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

The interest in vegetable oils has expanded beyond the culinary field and now extends into the realm of cosmetics. Soybean oil is no exception and offers numerous benefits for the skin and hair. What are these benefits? How is soybean oil extracted? What is its biochemical composition? Discover everything you need to know about this natural ingredient.

A Closer Look at Soybean 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 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, which is 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.

What active molecules can we find in soybean oil?

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

Active IngredientProperty(ies)
Linoleic AcidNourishing, hydrating
Oleic AcidMoisturizer
Palmitic AcidMoisturizer
Stearic AcidMoisturizer
Tocopherols (Vitamin E)Antioxidant
LecithinMoisturizing, anti-inflammatory, stimulates the synthesis of collagen and elastin
Isoflavone (traces)Reduces the level of LDL-cholesterol

Soybean Oil: What are the benefits for the skin?

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

  • Soybean oil is moisturizing.

    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 has antioxidant properties.

    Soybean oil can also counteract the effects of oxidative stress and protect cellular organelles and DNA. Indeed, it's worth noting that oxidative stress is the cause of premature skin aging and can also cause pigmentation disorders. Due to its vitamin E content, the soybean oil has a real photoprotective potential and is a valuable ally to prevent the appearance of wrinkles.

  • Soybean oil has a lightening effect.

    The soybean oil is also used to prevent or correct hyperpigmentation marks. Indeed, this ingredient can 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 tumor necrosis factor (TNF-α), which are pro-inflammatory cytokines. Lecithin also suppresses the transcriptional activation of the gene encoding 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 aging.

    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. Thus, soybean oil is a good ingredient for reducing the appearance of wrinkles.

The haircare properties of soybean oil.

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.

    Often subject 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 inherent in this ingredient.

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

    The high Vitamin E content in soybean oil also allows it to protect hair fibers 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 through various mechanisms to keep hair fibers 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 it more impermeable and better protected against external aggressions.

Adverse effects of soybean oil in cosmetic use?

It's important to note that the topical application of pure soybean oil is not recommended for pregnant women and children. This is a precautionary principle because 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. Otherwise, it means that your skin is sensitive to it and it would be better to avoid using soy oil in the future.

Sources

  • 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).

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