1.5 times more effective in its water holding capacity than glycerine.

Sodium lactate is the sodium salt of lactic acid, is a natural humectant and moisturiser and is a part of our own NMF (natural moisturising factor). It is applied in cosmetic formulations for its moisturising functions and to adjust the pH (specially when buffering is needed). In certain cosmetic products, the pH of the product might change with time and this would lead to destabilization of some certain ingredients. This happens very often by applying urea or weak acid based emulsifiers and ingredients (citrate derivatives for example: glyceryl oleate citrate). In such cases you need to stabilize the pH with a buffering system (blending sodium lactate and lactic acid)
Buffered solutions resist changes in pH upon addition of small amount of acids or bases. Our blood for instance is a buffered system and its pH would not easily change.