Betaine monohydrate (CAS 590-47-6), also known as trimethylglycine, is a naturally occurring zwitterionic compound isolated from sugar beet (*Beta vulgaris*). In cosmetics, it functions as an osmolyte that regulates cellular water balance and stabilizes proteins under environmental stress. This article reviews its hydration efficacy, protective mechanisms, and formulation benefits with supporting research data.

Moisturizing Efficac

Betaine's primary mechanism involves balancing water content inside keratinocytes without disrupting cellular function. When skin is exposed to dry air or UV radiation, cells naturally increase betaine uptake to restore hydration. *In vitro* comparative studies demonstrate that betaine monohydrate exhibits higher water-binding capacity than glycerin**, with sorption-desorption performance for sustained moisture retention. *In vivo*, a clinical evaluation with 16 volunteers found that an O/W emulsion containing **2.5% and 5% betaine** significantly improved skin moisturization at both 2 and 6 hours post-application compared to placebo control.

Protein Protection and Barrier Function

Recent 2025 research systematically evaluated betaine's protective effects on bovine serum albumin (BSA) under cosmetic-relevant stressors. At **0.50% w/w** under oxidative stress (simulating hair bleaching), betaine significantly enhanced protein stability. Under low-temperature stress (4°C), concentrations below 0.33% reduced protein stress effects from ~10% to 5–6%. Additionally, a four-week clinical study demonstrated that daily use of betaine-containing cream significantly reduced transepidermal water loss (TEWL), confirming improved skin barrier integrity. Combining betaine with glycerin also delivers better moisturization than glycerin alone while reducing tackiness.

Formulation and Sustainability

Betaine monohydrate is highly water-soluble and easy to incorporate into creams, lotions, and serums. Recommended usage levels range from **2.5–5.0%** for skin care products. Modern betaine is extracted from sugar beet molasses via green chemistry, achieving COSMOS and Natrue approval with a Natural Origin Index of 1, aligning with clean beauty trends.

Conclusion

With proven hydration, protein protection, and barrier-supporting properties, betaine monohydrate is a multifunctional ingredient backed by recent scientific data, making it a valuable choice for modern cosmetic formulations.