Sugar and Psoriasis: Does Diet Sugar Intake Matter?

Sugar's relationship with psoriasis has moved from folk wisdom to genuine epidemiological data in recent years. Here's what a major new cohort study, plus the broader research, actually shows.

The Key Study

A 2025 prospective cohort study using UK Biobank data — tracking a very large population over a median follow-up of 13.25 years — found that higher intake of total sugars, free sugars, and sucrose was associated with an increased risk of developing psoriasis. Comparing the highest to lowest intake groups, free sugar intake showed the clearest association (hazard ratio 1.22), while total sugars and sucrose showed smaller but still positive associations. Notably, people with both high genetic risk for psoriasis and high sugar intake had the highest overall risk — suggesting diet and genetics may compound each other rather than acting independently.

The same study found the opposite pattern for starch and fiber: higher intake of both was associated with a reduced risk of psoriasis (hazard ratios of 0.86 and 0.84 respectively for the highest intake groups) — a genuinely useful, actionable finding, since it points toward what to eat more of, not just what to avoid.

Why This Makes Biological Sense

Dietary sugar — particularly fructose — is metabolized differently than glucose and can promote synthesis of free fatty acids in the liver, which under the "lipotoxicity" theory can trigger inflammatory processes and oxidative stress. Separate research has specifically shown that free fatty acids play a critical role in exacerbating psoriasis-like skin inflammation, both in animal models and in psoriasis patients, where serum free fatty acid levels correlated with skin inflammation severity — independent of obesity.

An animal study published in the Journal of Investigative Dermatology found that genetically predisposed mice fed a high-sugar diet developed psoriasis and psoriatic arthritis, along with reduced gut bacterial diversity — and this happened even in mice that didn't become obese during the study, suggesting sugar's effect may operate independently of weight gain.

A Note on Mixed Evidence Elsewhere

It's worth being balanced here: not every study agrees on every detail. A 2018 study specifically testing low-glycemic-index diets found no measurable effect on inflammation, a reminder that glycemic index alone isn't necessarily the same variable as total sugar intake, and that dietary research in this space is still evolving.

What This Means Practically

• Reducing free sugar and sucrose intake has genuine, large-scale cohort evidence behind it as a psoriasis risk factor, not just theoretical plausibility
• Increasing fiber and complex carbohydrates (starch) appears protective in the same data — a positive, actionable dietary shift rather than just elimination
• This is about risk association, not a proven treatment — the UK Biobank study measured psoriasis incidence, not whether cutting sugar improves existing psoriasis severity, which is a related but distinct question
• This fits within broader evidence-based dietary patterns — our evidence-graded diet review covers the Mediterranean diet and weight loss, both of which naturally reduce free sugar intake as part of a broader pattern

Frequently Asked Questions

Does eating sugar cause psoriasis directly?

The evidence shows an association with increased risk, particularly in people with genetic predisposition — this isn't proof of direct causation for any individual, but it's a genuine, large-scale epidemiological signal worth taking seriously.

Will cutting sugar clear my existing psoriasis?

This specific question — sugar reduction as a treatment for existing psoriasis — has less direct trial evidence than the risk-association research discussed here, though it's a reasonable component of a broader anti-inflammatory dietary approach.

Next Steps

For the full evidence-graded picture on diet and psoriasis, see our complete diet review.

This article is for general educational purposes and is not a substitute for professional medical or nutritional advice.

Sources & References

• Association between carbohydrate intake and the risk of psoriasis: a prospective cohort study based on UK Biobank. PMC12465716
• Modulation of Dietary Fatty Acids in an Open-Label Study Improves Psoriasis and Dampens the Inflammatory Activation Status. PMC10097201
• Excessive intake of sugar: An accomplice of inflammation. PMC9471313