Hyaluronic acid is one of those increasingly popular, stand out ingredients that beauty companies use these days, which admittedly make a lot of skincare products sound more fancy, expensive and valid. It is specifically marketed as an intense hydration miracle worker and some even claim it has anti-ageing properties promising a healthier looking, less wrinkly skin. Interestingly, there are also claims that this ingredient can be used as an anti-oxidant, protecting from environmental damage, similarly to the effects of an SPF sun cream (see post “Everything you need to know about sunscreens and SPF”). It is also allegedly suitable for all skin types, so you don’t need to worry whether you have an oily, dry, sensitive or combination complexion. For a goo textured substance, it definitely promises some serious action!
Hyaluronic acid, also called hyaluronan, is a naturally occurring compound which can be found in our bodies, especially in our eye and joint fluids, acting as a cushion or lubricant, so it is no wonder why some people even use it to alleviate osteoarthritis. It is an FDA (Food and Drug Administration, US) approved compound for its use in eye surgery but it is a lot more popular for its application in plastic enhancement fillers, to soften out wrinkles or plumb up your lips!
So let’s dive into the evidence! What scientific proof is there out there for this molecule and do any of the claims have merit? I went through many peer-reviewed scientific reports, by scientists for scientists (no company promotions or beauty articles), and here’s what I found.
There are many scientific studies on hyaluronic acid and osteoarthritis and many propose that the topical application (as a cream or gel) of this compound has positive effects in affected patients. However, only a few of those studies actually include clinical trial data (actual experiments including real people) with a total population of less than 100 patients.  The articles claimed that the positive effects were due to inflammation control and while the evidence seems to point towards a positive direction, the sample size is very limited. 
But what about oral tablets? Do they have the same effect? In a study published by the University of Verona in Italy, there was evidence to show that hyaluronic acid taken either orally or topically as a cream/gel had positive effects in both cases although, similarly to the previous studies, the sample size was only based on 60 patients.  Hopefully there will be more studies in the future that offer a larger patient sample size and offer more solid data to shine more light on these promising results.
But let’s move to the moment we are all waiting for. Is hyaluronic acid actually hydrating? Yes it is! However, it should be noted that hyaluronic acid is not hydrating on its own, it owes this property to its ability to retain water (so you need water). Hyaluronic acid is a polymer, which means it is a molecule made of many identical repeating units. Those repeating units are “hydrophilic” which is Greek for a friend of water. This means that as those molecules like water they will absorb and retain it. As a result, because of the structure of this compound, containing a large number of water friendly molecules, hyaluronic acid can absorb a lot of water. In fact, it can hold thousands of times its weight in water! However, note that its ability to hold water will be directly dependant on the local conditions  it finds itself in and how long the molecule is, i.e how many of the water loving building blocks it has and this can vary (for more info see the “Beauty related chemistry behind hyaluronic acid” post). Bear in mind that, due to its high water retention property, it is also possible that hyaluronic acid, in tablet form, can make you feel bloated.
There is also a fair amount of studies on hyaluronic acid and wound repairing. A model study by the University Medical Centre in Virginia, showed that as wounds go through inflammation processes, the naturally present hyaluronic acid levels decrease as the compound is increasingly degraded.  This suggests that replenishment of hyaluronic acid on wounds could be beneficial for faster and healthier tissue regeneration and repair. Its water retaining capacity suggests that it could also play a role in facilitating nutrient transport within cells.  There is also some evidence that shows that this miracle worker molecule, can stimulate collagen and non-collagen protein synthesis  which are also ingredients required for a healthy and young looking skin.
This could be one of the reasons that have sparked attention to this molecule as an anti-ageing ingredient. Sadly, there is a lot of evidence that hyaluronic acid levels naturally decrease in maturing skin and during cellular ageing.  Let’s have a moment of silence for all that “fountain of youth” molecules that we have lost already! Bah!
Interestingly, a study published by Miyamoto and Nagase showed that there is an age-related change in molecular weight (i.e. how long the polymeric chain is), in rat skins , while others reported that age related molecule shrinkage was not observed but rather the topology, of where and in which layer of the skin, the hyaluronic acid is found. In my opinion, both age related shrinkage and topology changes make sense as the body goes through natural degradation and inflammation. However, I must admit, the evidence from these studies is not enough to make a solid conclusion.
So hyaluronic acid does indeed show promise in the anti-ageing action game (it is definitely very interesting that large amounts of it are found in fetuses!)  but the exact method of its work is neither clear nor fully understood. It could be either due to its hydrating property making the skin healthier and more plumb but it could also be due to the promotion of nutrients or collagen and other protein synthesis, inflammation control and wound repair.
This ingredient will not remove your wrinkles, sadly, you might need something a little more drastic for that like surgery or fillers (which usually contain hyaluronic acid!). However, depending on it’s exact structure and formulation, this miracle acid will be absorbed by your skin, the extend of which depends on the size of the molecule. Fillers tend to contain longer hyaluronic acid molecules to make them last longer before your body degrades them, whereas hyaluronic acid molecules found in skin care tend to be shorter to allow them easier passage through the skin. And while this water sponge material can pass through the skin barrier, it’s hydrating ability (water retention) will be less because the molecules are smaller.
According to a study at the Department of Dermatology of the Jefferson Medical College, additionally to the other negative effects, chronic sun exposure can also alter the content and distribution of molecules, like hyaluronic acid, in the affected skin. Instead of being located between collagen and elastic fibres as found normal skin, they can be deposited on the superficial dermis resulting in a weathered, sun-damaged, older-looking appearance.  So while hyaluronic acid cannot really act as your standard SPF protection, your SPF protection can actually protect your hyaluronic acid levels! Always aim to wear a minimum of SPF 15, even during a British rainy winter. (see post “Everything you need to know about sunscreens and SPF”)
There are also some suggestions that chemically altered hyaluronic acid molecules (containing a Carbon=Carbon double bond which they don’t naturally contain) have increased capability to interact with oxidation agents possibly slowing down ageing and other skin degenerative processes and can also selectively target cancer cells!  And as if the current evidence was not convincing enough, even cancer seems to think that this molecule is worth it, as it was shown that various tumours, including ovarian, colon, stomach and leukaemia, over-produce molecules that pick up hyaluronic acid, perhaps as part of their mechanisms of repair and growth. 
Finally, there are also other studies that explore the applications of hyaluronic acid in areas including: tooth bleeding (bad news here it actually makes the swelling and bleeding worse so…erm..don’t put it on your gums?),  cystitis prevention  and other urinary tract infections,  tissue engineering,  dry eye disease  and more. As scientists explore more and more variations of this chemical structure and introduce even better enhancements, I am sure this molecule will show up with even more potential applications.
If you are now going through all your beauty products looking if they include this magical ingredient, be aware that it might be present in different forms, either chemically altered, so the name will be different, or most commonly, in it’s salt form: sodium hyaluronate. The salt form is usually preferred in formulations as it makes the molecule a little more stable, lasting longer and interacting less with other compounds present, while retaining it’s water solubility.
Additionally, bear in mind that hyaluronic acid can, like anything, cause an allergic reaction if your body just doesn’t agree with it, but it is overall considered a safe compound. Toxicity and mutagenicity studies showed no evidence of impaired fertility or harm to fetus (doses up to 1.43mg/kg of body weight).  If you are concerned, always consult a medical doctor and try the product containing this, or any ingredient you want to test, in a small amount on your hand, at least 24 hours prior to using it in your daily routine.
Overall, I can say that hyaluronic acid is worth the hype and that there is some scientific evidence towards the claims (although more studies are needed)! I have already been including a hyaluronic acid containing day cream, in my daily skin care, and I have definitely seen a difference in terms of a healthier, softer, calmer looking skin. Let’s hope it slows down the ageing process too!
If you want to gain a little more understanding check out “The beauty related chemistry behind hyaluronic acid” post.
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