We discussed the role of vitamin C, peptides, and collagen in skin health here.  Collagen is a vital support structure in the skin and provides tightness and turgor along with hydration. Vitamin C assists in collagen cross linking and the use of topical vitamin C has been shown to boost collagen production in the skin.  Vitamin C also fights free radicals and reduces sun damage. While collagen supplementation is an unclear science, it is very clear that topical vitamin C can produce lasting improvement to the skin.  

So what’s next?  For the skin experts who have their sunscreen, moisturizer, tretinoin and vitamin C routine on point, what else can we turn to for skin rejuvenation?

Along with collagen, hyaluronic acid is a critical component of the skin and an exciting area of anti-aging research.  Firstly, to clear up any confusion, it’s important to point out that Hyaluronic Acid is not an acid like alpha and beta hydroxy acids.  Unlike acids that exfoliate, HA actually draws water into the tissues. HA is a glycosaminoglycan, which is a large protein molecule that organizes itself into a flexible, supple mesh throughout the body.  HA is found in its highest concentrations in the eyes, joints and skin, where it serves as a cushion and protective agent for these delicate structures.  

50% of the HA in our bodies is found in the skin, distributed between the epidermis and dermis.  Mother Nature certainly allocated this molecule well to maintain tightness and hydration for our skin but over time, HA can thin out, usually due to a combination of normal aging, sun and ultraviolet exposure, and other environmental exposures such as free radicals.  When functioning properly, HA molecules create an interlocking mesh that surrounds the skin cells, allowing moisture to glide effortlessly through the skin. HA is able to attract water in high amounts, with some studies suggesting that it attracts 1000x it’s own weight.  As we age or as ultraviolet light and free radicals damage the skin, HA molecules become less able to attract water, which results in a dry, loose appearance to the skin. HA molecules also become less organized and are not able to effectively transport water and healing mediators throughout the skin.  

Now that we understand the role of HA in the skin and thank Mother Nature for giving us so much to work with, how can we protect what we have and rebuild what has been lost?  Prevention is always the first and best strategy. Studies have shown that that HA degradation and redistribution is accelerated in sun exposed skin, beyond even what is seen in normally aging skin.  Normal aging skin also has lower levels of hyaluronidase, which is an enzyme that degrades HA, as compared to sun exposed skin in age matched controls.  Wearing daily sunscreen and sun protective clothing will slow down the process of HA changes and of course has a host of other benefits as we have discussed before.  

Moisturizers and serums containing HA can also be very helpful to support and restore HA in the skin.  In skin care products, HA can be thought of as a humectant, which draws in water and moisturizes the skin.  There are many different types of HA products available in skin regimens. The two most common are high molecular weight hyaluronic acid and low molecular weight hyaluronic acid.  There is also sodium hyaluronate, which is comprised of very small fragments of HA. High molecular weight HA is not well absorbed and tends to site on the skin, rather than intercalate between the cells.  While this type of HA can be a useful humectant, it is likely not going to provide benefit beyond that of a regular moisturizer. Low molecular weight HA however, can hydrate the skin more deeply and can be more useful in preventing and treating photoaging.

While topical HA is certainly an excellent humectant, it is important to note that the actual effects of HA on photoaging are mixed.  In many cases, the HA in topical products is simply too large to penetrate the skin effectively, similar to the collagen found in many topicals and serums.  Further, HA found in washes will not be effective due to being washed off and in very short contact with the skin. HA found in anti-aging serums may be effective in combination with tretinoin and other antioxidants, but that may have to do more with the non-HA components.  Interestingly, HA also has been shown to increase penetration of other products into skin, so if you are looking to boost your retinol or other product, pre-treating with HA can be very useful. Tretinoin has been shown to increase HA in the skin, so as always, tretinoin is an excellent part of all anti-aging regimes.  

So what’s the bottom line on topical HA? We know that’s important to maintain plump, youthful skin and we know that it is lost over time and that sun damage accelerates that process.  Preventing HA loss by using sunscreen is key but what about replacing HA? Some low weight replacement HAs may help to add tightness back to the skin but the majority of HA products will mainly moisturize and slightly smooth the skin- which is great for any skin care regimen.  Along with a great tretinoin and sunscreen, HA is a great choice as a humectant and protector of skin.  

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