Does Sugar Cause Acne? What the Trials Show
Several trials found low glycemic eating improved acne. A pooled analysis found nothing. Both are true, and here's how to read that.
This is one of the more genuinely interesting evidence questions in nutrition, and most writing on it picks a side.
The mechanism, which is plausible
High glycemic food raises insulin, and insulin raises insulin-like growth factor 1 (IGF-1). IGF-1 stimulates sebum production and skin cell proliferation — both central to how acne forms. It also reduces sex hormone binding globulin, leaving more free androgens circulating, and androgens drive sebum too.
That's a coherent chain, and it's why the question gets asked at all.
What the trials found
Positive results, repeatedly. A 12-week randomized trial in 43 young men found significantly greater reduction in lesion counts on a low glycemic load diet than on a conventional one. A 10-week Korean randomized trial in 32 patients found significant clinical improvement in both inflammatory and non-inflammatory lesions — and, notably, biopsies showed reduced sebaceous gland size and decreased inflammation. A two-week trial in 66 adults found a low GI/GL diet reduced IGF-1.
That last one matters because it demonstrates the mechanism operating, not just an outcome.
The complication
A recent meta-analysis pooling the available studies found no significant association between glycemic load or glycemic index and acne, with high heterogeneity between studies and moderate certainty of evidence.
So individual trials are positive and the pooled estimate is null. That's not a contradiction so much as a signal: the trials are small, they differ in design and population, and pooling them washes out the effect.
Another review reached a middle position — describing a modest but significant proacnegenic effect of high glycemic index and load.
How I'd read it
The mechanism is well characterized, the trials are consistently positive, and the pooled analysis is not. That combination usually means a real but modest effect that small studies detect unevenly.
Which makes this worth trying and not worth promising. If you have acne, several weeks of lower glycemic eating is a low-risk experiment with a plausible mechanism and some trial support. It is not a treatment, and it should not replace dermatological care.
What the trials actually did
Worth knowing, because "eat low GI" is vague. The intervention in the positive trials was roughly: 25% of energy from protein, 45% from low glycemic carbohydrate, with an emphasis on unprocessed food.
That's higher in protein than most people eat and it's the same shape as everything else on this site.
On dairy
You'll see this raised alongside. The evidence is mixed and may depend on population and sex. Skimmed milk appears more implicated than whole milk or cheese, which is an odd finding and not well explained. I wouldn't act strongly on it.
Try this week: if you want to test it, give it eight weeks rather than two. Skin turnover is slow and shorter trials mostly measure blood markers rather than lesions.
Education, not medical advice. Persistent or scarring acne should be seen by a dermatologist.
Sources
- Smith RN, Mann NJ, Braue A, et al. The effect of a high-protein, low glycemic-load diet versus a conventional, high glycemic-load diet on biochemical parameters associated with acne vulgaris: a randomized, investigator-masked, controlled trial. *J Am Acad Dermatol* 2007 View source
- Kwon HH, Yoon JY, Hong JS, et al. Clinical and histological effect of a low glycaemic load diet in treatment of acne vulgaris in Korean patients: a randomized, controlled trial. *Acta Derm Venereol* 2012 View source
- Burris J, Shikany JM, Rietkerk W, Woolf K. A low glycemic index and glycemic load diet decreases insulin-like growth factor-1 among adults with moderate and severe acne. *J Acad Nutr Diet* 2018 View source