Plagued by acne? Then you’ve probably wondered whether eating junk food gives you spots. Until now, the accepted thinking was that this was a myth, the sort of wishy-washy warning that a mother might resort to in an attempt to encourage her teenage children to eat more healthily. Before you grab a bag of crisps, however, it is worth noting the results of a study published recently in the American Journal of Clinical Nutrition. Scientists now believe it is not a particular type of food – such as pizza, chips or chocolate – that is to blame for triggering acne, but rather the typical western diet as a whole.

This thinking is based on a study conducted by nutritionists at the Royal Melbourne Institute of Technology in Australia, who followed two groups of young males, aged 15-25, with acne. Half of them followed their regular diet, which included plenty of processed foods with a high glycaemic index (GI) – the type of diet that is typical among westerners – while the rest were given a low-GI diet of whole grains, lean meat, fish and plenty of fruit and vegetables.

After 12 weeks, the low-GI group showed a measurable decrease in their acne, with 51% fewer pimples than when they embarked on the programme. “That is a better result than you would see from using a topical acne solution,” says Professor Neil Mann, who led the study. A high-GI diet raises levels of insulin and an insulin-like growth factor, IGF-1, which increases production of the male hormone testosterone. This, in turn, triggers the overproduction of sebum, the greasy substance that blocks pores and causes spots. “A diet rich in processed foods pushes glucose and insulin levels higher, exacerbating this problem,” Mann says. The trial was small, and more thorough investigation is necessary; however, it is the latest to provide evidence that diet is influential in causing acne.

It has always been a contentious issue. As long ago as 1969, studies seemed to prove that eating chocolate had no effect on the incidence of acne. Then followed research showing that peanuts, milk and cola did not have much influence on the condition, either, and the case for acne being triggered by food virtually fell apart. In fact, dark 70%-cocoa chocolate, a relatively low-GI food because of its low fat and protein content, is far from the worst food for acne-sufferers. Some researchers have even hinted that, because of the antiinflammatory properties of the flavonoids in cocoa, a bar of the dark stuff might even alleviate acne.

It is too early for the official advice to change, but dermatologists are coming round to the idea that a poor diet may contribute to acne. Here is the latest thinking on what to eat and what to avoid:

FOODS TO EAT Whole grains, 70% dark chocolate, lentils, brown rice, porridge, apples, dried apricots.

FOODS TO AVOID White bread, processed and refined foods, burgers and fries, sports and fizzy drinks, sweets.