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Une alimentation trop grasse ou trop sucrée provoque l'acné : vrai ou faux ?

Does a diet that is too fatty or too sugary cause acne: true or false?

The causes of acne are multifactorial. However, diet plays a significant role in this skin condition. It is often heard that excessively fatty and sugary foods trigger acne. But what is the actual truth? This article provides some answers.

A Reminder about Acne.

Acne is achronic inflammatory diseasethat presents itself through the emergence of spots on the face and/or body. The causes of acne aremultifactorial: genetic, hormonal, stress, the use of certain medications...

In the case of acne, we observe ahypersecretion of sebum(referred to as hyperseborrhea) at the level of the pilosebaceous follicles as well as ahyperkeratinisation. The sebum will clog the pores, which are the orifices of the sebaceous glands on the skin surface. This fat-rich environment will be conducive to the proliferation of the bacteria responsible for acne,Cutibacterium acnes(formerly Propionibacterium acnes) which primarily feeds on sebum. This bacteria secretes pro-inflammatory substances that cause inflammation and the formation of spots.

The connection between acne and excessive sugar consumption.

Many studies have focused on the link between acne and the glycaemic index of the diet. Theglycaemic index of a foodindicates its ability to raise blood sugar levels, that is, the concentration of glucose in the blood.

When a food has a high glycemic index, the level of glucose will rapidly increase in the blood. In response, the pancreas will stimulate the secretion of insulin, which is a hypoglycemic hormone.

Please note : a hormone is referred to as hypoglycaemic when it reduces the level of sugar in the blood. Conversely, a hyperglycaemic hormone increases the level of sugar in the blood.

Among the foods with a high glycaemic index, we can mention the white bread, potatoes, processed foods (pastries, baked goods, confectionery...), cooked carrots, fruit juices...

Insulinstimulates the secretion of IGF-1 (Insulin-like growth factor-1), also known as somatomedin C,which increases the levels of androgens in the blood. Androgens, through a positive feedback mechanism, also stimulate the secretion of IGF-1. Thus, the androgens and IGF-1 stimulate the secretion of sebum which is the cause of acne. In addition to stimulating the secretion of androgens, IGF-1 reduces the amount of the transcription factor FOXO1 in the cell nucleus, leading to theactivation of mTORC1 which is involved in the phenomena of hypersecretion of sebum as well as hyperkeratinisation.

Note : mTORC1 is also activated by the leucine, an amino acid that makes up meat and dairy products.

Please note : the dairy products have a low glycemic index but powerful insulin-stimulating properties.

Thus, foods with a high glycemic index, dairy products, as well as meat, are risk factors in the development of acne.

The connection between acne and a diet high in fat.

Although scientific studies have proven that high glycemic index foods, dairy products, and meat are risk factors in the development of acne, no study has established a link between fats (lipids) and acne.

Contrarily, studies have proven that lipids rich in omega-3 reduce the secretion of IGF-1 which is responsible for the overproduction of sebum and the phenomenon of hyperkeratinisation. Furthermore, they inhibit the synthesis of leukotriene B4 which is the root cause of inflammation.

However, it is advised against consuming the so-called "trans" saturated fatty acids which are primarily found in processed foods (fast food, sweets, fried foods, processed meats, pastries...). It is preferable to consume unsaturated fatty acids, such as omega 3 and omega 6, which are essential for the body's proper functioning. You can find these in nuts, avocados, oily fish (salmon, sardines..) or even in walnut oil.

Sources:

  • VARIGOS G. A . & al. A low-glycemic-load diet improves symptoms in acne vulgaris patients: a randomized controlled trial. The American Journal of Clinical Nutrition (2007).

  • TAN J. & al. Effects of diet on acne and its response to treatment. American Journal of Clinical Dermatology (2021).

  • MICALI M. D. & al. Diet and acne: review of the evidence from 2009 to 2020. International Journal of Dermatology (2021).

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