Published 9th June 2026
Does sugar increase inflammation?
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Research consistently links high intakes of added sugar with increased inflammation.
Added sugars found in soft drinks, sweets, and ultra-processed foods are the main concern, while natural sugars in whole fruits are not linked to increased inflammation.
When it comes to inflammation, your whole dietary pattern matters most.
Lifestyle factors such as sleep quality, physical activity, and stress management also play a significant role in regulating inflammation.
Inflammation is a vital immune response to infection or injury, but if it continues after the threat has passed, it can contribute to conditions such as heart disease, diabetes, and digestive disorders.
Sugar is often blamed for driving inflammation, yet the evidence is more nuanced than many headlines suggest, and not all sugars have the same effects.
Here, we explore the latest scientific evidence on sugar and inflammation, the biological mechanisms involved, the differences between added and natural sugars, and, most importantly, practical ways to reduce inflammation through diet and lifestyle.
A look at the evidence
A 2018 systematic review and meta-analysis of 13 controlled intervention studies found that dietary sugar intake, especially from sugar-sweetened beverages, is associated with raised C-reactive protein (CRP), one of the primary blood markers of inflammation.
Interestingly, a 2022 meta-analysis of 48 controlled trials involving 2,108 participants found that when sugar was swapped for another carbohydrate, but total calories were kept constant, there was no significant effect on inflammatory markers.
This suggests that the pro-inflammatory effect was most pronounced when sugar was added on top of a normal diet, pushing total energy intake up.
In other words, excess energy intake from sugar matters, not just sugar in isolation.
Recent research has further highlighted these risks. A 2025 systematic review of 45 studies found that high intake of added sugar is linked to a 66% increased risk of Crohn's disease and a 59% higher risk of ulcerative colitis.
For those consuming sugar-sweetened beverages, the risk for ulcerative colitis increased by 72%.
While these observational findings certainly don't prove that sugar is the sole cause, the consistency across the data is significant.
How might sugar trigger inflammation?
There is not one single mechanism by which sugar would trigger inflammation; several biological pathways may play a role:
Advanced glycation end products (AGEs)
When sugar reacts with proteins and fats in the bloodstream, it produces compounds called advanced glycation end products, or AGEs.
AGEs activate a receptor (RAGE) that triggers inflammatory signalling and generates oxygen species, which can, in turn, damage cells.
These interactions between AGEs and RAGE have also been linked to the development of diabetes, cardiovascular disease, and neurodegeneration.
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Insulin
Fructose is processed almost entirely by the liver. With large, regular amounts of fructose entering the liver, it starts converting the excess into fat.
Over time, this contributes to non-alcoholic fatty liver disease and the release of pro-inflammatory cytokines.
It also drives insulin resistance, where cells stop responding normally to insulin. Chronic insulin resistance generates further inflammatory signals, and the cycle feeds itself.
Gut
High sugar intake shifts gut bacteria away from species involved in immune regulation and toward pro-inflammatory species. Research in Frontiers in Cellular and Infection Microbiology found this pattern in mice fed high-fructose, high-fat diets.
A 2021 study in Nature Medicine from ZOE's PREDICT research, which involved deep metagenomic sequencing of 1,098 individuals, found that gut microbiome composition was predictive of inflammatory indices alongside blood glucose and blood lipid markers.
The gut bacteria associated with healthy dietary habits consistently overlapped with those associated with better cardiometabolic outcomes.
Sugar-heavy diets that are low in fibre and high in processed foods tend to produce the opposite microbiome profile.
Added sugar vs. natural sugar: Does it matter?
Sugar is not just one thing, and the form of sugar and how it’s consumed can make a difference to how it impacts your health.
Added sugars and sugar-sweetened beverages
This is where the clearest evidence is. Added sugars, primarily sucrose and high-fructose corn syrup, are in soft drinks, sweets, pastries, sauces, and most ultra-processed foods.
They can be hard to identify on labels, appearing under many names.
That's why we published a handy guide to spotting them.
Sugar-sweetened beverages are a particular concern because they're absorbed quickly and don't make you feel full.
Drinking 35 g of sugar in a can of cola doesn't make you feel full the way eating 35 g of sugar in a whole food would.
A review in Nature Reviews Endocrinology identified sugar-sweetened beverages as significant contributors to obesity and chronic disease, with inflammation as a key pathway.
Why whole fruit is different
The sugar in a whole apple does not have the same effect as the sugar in apple juice, let alone cola.
Whole fruit comes with fibre that slows absorption and feeds beneficial gut bacteria, plus polyphenols with well-documented anti-inflammatory properties. The food matrix matters.
High fruit and vegetable intake is associated with lower inflammatory markers in the research.
For instance, a 2018 meta-analysis in the American Journal of Clinical Nutrition found that fruit and vegetable intake decreased circulating levels of CRP.
The sugar in whole fruit isn't a concern. Stripping out the fibre changes the picture entirely, which is why juice is not as healthy as whole fruit.
What this tells us is that it's not sugar exactly, but sugar consumed without the plant compounds and fibre that normally accompany it in whole food.
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How much sugar is too much?
The WHO recommends keeping free sugars (added sugars plus those in fruit juice and honey) below 10% of total daily energy. For someone eating 2,000 calories, that's about 50 g, or 12 teaspoons.
Dropping to 5% (around 25 g, or 6 teaspoons) may bring additional benefit.
The American Heart Association sets tighter targets: 25g per day for women and 36 g for men from added sugars alone.
A single 330 ml can of cola has around 35 g. A flavoured yoghurt can have 15–20 g. A tablespoon of ketchup has about 4 g. It adds up faster than most people expect.
One piece of birthday cake isn't the issue. It's the baseline, what you're eating day in and day out, that moves the needle on inflammation.
What else in your diet affects inflammation?
Sugar is important, but it doesn't operate in isolation. Your broader dietary pattern is what the research shows is most important in the long run.
Foods linked to lower inflammatory markers include oily fish (for omega-3 fatty acids), olive oil, leafy greens, berries, nuts, legumes, and fermented foods.
Together, these form the core of the Mediterranean dietary pattern, the most rigorously studied anti-inflammatory dietary pattern we have.
Fibre feeds beneficial bacteria in your gut, which produce short-chain fatty acids that actively reduce inflammatory signalling.
A 2019 analysis in The Lancet drawing on 135 million person-years of data found that higher fibre intake was associated with a 15–30% reduction in all-cause and cardiovascular mortality.
Vegetables specifically show a direct signal. In 2021, a study by ZOE scientists was published in BMC Medicine . Including data from 986 healthy adults, it showed that higher vegetable intake was significantly associated with lower levels of white blood cells and inflammatory markers, including IL-6 and GlycA.
A fifth of the effect was mediated by the gut microbiome, specifically via a bacterium called Collinsella, which increases in numbers with increased intake of processed foods.
The finding didn't replicate in fruit, reinforcing that fibre and phytonutrient density, not sugar content, matter more.
Polyphenols, found in berries, tea, dark chocolate, and olive oil, have their own anti-inflammatory effects and support the gut microbiome.
If your diet is high in added sugar, it's often low in these compounds. That gap compounds the inflammatory issue.
Ultra-processed foods as a category also warrant attention. They're typically high in added sugars, refined carbohydrates, and industrial fats while being low in fibre.
A diet high in ultra-processed foods is associated with lower gut microbiome diversity, higher CRP levels, and greater chronic disease risk.
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Other lifestyle factors and inflammation
Sleep: Poor or short sleep raises inflammatory markers, including CRP and IL-6.
Chronically disrupted sleep activates the same inflammatory pathways that high-sugar diets do, which is one reason the two tend to compound each other.
Exercise: Regular moderate exercise is consistently anti-inflammatory. It reduces visceral fat (a major source of pro-inflammatory cytokines) and appears to directly suppress inflammatory signalling over time.
Intense exercise without adequate recovery can temporarily increase inflammation, but the long-term effects of regular activity are firmly protective.
Stress: Chronic psychological stress, over time, promotes a pro-inflammatory state. There's also good evidence that stress drives poorer food choices and that poorer food choices amplify stress responses.
Stress and poor diet often go hand in hand.
Smoking and alcohol: Both are pro-inflammatory. Smoking is one of the strongest dietary-independent predictors of elevated CRP.
Excessive alcohol raises markers like IL-6 and TNF-α, though the picture for moderate consumption is more complex.
Summary
Excess added sugar can impact the gut barrier, shift gut bacteria toward pro-inflammatory species, drive AGE formation, and contribute to insulin resistance and liver fat.
These mechanisms are interconnected and feed into chronic low-grade inflammation over time.
The strongest evidence points to sugar-sweetened beverages and to consistently high added-sugar intake.
Total energy intake plays a part, too: In controlled trials where sugar replaced other carbohydrates rather than adding to them, the inflammatory effect was much less clear.
Natural sugars in whole fruit and vegetables are not a concern. The research on fruit consumption and inflammation points firmly the other way.
Higher whole fruit intake is associated with lower inflammation levels.
Practical steps to reduce inflammation include reducing added sugar, especially from drinks, and building the rest of your diet around fibre-rich whole foods, polyphenols, and healthy fats and protein.
That combination does more for long-term inflammation than cutting any single ingredient on its own. Small, consistent changes over time are what the evidence actually supports.
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FAQs
Here are the answers to some commonly asked questions:
Does cutting sugar reduce inflammation?
Lower intake of added sugars, particularly from beverages, is associated with reduced CRP.
The effect is stronger when overall diet quality improves simultaneously. Simply cutting sugar while keeping everything else the same is unlikely to make a significant difference on its own.
How quickly does sugar affect inflammation?
A single high-sugar meal can raise blood glucose and trigger some oxidative stress within hours, which improves over time.
But the kind of sustained low-grade inflammation associated with disease risk builds over weeks and months of consistently high intake.
One meal doesn't move the needle. A habitual dietary pattern does.
Is sugar in whole fruit inflammatory?
No. Whole fruit contains fibre, water, vitamins, and polyphenols that change how sugar is absorbed and processed.
High fruit intake is consistently associated with lower levels of inflammatory markers in observational studies.
Which sugars are worst for inflammation?
The clearest evidence points to added sugars in liquid form, particularly sugar-sweetened beverages.
These are absorbed quickly without making you feel full, and they don’t contain the beneficial or protective compounds that come with whole foods.
