Hyaluronic acid is important for skin health, especially because it helps with skin flexibility and ease of movement. That is also true for joints, lungs and other tissues where hyaluronic acid is made.
With this information there are those that advocate that if it is important, and it may be deficient, then I will address the problem by taking it orally e.g., as supplement. The desire for the benefits is laudable, but sadly the taking hyaluronic acid orally will not work. What is needed is to stimulate the local production of hyaluronic acid where and when you need it and in the correct amounts.
The reason why ingested hyaluronic acid will not work is because the molecule is massively too large to be absorbed. For those seeking research papers demonstrate this basic fact will be disappointed. WHY? Because it would defy a very basic understanding of gut physiology, one that is over a century old.
The MW of hyaluronic acid is approximately 450,000. It is composed of saccharides arranged in a complex polymer. Saccharides (glucose as an example of an individual saccharide) have a molecular weight of approximately 180. To be absorbed saccharides must be in the individual form, not a polymer. Even sucrose, which is a disaccharide, must be broken down into the two individual saccharides before absorption (these are glucose and fructose ). In other words, hyaluronic acid is over 2600 times TOO LARGE to be absorbed. There is absolutely no need to prove it is not absorbed as it is just basic and fundamental knowledge of gut physiology and digestion.
Hyaluronic acid can be helpful for joint health when given as an injection (used in horses). Injection of hyaluronic acid obviates the destructive process of digestion. In joints it works to make joint movement easier by reducing friction.
It is clear that any group that advocates that hyaluronic acid is effective when taken orally either lacks the necessary understanding of how digestion works (just do not know better) although it is also apparent that some know that it cannot be absorbed intact but market it anyway.
Note that oral hyaluronic acid when it is digested, breaks down to the various elements that make it up - individual saccharides like glucose as is the case with carbohydrates in general. By way of further explanation, when one digests a potato the process takes the carbohydrates down to individual saccharides. It does not stop 2600x short and expect the saccharides to still be absorbed. One does not have chunks of potato circulating in the blood stream after a meal.
Another application where hyaluronic acid is effective when intact, is topically. It is quite effective because it smooths out the surface of the skin. Here the application is identical to gastropods (snails etc.) where they lack "feet/legs", so they exude a layer of mucus that reduces friction, allowing for the snail to move. HA is a component of mucus. This loss of friction associated with hyaluronic acid is used in many organs and tissues that need that - skin, joints, lungs are prime examples. In this case it is made locally in the amounts that are needed to perform that function. It is not absorbed intact from the diet.
To REPEAT there are no recent studies showing hyaluronic acid is NOT ABSORBED INTACT as that is basic and established science (century old understanding of gut physiology). It is just a pity that those that market oral HA set out to deceive the consumer.