Phytosterols: What are the benefits for the skin?

Phytosterols have the ability to capture and retain water, making them effective humectants. The topical application of these compounds supports the hydrolipidic film present on the surface of the epidermis and helps to limit transepidermal water loss, or TEWL. The moisturising property of phytosterols is particularly beneficial for individuals with dehydrated skin , which is often prone to feelings of tightness and discomfort.

However, it is important to temper the effectiveness of phytosterols for skin hydration. The moisturising power of these plant compounds is significantly less than that of hyaluronic acid or glycerine for example.

Phytosterols are primarily recognised for their anti-inflammatory and soothing properties. From a biological perspective, phytosterols work by inhibiting the activity of cyclooxygenase (COX) and lipoxygenase (LOX), two enzymes that play a key role in the production of prostaglandins. Prostaglandins are molecules responsible for several inflammatory phenomena such as redness or pain.

Furthermore, phytosterols can downregulate the activation of pro-inflammatory transcription factors such as the nuclear factor kappa B (NF-κB) and activator protein 1 (AP-1). These molecules modulate the expression of genes coding for inflammation proteins. By blocking these signalling pathways, phytosterols can reduce the production of pro-inflammatory cytokines such as interleukin-1β (IL-1β) and tumour necrosis factor-alpha (TNF-α). By acting on these various mechanisms, phytosterols soothe and calm the skin and reduce redness and feelings of discomfort.

Phytosterols also have the ability to aid skin restoration when it has been damaged, following a minor injury or acne scarring. Studies have shown that this active ingredient can act on the fibroblast growth factor and increase its activity. This allows for an intensification of collagen and elastin secretion by the fibroblasts, which is essential for the formation of scar tissue. Furthermore, the moisturising properties of phytosterols contribute to ensuring good wound healing. Indeed, when we get injured, a wound tends to be red and painful: the skin can burn, itch or feel tight. It is then necessary to hydrate it well.

Several mechanisms are responsible for skin sagging and the appearance of wrinkles. One can notably think of the gradual decrease in the synthesis of collagen and elastin by fibroblasts over time, proteins in the dermis ensuring the suppleness and elasticity of the skin. Several active ingredients are suspected of having protective properties on collagen and elastin fibres and being capable of slowing down skin ageing. This is particularly the case with phytosterols.

A study involving 10 individuals examined the photoprotective effects of a cream containing phytosterols. However, the concentration and type of phytosterols were not disclosed. This cream was applied to certain areas of the arm for 10 days. At the end of these 10 days, the skin on the arms of the individuals was irradiated with UVA at a rate of 100 J/cm2. For comparison, 200 J/cm2 of UVA corresponds to an average week of sunlight in September in Belgium. Following this irradiation, as expected, the scientists observed an upregulation of genes coding for collagenase in the areas not protected by the cream, an enzyme that breaks down the peptide bonds of collagen. This breakdown results in the loss of structure and function of collagen. However, the researchers did not observe this effect on the areas of the skin where the cream had been applied. This suggests that phytosterols have a photoprotective action and contribute to the slowing down of photoaging of the skin.

Please note : caution should be exercised regarding the effects of phytosterols on skin sagging. Indeed, only one study has highlighted these effects, and it only involved 10 volunteers, which is a small sample size.

When the skin is frequently exposed to UV rays, pollution or cigarette smoke, it responds by generating oxidative stress within its cells. Oxidative stress refers to an imbalance between the number of free radicals and antioxidants in the body. Free radicals are reactive and unstable species that attack cells, DNA, and proteins, causing various damages (hyperpigmentation, premature ageing, melanomas...).

To prevent these inconveniences, it is recommended to incorporate antioxidants into your skincare routine. Phytosterols can fulfil this role. Indeed, their chemical structure allows them to donate an electron to free radicals, which stabilises them and prevents them from acting. This helps to prevent oxidative damage, protect cell membranes, and preserve the integrity of cells and tissues. Moreover, some studies suggest that phytosterols can stimulate the activity of endogenous antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase. These are essential proteins in the mechanism of eliminating free radicals.

A recent study has highlighted the antibacterial properties of β-sitosterol, a phytosterol found in the seeds of certain plants such as walnut, pumpkin, or wheat. The experiment conducted in vitro by the scientists demonstrated that this compound was capable of inhibiting the growth of Staphylococcus aureus, a Gram-positive bacteria. However, the mechanism of action of β-sitosterol has not yet been determined. By extrapolating these data, it can be suggested that phytosterols may be allies in combating certain bacterial infections.

• QUIRIN K. W. & al. Phytosterol-Rich Soy Germ and Guggul Extracts Provide Anti-Ageing Benefits. Cosmetic science technology (2011).

• PUGLIA C. & al. In vitro Percutaneous Absorption of Niacinamide and Phytosterols and in vivo Evaluation of their Effect on Skin Barrier Recovery. Current Drug Delivery (2016).

• SURINA I. & al. Antibacterial and antifungal activity of phytosterols and methyl dehydroabietate of Norway spruce bark extracts. Journal of biotechnology (2018).