Does sugar cause inflammation?

Not in the trials we have, which were short and mostly in healthy adults. A 2022 meta-analysis of 64 controlled feeding trials in 4094 people found that sugars containing fructose did not raise C-reactive protein (CRP), a blood marker of inflammation, at any level of calorie control. When sugar was added on top of the diet, CRP fell slightly, by -0.18 mg/L (95% CI -0.33 to -0.03). The trials had a median length of 6 weeks, so what years of a high sugar diet do is unknown.

Myth. Eating sugar does not, by itself, push up inflammation markers in healthy adults over weeks. The largest meta-analysis of controlled trials found that, with certainty rated moderate to low for most comparisons, and two others found no sugar more inflammatory than another. The source of the sugar seems to matter more than the sugar.

What the trials found

Total sugar: no rise in CRP

The 2022 meta-analysis sorted its trials by how calories were handled. Sugar swapped for other carbohydrate at the same calories changed CRP by 0.07 mg/L (95% CI -0.08 to 0.22). Removing sugar changed it by 0.14 mg/L (95% CI -0.29 to 0.56), and letting people eat freely by -0.09 mg/L (95% CI -0.44 to 0.25). None of these reached significance. The two other inflammation markers measured, TNF-alpha and IL-6, did not move either. Most participants were healthy adults, some with overweight or obesity.

Which sugar does not matter much

Fructose has the worst reputation, and on this marker it has not earned it. A 2018 meta-analysis of 13 intervention studies in 1141 people found fructose raised CRP no more than glucose did, a difference of -0.03 mg/L (95% CI -0.52 to 0.46). High-fructose corn syrup against table sugar gave 0.21 mg/L (95% CI -0.11 to 0.53), also not significant. Certainty was low for both. A 2020 network meta-analysis of 38 randomized trials in 1383 people found that swapping fructose, glucose, sucrose or starch for one another at equal calories did not change CRP, on very low to moderate certainty evidence.

Single trials point the same way. In a crossover trial, 24 adults drank fructose, glucose or high-fructose corn syrup drinks supplying 25 percent of their calories for 8 days each, and CRP and IL-6 did not differ between the sugars. That trial had no sugar-free comparison. A 2026 crossover trial filled that gap in 39 healthy young adults: 66 g of sucrose a day for 14 days left CRP no different from saccharin or stevia, though triglycerides were higher after sucrose.

The food the sugar comes in

Here the 2022 review found its only clear movements. Fruit added to the diet, mostly berries at a median of 3.8 percent of energy, lowered CRP by 0.50 mg/L (95% CI -0.75 to -0.25) and TNF-alpha by 0.89 pg/mL across 9 and 3 trials. Fruit brings fiber and polyphenols with its sugar, so this is a finding about fruit.

Unsettled. Sugary drinks are the one source with a signal in the other direction. In six substitution trials, mixed diets that included sugar-sweetened beverages raised CRP by 0.64 mg/L (95% CI 0.12 to 1.17). The six trials disagreed with each other a lot, and the rise stopped being significant when single trials were taken out. Treat it as a warning sign worth testing.

What observational studies add

In US national survey data on 6856 adults, heavy sugary drink drinkers had CRP 0.26 mg/L higher than non-drinkers, and when the analysis was split by body weight, the link appeared only in people with obesity. That is one measurement in time, and people with higher CRP may drink differently for other reasons. A 2025 meta-analysis of 45 observational studies linked high added sugar intake with 1.66 times the odds of Crohn's disease and 1.59 times the odds of ulcerative colitis. Most of those studies asked people with the disease to recall their past diet, which invites recall bias. Odds are odds here, and none of it shows cause.

Who should be careful

The calm answer above is about people without chronic disease. In the 2022 meta-analysis, trials in people with chronic kidney disease, non-alcoholic fatty liver disease or irritable bowel syndrome showed CRP rising on fructose-containing sugars, while trials in everyone else showed no effect. That came from a subgroup analysis across few trials, and the review gives no size for it.

Not for everyone. Three other groups show the same direction in weaker data. In a crossover trial of 55 adults taking 50 g of sugar a day for 2 weeks, high-sensitivity CRP rose with honey, sucrose and corn syrup alike in the 27 with impaired glucose tolerance, with no sugar-free arm to compare. In 1133 people who already had inflammatory bowel disease, drinking 7 or more sugary drinks a week went with 1.6 times the odds of raised CRP, in self-reported data. In the US survey, the sugary drink link with CRP appeared only in people with obesity. If you have one of these conditions, the trials in healthy people do not cover you.

What expert bodies say

WHO strongly recommends that adults and children keep free sugars below 10 percent of daily energy and suggests going below 5 percent. The limit is for free sugars and leaves out sugar inside whole fruit, vegetables and milk. WHO says plainly that these limits rest on evidence about body weight and tooth decay. We found no major agency that sets a sugar limit on grounds of inflammation.

How we searched

What would change this answer

• Longer trials. The best evidence lasted a median of 6 weeks and measured blood markers. We found no randomized trial of cutting sugar with an inflammatory disease as the outcome.
• Trials of sugary drinks on their own. The one signal of harm in controlled trials comes from six mixed trials that did not hold up when single trials were removed.
• Trials in people with chronic kidney disease, fatty liver, bowel disease or impaired glucose tolerance. The subgroups that showed a rise are small, and they are where the answer may differ.
• A newer synthesis. We found no meta-analysis of sugar and inflammation markers published from 2024 to 2026.

More on sugar as a food is on the sugar page.

Sources

1. ev-sgi-01 · Meta-analysis or systematic review · systematic review and meta-analysis of controlled feeding trials · n = 4094
   Total fructose-containing sugars decreased CRP in addition trials and had no effect in substitution, subtraction or ad libitum trials.
   
   Who: predominantly healthy adults of mixed weight or with overweight or obesity, controlled feeding trials of 7 days or more, median 6 weeks
   Effect: CRP addition trials -0.18 mg/L (95% CI -0.33 to -0.03, 37 trials); substitution +0.07 mg/L (95% CI -0.08 to 0.22); subtraction +0.14 mg/L (95% CI -0.29 to 0.56); ad libitum -0.09 mg/L (95% CI -0.44 to 0.25); no effect on TNF-alpha or IL-6
   Certainty: GRADE moderate to low for most analyses; most participants healthy; follow-up median 6 weeks.
   Nutrients, 2022 · checked 2026-10-06 · we read the abstract
2. ev-sgi-02 · Meta-analysis or systematic review · systematic review and meta-analysis of controlled feeding trials · n = 6 trials
   The evidence provides good indication that mixed sources that contain SSBs increase CRP, while most other food sources have no effect with some sources (fruit, 100% fruit juice, sweetened soy beverage or dark chocolate) showing decreases, which may be dependent on energy control.
   
   Who: substitution trials of mixed food sources including sugar-sweetened beverages
   Effect: CRP +0.64 mg/L (95% CI 0.12 to 1.17), I2 82.9%; significance lost when single trials were removed
   Certainty: Six heterogeneous trials; the increase did not survive leave-one-out sensitivity analysis.
   Nutrients, 2022 · checked 2026-10-06 · we read the abstract
3. ev-sgi-03 · Meta-analysis or systematic review · systematic review and meta-analysis of controlled feeding trials · n = 9 trials (CRP), 3 trials (TNF-alpha)
   In addition trials, fruit at a median dose of 3.8%E (ranging from 1.6%E to 10%E) led to a small important reduction in CRP (−0.50 mg/L) and TNF-α (−0.89 pg/mL), while sweets and desserts as dark chocolate at a dose of 1.1%E led to a large reduction in IL-6 (−8.79 pg/mL).
   
   Who: addition trials of fruit, mostly berries, median dose 3.8% of energy
   Effect: CRP -0.50 mg/L (95% CI -0.75 to -0.25); TNF-alpha -0.89 pg/mL (95% CI -1.58 to -0.20)
   Certainty: Fruit brings fiber and polyphenols with its sugar; the effect is about the food, not the sugar.
   Nutrients, 2022 · checked 2026-10-06 · we read the fulltext
4. ev-sgi-04 · Meta-analysis or systematic review · systematic review and meta-analysis of controlled feeding trials · n = —
   There was significant effect modification by health status (trials of participants with other chronic conditions, such as chronic kidney disease, non-alcoholic fatty liver disease and irritable bowel syndrome, showed increases while trials with other participant types showed no effect)
   
   Who: trial participants with chronic conditions such as chronic kidney disease, non-alcoholic fatty liver disease and irritable bowel syndrome
   Effect: significant effect modification by health status in subgroup analysis of CRP; size per subgroup not stated in the text
   Certainty: Subgroup analysis across few trials; hypothesis-generating.
   Nutrients, 2022 · checked 2026-10-06 · we read the fulltext
5. ev-sgi-05 · Meta-analysis or systematic review · systematic review and meta-analysis of controlled feeding trials · n = 64 trials
   The certainty of evidence was moderate-to-low for the majority of analyses.
   
   Who: 64 controlled feeding trials of fructose-containing sugars
   Effect: GRADE moderate to low for the majority of analyses
   Certainty: Short trials of biomarkers, not of inflammatory disease.
   Nutrients, 2022 · checked 2026-10-06 · we read the abstract
6. ev-sgi-06 · Meta-analysis or systematic review · systematic review and meta-analysis of controlled intervention studies · n = 1141
   The limited evidence available to date does not support the hypothesis that dietary fructose, as found alone or in HFCS, contributes more to subclinical inflammation than other dietary sugars.
   
   Who: adults or adolescents in controlled intervention studies of 2 weeks or more with 20 or more participants
   Effect: hsCRP fructose vs glucose MD -0.03 mg/L (95% CI -0.52 to 0.46), I2 44%; HFCS vs sucrose MD 0.21 mg/L (95% CI -0.11 to 0.53)
   Certainty: NutriGrade low for both comparisons; only CRP had enough studies to pool.
   Nutrients, 2018 · checked 2026-10-06 · we read the abstract
7. ev-sgi-07 · Meta-analysis or systematic review · systematic review and network meta-analysis of randomized controlled trials · n = 1383
   No significant effects were observed for TG, HbA1c, CRP, ALT, and AST.
   
   Who: participants in isocaloric substitution RCTs of dietary sugars and starch
   Effect: no significant effect on CRP for any sugar or starch exchange
   Certainty: CINeMA certainty very low to moderate.
   Am J Clin Nutr, 2020 · checked 2026-10-06 · we read the abstract
8. ev-sgi-08 · Randomized controlled trial(s) · randomized double-blind crossover controlled trial · n = 24
   Fasting plasma concentrations of C-reactive protein and IL-6 did not differ significantly at the end of the 3 diet periods.
   
   Who: normal-weight to obese adults without fructose malabsorption
   Effect: no significant difference in fasting CRP or IL-6 after three 8-day periods; intake 116% of energy needs
   Certainty: Compares sugars with each other, no sugar-free control; 8-day periods.
   Am J Clin Nutr, 2016 · checked 2026-10-06 · we read the abstract
9. ev-sgi-09 · Randomized controlled trial(s) · randomized crossover trial · n = 55
   An increase in high-sensitivity C-reactive protein (hsCRP) was observed in the IGT group in response to all sugars.
   
   Who: 28 adults with normal glucose tolerance and 27 with impaired glucose tolerance
   Effect: hsCRP increase in the impaired glucose tolerance group with all three sugars; no effect on IL-6
   Certainty: No sugar-free control arm; within-group pre-post change.
   J Nutr, 2015 · checked 2026-10-06 · we read the abstract
10. ev-sgi-10 · Randomized controlled trial(s) · randomized double-blind crossover trial · n = 39
    Triglycerides were higher after sucrose than saccharin (p < 0.05), while no differences were seen for cholesterol, apolipoproteins, or CRP.
    
    Who: healthy normal-weight adults
    Effect: no difference in CRP between sucrose (66 g/day), saccharin and steviol glycosides after 14 days; triglycerides higher after sucrose
    Certainty: Short, healthy young adults.
    Nutrients, 2026 · checked 2026-10-06 · we read the abstract
11. ev-sgi-11 · Observational data · systematic review and meta-analysis of observational studies · n = 523,730 (Crohn's), 787,228 (ulcerative colitis)
    Pooled analysis showed that added sugar intake was associated with increased risk of Crohn's disease (OR 1.66; 95% Cl 1.21-2.29; n = 523,730; 14 studies) and ulcerative colitis (OR 1.59; 95% CI 1.25-2.02; n = 787,228; 18 studies).
    
    Who: participants of 11 prospective and 34 retrospective studies
    Effect: Crohn's disease OR 1.66 (95% CI 1.21 to 2.29, 14 studies); ulcerative colitis OR 1.59 (95% CI 1.25 to 2.02, 18 studies)
    Certainty: Mostly retrospective (recall bias); association, not cause.
    United European Gastroenterol J, 2025 · checked 2026-10-06 · we read the abstract
12. ev-sgi-12 · Observational data · cross-sectional analysis of national survey data · n = 6856
    Medium and heavy SSB consumers with obesity had 0.58 and 0.50 higher CRP than non-SSB consumers, respectively (P = 0.014 and 0.013).
    
    Who: US adults, NHANES 2007-2010
    Effect: CRP +0.26 mg/L in heavy SSB drinkers; with obesity +0.58 (medium) and +0.50 mg/L (heavy); no association in normal weight or overweight
    Certainty: Single time point, two 24-hour recalls; reverse causation possible.
    Int J Public Health, 2020 · checked 2026-10-06 · we read the abstract
13. ev-sgi-13 · Observational data · prospective cohort study · n = 1133
    In terms of disease severity and inflammatory biomarkers, high SSB consumption was associated with increase odds of elevated erythrocyte sedimentation rate (odds ratio 2.04, 95% CI 1.31 to 3.18), elevated C-reactive protein level (odds ratio 1.60, 95% CI, 1.07-2.37), eosinophilia (odds ratio 1.88, 95% CI 1.06 to 3.335), and monocytosis (odds ratio 1.81, 95% CI 1.18 to 2.79) when compared with low SSB consumption after adjusting for baseline differences.
    
    Who: adults with Crohn's disease or ulcerative colitis at a US tertiary center
    Effect: elevated CRP OR 1.60 (95% CI 1.07 to 2.37); elevated ESR OR 2.04 (95% CI 1.31 to 3.18); hospitalization HR 1.55 (95% CI 1.06 to 2.27)
    Certainty: Self-reported intake; confounding by overall diet possible.
    J Acad Nutr Diet, 2022 · checked 2026-10-06 · we read the abstract
14. ev-sgi-14 · Position of an expert body · WHO guideline · n = —
    In both adults and children, WHO recommends reducing the intake of free sugars to less than 10% of total energy intake2 (strong recommendation). WHO suggests a further reduction of the intake of free sugars to below 5% of total energy intake (conditional recommendation3).
    
    Who: adults and children
    Effect: free sugars <10% of energy (strong), <5% (conditional)
    Certainty: Upper limit for intake; applies to free sugars, not sugars inside whole fruit, vegetables or milk.
    WHO, 2015, Guideline: sugars intake for adults and children · checked 2026-10-06 · we read the section
15. ev-sgi-15 · Position of an expert body · WHO guideline · n = —
    These recommendations were based on the totality of evidence reviewed regarding the relationship between free sugars intake and body weight (low and moderate quality evidence) and dental caries (very low and moderate quality evidence).
    
    Who: adults and children
    Effect: evidence base: body weight (low and moderate quality), dental caries (very low and moderate quality)
    Certainty: No major agency sets a sugar limit on inflammation grounds.
    WHO, 2015, Guideline: sugars intake for adults and children · checked 2026-10-06 · we read the section