Does Sugar Weaken Your Immune System?

3.12.2025 0 comments

Author: Trisha Houghton, CNS, ASIST

Too much sugar doesn’t just affect your waistline—it can also weaken your immune system. 

It slows down your body’s ability to fight off infections, leaving you more vulnerable to illness. Cutting back isn’t just about diet; it’s about giving your body a better defense.

In this post, we’ll look at the danger sugar poses to your bodily functions—not just your overall health, but your immunity, your probability of chronic disease, and even your levels of inflammation.

We’ll take a deep dive into the effects of sugar to see just what kind of harm it can cause. But don’t worry: we’ll also end with dietary recommendations that will help counteract the immune-suppressing effects of a diet high in sugar, as well as healthy alternatives to refined sugar you can add to your meals. 

Sugar Is Everywhere, and It Is Hurting You

Sugar is present in so many foods, it’s nearly impossible to avoid it in our modern diet.

From sauces and soups to canned goods, bottled drinks, candy, and cake, nearly every food today contains some form of sugar or sweetener.

But if you had any idea just how bad sugar is for you, you’d make far more of an effort to find those foods. Because as you’ll see below, over time and with high rates of consumption, sugar can make you very sick and do real harm to your body.

How Sugar Affects the Body

The simplest way that sugar affects your body—negatively—is by driving up your blood glucose levels.

When you eat sugar, your body absorbs it into your bloodstream. High levels of sugar in your blood cause your pancreas to release insulin, the hormone responsible for keeping blood sugar levels in check. A flood of insulin into your bloodstream lowers sugar levels significantly, causing you to feel a “crash” in energy and an increase in appetite. As a result, you’ll end up feeling a sugar craving, so you eat more sugary foods, which starts the whole dirty cycle all over again.

In the short-term, this succession of energy spikes and crashes can wreak havoc on your day. But it’s the long-term effects you really need to be worried about. Over time, your body becomes resistant to insulin or loses its sensitivity to the hormone, so your pancreas has to release more insulin to have the same effect. 

Insulin resistance leads to prediabetes and eventually diabetes, which has a whole host of additional complications.

High sugar intake also leads to higher obesity rates. When there is more sugar in your bloodstream than can be used, your body converts it into fat to store in your adipose tissue for later use. The more you keep adding (by eating more high-calorie, high-sugar foods than your body needs) to those fat stores, the more weight you gain. And it’s the bad kind of weight, visceral weight, which can slow down organ function and lead to higher cardiovascular disease risk.

Given this, it should come as no surprise that sugar is one of the worst things that you can put in your body if you want to stay healthy.  

The Link Between Sugar and Inflammation

Research has proven that sugar definitely leads to inflammation.

Research suggests that high sugar intake “can cause metabolic disorders and induce the increase of inflammatory mediators and certain pro-inflammatory cytokines in various tissues, which leads to insulin resistance and low-grade chronic inflammation”. [1]

It does so in a number of ways. First off, it can increase inflammatory factors secreted by adipose tissue and your liver. This raises the level of inflammation-causing cells (like inflammatory cytokines), which can increase the risk of widespread, low-grade, and chronic inflammation.

Sugar intake can also increase the production of uric acid (which is present in your urine). One study [2] found that people who consume a lot of sugar had significantly higher uric acid levels in just a matter of months. Uric acid is a trigger for both insulin resistance and inflammation.

High sugar consumption may lead to the production of Advanced Glycated End-Products, or AGEs. These are harmful compounds that form in your body when sugar combines with either fat or protein cells in the body. s. AGEs can place stress on your body (oxidative stress) and trigger widespread inflammation.

Another way that sugar can cause inflammation is by increasing the permeability of your gut. A high-sugar diet has been proven [3] to increase intestinal permeability, allowing larger, less-processed nutrients to pass through the walls of your intestines. This can have long-term consequences on your digestive health, but in the short-term, can negatively impact your gut microbiota (beneficial bacteria) and trigger inflammation.

Does Sugar Suppress Immune Function?

Sugar can absolutely have a negative effect on even a strong immune system, effectively suppressing or limiting your body’s ability to respond to invading threats.

Your white blood cells are responsible for a significant amount of your immune activity. They are highly mobile and active cells that travel throughout your entire body to neutralize and eliminate any threats. They’re also crucial for the proliferation of healthy cells and mediation of inflammatory response.

But, as one study states [4], “a high amount of glucose may lead to impaired function of the immune system and pathological conditions”. 

Glucose (aka, sugar) can suppress your white blood cells’ function—for up to multiple hours,  following high sugar consumption. Your white blood cells become less effective at engulfing and eradicating threats. Your immune response is weakened and immune response times significantly slowed because of the excess sugar in your bloodstream.

And that’s not even taking into account the inflammatory effects that sugar can have. When the levels of inflammatory markers rises in your bloodstream, your immune system can become compromised (as you’ll see below).

Short-Term vs. Long-Term Effects of Sugar on Immunity

As you saw above, high sugar intake can make you more susceptible to disease and infection in the short-term because of dampened white blood cell activity.

But over time, if you maintain a high sugar intake, the problem can continue to escalate to some pretty serious heights. 

First off, as inflammation increases in your body, your immune system has to work harder to separate real threats (invading pathogens and carcinogens) from the inflammation caused by high sugar intake. It ends up working overtime, which taxes your immune system and decreases its effectiveness at curbing disease. It becomes harder to fight off infections thanks to the increased inflammation and reduced immune function.

You’ll notice that you heal more slowly, too. This is a direct result of a slowed immune response and the prevalence of widespread chronic inflammation.

Your blood sugar levels will rise, both as a result of high sugar intake and increasing insulin resistance. Chronically high blood sugar can lead to prediabetes and diabetes, which only dampens your immune system further, slows down healing, and increases the strain on your body.

Due to increased intestinal impermeability, your body absorbs more glucose but less of the nutrients it actually needs. Inflammation in your gut (the result of the intestinal issues) decreases the absorption of critical vitamins, minerals, proteins, and antioxidants. You end up at a much greater risk of nutrient deficiencies as a result of consuming excess sugar.

Your gut bacteria also suffers in the long term. The balance of beneficial bacteria that keep your gut healthy—and which plays a role in everything from brain function to immune health—is negatively impacted by high sugar diets. Your entire body suffers due to poor gut microbiome health.

Naturally, because your gut bacteria function is impaired, they’re no longer able to effectively neutralize harmful bacteria in the food you eat. You end up at greater risk of infectious diseases that can further jeopardize your health.

Sugar and Chronic Diseases: Implications for Immunity

High sugar intake can lead to an increased risk of a number of medical conditions, including:

• Diabetes
• Obesity
• Metabolic syndrome
• Heart disease
• Alzheimer’s
• Decreased cognitive function
• Blood vessel damage
• and the list goes on!

It’s clear that eating sugar can have serious negative repercussions for your health—not just in the short-term, but very much in the long-term. 

The more sugar you eat, the more you put your body at risk of serious illness due to reduced immune health and increased inflammation. 

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Dietary Recommendations for Supporting Immune Health

Our modern diet tends to be very high in sugars, due to the prevalence of refined sugar and sweeteners used in the foodstuffs sold at supermarkets. 

The simplest solution for cutting back on sugar intake is to avoid the foods that could contain them—which nowadays, means anything that is pre-packaged and pre-prepared.

A healthy goal would be to buy all foods either raw or frozen and cook or prepare it yourself. If you have to purchase cans, make sure they are organic and do not contain high fructose corn syrup, or anything artificial. A good rule of thumb is if I do not know what the ingredient is, I pass. You can go online for some simple dressing and sauce recipes to make a home without sugars or artificial ingredients.

If you want some sweet foods, please buy the organic maple syrup or organic cane sugar and cook with as little sugar as possible. That’s the only way you can be 100% sure of just how much sugar you’re putting in your body.

For a diet that contains a good balance of sugar, try to eat more nutrient-dense foods:

• More vegetables. Though some veggies (like carrots and tomatoes) contain some sugars, they are present in low enough quantities that it’s not too concerning if you eat them as part of a balanced diet. Aim for 5-8 servings of veggies each day.
• Some fruit. Fruit contains natural sugars (fructose) that don’t have the same negative impact on your health as refined sugars if eaten in moderation. Aim for a maximum of 3 servings of fruit per day. Try to eat more of the fruits that contain more antioxidants, such as berries, red grapes, plums, oranges, and apples.
• Healthy fats. Nuts and seeds are a great source of healthy fats that can have a natural anti-inflammatory effect, curbing the inflammation caused by high sugar intake. Have a handful or two of your favorites—almonds, sunflower seeds, sesame seeds, cashews, Brazil nuts, and pecans—every day to decrease inflammation and improve heart health.
• Whole grains. Brown rice, millet, quinoa, sorghum, buckwheat, amaranth, and barley are all excellent for your health. Not only do they provide glucose for your body to use as energy, but they deliver it with plenty of fiber to slow down the rate of absorption. Whole grains are also packed with antioxidants, vitamins, and minerals and can reduce chronic inflammation in your body.

Eating more of these foods will restore healthy immune function and drastically reduce inflammation. 

7 Highly Immune-Boosting, Sugar-Reducing Foods to Add to Your Diet

Here are seven foods you need to add to your healthy lifestyle today to start curbing the immune-suppressing effects of sugar:

1. Citrus fruits, such as lemons, oranges, and grapefruits. They’re rich in Vitamin C, which supports white blood cell activity in your body, and contain antioxidants that will curb inflammation.

2. Turmeric contains curcumin, a potent inflammation-fighting, immune-enhancing antioxidant. It may even have antimicrobial properties to aid your immune cells in keeping infections at bay.
3. Garlic is a natural anti-inflammatory that has potent immune-boosting properties. A clove or two of garlic can do wonders to fight off infections and improve cardiovascular health in the process.
4. Red bell peppers contain nearly triple the amount of the Vitamin C content of an orange, along with plenty of Vitamin A-producing beta carotene.
5. Olive oil contains natural fats that will reduce inflammation and improve your heart and brain health.
6. Papaya contains the enzyme papain, which aids in digestion, speeds up wound healing, and curbs inflammation. It’s also loaded with Vitamin C.
7. Dark, leafy greens such as kale, spinach, and broccoli are all loaded with Vitamin C, beta carotene, and other antioxidants that can increase your body’s immune response.

Make sure these are a part of your diet—at least one each day—and you’ll see massive improvements in your long-term health.

Alternatives to Refined Sugar for Better Health

If you’re looking for a healthier sweetener to use instead of sugar, try these:

• Stevia. Stevia is a plant-based product that some may think tastes sweeter than refined sugar, however it  won’t impact your blood sugar like refined sugar does.
• Monk fruit. Made from the monk fruit native to China, monk fruit sweetener has no calories and won’t affect blood sugar spikes.
• Dates. Often used to sweeten Middle Eastern dishes, dates are naturally sweet but pack a nutrient punch: manganese, potassium, magnesium, Vitamin B6, polyphenols, antioxidants, and a lot of dietary fiber.
• Honey. Honey is a natural sweetener with potent anti-inflammatory and immune-boosting properties. Best to consume it in moderation, though, as it does have similar blood sugar-raising effects.
• Molasses. Rich in vitamins, minerals, and antioxidants, molasses is a healthier alternative to sugar, but like honey, should be consumed in moderation.
• Coconut sugar. Made from the sap of coconut palm trees. It contains some trace vitamins and minerals and has a much smaller effect on blood glucose levels than regular sugar. As a bonus, it’s also one of the most sustainable sweeteners on the planet. 

Choosing alternatives to refined sugar is more than just reducing calories. Many natural sweeteners provide vitamins, minerals, and antioxidants that support overall health. Understanding their unique benefits helps you make informed decisions and balance flavor with nutrition in your daily diet.

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Wrapping Up

Decreasing refined sugars from your diet supports the goals of leading a long and healthy life.

As you saw above, sugar can have serious consequences for your health—from your immune system to widespread inflammation. It is also linked to obesity and cardiovascular disease. 

Worse, the longer you eat a high-sugar diet, the more the consequences will impact your body.

With the information we shared above, you have everything you need to shift to a natural, low-sugar diet rich in healthy, immune-boosting, and inflammation-fighting foods. And if you need something sweet, you can always use one of the sugar alternatives like stevia or monk fruit which has a lower impact on blood sugar.  

Frequently Asked Questions

Does sugar make your cold worse?

Typically, sugar won’t make your cold symptoms worse. However, it will weaken your body’s immune response and make it harder to fight off the infection. The symptoms may last longer—and, if the viruses or bacteria persist, possibly even worsen.

Does reducing sugar improve the immune system?

Reducing sugar can have a significant positive impact on the immune system. By removing the inflammation-causing, white blood cell-suppressing food from your diet, you give your immune system a fighting chance against disease and infection.

How long does it take for inflammation from sugar to decrease?

You can see positive changes in your internal inflammation improve in as little as a few weeks  after reducing sugar. However, the full benefits of a low-sugar diet typically take longer to present, and your body does take time (weeks or months) to adjust to less refined sugar and quickly available energy.

Resources

Harmful effects of high amounts of glucose on the immune system

Your Immune System and Diabetes

Dietary sugar lowers immunity and microbiota that protect against metabolic disease

Excessive intake of sugar: An accomplice of inflammation

Sugar and the Brain

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