Skin comprises three layers, namely the epidermis, dermis and subcutaneous tissue, and provides protection against bacteria, UV radiation and other external factors. The subcutaneous tissue accumulates fat as adipocytes, with the subcutaneous blood flow being related to the thickness of the tissue layer or total body fat mass. Obese individuals accumulate subcutaneous adipose tissues and have a higher subcutaneous blood pressure, increasing the risk of cardiovascular disease.

The function and appearance of skin are significantly affected by nutritional conditions. In particular, linoleic acid is an important factor in maintaining healthy skin. Evening primrose oil, blackcurrant seed oil and borage oil are rich in γ-linolenic acid (GLA), which exhibits anti-inflammatory and immunomodulating effects. Dietary supplementation with these oils can increase levels of GLA in the epidermis.

Conjugated linoleic acid (CLA) comprises a mixture of positional and geometric isomers of linoleic acid, found mainly in foods produced by ruminant animals. Studies have shown that CLA reduces epididymal white adipose tissue weight, adipose depots and adipocytes in the subcutaneous tissue, and inhibits the growth of cancer cells and induces apoptosis in the liver and adipose tissue. Furthermore, CLA appears to be beneficial for skin composition and, alone or in combination with GLA, shows anti-obesity effects on visceral fat.

A study by Oikawa et al.¹ investigated the effects of CLA, GLA and/or linoleic acid on skin composition in mice. Triacylglycerol content, fatty acid composition and collagen content were determined, and thicknesses of the dermis and subcutaneous tissue were measured together with the size and number of adipocytes. The skin fatty acid composition was modified depending on the fatty acid composition of the supplemented oils. Results showed that CLA, alone or combined with linoleic acid and/or GLA, can strongly modify skin composition in the mice.
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¹ Oikawa, D; Nakanishi, T; Nakamura, Y-N; Yamamoto, T; Yamaguchi, A; Shiba, N; Iwamoto, H; Tachibana, T; Furuse, M (2005). Modification of skin composition by conjugated linoleic acid alone or with combination of other fatty acids in mice. British Journal of Nutrition 94 (2) 275-281.

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