Retinol

A story that begins with vitamins

Before becoming a serum ingredient, vitamin A belongs to the history of nutrition. Researchers seek to identify substances present in small quantities in food, but necessary for the functioning of the body. Understanding their composition becomes a decisive step: we can finally link a biological effect to a specific molecule, instead of working only with complex extracts.

At the beginning of the 1930s, Paul Karrer elucidated the structure of beta-carotene, then that of vitamin A. This work contributed to the recognition which earned him the Nobel Prize in Chemistry in 1937. It shed light in particular on the link between certain plant pigments and the vitamin that the body can obtain from them. We are still far from anti-wrinkle cream: the first challenge is to understand the chemistry of life.

Dermatology is interested in this family

Research on vitamin A and its derivatives then opens another avenue: acting locally on the way skin cells develop and differentiate. Retinoids play an important role in the treatment of acne, particularly with tretinoin applied to the skin. This medical history precedes their cosmetic popularity and explains why very similar names today cover products with different uses.

Acne thus provides a field of study for this family of molecules, but the question does not remain limited to pimples. Dermatologists are also interested in skin marked by years of sun exposure: roughness, pigmentation irregularities and fine wrinkles. Can we improve some of these changes by modifying cell activity? Research from the 1980s began to provide experimental answers.

From acne treatments to wrinkle trials

In 1986, a publication by Kligman and colleagues described the effects of tretinoin on skin aged by the sun. In 1988, a controlled trial published in JAMA in turn studied the improvement of photoaging. This work contributes to making retinoids a reference in this field. However, they relate to tretinoin: their results cannot be automatically attributed to just any retinol serum.

The cosmetic industry then develops formulas with precursors such as retinol, from which the skin can produce retinoic acid. The challenge is to find a compromise between activity, tolerance and stability in the bottle. This difference with a drug is important: the common family name does not make the concentrations interchangeable and does not exempt from studying each formula under its own conditions of use.

Studying Retinol for Itself

In 2007, Reza Kafi's team published a trial on 36 elderly people: a 0.4% retinol lotion was compared to its base without active ingredients, on the arms, for 24 weeks. Fine lines improve more on the treated side. This result supports the benefit of retinol on aged skin, but we must keep the real setting of the study in mind: arms, an elderly population and a precise formula.

A study published in 2009 looked directly at the faces of middle-aged Japanese women, with a comparison between the two sides over 26 weeks. She observes a more frequent improvement of several signs of aging on the retinol side. These trials move the issue beyond just the results obtained with tretinoin. They also tell the same rhythm: benefits are built over months, far from promises of immediate transformation.