Diet and Acne — What Science Really Says About the Link Between Food and Skin

For decades, dermatologists repeated the same line: “diet has no effect on acne.” That position began to shift around 2005, when new epidemiological and interventional studies emerged. Today we know that a link between diet and acne does exist — but it is far more nuanced than the headlines on social media suggest.

Glycaemic index and glycaemic load — the strongest evidence

Of all dietary factors, it is the glycaemic index (GI) and glycaemic load (GL) that have the best-documented effect on acne. The mechanism is relatively clear: high-GI meals cause a rapid rise in blood glucose, which triggers a surge of insulin. Insulin, in turn, stimulates the production of IGF-1 (insulin-like growth factor 1), which:

• Increases sebum production in the sebaceous glands.
• Stimulates the proliferation of keratinocytes (skin cells), leading to clogged pores.
• Activates the mTORC1 pathway — a key regulator of cell growth.

A 2015 Cochrane systematic review analysed the available randomised controlled trials (RCTs). The findings indicated that a low-glycaemic diet may reduce the number of acne lesions, although the authors stressed the limited methodological quality of many studies. One of the better trials (Smith et al., 2007, American Journal of Clinical Nutrition) showed that a 12-week low-glycaemic diet reduced the number of acne lesions by 23.5% compared with the control group. Check the details in our ingredient encyclopaedia.

In practice, this means cutting back on white bread, sweets, sugary drinks, white rice and processed foods — in favour of wholegrain products, vegetables, protein and healthy fats.

Dairy — controversy and the IGF-1 mechanism

The link between dairy and acne is plausible but less well proven than that of the glycaemic index. The largest observational studies (Adebamowo et al., 2005, 2006, 2008 — Nurses' Health Study II) found a positive correlation between milk consumption (especially skimmed milk) and the risk of acne in women and teenagers.

The proposed mechanism involves the IGF-1 naturally present in cow's milk. Skimmed milk may paradoxically show a stronger association than full-fat milk, because the skimming process alters the proportions of whey proteins — and these can further stimulate insulin production.

It is important, however, to stress some significant limitations:

• Most of the data comes from observational studies, which do not prove causation.
• There is a lack of large, well-designed interventional studies (RCTs).
• Yoghurt and fermented cheeses may have a different effect than liquid milk.

Complete elimination of dairy is not recommended by most dermatological societies — it is a matter of individual observation.

Chocolate — myth or something more?

The myth of chocolate causing acne has a long history, but the scientific evidence is weak and inconclusive. The classic study by Fulton et al. (1969) found no link — but it had serious methodological flaws (a small sample and a short duration).

More recent, small studies (Caperton et al., 2014; Vongraviopap and Asawanonda, 2016) suggest that 100% cocoa may slightly increase the number of acne lesions in predisposed individuals. The problem is that these studies involved only a dozen to a few dozen people and lasted 1–4 weeks.

If chocolate has any effect at all, it is probably not through the cocoa itself, but through the high sugar and fat content of milk chocolate — which brings us back to the glycaemic mechanism. Dark chocolate (>70% cocoa) has a low GI and is a less likely culprit.

Zinc — a moderate benefit

Zinc is a trace element with proven anti-inflammatory and keratinisation-regulating properties. The meta-analysis by Yee et al. (2020) in Dermatologic Therapy confirmed that acne patients often have lower serum zinc levels than healthy individuals.

Zinc supplementation at a dose of around 30 mg/day (as zinc gluconate or zinc picolinate) has shown moderate effectiveness in reducing inflammatory lesions — but the effects are more modest than those of antibiotics or retinoids. Zinc works better as a supplement to dermatological treatment rather than as a standalone therapy.

Important: long-term zinc supplementation at high doses (>40 mg/day) can lead to copper deficiency. Before starting supplementation, it is worth consulting a doctor and testing your blood zinc level.

Omega-3 — an anti-inflammatory effect

Omega-3 fatty acids (EPA and DHA) have an anti-inflammatory effect by inhibiting pro-inflammatory prostaglandins and leukotrienes. Acne is an inflammatory disease, so in theory omega-3 should help.

A pilot study by Rubin et al. (2008) showed improvement in patients with inflammatory acne after two months of EPA supplementation. However, the evidence base is still too small to draw firm recommendations. Omega-3 will certainly do no harm — and offer many other health benefits — but they will not replace dermatological treatment.

You can read more about omega-3 and the skin in our skincare guide.

Summary — what to do in practice?

• A low-glycaemic diet has the strongest evidence — it is worth considering as support for treatment.
• Dairy — observe your individual response; do not eliminate it preventively.
• Chocolate — probably not a problem if it is dark and eaten in moderation.
• Zinc and omega-3 — may help, but will not replace a visit to a dermatologist.

Diet is one of many factors that influence acne — alongside genetics, hormones, stress and skincare. If you are struggling with persistent acne, consult a dermatologist, who will choose the right treatment. Check the ingredients of your cosmetics with the PurScore search engine — make sure they do not contain comedogenic ingredients.