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6 Foods That Weaken Your Immune System

There are many foods that support the immune system, but what about foods that weaken the immune system? It's best to severely limit or avoid these foods to support optimal immune health.
Sep 12, 2023 | Joy McCarthy

You’ve likely already experienced how your diet impacts your energy, your digestion, or maybe you’ve even noticed how your skin reacts to your dietary choices. Those are all pretty obvious signs. But what might not be as obvious is how what you eat every day impacts your immune system. It's always working in the background whether you realize it or not because you come into contact with hundreds of germs per day.

A nourishing whole-foods based diet supports and strengthens your immune defences but and it's a big but, a diet that’s nutrient-poor, calorie high and rich in processed foods will negatively impact your immune function and so much more.


Here are 6 foods that can weaken your immune system.

1. Commercial baked goods such as cakes, pies, cookies and brownies.

These prepared foods bought from grocery stores are the furthest thing from healthy or homemade unless it’s your local bake shop.

These foods are full of processed oils and omega-6 fatty acids while being loaded with refined sugar. Humans need a healthy balance of omega-3 and omega-6 to thrive.

Western diets are chock full of processed seed oils that are very high in omega-6 which can promote pro-inflammatory proteins that can weaken the immune response.

Solution: Bake your own treats from wholesome ingredients. These Cosmic Brownies are packed with fibre and this Chocolate Chip Cookie cake is a winner, rich in healthy fats and protein.

Chocolate Chip Cookie Cake

2. Fried foods.

As delicious as French fries, chicken fingers and potato chips may be, eating them on a daily basis is not a wise choice for overall health. Not only can fried foods increase your risk of cancer due to the presence of acrylamide particularly in the case of French fries but they also increase harmful compounds called AGES (advanced glycation end products).

These are created when certain foods are cooked at high temperatures. High levels of AGES have been linked to inflammation and many different diseases as well as premature aging. Definitely not a good choice when trying to strengthen your immune system.

Solution: If your love of fried foods comes from the salty factor, add healthy Celtic or Himalayan sea salt to your meals. If it’s the crunchy aspect, than bake or light roast food. Try these Rosemary Sweet Potato Wedges or the Chicken Fingers from The Joyous Cookbook.

3. Food additives.

Processed and ultra-processed foods like microwave dinners, frozen pizza, ice cream and the like are high in food additives from flavouring and colouring chemical agents, to preservatives and stabilizing chemicals.

These kinds of foods are nutrient-poor, calorie and additive rich.

One study found that eating foods containing additives may increase the risk of several chronic inflammatory or metabolic conditions. The study looked at additives such as sucralose, aspartame, carboxymethylcellulose, polysorbate-80, sodium, and carrageenan - these are found in our food supply in abundance. Animal studies have linked some of these additive to immune dysfunction.

Solution: Read labels and limit or avoid foods with food additives. Buy fewer packaged foods.


4. Refined carbohydrates.

Commerical breads, cereals and granola bars can give the illusion of a healthy food depending on the marketing, but the large majority of these products lining grocery store shelves are loaded with food additives, sugar, preservatives and refined grains. When the packaging says "whole" grain, it can mean one ingredient contains the whole grain so it's a bit misleading to consumers unless you're reading the full ingredient label.

White pasta and white bread should be considered a treat, or an indulgence, and best avoided if you have blood sugar issues like insulin resistance or diabetes.

When a grain is refined it is stripped of its essential fatty acids, fibre and minerals what you're left with is starch. Starch is a refined carbohydrate and broken down in the gut very quickly due to the lack of fibre. This elevates blood glucose levels and causing a surge of insulin. This yo-yo effect of blood sugar and insulin can lead to insulin resistance and eventually diabetes, which has many long-term health consequences.

Solution: Choose truly "whole grain" breads, limit or avoid packaged boxed cereals, read all the labels for granola bars and other snack foods. Be mindful of "gluten-free" options which can be just as refined as their glutenous cousins!

Bowl of gluten-free veggie pasta.

5. Alcohol.

It's likely no surprise that chronic long-term alcohol use negatively impacts the immune system. People who drink daily are more likely to suffer from upper respiratory illness such as pnemonia. Not only that, it's been well established in research that there is a much greater risk of sepsis, alcoholic liver disease (ALD), and certain cancers; a higher incidence of postoperative complications; and slower and less complete recovery from infection and physical trauma, including poor wound healing.

What about people who are not alcoholics? Moderate drinkers like the majority of people.

Well let's consider the pathway in the body of alcohol. The gastrointestinal (GI) system is the first point of contact for alcohol as it passes through the body and is where alcohol is absorbed into the bloodstream. One of the most significant immediate effects of alcohol is that it affects the structure and integrity of the GI tract. Alcohol alters the numbers and relative abundances of microbes in the gut microbiome, an extensive community of microorganisms in the intestine that aid in normal gut function and are critical in the health of the immune system.

Solution: Consider severely limiting your alcoholic consumption. There are many conflicting expert opinions on how much is acceptable. I'm a bit biased because I am a non-drinker other than a sip here or there of my hubby's beer or wine. Looking for an alcohol-free alternative that's still fun to sip on? Try one of these delicious Easy Summer Mocktails!

6. Sugar

Juice, soda pop, candy, cookies, chocolate - you name it, if sugar or any ingredient ending in "ose" is within the first 5 ingredients, you're eating sugar which is broken down into glucose. This is especially problematic because sugar is hidden in many different foods from pasta sauce to salsa to granola bars making it easy to overdo it. Eating a diet high in sugar has many consequences to the body but we will stay on topic here and focus on immunity.

Even though glucose is vital for the function of the immune system, a high amount of sugar leads to impairment. When you eat a sugary substance the immune system and immune cells are activated for glucose metabolism to occur. Research shows that elevated amounts of glucose leads to excessive proinflammatory cytokines production.

Solution: Avoid sugary foods and especially beverages like soda pop. Save them for a treat such as a birthday or celebration. That being said, there are plenty of lower sugar options right here on Joyous Health. Like these crowd-pleasing and blood-sugar balancing Chocolate Almond Butter Cups! Use natural sugars in moderation too though.

I have written extensively about how to support your immune system, but here's a quick summary.

Immune supportive foods to eat.

  • Choose protein at every meal and snack. Animal foods including pasture-raised chicken and eggs, grass-fed lamb or beef, organic yogurt or kefir. Plant-based foods including beans and legumes, hemp hearts, tempeh, nuts and seeds. Protein helps your body recover and repair, make antibodies that fight infection and promotes the synthesis of glutathione needed for healthy immunity and more.
  • Eat colourful immune-supportive superfoods. Leafy greens, broccolicauliflowersweet potato, turmeric, winter squash are just a few of the foods that contain abundant phytonutrients that support your immune system. Check out all these immune supportive recipes here.
  • Eat vitamin C rich foods. Lemon and limes, broccoli, yellow sweet peppers, dark berries, grapefruit, papayas, tomatoes and Brussels sprouts. Vitamin C rich foods help make white blood cells that your body ward off infection.
  • Eat zinc-rich foods. Oysters, mussels, eggs, chickpeas, beef, nuts and seeds. Zinc is a very important mineral as it supports the immune system as it's crucial for normal development and function of cells mediating innate immunity, neutrophils and natural killer cells. Macrophages also are affected by zinc deficiency. Phagocytosis, intracellular killing, and cytokine production all are affected by zinc deficiency. If that's not enough, zinc helps cool off inflammation.
  • Superfoods. Garlic, onions, ginger and turmeric all have unique phytonutrients, vitamins and minerals but one thing they all have in common is they are immune strengthening superfoods.


Want to learn more? Here are some podcasts on immunity.

I truly hope this blog post provides you with valuable information to support your immune system. Any questions, please post below!

Joy xo

Barbara North   •   September 12, 2023

Thank you, Joy! I’m a grandma and I needed to hear this 👍😊

Joy McCarthy   •   September 13, 2023

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