10 Foods That Could Ruin Your Immune System

Your diet affects how you feel and how well your body functions.While a nutrient-dense, well-rounded diet supports your immune system, a diet that’s low in nutrients and high in ultra-processed foods impairs the immune system.

This article lists 10 foods that may weaken your immune system.

1. Added sugar

Limiting added sugar consumption is crucial for overall health and immune function. High-added sugar foods increase the production of inflammatory proteins, such as TNF-α, CRP, and IL-6, which negatively affect immune function. This is especially important for people with diabetes, as they may have elevated blood sugar levels for longer. High blood sugar levels may also inhibit immune cell response, harm gut barrier function, and increase susceptibility to autoimmune diseases. By limiting sugar intake, individuals can improve overall health and promote healthy immune function.

2. Salty foods

Salty foods, such as chips, frozen dinners, and fast food, can impair the immune response and increase the risk of autoimmune diseases. A 2016 study found that men on high salt diets had higher monocyte levels and inflammatory markers, while lower anti-inflammatory protein levels. Excessive salt intake may increase autoimmune diseases in Western countries and worsen existing ones. Reducing table salt and high-salt foods may improve immune function.

3. Foods high in omega-6 fats

Your body needs both omega-6 and omega-3 fats to function.

Western diets tend to be high in omega-6 fats and low in omega-3s. This imbalance has been associated with increased disease risk and possibly immune dysfunction.

Diets high in omega-6 fats seem to promote the expression of pro-inflammatory proteins that may weaken the immune response, while diets higher in omega-3 fats reduce the production of those proteins and enhance immune function.

What’s more, studies on people with obesity indicate that a high dietary intake of omega-6 fats may lead to immune dysfunction and increase the risk of certain conditions like asthma and allergic rhinitis.

However, the relationship between omega-6 fats and the immune response is complicated, and more human research is needed.

Regardless, researchers recommend that you maintain a healthy balance of omega-6 to omega-3 fats, which is considered to be around 1:1 to 4:1, to promote overall health.

This means eating more foods that are high in omega-3s — like salmon, mackerel, sardines, walnuts, and chia seeds — and fewer foods that are high in omega-6s, such as sunflower canola oil, corn oil, and soybean oil.

4. Fried foods

5. Processed and charred meats 

Like fried foods, processed and charred meats are high in AGEs.

For example, a study that analyzed the AGE content of 549 foods found that fried bacon broiled hot dogs, roasted skin-on chicken thighs, and grilled steak had the highest AGE contents.

Processed meats are also high in saturated fat. Some research suggests that diets high in saturated fats and low in unsaturated fats may contribute to immune system dysfunction.

Plus, diets high in saturated fat may contribute to systemic inflammation and harm immune function.

Additionally, a high intake of processed meats and charred meat has been linked to various diseases, including colon cancer.

6. Fast food 

Fast food has been linked to many negative health outcomes. Eating it too frequently may also take a toll on your immune system.

Diets high in fast food and highly processed foods may drive inflammation, increase gut permeability, and cause bacteria imbalance in the gut, all of which can negatively affect your immune health.

Fast food can also contain the chemicals bis(2-ethylhexyl) phthalate (DEHP) and diisononyl phthalate (DiNP), which are two types of phthalates. Phthalates can leach into fast food, for example, through packaging or plastic gloves worn during food preparation.

Phthalates are known to disrupt your body’s endocrine, or hormone-producing, system. They may also increase the production of inflammatory proteins that can weaken your immune response to pathogens and cause immune dysregulation.

In addition, phthalates may reduce gut bacteria diversity, which can negatively affect your immune system.

7. Foods that contain certain additives

Many food items, especially ultra-processed foods, contain additives to improve shelf life, texture, and taste. Some of these may negatively affect your immune response.

For example, some emulsifiers, which are added to processed foods to improve texture and shelf life, can alter gut bacteria, harm your gut lining, and induce inflammation, all of which can cause immune dysfunction.

Carboxymethylcellulose (CMC) and polysorbate-80 (P80) are commonly used emulsifiers that have been linked to immune dysfunction in rodent studies.

Similarly, human and animal studies have shown that the common additive carrageenan may induce intestinal inflammation and inhibit immune response, although more research is needed to better understand these effects.

Lastly, corn syrup, salt, artificial sweeteners, and the natural food additive citrate may also negatively affect your immune system.

8. Highly refined carbs

Eating highly refined carbs like white bread and sugary baked goods too often may harm your immune system.

These are types of high glycemic foods that cause a spike in your blood sugar and insulin levels, potentially leading to the increased production of free radicals and inflammatory proteins like CRP.

Plus, a diet rich in refined carbs may alter gut bacteria, which can negatively affect your immune system.

Choosing nutritious, high-fibre carb sources like starchy vegetables, oats, fruit, and legumes over refined carbs is smart to support immune health.

9. Certain high-fat foods

A diet high in saturated fats and low in unsaturated fats has been associated with immune dysfunction.

High saturated fat intake can activate certain signaling pathways that induce inflammation, thus inhibiting immune function. High-fat diets may also increase your susceptibility to infection by suppressing your immune system and white blood cell function.

Additionally, rodent studies have suggested that high-fat diets can cause gut bacteria changes and damage the intestinal lining, potentially increasing infection and disease risk.

Researchers are still investigating how different fatty acids affect the immune system, and more human studies are needed.

That said, eating a well-balanced diet high in fibre and healthy fat sources is likely a good way to support immune health.

10. Artificially sweetened foods and beverages

Certain artificial sweeteners have been linked to altered gut bacteria composition, increased inflammation in the gut, and blunted immune response.

Increasing evidence suggests that artificial sweeteners, including sucralose and saccharin, may induce gut bacteria imbalances. Some researchers postulate that overusing artificial sweeteners may be detrimental to immune health.

Furthermore, some research in rodents and limited case studies in humans also suggests that a high intake of artificial sweeteners may contribute to the progression of autoimmune diseases. However, more research is needed.

That said, not all studies agree, and some have shown that moderate daily intake of those sweeteners does not cause changes in gut bacteria or immune function.

The bottom line

You can support your immune system by living a healthy lifestyle.

This means limiting foods and beverages that are high in added sugars and salt, processed meats, and fried foods, all of which may have adverse effects on your body’s immune function.

To support your immune system, it’s best to follow a balanced diet rich in whole, nutrient-dense foods and limit your intake of ultra-processed foods as much as possible.

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