NAD+ 101: What It Is, Where It Comes From, and What It Actually Does for Your Body and Your Skin

By Nicole, Licensed Esthetician | Skin & Soul Cosmetics

NAD+ has gone from a biochemistry textbook term to a wellness buzzword, showing up in IV drips, supplements, and now skincare. But most of the marketing skips right past what it actually is. Understanding the biology first makes it a lot easier to tell which claims hold up, especially when it comes to putting it on your skin versus taking it into your body.

What NAD+ Actually Is

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme found in every single cell in your body. Think of a coenzyme as a helper molecule that other enzymes need in order to do their job. NAD+ has two main jobs it helps carry out constantly: producing cellular energy and repairing DNA.

On the energy side, NAD+ shuttles electrons around inside your mitochondria (the energy-producing structures inside your cells) as part of converting food into usable energy, called ATP. On the repair side, NAD+ is required fuel for two families of enzymes, sirtuins and PARPs, that fix damaged DNA and help regulate inflammation and cellular aging. No NAD+, no fuel for either process.

Where NAD+ Actually Comes From

Your body makes NAD+ on its own, mainly from vitamin B3. There are a few forms of B3 that all feed into NAD+ production, including niacin, nicotinamide (also called niacinamide), and the newer, more talked-about precursors nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN). Your body also makes a smaller amount of NAD+ from the amino acid tryptophan through a separate pathway.

The catch is that NAD+ production naturally slows down as you age. Research estimates NAD+ levels can drop by roughly half between young adulthood and age 50. UV exposure, chronic stress, and oxidative damage accelerate that decline further, which is a big part of why NAD+ has become such a focal point in both longevity research and skincare.

What NAD+ Does for the Body

Systemically, healthy NAD+ levels are tied to how efficiently your mitochondria produce energy, how well your cells repair DNA damage day to day, and how your body regulates inflammation. This is why NAD+ has become a major focus of aging and longevity research; it sits at the intersection of energy metabolism and cellular repair, two processes that decline together as we get older.

What NAD+ Does for the Skin

Skin cells run on the same NAD+-dependent processes as the rest of the body. Keratinocytes and fibroblasts (the cells responsible for skin renewal and collagen production) need adequate NAD+ to keep their own energy production and DNA repair running properly, especially after UV exposure, which directly damages skin cell DNA and depletes local NAD+ in the process.

In topical form, supporting this pathway is associated with better resilience against environmental and UV-driven oxidative stress, and with supporting the skin's own repair and renewal processes over time. This is a supportive, cellular-health role rather than an instant visible-texture change, which is an important distinction from actives that work more immediately on the surface.

The Molecular Size Problem (A Callback to Our Serum 101 Post)

Here's where it gets interesting. NAD+ itself is a relatively large molecule, weighing in at roughly 663 Daltons. That's well above the roughly 500 Dalton threshold most dermatological research points to as the practical cutoff for a molecule to penetrate the stratum corneum on its own. In plain terms: applying pure NAD+ directly to skin faces a real absorption challenge.

This is why most topical "NAD+" skincare is actually built around niacinamide, one of NAD+'s own precursors. Niacinamide is a much smaller molecule (about 122 Daltons), well studied for topical use, and readily absorbed. Once inside the skin, it can be converted into NAD+ locally, feeding the same energy and repair pathways without needing to get the larger, harder-to-absorb NAD+ molecule through the barrier directly. In other words, a lot of the real benefit of "topical NAD+" comes from delivering a smaller, smarter precursor and letting your skin cells do the conversion themselves.

The Bottom Line

NAD+ is a real, essential coenzyme powering energy production and DNA repair in every cell you have, and its natural decline with age is well documented. On skin specifically, the science supports a genuine supportive role for cellular resilience and repair, but the molecule's size means the smartest formulations lean on well-absorbed precursors like niacinamide rather than NAD+ itself. Knowing that distinction is the difference between understanding what you're actually putting on your skin and just buying the buzzword.