Food can fuel us, but it can also fail us. While some give your immune system a boost, others actually make it weaker, leaving you vulnerable to inflammation and infections. Here are 10 foods that might be dragging your defenses down.
10. Refined Grains
That fluffy white bread you love isn’t exactly what your body wants. Since refined grains are stripped of their fiber and nutrients, your body quickly converts these carbs to sugar. This sugar spike can trigger an inflammatory response, putting your immune system on high alert. A 2024 Harvard Health study also confirmed that white bread and pastries are a major source of inflammation.
9. High-Sodium Foods
A little salt is essential for your body to function, but let’s be real…most of us consume far more than we need. The culprits? Processed foods. According to studies, a high-salt diet can reprogram your immune system to be more aggressive and inflammatory. This chronic inflammation can wear down your immune defenses, making you more vulnerable to infections.
8. Processed Meats
Speaking of processed foods, let’s talk about meats. A recent study in the Journal of Food Science revealed that ultra-processed meats can contribute to gut dysbiosis. This is a condition where the balance of good and bad bacteria in your gut is thrown off, which eventually triggers inflammation. So, while that hot dog is tempting, you’re better off with a less processed protein source, like grilled chicken or fish.
7. Trans Fats
Those crispy fries and flaky pastries? They often contain a hidden danger: trans fats. It’s true that many food manufacturers have reduced their use of these artificial fats, but they still lurk in some fried and processed foods. Trans fats, if consumed regularly, can trigger chronic inflammation and leave you vulnerable to infections.
6. High-Fat Western Diet
Researchers at Emory University and other institutions found that a high-fat diet can drive inflammatory conditions like psoriasis. This happens when a specific type of T cell, which normally keeps inflammation in check, gets depleted. When these protective cells are diminished, this can lead to inflammation and a weakened ability to fight off actual threats.
5. Fast Food
We love fast food for being so quick and convenient, but it could be costing us our immune health. Fast food is an example of a high-fat meal that could weaken your gut’s defenses in just two days, according to a recent study. When these defenses weaken, harmful bacteria can slip into the bloodstream, causing extra stress on the immune system.
4. Refined Sugar
High consumption of free sugars can alter your gut microbiome, which is a community of bacteria in your intestines that helps with immune function. A little sweetness now and then is fine, but a consistent high sugar intake can leave your immune system struggling to keep up.
3. Ultra-Processed Foods
Those ready-to-eat meals and snacks might be doing more harm than we realize. They’re often packed with thickeners, emulsifiers, and other additives that can disrupt the balance of our gut microbiome. And you know what happens next: it can trigger a state of chronic inflammation. The lack of fiber in these foods also starves the good bacteria in your gut.
2. Fried Foods
Your gut can act like a shield that keeps harmful microbes away, but that can be disrupted by high-fat meals like fried food. Specifically, they can reduce protective proteins (such as IL-22) that maintain the defenses. So, the next time you crave for that crispy texture, think twice and consider getting something grilled or air-fried instead.
1. Sucralose (Artificial Sweetener)
That yellow packet of sucralose you stir into your coffee? It could weaken a person’s ability to fight cancer. A study published in Cancer Discovery in July 2025 found that sucralose consumption was linked to a poorer response to cancer immunotherapy. It further revealed that sucralose disrupts the gut microbiome, leading to weakened immune cells.