You likely consume it in different forms every day, but nutritional scientists learned it can elicit a strong immune response.
Chronic inflammation is a key contributor to a range of life-threatening conditions, from cardiovascular disease and cancer to diabetes and dementia. Previous research indicates that “chronic inflammatory diseases are the most significant cause of death in the world”—a factor that experts warn “is anticipated to increase persistently” in the U.S. over the next 30 years.
The good news? A growing body of research suggests that what we eat can shape our immune systems and inflammation levels—and suggests that consuming certain foods more consciously can ultimately reduce our risk of chronic illness and premature death.
When a group of Austrian nutrition researchers at the University of Vienna looked at the impact of sugar on inflammation, they found that one type was especially likely to quietly spike your levels. That September 2025 research reports that fructose intake can make immune cells more reactive to bacterial toxins, increasing the body’s inflammatory response even after short-term consumption.
The study, led by Ina Bergheim, PhD, and published in the journal Redox Biology, focused on monocytes, a type of white blood cell that plays a frontline role in immune defense. In two randomized trials involving healthy adults, participants consumed beverages sweetened with either fructose or glucose. The difference was striking: fructose, but not glucose, made the receptors on these blood cells react more intensely to bacterial toxins.
As Dr. Bergheim explains, increasing the number of toxin-sensing receptors “means that the inflammatory response increased,” shifting the reaction from protective to potentially harmful.
Notably, this effect was seen even in healthy people after relatively short-term fructose intake. That finding raises concerns about frequent exposure to fructose, especially from sugary drinks and sweets, which deliver large amounts quickly.
The researchers stress that the implications may be even greater for people with underlying metabolic conditions, such as type 2 diabetes or fatty liver disease. These individuals already face chronic low-grade inflammation, and heightened immune sensitivity could further increase infection risk.
Though the study does not elaborate on common sources of fructose, Mayo Clinic experts explain that fructose occurs naturally in fruit, fruit juice, some vegetables, and sweeteners like honey. It’s also part of table sugar (sucrose) and is widely used as high-fructose corn syrup in processed foods and drinks.
Ingredients like high-fructose corn syrup, agave, honey, molasses, coconut sugar, and invert sugar are common sources of fructose. But according to nutrition experts from the University of Virginia, there are some lesser-known culprits, too. High-fructose fruits include watermelon, apples, applesauce, dried fruit, grapes, kiwis, lychees, and more. Foods like ketchup, sweet corn, and tomato sauce are also higher in fructose, but tend to fly under the radar.
While more research is needed to understand the long-term effects of fructose on inflammation, the current evidence suggests that high fructose consumption doesn’t just affect metabolism—it may also prime the immune system toward inflammation. Limiting fructose-heavy foods and beverages could help keep immune responses better balanced, and for everyday health, limiting your overall sugar intake is best.
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