Nutrition and acne: what science really says.

A historical error of medicine.

Let's go back in time. 1960s: you see your dermatologist for acne, and he tells you that your diet has nothing to do with it. This position was based on two studies which, a few years earlier, had found no link between acne and eating habits. The consequence was radical: for the medical profession, the relationship had not been scientifically established.

We now know that both studies had major design flaws. In one study, patients were asked to consume either chocolate bars or placebo bars. The problem: placebo bars were just as high in sugar and fat as chocolate bars. Under these conditions, it's difficult to reach valid conclusions.

For almost forty years, no further research was carried out and the subject fell into oblivion. The link has only recently been re-examined. In 2002, Loren Cordain published a study of populations in Paraguay and New Guinea in the Archives of Dermatology. It revealed that communities living away from the industrialized world, with a diet close to Paleolithic, were virtually free of acne. (Cordain L et al., Arch Dermatol, 2002). An observation already made by an American dentist at the beginning of the XXᵉ century.

Even more telling: when these populations adopt a Western diet, rich in sugar and dairy products, acne appears. These findings have prompted the medical profession to change its position. Today, studies on the relationship between diet and acne are multiplying every year.

Understanding acne: the four key factors.

A reminder is in order. In Western countries, acne affects 80 % of teenagers and a third of women between the ages of 20 and 50.

A study from 2021 clearly illustrates the complexity of these interactions between diet, hormones and acne mechanisms (review, 2021). An unbalanced diet increases blood levels of insulin, IGF-1 (insulin-like growth hormone) and androgens, which in turn increases sebum secretion.

Sebum production is in itself a natural phenomenon, and the lipidic film is essential for protecting the skin. But when this production becomes excessive, sebum is no longer evacuated properly: it accumulates in the sebaceous glands and triggers inflammation. Add to this colonization by Cutibacterium acnes, and both inflammation and acne become difficult to control.

The role of food in high glycemic index.

Let's get to the heart of the matter with the glycemic index, the criterion now unanimously accepted by the scientific community. Foods with a high glycemic index are those that trigger insulin peaks.

Insulin is a hormone secreted by the pancreas to regulate blood sugar levels. Some very sweet foods cause blood sugar levels, and therefore insulin, to rise sharply. The glycemic index precisely measures this effect: that of glucose is 100, that of an apple 35.

With low-glycemic index foods, the rise in insulin remains moderate and no hypoglycemia follows the meal. Conversely, foods with a high glycemic index cause insulin to explode, resulting in reactive hypoglycemia and triggering a hormonal cascade.

Proof with Laron syndrome

A striking example confirms this link. Patients suffering from Laron syndrome, a form of dwarfism due to the absence of a growth hormone receptor, develop virtually no acne - or cancer, for that matter. However, when supplemented with IGF-1, they begin to develop acne. (Ben-Amitai D, Laron Z, 2011).

Based on these findings, numerous studies have established a direct link between a low-glycemic index diet and a reduction in androgens, IGF-1 and acne lesions. The scientific evidence is solid A proper diet can play a major role in combating acne and blemishes.

Good news: reducing the glycemic load of your meals also helps you lose weight more easily, reduce the risk of vascular accidents and prevent diabetes. Collateral benefits that are far from negligible.

How to reduce the glycemic load of your meals

To limit insulin spikes, it's best to avoid foods with a high glycemic index, or to eat them at the end of a meal. This mainly concerns all sources of sugar: added sugar and sugar from industrial products (cookies, cakes, soft drinks). But there are some interesting subtleties.

Visit dairy products and acne.

A 2020 study of nearly 24,000 people found a link between acne and dairy consumption. (Aghasi M et al., 2020). As with chocolate, we're talking about a strong presumption, not a certainty.

Casein accounts for 80 % of cow's milk protein, the remaining 20 % being whey. Casein tends to increase IGF-1, whereas whey raises insulin levels. However, whey-induced hyperinsulinemia also leads to an increase in IGF-1. This explains why some athletes who supplement with whey can trigger or aggravate acne - but only in a minority of people.

A distinction must also be made between milk, with its high glycemic index, and cheese, with its low glycemic index. This difference sheds light on certain inconsistent results between studies. An often useful approach is to stop using dairy products for a month, then gradually reintroduce them.

Visit chocolate and acne.

Here's a great subject of controversy. In 2014, a double-blind study was carried out on men suffering from acne: they were given either an unsweetened cocoa capsule or a gelatin capsule. Result: a statistically significant increase in acne lesions in those who received cocoa, with a correlation between the quantity of cocoa and the number of new lesions (Caperton C et al., 2014).

Numerous other studies followed, with contradictory results. The question remains open: is chocolate responsible through the cocoa itself, or simply through the sugar it contains? It's hard to say at this stage; more research is needed, and for the moment it's a presumption.

In practice: if you have an important appointment in the next few days and a sudden craving for chocolate, it may be better to abstain when you have acne-prone skin.

Omega-3, probiotics, zinc and antioxidants.

Omega-3 fatty acids

Omega-3 and omega-6 fatty acids, found in fish and olive oil, are known to reduce IGF-1 levels, responsible for increased sebum production and pore clogging. One study compared two groups of acne sufferers, one supplemented with omega-3 and linoleic acid for ten weeks. At the end of this period, the supplemented group showed a statistically significant reduction in lesions. (Jung JY et al., 2014).

Probiotics

Probiotics offer promising leads. A 2016 study divided twenty acne-prone adults into two groups: one receiving a probiotic supplement, the other a placebo, for three months. At the end of the trial, the probiotic group experienced a significant reduction in lesions, and biopsies revealed a drop in IGF-1 levels. These results are encouraging, but require further research before probiotics can be considered a reference treatment.

Zinc and antioxidants

Zinc is considered a potential treatment for acne, both orally and topically. Studies show a real but modest benefit: it is useful, as long as consumption remains reasonable. More generally, a diet rich in antioxidants is always beneficial for the skin, especially acne-prone skin.

What you need remember.

Your questions about diet and acne.