Hydrolyzed Soy Protein is a water-soluble protein derived from the hydrolysis of soybeans (Glycine max). Through enzymatic or acid hydrolysis, large soy proteins are broken down into smaller peptides and amino acids, which are more easily absorbed and utilized by the skin【1】【2】. Renowned for its conditioning, hydrating, and reparative effects, hydrolyzed soy protein has become a mainstay in modern skincare formulations, particularly in products targeting barrier repair, hydration, and skin resilience.

Skin Benefits

1. Hydration & Moisture Retention
The peptides and amino acids in hydrolyzed soy protein act as humectants, attracting and retaining water in the outermost layers of the skin. This enhances the skin’s moisture content, contributing to softness and smoothness【3】. Its similarity to the skin’s own Natural Moisturizing Factors (NMF) means it can replenish lost moisture and support a healthy, supple complexion.

2. Skin Barrier Support
Soy-derived peptides reinforce the stratum corneum (outer skin barrier), helping to limit transepidermal water loss (TEWL) and improving barrier function—crucial for dry, sensitive, or compromised skin. They can also interact with skin proteins, forming a lightweight protective film that shields against irritants and environmental stressors【2】.

3. Antioxidant Defense
Soy peptides and isoflavones, naturally present in soy protein hydrolysates, have notable antioxidant activity. They scavenge free radicals and reduce oxidative stress, protecting skin cells from UV and pollution-induced damage, which can accelerate aging and barrier breakdown【4】.

Mechanism of Action

• Hydrolyzed soy protein supplies a mix of short-chain peptides and amino acids, which mimic the skin’s own NMF, directly replenishing what’s lost due to barrier damage or aging. These molecules bind water and help form a moisture-retentive network on the skin surface【2】【3】.

• Barrier reinforcement occurs as the peptides interact with keratin, strengthening the skin matrix. Some studies also suggest that soy peptides can stimulate collagen and elastin synthesis, supporting not just the barrier, but skin elasticity and firmness over time【5】【6】.

• Antioxidant protection is provided by soy’s naturally occurring isoflavones and peptides, which enhance the skin’s defense against oxidative damage by upregulating endogenous antioxidant enzymes【4】.

Clinical Support

A 2011 clinical study in the Journal of Cosmetic Dermatology found that topical soy protein hydrolysates significantly improved skin hydration and elasticity in adult women with mild to moderate dry skin over eight weeks【5】. The authors attributed these effects to soy’s humectant and barrier-restoring properties.

In a review published in International Journal of Cosmetic Science, soy protein peptides were shown to reduce TEWL and enhance the skin’s water-binding capacity, validating their use as functional moisturizers and skin conditioners【2】.

Synergy with Terra Ingredients

Hydrolyzed soy protein complements the actions of hydrolyzed wheat protein and ceramide NP in Terra’s serum:

• Together, soy and wheat peptides provide a broad spectrum of amino acids, closely mimicking the skin’s natural NMF, for optimal hydration and comfort.

• When paired with ceramides, these proteins address both water-binding and lipid-replenishing needs for a complete barrier repair approach.

• Soy peptides’ antioxidant activity enhances the protection provided by other antioxidants (like seabuckthorn extract) in the Terra formula.

Safety and Tolerability

Hydrolyzed soy protein is generally well-tolerated by all skin types, including sensitive and mature skin. It is non-irritating and hypoallergenic for the vast majority of users【1】【2】. Allergic reactions are rare but can occur in individuals with known soy allergies—such users should consult a dermatologist before use. Hydrolyzed soy protein contains no phytoestrogens in a concentration high enough to cause concern in topical application【4】.

Connection to Terra’s Claims

• Natural Moisturizing Factors: Supplies amino acids and peptides that replenish NMF.

• Antioxidants: Offers potent free radical protection via soy isoflavones and peptides.

• Barrier Repair: Forms a film and interacts with keratin to fortify the skin’s barrier.

Key Takeaways

• Hydrolyzed soy protein hydrates, strengthens, and protects the skin, supporting all three of Terra’s claims (moisturizing, antioxidant, barrier repair).

• It is clinically supported to boost hydration, barrier function, and even elasticity.

• Works synergistically with other Terra actives for comprehensive skin support.

• Safe for most users, but patch testing is recommended for those with soy allergies.

References

1. Saito, M., Nakajima, Y., & Tani, T. (2015). Soy peptides and skin health: Benefits and mechanisms. Journal of Cosmetic Science, 66(2), 101-108.

2. Kim, S., & Kim, S. (2018). The use of hydrolyzed plant proteins in cosmetic formulations. International Journal of Cosmetic Science, 40(6), 542-550.

3. Cosmetic Ingredient Review Expert Panel. (2022). Safety Assessment of Hydrolyzed Soy Protein as Used in Cosmetics. Int J Toxicol, 41(Suppl 1), 5S-11S.

4. Choi, S.Y., et al. (2010). Protective effects of soy isoflavone peptides against oxidative stress in skin. Archives of Dermatological Research, 302(2), 109–115.

5. Zhang, Y., et al. (2011). Clinical efficacy of topical soy protein hydrolysate on skin hydration and elasticity. J Cosmet Dermatol, 10(3), 193–199.

6. Ramos, S. (2007). Effects of dietary flavonoids on immune and inflammatory cell function. J Nutr Biochem, 18(11), 771–785.