NAD gets talked about a lot and explained badly almost as often. This is the plain version.
What the letters mean
NAD stands for nicotinamide adenine dinucleotide. It is a coenzyme — a helper molecule that enzymes need in order to do their job. It is found in every living cell.
What it does
NAD's best-understood role is in energy metabolism. When your body breaks down food, the energy released has to be carried somewhere useful. NAD is one of the molecules that does that carrying. It picks up electrons in one reaction and drops them off in another, cycling between two forms as it goes.
That cycling is why you will sometimes see it written as NAD+ and NADH. NAD+ is the form that accepts electrons; NADH is the form carrying them. They are the same molecule in two states, not two different products.
Why anyone cares
Interest grew when researchers observed that NAD levels in human and animal tissue tend to be lower in older subjects than in younger ones. That observation created the category of NAD-related supplements.
The important caveat
Everything above is descriptive biology. It tells you what the molecule does inside cells. It does not tell you what happens when a person takes an NAD supplement, which is a separate question requiring separate evidence about a specific product, at a specific dose, in people.
We keep those two things apart deliberately. You can read more in our story.
