Soybean Oil: Everything you need to know about this vegetable oil.

Originating from China, soy has been cultivated in Asia for millennia. Rich in proteins, it is one of the essential components of the vegetarian diet. While it is very popular today, soy was long unknown in Europe. Indeed, its introduction was made late, in the 18th century, under the impetus of the Swedish botanist Carl Linnaeus.

It is possible to extract an oil from the seeds of this legume, highly valued for its taste properties but also used to formulate skin and hair care products. From an organoleptic perspective, soybean oil takes the form of a golden liquid, without any particular fragrance and is relatively easily absorbed by the skin.

The oil extracted from soybean seeds is rich in active ingredients beneficial for the skin and hair. The table below summarises the main molecules present within this vegetable oil, along with the properties associated with them.

The soybean oil is a very interesting natural ingredient for taking care of one's skin.

• Soybean oil is moisturising.

  Compounds found in the hydrolipidic film of the epidermis, the oleic, stearic and palmitic acids of soybean oil strengthen this protective veil and shield the skin from cold, dryness and other external aggressions.

• Soybean oil has nourishing properties.

  Soybean oil also plays a role in strengthening the stratum corneum. Indeed, the linoleic acid present in this oil reacts with the ceramides in this area, which triggers an esterification reaction during which the linoleic acid and lipids bind, thereby forming the impermeable barrier of the skin.

• Soybean oil possesses antioxidant properties.

  Soybean oil can also counteract the effects of oxidative stress and protect cellular organelles and DNA. Indeed, it is worth noting that oxidative stress is the cause of premature skin ageing and can also cause pigmentation disorders. Due to its vitamin E content, thesoybean oil has a genuine photoprotective potential and is an excellent ally for preventing the appearance of wrinkles.

• Soybean oil has a lightening effect.

  The soybean oil is also used to prevent or correct hyperpigmentation marks. This ingredient can indeed inhibit the activation of the PAR-2 receptor, which is involved in the transfer of melanin from the deep layers of the skin to the superficial layers. By doing so, the pigmentation of the epidermis is reduced.

• Soybean oil has anti-inflammatory properties.

  It has also been demonstrated that lecithin from soybean oil can downregulate the production of interleukin-1β (IL-1β), and tumour necrosis factor (TNF-α), which are pro-inflammatory cytokines. Lecithin also suppresses the transcriptional activation of the gene coding for cyclooxygenase (COX), a key enzyme in the biosynthesis of compounds that increase inflammation. These various actions of soybean oil explain why it is sometimes used to alleviate irritations and itching.

• Soybean oil helps to prevent skin ageing.

  Finally, several studies suggest that soybean oil has a tightening effect that allows it to combat skin sagging. This natural ingredient not only stimulates the production of collagen and elastin, but also inhibits the activity of certain elastases, enzymes responsible for the degradation of elastin. Soybean oil is therefore a good ingredient for reducing the appearance of wrinkles.

The benefits of thesoybean oil extend beyond the skin, and this ingredient is also used in the formulation of treatments intended for the scalp and hair.

• Soybean oil soothes scalp itchiness.

  Occasionally prone to tightness and irritation, the scalp also deserves care and attention. The application of soybean oil during these times can be beneficial due to its soothing and anti-inflammatory properties of this ingredient.

• Soybean oil protects the tips and prevents the occurrence of split ends.

  The abundance of Vitamin E in soybean oil also allows it to protect hair fibres from oxidative stress, which can weaken the hair bulb and promote hair loss and the appearance of split ends.

• Soybean oil hydrates and strengthens the lengths.

  The fatty acids found in soybean oil work via various mechanisms to keep hair fibres hydrated and protected. Indeed, these active ingredients strengthen the presence of the hydrolipidic film that coats the hair and contribute to the cohesion of the cuticle scales, making the latter more impermeable and better protected against external aggressions.

It is important to note that the topical application of pure soybean oil is not recommended for pregnant women and children. This is a precautionary principle as this vegetable oil is suspected to be an endocrine disruptor, due to the traces of isoflavones it may contain, phytoestrogens that could interact with the hormonal system. However, it is crucial to clarify that soybean oil only contains minute traces of isoflavones, making its estrogenic power almost negligible.

Another recommendation pertains to individuals allergic to soy. Even though food and cosmetic allergies are not necessarily correlated, it is advisable for these individuals to seek medical advice before applying soy oil. To avoid an unexpected allergic reaction, it is also recommended for all users to perform a tolerance test. To do this, simply apply a small amount of soy oil to the skin. If you observe no redness, swelling, or irritation within the following 24 hours, this indicates that your skin tolerates this ingredient well. Conversely, if you do experience these symptoms, it suggests that your skin is sensitive to it and it would be better to avoid using soy oil in the future.

• BUCK D. Antioxidants in soya oil. Journal of the American Oil Chemists’ Society (1981).

• SHAPIRO S. & al. Soymilk reduces hair growth and hair follicle dimensions. Experimental Dermatology (2001).

• HARRATH A. H. & al. Phytoestrogens and their effects. European Journal of Pharmacology (2014).

• MURTAZA G. & al. Dermatological and cosmeceutical benefits of Glycine max (soybean) and its active components. Acta Polonia Pharmaceutica (2015).