In the pursuit of younger, healthier, better-looking skin, people are willing to try all kind of things.
From skin treatments to topical creams to good old-fashioned diet and exercise, something that's risen in popularity is collagen.
Whether it's in your morning coffee, added to a smoothie or taken as a tablet, collagen supplements seem to be everywhere.
But what is collagen, and what do collagen supplements do for your skin?
What is collagen?
Collagen is present everywhere in your body — there are about two dozen different types in your skin, your bones, in your cartilage, and even in your hair.
"Collagen is a protein. In fact, it is the most abundant protein in mammals," Dr Karl Kruszelnicki explains on Great Moments in Science.
"In humans, collagen makes up about 30 per cent of all the protein in the body."
Like all proteins, collagen is made from amino acids — in this case, about 1,000 — which form a triple helix amino acid chain to create strong connective tissue.
There are about two dozen different types of collagen in our bodies, found in our hair, in cartilage, and even in the placenta.
It's "the kind of tissue that if we ate it in our dinner, we'd probably spit it out", says Geraldine Moses, a clinical pharmacist at the University of Queensland.
"It's a bit like the gristle on meat."
Collagen fibres provide a support structure for the cells in our skin, which keeps it from sagging.
As you age and your body produces less collagen, your skin loses this plumpness and fine lines and wrinkles start to appear.
The collagen found in wellness products typically comes from fish scales (known as marine collagen), or the cartilage, bones, tendons or hides of various animals (sometimes called bovine collagen).
In the form of a supplement, it purports to eliminate wrinkles and make your skin glow from the inside out.
But how true are those claims?
Does taking collagen work on your skin?
Clinical trials have shown that there is "not really any good evidence" that collagen supplements make your skin look better.
The data available is limited, and there just aren't enough good quality randomised controlled trials to draw consistent conclusions.
"Lots of the studies are not independent — they are funded by the corporations that sell the collagen supplements," Dr Karl says.
"What's more, often these studies aren't carried out in the way you'd expect of a high-quality trial."
Loading...Dr Karl says one of the problems with collagen supplements is that, because the collage protein is so big, it simply cannot get into your bloodstream to end up having an effect on your skin.
Before any proteins can get into the bloodstream, they have to enter the cells lining the gut, called endothelial cells, he explains.
These cells only allow proteins of fewer than three amino acids in — and only one amino acid can get out of these endothelial cells and into your bloodstream.
"The 1,000 amino acids that make up a single molecule of collagen have to be broken down into 1,000 separate, and individual, amino acids," Dr Karl says.
"Only then, can they individually get into your bloodstream, to finally arrive at your skin to be recombined in half a dozen complex steps to make collagen — to then presumably iron away your wrinkles.
"There's just no way that the individual amino acids that were in the collagen that you ate or drank, will automatically regroup into individual molecules of collagen to smooth out the fine wrinkles on your face."
Cosmetic chemist Michelle Wong says "in general, [collagen supplements] don't have a ton of evidence".
But, she says, some small studies suggest collagen that is broken down into smaller, easier-to-process fragments — known as hydrolysed collagen — may get through the blood barrier.
"There have been studies that have found that if you take hydrolysed collagen that has [the amino acid] hydroxyproline in it, it breaks up and the hydroxyproline survives in your stomach, making it into your blood."
Studies in test tubes suggest that while these fragments don't reform to make collagen, they may stimulate the production of hyaluronic acid.
"In in vitro studies, they take these fragments and put them on skin cells, and the cells have produced more hyaluronic acid, which is one of the things in your dermis that can plump up your skin," Dr Wong says.
"So these fragments in your blood could potentially tell your skin to plump itself up."
But one of the problems with hydrolysed collagen is that there are so many ways to break it down, you don't know which one you're getting as a consumer, Dr Wong says.
"It could be chopped in half, it could be chopped into tiny fragments, it could be chopped into larger fragments," she says.
"It's like buying different brands of chips; it's variable. Some are delicious, some are not going to be as good as others.
"So some collagen supplements could potentially work, but I'd recommend trying more proven ways of boosting collagen in your skin first, like wearing sunscreen and using retinoids."
And as for adding collagen powder to your coffee to make it more effective — well, there's bad news there too.
"Collagen molecules come apart when the temperature climbs. The molecules would be destroyed by the heat of [a] morning cuppa," Dr Karl says.
So how did collagen make its way into our coffee mugs and wellness products in the first place?
From filler to filter coffee: Collagen's progression
Collagen's popularity stems from its use in the 80s as a filler — it's injected into lips or cheeks to make them plump.
"That worked of course, but … swallowing stuff is not the way to go," Dr Moses says.
"Generally speaking, it doesn't get absorbed."
But regardless of efficacy, our desire for younger-looking skin is an advertising dream.
There is no obligation on a corporation's part to prove collagen's effectiveness; just as is the case with some beauty treatments, there is no industry regulation.
"These products are never tested, they never have to prove that they work, so we're putting blind faith into the industry," Dr Moses says.
"Manufacturers can make these claims and they know that they're not obligated to prove anything."
This is also the case with another beauty supplement, silica, she says.
Silica shows 'no oral bioavailability'
You probably remember silica being in the first ever hair, skin and nails supplement you bought from the supermarket when you were younger.
Well, it's still being marketed in products as an essential ingredient to encourage skin, hair and nail health.
"The scientific name for silica is silicon dioxide — and the everyday name for that is sand, which you find at the beach," Dr Moses says.
"Anyone who's been at the beach with a baby knows that sand will just go straight through you. There's no oral bioavailability."
Silicon dioxide is widely used in food products as an anti-caking ingredient to stop dry ingredients from clumping together; in things like lipsticks; and in some medicines to stabilise active ingredients.
As well as being found naturally in the earth, silicon dioxide is in foods like oats, brown rice and leafy greens.
It also exists in the human body, and is thought to play a part in the synthesis of collagen — but there are question marks over whether a deficiency requiring a silica supplement is likely.
Clinical studies on the bioavailability and efficacy of silica supplements for your skin are lacking.
Rather, the idea that silica has a benefit to hair, skin or nails in supplement form is "taking advantage of people's ignorance," Dr Moses says.
"[A silica supplement] is harmless in the sense that it's not dangerous to you.
"But there is harm in spending money you didn't need to spend."
So what, if anything, can we ingest to help our skin?
Getting back to basics
It sounds boring, but the best thing you can do for your skin is to eat well and drink lots of water.
Clare Collins, Laureate Professor in Nutrition and Dietetics at the University of Newcastle, says you're far better off spending your money on foods that are rich in the nutrients we know have a positive benefit on the skin.
"Spend whatever you like on your cosmetics, but first up, protect yourself from within by prioritising the money you spend on your food," she says.
"Keep a record of how much you spend, and rather than spending on non-evidence-based products, spend it on high-quality basic foods, and see the difference."
Professor Collins suggests eating foods rich in protein that can be broken down into the individual amino acids that your body needs to make collagen — things like meat, chicken, fish, eggs, milk, cheese, nuts and tofu.
"Collagen is stabilised in the presence of vitamin c, and if you don't have enough vitamin c, the collagen helix starts to break up," she says.
"Foods that are rich in vitamin C are better for collagen [than supplements], so things like fresh veggies and fruit — not just oranges and lemons but broccoli, capsicum, tomatoes, baby spinach, kiwi fruit.
"Foods that are rich in vitamin A are also needed to help mature skin cells.
"Beta-carotene is converted to vitamin A in the body, and the easiest way to get that is in carrots and other orange vegetables, and fruits like pumpkin and rockmelon, and in green leafy vegetables."
Foods rich in zinc, like seafood, meat, chicken, dried beans and nuts, as well as foods rich in polyphenols like fruit, herbs and spices, are also beneficial for skin health.
As for whether a powdered supplement containing these vitamins and minerals can benefit your skin? Professor Collins says they're no match for the real stuff.
"You cannot get the longer-term health benefits from supplements out of a bottle," she says.
"If you had a nutrient deficiency in any of those things, your skin is the least of your worries. If your diet is that poor, you're at risk of a whole lot of other chronic conditions beyond poor skin health.
"Your body is made out of the foods you eat. You can't have healthy skin if you don't have the raw materials."
Alongside a variety of foods in your diet, the best way to keep your skin looking good is to avoid sun damage.
"Maybe the secret to glowing skin is as simple as eating healthy food and slapping on some sunscreen," Dr Karl says.