For decades, traditional dermatology maintained that acne had no significant connection to diet: "eat chocolate or pizza, it makes no difference." Research over the past 20 years has overturned this position. Not entirely: genetics, hormones, and skin microbiota remain the primary factors. But diet modifies the hormonal and inflammatory environment in which acne develops. The evidence is now sufficient to say that diet is a relevant modifiable factor in acne management.

The mechanism: how sugar and milk fuel acne

Acne vulgaris is caused by four reinforcing factors: excess sebum production (oily secretion), pilosebaceous follicle obstruction, proliferation of Cutibacterium acnes (opportunistic bacteria), and inflammatory response. Diet influences these mechanisms through insulin and IGF-1. High-glycemic carbohydrates cause spikes in insulin and IGF-1 (insulin-like growth factor 1). IGF-1 directly stimulates sebaceous glands to produce more sebum and increases keratinocyte proliferation (responsible for follicular obstruction). Insulin increases available testosterone by reducing SHBG. The result: more sebum, more obstruction, more inflammation.

High-glycemic diet and acne: clinical evidence

Three Australian studies conducted by Dr. Neil Mann (RMIT University) showed that a low-glycemic diet significantly reduces acne lesions compared to a high-glycemic diet in adolescents and young adults with moderate-to-severe acne. The reduction in lesion count was 23-27% after 12 weeks. The low-glycemic diet also improved insulin sensitivity and reduced IGF-1 levels. These studies provided the first randomized clinical evidence of the diet-acne link.

Milk and dairy: the hormonal connection

Cow's milk contains natural growth hormones (bovine IGF-1, pregnancy milk hormones) and insulinotropic peptides (whey protein, casein) that stimulate insulin and IGF-1 production in the body. A Harvard School of Public Health study (Adebamowo et al., 2006) of 47,355 women showed a significant association between skim milk consumption (more than whole milk) and acne. Skim milk has more whey protein than whole milk (fat has been removed, leaving more room for protein): this could explain its stronger association with acne. Subsequent meta-analyses confirm the association between dairy consumption (especially milk and cottage cheese) and acne.

Chocolate and acne: the research verdict

The old myth "chocolate causes acne" was ridiculed for decades. Then more precise studies showed that milk chocolate (high in sugar and dairy) is associated with worsening acne, while 85% dark chocolate is not. Cacao isn't the problem: it's the sugar and dairy in milk chocolate. Pure cacao actually has antioxidant effects. The conclusion: 85%+ dark chocolate is acceptable, milk chocolate and hazelnut spreads should be limited.

Omega-3s and inflammatory acne

Acne is fundamentally an inflammatory disease. Omega-3 EPA and DHA reduce the synthesis of inflammatory mediators that amplify the acne response. A 2014 Korean study (Kim et al.) showed a 40-42% reduction in inflammatory acne lesions with omega-3 supplementation (2g EPA+DHA daily for 10 weeks) compared to placebo. It's not a first-line treatment, but it's concrete anti-inflammatory support for moderate inflammatory acne.

Gut microbiota and acne

The gut-skin axis is an emerging field. Studies show that people with acne have less diverse gut microbiota and greater intestinal permeability compared to controls. Bacterial lipopolysaccharide (LPS) that leaks through the permeable intestine stimulates systemic inflammation that can manifest on the skin. A diet rich in fiber and fermented foods for the microbiota could reduce skin inflammation through this mechanism.

The anti-acne diet: what to eliminate for one month

To assess the impact of diet on your acne, follow this elimination protocol for 4 weeks: no cow's milk (replace with unsweetened oat or soy milk), no fruit juices or sugary drinks, no industrial sweets and packaged cookies, no white bread and refined cereals. Keep everything else. Note your lesions weekly (photograph under standard lighting conditions). If after 4 weeks you notice improvement, you've identified your dietary triggers. Then reintroduce one food at a time to pinpoint the specific culprit.

The diet to follow if you have acne

Prioritize: whole grains instead of refined (lower glycemic index), legumes (protein but low glycemic index), non-starchy vegetables in abundance, whole fruit (not juices), fatty fish 2-3 times a week (anti-inflammatory omega-3s), pumpkin seeds and nuts (essential zinc for skin and reducing acne inflammation), green tea (antioxidant, mildly anti-androgenic), extra virgin olive oil. Limit: skim milk and cottage cheese, high-glycemic foods, sweets and snacks, sugary drinks, alcohol (increases androgen production).

Zinc for acne: the supplement with the best evidence

Zinc is the nutrient with the best clinical evidence in acne after medications. Meta-analyses show a 49% reduction in inflammatory lesions with zinc acetate or gluconate (30-45 mg elemental zinc daily). The mechanism: reduced sebum production, antibacterial effect against C. acnes, reduced inflammation. Less effective than topical or systemic tetracycline, but with a superior safety profile for long-term use. Take it with meals (reduces nausea). Dietary sources of zinc to include: pumpkin seeds, oysters, lean meat, legumes.