Many people suffer from acne during puberty and adulthood. It is often said that some foods, like chocolate, can aggravate acne. Is there any truth to this – can diet really affect acne?

We asked five experts in dermatology, acne, and microbiology if diet can make acne worse; here is what they said.

What is acne?

Acne is a skin condition where hair follicles under the skin become clogged and can cause oiliness and spots. It most commonly affects younger people and can appear on the face, back, and chest.

How do we know whether diet makes acne worse?

There are multiple ways to study the relationship between diet and acne. Dr Gregory Delost, an expert in dermatology, describes a "systematic review between January 2009 and April 2020, [in which] the authors evaluated 42 observational studies and 11 interventional clinical trials and found multiple dietary factors associated with acne".

'Observational studies' means studies which simply compare two groups of people, in this case, people who have different diets. 'Interventional clinical studies' means studies where groups of people are asked to change their diet and the effect on their acne is measured.

Whilst overall the review concluded that there is an association between acne and diet, the interventional studies found a weaker link than the observational ones.

Each study comes with its own caveats. For example, some of the observational studies depended on people keeping a food diary.

Dr Delost says, "Nutritional research relies heavily on dietary recall, which is fraught with limitations, bias, and confounding variables as people tend to underreport 'bad' foods and overreport 'good' foods, while not paying close enough attention to ingredients and portions. Some critics of diet-based studies even go as far to claim that they do not follow the scientific method and should be regarded as pseudoscience."

Which foods are linked to acne?

Professor Gabriella Fabbrocini, an expert in acne from Naples University in Italy, says "High glycemic load diet and frequent dairy consumption, in particular total and skim milk, are the leading factors in establishing the link between diet and acne."

High glycemic load (GL) means foods with carbohydrates that are broken down quickly in the body. These include sugary foods and drinks, white bread, and rice.

Dr Delost adds, "Acne-promoting factors include high GL food, dairy products, fatty food, and chocolate, whereas acne-protective factors include fatty acids as well as fruit and vegetable intake."

How might diet lead to acne?

Dr Jerry Tan, a dermatologist from Western Ohio University, says "High glycemic index foods can elevate insulin and insulin-like growth factor 1 levels. Both these hormones can increase sebum excretion and change components of sebum to ones that are more pro-inflammatory".

Sebum is an oily substance made by sebaceous glands in the skin.

What other factors affect acne?

Dr Kelly Haas, an expert in skin microbiology from Massachusetts University, says "Acne pathophysiology is multifactorial (and largely still unknown), so dietary changes may not work for all cases."

Acne is associated with hormone levels which can vary during puberty, menstrual cycles, and pregnancy. It is also well as genetics and reactions to medications or cosmetic products.

Takeaway: Although more research is needed, diet may be associated with acne.

Based on 5 expert answers from this question: Can diet make acne worse?

This expert response was published in partnership with independent fact-checking platform Subscribe to their weekly newsletter here.