What Is NAD? A Simple Guide

What is NAD?

NAD stands for nicotinamide adenine dinucleotide. It’s a coenzyme—a helper molecule that works alongside enzymes to drive chemical reactions inside your cells.

Every cell in your body contains NAD. Without it, the basic processes that keep you alive—turning food into energy, supporting DNA repair pathways, and regulating your internal clock—wouldn’t function properly. 

NAD exists in two forms: NAD+ (the oxidized form) and NADH (the reduced form). These two forms pass electrons back and forth during metabolic reactions, which is how your cells extract energy from the nutrients you eat. 

And the buzz around NAD grew when scientists realized that NAD levels don’t remain stable forever. Research over the past two decades suggests that NAD levels naturally decline with age, and this drop appears to be associated with changes in how efficiently cells produce energy and maintain themselves over time.

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What Does NAD Do?

NAD is involved in hundreds of biological processes, but its primary functions come down to two things—energy production and cellular maintenance.

On the energy side, NAD is essential for metabolism. When you eat, your body breaks down carbohydrates, fats, and proteins into usable fuel. And NAD shuttles electrons through a series of reactions that ultimately produce ATP, the molecule your cells use for energy. Without adequate NAD, this process becomes less efficient.

But NAD does more than power your cells. 

It also supports the activity of enzymes called sirtuins, which are involved in DNA repair, inflammation regulation, and stress response. When NAD levels are sufficient, these protective pathways can stay active. When levels drop, their activity may decrease.

NAD also influences your circadian rhythm—the internal clock that governs sleep, hormone release, and metabolism. Research suggests that NAD levels fluctuate throughout the day and may play a role in keeping this clock running on schedule.

In short, NAD supports the infrastructure that keeps your cells functioning, repairing, and communicating properly. Lower NAD levels are associated with aging and changes in cellular efficiency over time.

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Why NAD Levels Change Over Time

Your NAD levels fluctuate based on age, lifestyle, and what your body is dealing with on any given day. Some of these factors are within your control; inevitably, others aren’t. So, here are the main factors contributing to shifts in NAD levels.

Changes in Metabolism

The evidence suggests that NAD levels naturally decline as you get older. The reasons are still being studied, but it appears to involve both reduced production and increased demand. 

As cells age, they require more NAD for repair and maintenance, but the body’s ability to synthesize it may slow down. This results in a widening gap between supply and need.

Alcohol Consumption

Your liver uses NAD to metabolize alcohol. When you drink, the process of breaking down ethanol uses NAD, leaving less available for other cellular functions in the moment. 

Thus, chronic or heavy drinking may contribute to lower available NAD for other cellular processes and may also contribute to the fatigue, cognitive fog, and slower recovery that often accompany excessive alcohol use.

Stress, Illness, and UV Exposure

Many things that damage your cells can increase demand for NAD. This means that physical stress, chronic illness, and even sun exposure, which can rely on NAD-dependent enzymes for necessary repair processes, may lead to lower levels.

For example, UV exposure can cause DNA damage in skin cells, and fixing that damage can involve NAD-dependent repair processes. 

Poor Diet

NAD is synthesized in the body from dietary precursors—primarily forms of vitamin B3, such as niacin and nicotinamide, with smaller contributions from the amino acid tryptophan. Because these compounds provide the raw materials for NAD production, a diet lacking adequate vitamin B3 may limit how much NAD the body can produce.

Additionally, processed foods, restrictive eating patterns, and nutrient-poor meals can all contribute to lower baseline levels over time.

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Final Thoughts

Scientific research is still evolving. However, evidence indicates that NAD supports energy production, cellular repair, and a range of processes that keep your body functioning well. And while declining levels are a normal part of aging, lifestyle factors, such as diet, alcohol consumption, and chronic stress, can accelerate this drop.

At the same time, it’s important to always discuss your options with your doctor before introducing any new supplement into your routine. A licensed healthcare provider can help determine if it makes sense for you and your health.

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