R. E. Willard, P. J. McMillan, S. Y. Cho, A. R. Magie, U. D. Register, Role of sugars in human neutrophilic phagocytosis, The American Journal of Clinical Nutrition, Volume 26, Issue 11, November 1973, Pages 1180–1184, https://doi.org/10.1093/ajcn/26.11.1180