10 Foods That Weaken Your Immune System

Health + Wellness
Woman Holding Hot Dog

We often hear about foods that can boost our immune systems, but did you know there are dietary choices that can actually weaken your body’s ability to fight off infections? Studies show that ultra-processed foods, and those full of empty calories without nutrients can be detrimental to your health.

Our immune systems exist to protect us from bacteria and other microbes like viruses and parasites, and with a healthy diet, they have a better chance of thwarting those diseases and pathogens. A balanced diet is one that includes a plethora of vitamins and minerals, in addition to the calories we need to burn to survive.

So, we know what helps us, but what hurts us?

1. Sugary Foods



When we think of sugary foods, baked goods, candy, chocolate, and other processed sweets come to mind. But even dried or canned fruits or juices contain a lot of added sugar which can put your system out of whack. The microbiome living in our guts keep harmful bacteria in check, but the glucose and fructose in sweetened foods feed those unhealthy microbes, making it harder to fight infection. In addition, sugar begets craving more sugar, as the yeast and other sugar-loving microbes in your system get used to the added sugar in your body.

In addition, adding too much sugar to your diet can raise your blood sugar, which increases inflammatory proteins — particularly in those with diabetes whose blood sugar stays higher for longer. High sugar levels could also inhibit immune cells that protect the body against infection.

Those with a high-sugar diet may be more susceptible to autoimmune diseases like rheumatoid arthritis, as well.

2. Salty Foods

Salt makes food taste so much better. It brings out natural flavor, and spices bland dishes up. But it’s bad for you. It can stop immune functions from working normally, alter your gut bacteria and increase the risk of autoimmune diseases. Preliminary research indicates that the Western world’s rate of autoimmune diseases. It also can exacerbate existing autoimmune diseases like colitis, Crohn’s disease and lupus. One small 2016 study showed that men on a high salt diet had higher levels of monocytes and inflammatory markers, which indicates an excessive immune response.

3. Processed Meats

Time to give up the hot dogs and deli meats — not eating processed meats is not just for pregnant people anymore. These meats have been linked to several diseases, including colon cancer.

High in saturated fat, these meats have been shown to contribute to immune system dysfunction and contribute to inflammation in some people.

The meats also have advanced glycation end products which are harmful compounds that form when fat and protein mix with sugar in the blood. Most AGEs come from the foods we eat, and if we have too many, we cannot regulate them out, and they cause oxidative stress and inflammation. Fried bacon, hot dogs, roasted chicken thighs and steak have high levels of AGEs.

4. Fast Food

burger and fries


Everyone knows fast food isn’t great for you, but sometimes the convenience and deliciousness overcome those facts. Still, fast food isn’t just bad for your weight, it can actually harm your immune system. It’s bad for your gut biome, and can increase inflammation. In addition to holding a lot of that salt we just talked about, it has added chemicals, sometimes from the plastic or Styrofoam packaging, which mess up hormone production in humans, weaken immune responses and even cause dysfunction.

5. Foods with Additives

The more processed a food is, the more additives it contains — to improve texture, taste, preservation and the like. These additives, particularly emulsifiers and carrageenan, can cause immune dysregulation by altering gut bacteria and increasing inflammation. Studies have linked these additives to immune dysfunction in rodents. What foods are highly processed? In addition to lunch meats and bacon, canned soups, canned vegetables, frozen dinners, snack foods and anything else with a long shelf life.

6. Certain Fatty Foods

Onion rings on plate

Michael Rheault / Moment / Getty Images

There are some fats that are good for us, but saturated fats are bad for the immune system. They can activate pathways for inflammation, which inhibits immune response, and they suppress white blood cell function which can increase risk of infection. Studies in rodents have shown a high-fat diet could even damage intestinal lining, which increases susceptibility to disease.

Western diets tend to include many omega-6 fats and far fewer omega-3s. The omega-6 fats have been shown to promote inflammatory proteins that weaken our immune systems. Studies also show that omega-6 fats possibly increase the risk of asthma and allergic rhinitis.

7. Artificially Sweetened Foods

It’s not just sugar that can harm your immune system. The sweeteners we use when we are trying to avoid sugar can be just as harmful if not more. They are connected to altered gut bacteria, more inflammation and a slower immune response. Sucralose and saccharin in particular can cause gut biome imbalance. It could even push forward the progression of autoimmune disease.

8. Fried Food

Fried foods compete with fast foods and processed meats for AGE content. Remember, these end products increase risk of cell damage and inflammation. They also drain your body of antioxidant mechanisms, disrupt gut bacteria and introduce cell dysfunction. All this could lead to increased risk of certain cancers, heart disease, and even malaria. So, as much as we would love to kick back and enjoy some fried deliciousness, lay off the fries, potato chips, fried chicken, bacon and fish and chips for a healthier germ-fighting response.

9. Caffeine and Alcohol

beer on a table on  a patio


Caffeine in and of itself won’t hurt your immune system, but lack of sleep will, and if you consume caffeine anywhere close to bedtime, you may find yourself awake in the wee hours. We’re not talking just coffee. Certain types of teas, chocolate, even protein bars can contain the stuff.

Alcohol suppresses immune response by reducing the number of cells that fight infection. This makes you more susceptible to sepsis, poor wound health, pneumonia and inflammation of the lungs.

If you do drink alcohol, limit yourself to one drink a night for best results. Consider replacing the drinks with fruit-infused water or teas (without caffeine).

10. Refined Carbohydrates

Not all carbohydrates are bad for you; they do give you a long-term energy boost, especially the whole grain varieties. But refined carbs, like white bread, pasta, bleached flour, and, of course, sugar, can cause imbalance in gut bacteria which will compromise your immune system. They are also high glycemic foods, which cause blood sugar and insulin levels to rise, which could result in free radicals and inflammatory proteins roaming the body.


It’s not just diet that impacts our immune health. Other factors include age (the older we are the less efficient our organs become at producing immune cells), environment (if you are a smoker or live in an area with increased air pollution), weight (heavier people have more issues with chronic inflammation, which taxes the immune system), chronic physical or mental diseases like autoimmune diseases or prolonged heightened stress levels, and lack of sleep.

For true immune health, we need to live a balanced life with conscientious dietary, exercise, and self-care decisions.

Darlena Cunha is a freelance writer and a professor at the University of Florida, with degrees in communications and ecology.

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