Collagen, Glutathione, NAD+: Supporting Your Skin From the Inside Out

Reviewed by: Yiming (Amy) Qin, PhD, RD

Walk into any pharmacy and you will find an entire aisle dedicated to collagen. Drinks, powders, capsules, creams. The claims are everywhere. But ask most people what collagen actually is, where it lives in the body, or what happens to it as you age, and the answers get vague fast.

Understanding how your skin actually works changes how you think about all of it. Not just what to buy, but what your skin genuinely needs and why.

Why Most Skin Products Work at the Wrong Level

Your skin has layers, and which layer you are talking about matters more than most people realize.

The outer layer, called the epidermis, is what you see and touch every day. It is mostly made of a protein called keratin, which gives skin its protective barrier and its surface texture. This is the layer that most creams, serums, and moisturizers interact with. It renews itself continuously, with the full cycle from new cell to shed cell taking around 28 to 50 days in healthy adult skin, a process that slows further with age.³

Below that sits the dermis, and this is where the real architecture of skin lives. The dermis is made up of a dense network of collagen fibers, the structural protein that gives skin its firmness and strength.² Alongside that network sits hyaluronic acid, a molecule naturally found in the dermis with a remarkable ability to attract and hold water, keeping the tissue hydrated, cushioned, and plump.¹ Together these two structures are responsible for most of what people mean when they talk about skin looking young or aging well.

Crucially, most of the changes associated with aging happen here in the dermis, not at the surface where most products are applied. A cream that hydrates the epidermis can make skin feel softer temporarily. But the deeper structural changes that determine how skin ages over time happen below the surface.

Layer	Key components	What it does
Epidermis	Keratin	Protective barrier and surface texture. Renews itself every 40 to 56 days, a process that slows with age.³
Dermis	Collagen	Gives skin its firmness and structural strength. Declines by about 1% per year from the mid-20s.²
Dermis	Hyaluronic acid	Attracts and holds water, keeping tissue hydrated, cushioned, and plump. Declines steadily with age.¹

What Breaks Skin Down Over Time

Skin aging is not one single process. Several different things are working against it at the same time, and they each hit the dermis differently.

UV radiation: This is the biggest external factor. Every time we expose ourselves to the sun, enzymes inside our skin start breaking down the collagen in the dermis. Not to mention, it also creates small molecules called free radicals that damage our own skin cells. Studies have shown that up to 80% of visible facial aging comes from UV exposure rather than time alone.⁴
Oxidative stress: Think of this as the broader version of UV damage. Free radicals are not just made by the sun. Pollution, chronic stress, poor sleep, and even normal everyday metabolism all produce them too. When the skin cannot neutralize them fast enough, they quietly chip away at collagen and make it harder for skin cells to repair and rebuild.⁵
Glycation: This one is less talked about but just as important. Every time there is excess sugar in the bloodstream, some of it sticks to collagen fibers and makes them stiff. The collagen that used to give skin its bounce becomes rigid instead, and that rigidity shows up as reduced elasticity and deeper lines over time.⁶
Time itself: This one runs in the background no matter what else you do. From around the mid-20s, the body produces about 1% less collagen every year.² Hyaluronic acid levels in the dermis drop too.¹ The skin gradually becomes thinner, drier, and less able to bounce back from the other three.

The Glutathione Angle: Your Skin's Internal Defense System

You have probably seen the word antioxidant on just about everything. Food labels, supplements, skincare, drinks. It is one of those terms the industry loves but rarely explains.

Here is the simple version. Free radicals are essentially broke at the molecular level. They are missing an electron and will take one from wherever they can find it, a collagen fiber, a skin cell, it does not matter. Antioxidants work by offering up their own electron first, neutralizing the free radical before it can steal from anything important. And the most abundant & Important antioxidant your body has is one it makes itself, called glutathione.⁷

The problem is that our bodies produce less of it as we age. By the time most of us reach our 40s and 50s, glutathione levels have dropped enough that the skin has a harder time keeping up with the oxidative damage coming in. This is part of why the same amount of sun exposure that left no mark in your 20s starts showing up differently later in life.⁷

NAC takes a different approach. N-acetyl cysteine, which is what NAC stands for, is what the body uses as a raw material to make glutathione. Rather than trying to take glutathione directly, which the body does not absorb well when you take it as a capsule, NAC gives your cells what they need to produce more of it on their own.⁸

Things Worth Knowing Before You Buy Anything

Does the collagen I eat actually become collagen in my skin?

Not in the way most people think. When you swallow collagen, your body breaks it down the same way it breaks down any protein, into individual building blocks. None of it travels intact to your skin. What the research does show is that certain collagen peptides can signal the cells in your dermis to start producing more collagen on their own.¹⁰ So it is less like topping up a tank and more like sending a message.

I have been taking collagen for months. Why am I not seeing results?

Usually it is something missing from the picture. Collagen cannot be built without vitamin C. It acts as a direct helper in the process, and without it the body simply cannot form the stable, functional collagen structures required to maintain healthy skin no matter how much collagen you are taking.¹¹ On top of that, things like sun exposure, high sugar intake, and oxidative stress can break collagen down faster than it is being built. If those are not being addressed, the supplement is fighting an uphill battle.

Does hyaluronic acid (HA) in a cream actually hydrate my skin deeply?

Mostly at the surface, and here is why. The HA molecules in most creams are too large to reach the dermis where hyaluronic acid does its structural work.⁹ What you get is surface hydration, which makes skin feel temporarily softer and plumper, but it is not the same as the HA your body produces internally. Oral HA supplementation has shown benefits for skin hydration in clinical trials, and supporting your body's ability to make more of it is a more direct approach than applying it from the outside to the skin.¹

I take glutathione supplements for my skin. Are they working?

Possibly less than you think. Most oral glutathione does not survive the journey through digestion well enough to actually raise your levels in a meaningful way.⁷ NAC is a smarter route because instead of trying to deliver glutathione pre-made and hoping it arrives intact, it gives your cells the raw material to make more of it themselves, which is how the body prefers to work anyway.⁸

Where NAD+ Fits In

Every day, UV radiation, oxidative stress, and normal everyday activity your cells do, create small errors and breaks in the DNA of your skin cells. Your body has repair systems designed to fix this damage before it becomes a problem, and those repair systems run almost entirely on a molecule called NAD+.¹³

The problem is that NAD+ levels decline gradually with age.¹² As they fall, those repair systems slow down. Damage that would have been fixed quickly in your 20s starts to linger. In skin cells specifically, where UV exposure is constant, the slower repair means faster accumulation of the damage in your skin cells.¹²·¹³

NAD+ is not a skin ingredient in the traditional sense. It is a molecule found in every cell that powers the systems in your healthy cells. Supporting it is less about targeting skin directly and more about giving the body what it needs to do its own repair work properly.

Where to Start

Most of what is sold for skin works at the wrong level. The real action is happening deeper, and that is where it makes sense to focus. Supporting skin from the inside is not about finding one miracle ingredient. It is about not leaving gaps.

Vitamin C: This is a non-negotiable for collagen synthesis.¹¹ Without it the body cannot complete the process regardless of what else you are taking. It also works alongside glutathione as part of the body's antioxidant network, with each supporting the other's ability to stay active.⁷·¹⁴
NAC: This gives the body the raw material it needs to produce glutathione on its own, which is more effective than trying to take glutathione directly.⁸
Hyaluronic acid (HA): is best supported from the inside. The HA that actually maintains skin structure and volume is made by your own cells in the dermis, and keeping those cells healthy and nourished is a more direct approach than applying it topically.¹
NAD+: Its support helps maintain the cellular energy system that all of these processes depend on, including the repair systems that address daily UV and oxidative damage.¹²·¹³
Sun protection: This remains the most evidence-backed single step you can take for preventing visible skin aging.⁴ Everything else works better when UV damage is being limited.

If you are looking for nutritional support that addresses several of these at once, the Neumina Skin Brightening Complex combines vitamin C for collagen synthesis, NAC as a glutathione precursor, sodium hyaluronate to support skin hydration from within, and biotin for skin structure. For the cellular energy layer, Neumina NAD+ works alongside it, supporting the power supply that all of these processes depend on. Neither is a substitute for sun protection or a balanced diet. But together they address the internal foundations that topical products cannot reach.

Explore Neumina Skin and Beauty Complex →

Explore Neumina NAD+ →

*These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.*

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