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How Sugar Affects The Immune System

Updated: Jun 19, 2019

You’ve have planned a delightful weekend at an amusement park with your kids that includes a few sugary indulgences, or maybe you will go abroad and indulged in that local region’s desserts.

You’re driving or flying back when you suddenly feel achy, tired, drowsy, with an unpleasant feeling you might be coming down with a cold or the flu.

“Did eating too much sugar crash my immune system?” You wonder. “And if so, what can I do to boost the immune system and minimize its impact?”

Beyond immediate gratification, very few health effects of sugar are positive. Eating too much sugar can affect the brain and body, including increased risk for cavities, weight gain, cognitive decline, and increased risk for a disease.

Many of us eat too much sugar, far exceeding the recommended less than 10 percent of our total daily calories from added sugar.

“Some estimates from US government surveys say that the average American consumes 152 pounds of sugar and about 133 pounds of flour [which convert to sugar] annually,” says Mark Hyman, MD, in Food: What the Heck Should I Eat?.

Altogether, that’s more than three-quarters of a pound of sugar and flour for every American daily, which Hyman calls “a pharmacologic dose our bodies were not designed to handle.”

Sugar’s Impact on The Body

Sugar’s impact on your health and the immune system is a complex interplay of hormonal, metabolic, and immunologic processes that can severely threaten human health.

Some of that impact is immediate. Refined sugar can reduce how white blood cells performand increase inflammatory markers. In fact, obese people have fewer white blood cells with a reduced capability to fight infection.

But as these factors reveal, sugar’s impact on the immune system can also be cumulative and far-reaching.

Hormonal Balance

The hormonal effects of sugar and the immune system are complex, but insulin is a major player.

When you eat large amounts of sugar, your blood sugar increases. Insulin helps normalize those blood sugar levels, but over time, your cells become overwhelmed and resistant to the signals of this hormone.

We call this condition insulin resistance, which leads to type 2 diabetes and all of its related complications including impairing the immune system.  


Eating a little sugar can leave you wanting more sugar. In fact, studies suggest that sugar might be more addictive than cocaine.


Part of sugar’s addictiveness stems from its impact on your brain’s chemical messengers. Daily binging on sugar releases dopamine, associated with your brain’s reward center.

But that feeling doesn’t last — after the initial dopamine release comes the negative effects of sugar on the brain. Consuming food and beverages with refined sugar can trigger depressive symptoms.

Psychological Stress

Sugar can also impact long-term psychological health. Insulin sometimes over-compensates and pulls your blood sugar down too low, creating mood swings, fatigue, and mental fog that can make your day stressful.

Excessive sugar can also impact your adrenal glands, which produce cortisol. Research shows large amounts of sugar can keep this stress hormone chronically elevated and increase levels of visceral fat, the most dangerous kind of fat that sets the stage for type 2 diabetes and other complications.  

“Whenever your blood sugar level changes too fast, your adrenal glands release cortisol to pull it back up again,” says Alan Christianson, ND. “Unstable blood sugar can make you feel the same as you would feel when an event makes you angry, frustrated or frightened.”

That stress makes us gravitate towards pleasurable, palatable sugary foods, which only exacerbates psychological stress that weakens the immune system.

Nutrient Intake

Many foods that are high in refined sugar are low in nutrients that support a healthy immune system. Nutrient deficiencies can increase your risk for infections. Sugary, processed foods can also deplete nutrients from other foods.


Chronic, low-grade inflammation is a key factor for numerous diseases including cardiovascular disease, diabetes, and dementia. Sugar (especially sugar-sweetened beverages and soda) is one of those inflammation triggers.

Refined sugar breaks down into two simple sugars in your body: glucose and fructose. While nearly every cell can use glucose, only liver cells can metabolize fructose. Studies show fructose can increase inflammation while raising your stress hormone cortisol, which in turn increases belly fat.

Oxidative Stress

Free radicals are a byproduct of cellular metabolism. Your body’s antioxidant defenses can handle normal amounts. But under certain conditions, your defense system becomes overwhelmed, leading to what’s called oxidative stress.

Oxidative stress plays a major part in nearly every chronic and degenerative illness. Many variables can increase oxidative stress, including too much sugar.


Glycation occurs when a sugar molecule sticks to a protein molecule, inhibiting that protein molecule’s ability to perform its physiological function.

This can impact immune responses and contribute to disease. Glycation eventually leads to advanced glycation end products (with the appropriate acronym AGEs).

The body produces AGEs naturally as it processes sugar, and excessively high levels of AGEs can trigger the disease.


Research shows that obesity, chronic inflammation, and immune health are interrelated. Being overweight or obese increases inflammation, which makes your body hold onto excess weight and increases your risk for illness.  

Can Sugar Ever Be Healthy?

Consumers know sugar is bad. Always several steps ahead, manufacturers know how to disguise sugar as not-so-obvious ingredient names including agave nectar, palm sugar, and organic cane juice.

While they might suggest a healthier aura, these sugars essentially break down in your body the same as table sugar. Agave, frequently positioned as a healthier sweetener, is up to 90 percent fructose, which studies show contributes to diabetes and other health complications.  

“No matter what it’s called, sugar is sugar, and it can negatively affect your body in many ways,” says Locke Hughes on WebMD.  

One of the most powerful things you can do to boost the immune system is to minimize sugar, especially those that come from processed foods.

While a few natural sweetener alternatives including stevia can be healthy in small amounts, artificial sweeteners are often worse than sugar. One animal study found that sucralose (Splenda) induces liver inflammation and adversely impacts your gut microflora.

That’s a double whammy for your immune system — about 70 percent of your immune system exists in your gut, and your hardworking liver converts harmful toxins into harmless substances.

A sugar-free diet doesn’t mean you have to consume no sugar, but rather avoid refined sugar in processed foods.

Fruit, legumes, tubers like sweet potatoes, and even leafy or cruciferous vegetables contain some sugar. But they also come with dietary fiber, vitamins, minerals, antioxidants, and other nutrients that buffer sugar’s impact on your body.

How to Boost Your Immune System: 7 Ways to Minimize Sugar’s Impact