What Is NAD? Here's Everything to Know Before You Start Taking Supplements

These days there are so many different types of vitamins and supplements on the market. Every time you walk down the supplement aisle, it can feel a bit like swimming in alphabet soup between vitamins C, D, and E and now trendy newcomers like nicotinamide adenine dinucleotide, or NAD.

In 2024, the global nicotinamide adenine dinucleotide market was valued at $3.5 billion, and it is projected to grow from $4.5 billion in 2026 to $12.2 billion by 2033, according to Grand View Research.

With a market size that big, this must be a magic pill, right? We reached out to experts to get the lowdown on what NAD is, how to get NAD from your diet, and how to choose a supplement that best works for your lifestyle.

Simply put, NAD is an essential molecule found in every cell that our bodies must have to function. "Without it, life stops in seconds," says David A. Sinclair, Ph.D., a professor of genetics at Harvard Medical School Paul F. Glenn Center for Biology of Aging Research and the author of Lifespan: Why We Age — and Why We Don’t Have To. “NAD is used by the body to carry out chemical reactions involved in processes such as energy production, DNA repair, and activating longevity-promoting enzymes like sirtuins.”

It's linked to your circadian rhythm as well as oxidative damage (which can contribute to skin aging like wrinkles and fine lines). Some studies in mice have found that higher levels of NAD may prevent fatty liver disease, improve kidney function, strengthen muscles, maintain a healthy cardiovascular system, lower inflammation, protect neurons, and slow aging.

As for humans, recent research (from 2023) has shown that NAD appears to be relatively promising in short-term studies, but there isn’t enough research on humans yet to definitively say that increasing the amount of NAD in your body will result in all of those health benefits. The good news is scientists are exploring the possibilities.

Unfortunately, our level of NAD tends to decline with age—and the amount by which it drops varies by type of tissue, research has found. That's why some people turn to supplements.

Right now, testing for NAD levels is not a routine part of health care and there’s no established recommended daily intake. That said, there are ways to evaluate the amount of NAD you have. “High-functioning organs like the brain, heart, liver, and muscles require greater amounts of NAD,” says Toby Amidor, M.S., R.D., C.D.N., F.A.N.D., a nutrition expert and partner with Niagen Bioscience, which sells NAD booster products. “While direct measurement in these tissues typically requires biopsies or advanced imaging like MRIs, a less invasive way to assess overall NAD status is through blood testing.”

Sometimes, how your body feels is the best indicator that something is amiss. “Fatigue, brain fog, and metabolic slowdown could be signs that your NAD levels are declining,” says Sinclair. Of course, many other things can cause those symptoms as well, so if you’re feeling off and think low levels of NAD could be a contributing factor, talk to your physician.

First, talk to your doctor to make sure they think it’s a good idea. The NAD molecule itself is so large and unwieldy that it’s difficult for the body to use when taken as a supplement. “Supplements called NAD boosters typically contain either NMN (nicotinamide mononucleotide) or NR (nicotinamide riboside),” says Sinclair. “The body uses NR to make NMN, which is then converted to NAD.” A recent 2026 study showed that NR and NMN both increased circulating NAD+, but nicotinamide did not produce the same sustained increase which indicates how they both interact differently with the gut microbiome.

“There are a few ways to elevate NAD, including oral capsules and IV or injection therapy,” says Amidor. “It’s important to remember that supplementing or infusing with NAD directly is not efficient or as effective to raise NAD. Although NAD IV is popular amongst celebrities and athletes, it can take hours and induce severe side effects, such as nausea, headache, and diarrhea.”

If your doctor gives you the green light and recommends a dosage, here are some tips to consider when selecting an oral supplement to increase NAD levels:

• “Look for the most well-studied and bioavailable forms: nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN),” says Poon. “These have been shown to effectively raise NAD levels and support cellular health.”
• “Check for third-party certifications, testing, and evidence of clinical research,” says Amidor. The FDA regulates dietary supplements but doesn’t approve them all before they are sold. “As a result, product quality and safety become the responsibility of the manufacturers, but not all companies take this seriously,” adds Amidor. U.S. Pharmacopeia (USP) and NSF International are two reputable third-party testing organizations. You can also request a Certificate of Analysis from the manufacturer, Poon says.
• “Avoid vague ‘proprietary blends’ or ‘extracts’,” suggests Sinclair. You should know exactly what you’re ingesting and these extras really are not needed in an NAD booster.

“While we don’t absorb NAD directly from food, our bodies can produce it from specific nutrients found in whole foods,” says Serena Poon, C.N., C.H.C., C.H.N., a certified nutritionist and founder of the wellness brand Serena Loves. Here are some strategies for obtaining NAD precursors through food:

• NMN: “Broccoli and green beans are especially rich in NMN,” says Poon. “Beetroot, cucumber peel, spinach, carrots, scallions, and collard greens are also valuable sources.”
• NR: “For NR, top choices include wild chicory, bananas, oranges, avocados, leeks, cilantro, and purple taro,” says Poon.
• Niacin/vitamin B3: “Niacin-rich foods—like mushrooms, sunflower seeds, peanut butter, brown rice, sweet potatoes, oats, quinoa, and green peas—support NAD production,” says Poon. Fish and poultry also contain niacin, adds Amidor.
• Tryptophan: “Tryptophan, an amino acid that converts into niacin, is found in pumpkin seeds, lentils, tofu, tempeh, chickpeas, almonds, and cashews,” says Poon.

“It’s also worth noting that preparation matters,” says Poon. “Steaming is an ideal cooking method for preserving NMN in foods like green beans and beets, while NR is more heat-sensitive, so enjoying certain fruits and leafy greens raw can help maintain their potency.” Just keep in mind that it’s probably not possible to eat enough food to bring NAD levels up to youthful levels, according to Sinclair.

Research suggests that short bursts of hot or cold exposure (such as in a sauna), a diet that’s not high in fat or sugar, exercising, and cutting calories may help increase NAD in your body. However, these methods aren’t recommended for everyone, and they may not lead to a meaningful long-term difference in NAD levels, so many people depend on NAD booster supplements instead.

Our bodies need NAD to function. However, levels decline as we age. If you’re low on NAD, your doctor may recommend supplementing with an NAD booster (NMN or NR), but there’s no guarantee that doing so will result in substantial health benefits. Fortunately, more research on NAD and the human body is emerging every year, so we should have more guidance soon.

Medically reviewed byEric M. Ascher, D.O.

Eric M. Ascher, D.O. is a board-certified family medicine physician. He completed medical school at the New York College of Osteopathic Medicine, his family medicine residency and fellowship at Northwell Health, and has been working for Northwell Health since. Dr. Ascher practices in New York City and focuses on preventative medicine and healthy lifestyles. He has been recognized annually on The Super Doctor’s List posted in the New York Times and has been recognized by Northwell Health as a Rising Star and Physician of the Year. He hosts a series on YouTube in collaboration with Northwell Health called “Hack Your Health,” where viewers are taught why household items may relieve their ailments. Dr. Ascher is an assistant professor of the Zucker Hillside School of Medicine at Hoftsra Northwell, has been a pioneer for telehealth throughout his career, has been a media expert, and is heavily involved in practice and technology optimization. He appreciates building relationships with his patients and their families to encourage long, happy, and healthy lives.