How soybean oil helps rejuvenate the skin

Grandparents often advise that one needs to look no further than the kitchen shelf for wellness products. Curiously though, while the soybean consistently features in South East Asian kitchens, soybean oil has only recently made an entry into the world of skin care. Rich in unsaturated omega-3 fatty acids, soybean oil completes the necessary balance of oils in the Enrich formulation from griffin+row.

Introducing Glycine soja (Soybean)

The soybean is a leguminous plant native to China. Its botanical name was given by Linnaeus based on its supposed sweet taste (Glycine) and the large nitrogen-fixing nodules on the roots (max) ¹. The species name of “max” may also be a version of the Portuguese inscription of the Persian name “moot” for the bean. The INCI (International Nomenclature for Cosmetic Ingredients) name for the oil extracted from Glycine max is Glycine soja oil ². The bean also goes by the names Phaseola max, Soja max and Glycine hispida. The common name ‘soybean’ is a corrupted form of the Chinese ‘chiyou’ or Japanese ‘shoyu’ which refer to soy sauce ³.

The soybean is often called ‘gold from the soil’ in several South East Asian countries where it has been a staple food for centuries. Large scale cultivation and use of soybean started in the Western hemisphere only in the 20^th century. USA is now the leading producer of soybean, followed by Brazil, Argentina, China, and India ⁴

Traditional uses of soybean

The human use of the soybean dates back to at least 4,000 years. There is archaeological evidence of the bean in excavated sites in China and Korea. An ancient Chinese legend states that travelling merchants discovered the plant and its edible bean ⁵. Consequently, wild soybean which is sensitive to exposure to daylight hours was cultivated by Chinese farmers at different times of the year and in different soil types. The rise of the soybean as a regular food crop may have come about because of the vegetarian Buddhist monks who arrived in China in the 3^rd century BCE. For them, soybean was a perfect protein-rich vegetarian food. So while soy flour had earlier been compressed into cakes for travellers and soldiers, the monks developed methods to make soybean milk, curd and sauce. In 2838 BCE, the Chinese Emperor Sheng-Nung authored a Materia Medica which documented the cultivation of soybean and its medicinal uses. He even ordained it with a sacred status along with wheat, rice and millets. The uses of the soybean moved with Buddhism to Vietnam (circa 200 BCE), Korea (circa 1^st century CE) and from there to Japan in the 6^th century CE, becoming a staple food in the latter country. Thailand was introduced to soybean from southwest China in the 6^th century and while India had a relatively late introduction in the 12^th century ¹.

In South East Asia, whole soybean is sprouted and added to foods. The flour obtained from the beans is used in thickening soups. The watery suspension (soymilk) is used as a milk substitute for the population that is largely lactose intolerant. The fermented soybean is the base for soy sauce while tofu is the curd obtained from fermented soy milk. The watery waste ‘okara’ obtained while making tofu is given to livestock since it has poor keeping quality.

Europe was introduced to the soybean by the German botanist Ernest Kaempfer. As a guest of the Dutch East India Company, Kaempfer noticed the importance given to soy in Japanese cuisine. He not only wrote about it in his book on Japan in 1712, but also attempted to introduce the plant to Europe. This did not meet with much success at a time when the continent was just coming to terms with New World crops like maize and potato. Botanists, however, were happy to study the new plant and Carolus Linnaeus christened it Glycine max. 

The Portuguese re-introduced the soybean to the Western world when it established trading ties with the East. This time, Portuguese colonies in Brazil successfully cultivated the bean. However, Samuel Bowen, a sailor with the East India Company, is credited for the first ever cultivation of soybean on American soil. Unfortunately, although he gave up his sea-faring career in 1765 and grew soybean in Savannah, Georgia, the soy products did not appeal to the people. For a long time afterwards soybean was cultivated as a forage plant, often being harvested when the beans were still green ¹.

Another attempt to grow soybean was made after the Civil War to meet the demands of food for immigrants. Soybean oil extracted at that time was not received well by the public. Its saturated fatty acid content caused it to solidify at low temperatures and α- linolenic acid gave the oil an unpleasant smell. In 1909, when the oil was used to make soap called ‘Sunlight soap’ by the Lever brothers in England there was no reference to the oil.

Attempts to improve the oil quality paid off in the 1920s, when the cotton crop in southern USA was attacked by the boll worm. Soybean with its high oil content took the place of cottonseed as an oilseed and a cash crop. Southern farmers even started crop rotation in order to enrich the soil. In addition to this, soybean cultivation in Manchuria – the main soybean producing region in China – suffered heavy losses due to political turmoil ⁶. This resulted in the USA overtaking China in soybean production. The soybean became America’s “Cinderella crop” and “miracle bean”. Soybean oil was marketed as food-grade cooking oil. It was also used in the manufacture of vegetable margarine ¹.

This, however, decreased the use of soybean oil in the manufacture of waterproof materials, candles and as an industrial lubricant. Henry Ford, the famous car manufacturer, who envisioned motor cars made from materials derived from soybean oil and using the same for fuel, had to abandon those plans. Only a small percentage of oil was allowed for industrial use to manufacture dyes, varnishes, linoleum and rubber.

Soybean is now a major food crop, cultivated for both its meal and its oil. Soy meal is sold as protein-rich chunks that can be added to various dishes. Other than the traditional tofu and soy sauce, okara is also used in Japanese and Chinese dishes. Tempeh from Indonesia and miso from Japan are variations on the tofu theme. Soy protein isolate and fried soy nuts have gained popularity in the West. Texturised meat alternatives have also been prepared from soy flour ⁷.

Recently, okara-based soaps have been developed. The high level of phenolics in okara gives it significant antioxidant properties ⁸.

The medicinal use of soybean dates back to 500 BC when mouldy soybean curd was applied to infected sores ⁹. In the 21^st century, soybean oil is used in formulations for drug delivery ¹⁰ and cosmetics. It is also a preferred vegetable oil for the production of biodiesel ¹¹.

Bioactivity and associated components of the plant

Only the seed of the soybean has significant bioactivity, with the rest of the plant being used as cattle feed. With its high protein content (20%), the seed ranks among the top protein-rich foods. The seed is processed in two ways:

• Extraction with hexane or supercritical carbon dioxide to yield soybean oil
• Extraction with water and glycerine which is marketed as soybean extract

A) Soybean oil: The chemical extraction of soybean oil using organic solvents such as hexane has now been replaced with a physical extraction using supercritical carbon dioxide. Cold pressed and unrefined oils are also available. The main constituents of soybean oil are:

• Saturated fatty acids: Palmitic acid is the main saturated fatty acid, making up to 9-13% of the oil. Other saturated fatty acids are myristic, stearic, arachidic, behenic and lignoceric acids.
• Unsaturated fatty acids: Linoleic (48-58%), oleic (17-30%) and linolenic (4.5-10%) acids are the main unsaturated fatty acids. Erucic acid may also be present in small quantities.

A significant percentage of fatty acids are found as triglycerides which have 51% linoleic acid, 23% oleic acid and 7% linolenic acid. Tocopherols, lecithin, sterolins (phytosterols), choline and inositol make up the rest of the oil ¹². The important phytosterols are stigmasterol and β- sitosterol. A small amount of ergosterol may be present in the oil from some cultivars ¹³. Soybean oil does not contain the isoflavones genistein and diadzein ¹⁴.

B) Soybean extract: The aqueous extract of defatted soybean contains the bulk of phytonutrients. These include:

• Proteins: The major proteins in soybean extract are β-conglycinin and glycinin. Soybean Trypsin inhibitor (SBTI) and Bowman-Birk protease inhibitor (BBPI) which are present in smaller quantities, have been shown to inhibit PAR-2 (protease activated receptor-2) in keratinocytes, reducing melanogenesis ¹⁵.
• Polyphenols: These secondary plant metabolites have a number of functions including anti-microbial activity. In humans, their actions range from antioxidant, anti-inflammatory, anti-tumorigenic, anti-hypertensive, and immune-stimulation. In soybean, the main phenolic acids are ferulic acid, synaptic acid and syringic acid.
• Isoflavones: Isoflavones are a set of polyphenol compounds that share a common chemical structure. Soybean has the highest concentration of isoflavones among plant seeds. Genistein and diadzein are the best known phytoestrogenic isoflavones found in soybean. Phytoestrogens mimic the action of oestrogen and are recommended for the prevention of post-menopausal bone resorption. Both compounds also have anti-tumorigenic and anti-inflammatory activities ¹⁵.

Oleic acid and linoleic acid: a spotlight on the key ingredients

• Linoleic acid is a polyunsaturated fatty acid.

Linoleic acid is important for cutaneous health and texture. It is a precursor for the synthesis of ceramides, which prevent trans-epidermal water loss and maintain a healthy skin barrier against infections ¹⁶.

• Oleic acid is a monounsaturated fatty acid.

Along with linoleic and palmitic acid, oleic acid redistributes the fatty acids that are naturally found in the dermal and epidermal layers of the skin ¹⁷.

Both linoleic and oleic acids can penetrate the layers of the skin ¹⁷. This ensures that active ingredients mixed with these compounds reaches deep into the skin.

Benefits and uses of soybean oil

Soybean oil is light yellow in colour, moderately viscous, odourless and bland. It is effective in controlling blood cholesterol levels, hypertension and tumour progression. Topical application is effective since it spreads easily, has deep penetration and good moisture retention properties ².

Soybean oil is a preferred base for both rinse-off and leave-on cosmetic formulations. Some of the documented advantages of using soybean oil are listed below:

• Moisturising effect: Linoleic acid is an essential fatty acid which is used in the synthesis of skin ceramides. Topical application increases the level of ceramides and creates a natural trans-epidermal barrier that prevents dehydration of the skin ¹⁶.
• Antioxidant effect: Tocopherol (vitamin E) in soybean oil is an effective antioxidant and decreases free-radical formation. This prevents lipid peroxidation, damage of cells and tissues.
• Rejuvenation of skin: Soybean oil makes a good carrier oil due to its deep penetration properties. This ensures that smaller molecules with skin-regeneration activity reach both the dermal and epidermal layers of the skin ¹⁶.
• Anti-ageing effects: The combined effects of enhanced hydration and effective delivery of lecithin, vitamin E and sterols contained in the oil makes it an effective anti-ageing agent.

Botany and grow it yourself

Soybean belongs to the family Fabaceae which includes many leguminous plants, pea and bean plants ³.

The soybean is unique in that it is a crop affected by day-length. The growth of the plant before it blooms determines the number of bean pods that are borne. The plants need to grow to a height of 3-4 feet before they bear flowers; the taller the plant, the larger the number of bean pods. Seeds are planted so that germination takes place just before the days get longer. Leaves are trifoliate and appear at the nodes. Root nodulation takes place from the time the fifth node appears. Soybean flowers are small, self-fertile and can be white, purple or pink. The flowers appear at the axilla of the leaf. The fruit appears as a pod covered with fuzz. Each pod bears 3-4 seeds.

Soybean is grown around the year in the tropics and can withstand considerably hot weather. Temperatures below 15°C are deleterious to the crop. The plant is also fairly drought resistant and suffers stunted growth in waterlogged soil. This is because thick clayey soils choke the nitrogen-fixing Rhizobia in the roots ¹⁸.

Soybean does not require nitrogen fertiliser due to its Rhizobia in the root nodules. This also makes it a good crop to be grown after the main crop (for example corn) has been harvested.

Soybean pods are allowed to dry on the plant as much as possible. Harvesting the beans is usually done by manual threshing. The beans are then dried and stored in air-tight containers until they are processed.

Read about the five simple steps of the griffin+row skincare system: 1 Cleanse     2 Exfoliate     3 Hydrate     4 Nourish     5 Enrich

 

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References and sources

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