4 Foods that Weaken Immune System Health

foods that weaken immune system health
Reading Time: 4 minutes

We have plenty of resources available in this blog and on our website about what you can do to boost your immune system. The other side of the healthy-immune-system coin, however, is avoiding the foods that weaken immune system health. 

By removing the damaging ingredients from our cooking, we can raise the baseline of our immune function. This way, added boosters can support immune function to a higher degree!

1. Sugar

This one is BIG. There really isn’t much in the “pros” column to say about added sugar, aside from its taste. You already know it’s not good for you. Here is just one more reason: sugar-sweetened foods can weaken the immune system.

Sugar is inflammatory and causes added oxidative stress. Even one, single meal that significantly raises blood sugar (e.g. white bread, white flour, and those high in added sugars) can increase the production of inflammatory proteins that negatively affect immune function [1]. 

Plus, when we do get sick, high blood sugar levels can inhibit the response of neutrophils and phagocytes (two types of immune cells) [2].

Furthermore, high blood sugar levels may harm both the function of the gut barrier and cause dysbiosis of the microbial population. Both of these issues can alter your immune response and make your body more susceptible to getting sick [3].

Try this instead!

If you’re a sucker for sweets, try sweetening your food and drinks with natural, low-glycemic sweeteners. It may take some trial and error to find the one you like best, but there are natural sweeteners that don’t cause a blood sugar spike out there. Nor do they mess with your brain and body chemistry like some lab-made sweeteners.

Agave might be the most well known, which is made from the same cactus harvested for tequila. Agave has a glycemic index score of 15, compared to white sugar’s 60. 

Other great options are monk fruit extract, yacon syrup, erythritol, or xylitol. Some people like the sweet taste of glycine as a drink sweetener. As a pure amino acid, glycine is carbohydrate-free and health-supportive. One of its benefits includes helping to prepare your body for sleep.

2. Artificial Sweeteners

Whatever you do, don’t let the above info have you reaching for the “diet” or “light” version of anything without reading the label. Generally, those are loaded with laboratory-made chemical sweeteners. 

While they won’t spike your blood sugar, artificial sweeteners are also on the list of foods that can weaken the immune system. Certain artificial sweeteners have been linked to altered gut bacteria composition, unhealthy inflammation in the gut, and blunted immune response [4,5].

Artificial sweeteners, including sucralose (Splenda) and saccharin (Sweet n’ Low), may cause dysbiosis of the gut microbiota, which dictate immune health to a fair degree [6]. Multiple clinical studies have concluded that overusing artificial sweeteners may be detrimental to immune health [4-7].

Try this instead!

Check out our list of natural non-refined-sugar sweeteners above. 

Note: Stevia is not on the list because there is some controversy over how “natural” it truly is by the time it reaches its white, powdered form. If you like stevia, do a little research to find a brand whose process you trust.

3. Salt

If you have ever had concerns over your blood pressure, you may already be paying attention to the salt content of your food. Salt is well known for its relationship to water retention and vasoconstriction. Lesser known, however, is the fact that salty foods can weaken the immune system by creating oxidative stress and negatively affecting the function of endothelial cells [8]. 

Endothelial dysfunction and increased arterial stiffness are concerning for your health, independent of blood pressure, and oxidative stress has a negative effect on immune system function. 

A high-salt diet has been associated with specific levels of inflammatory markers that indicate over-activity of the immune system [9]. 

Salt may also inhibit normal immune function, suppress healthy inflammatory responses, alter gut bacteria, and promote the development of autoimmune issues [10,11].

Try this instead!

We like salt because it tends to bring out the more subtle flavors in a dish. SO, if you’re adding less salt, add more flavor! 

Acids like citrus and vinegar can bring a tang to the recipe that will help you forget about salt, or find a new favorite herb blend to sprinkle on savory foods. For example, “Mrs. Dash” seasoning blend was designed specifically as a salt replacement. More flavor on your food without altering your blood pressure… or weakening your immune system.

4. Omega-6 Fats

We’re crazy for omega-3 fatty acids. We could do with fewer omega-6s. 

Yes, you need a little bit of both types for human survival. The problem with a Western diet is that omega-6s are everywhere while omega-3s are scarce. 

Omega-3s are generally found in fatty ocean fish and seeds. Omega-6s, on the other hand, are found in seeds and fish, all other meats, cooking oils (canola, corn, peanut, sunflower, and safflower), eggs, nuts, avocados, and a number of other common foods. 

The imbalance between omega-6 and omega-3 consumption is credited with increased disease risk and immune dysfunction [12]. 

Diets high in omega-6 fats seem to promote the expression of pro-inflammatory proteins that may weaken the immune response [13]. Furthermore, people with obesity and high dietary intake of omega-6 fats are more likely to experience immune dysfunction [14].

Try this instead!

According to nutrition research, a balance of 4:1 omega-6 to omega-3 is ideal. If you aren’t eating a ton of fish, walnuts, soybeans, or flax, you may need more omega-3s in your diet. If the idea of eating more of those foods isn’t appetizing, an omega-3 supplement can help bring balance to your omega-6 intake. 

Also, when you can, use olive oil to cook in place of other oils. While olive oil still contains more omega-6 than omega-3, it’s highest in omega-9. Olive oil is associated with many health benefits of the Mediterranean Diet, including promoting healthy inflammatory response and healthy immune function [15]. 

Back to Nutrition Alert


  1. https://www.mdpi.com/2072-6643/12/6/1562
  2. https://www.sciencedirect.com/science/article/abs/pii/S0002962915000270
  3. https://www.nature.com/articles/s41467-019-09964-7
  4. https://www.hindawi.com/journals/bmri/2018/1345282/
  5. https://www.frontiersin.org/articles/10.3389/fnut.2020.598340/full?ref=assuma-o-controle-de-sua-saude.com
  6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7257251/
  7. https://www.frontiersin.org/articles/10.3389/fimmu.2017.01478/full
  8. https://www.sciencedirect.com/science/article/abs/pii/S193152441400423X
  9. https://www.mdpi.com/2072-6643/11/5/1013
  10. https://www.jci.org/articles/view/84690
  11. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7721408/
  12. https://www.mdpi.com/2072-6643/11/12/2990
  13. https://www.atsjournals.org/doi/full/10.1165/rcmb.2018-0215OC
  14. https://www.mdpi.com/2072-6643/11/12/2941/htm?ref=blog