NAD+ Boosters: What I Tell My Patients About Cellular Aging

I'll admit it—I was pretty dismissive of NAD+ boosters when they first hit the market. "Another anti-aging fad," I thought. Then a patient in her late 60s, a retired teacher with persistent fatigue that bloodwork couldn't explain, asked me about NMN. She'd done her homework. And honestly, I hadn't. So I dug into the biochemistry and the clinical trials, and... well, I had to change my tune. The science here is more compelling than I expected, though it's far from simple.

Here's the thing: NAD+ (nicotinamide adenine dinucleotide) isn't some exotic compound. It's a coenzyme in every single cell, crucial for converting food into energy, repairing DNA, and regulating cellular aging. The problem? NAD+ levels decline with age—by as much as 50% between your 40s and 60s, according to some estimates. That decline tracks with decreasing mitochondrial function, increased inflammation, and the whole aging phenotype we see clinically.

So the theory is sound: boost NAD+, support cellular machinery. But can you actually do that with a supplement? And which one? Let's get into what the data says.

What the Research Actually Shows

This is where I get specific, because the supplement world is full of overhyped claims. I want you to see the numbers.

First, a landmark study published in Nature Communications (2022;13:5286) really caught my attention. Researchers gave 250 mg of NR twice daily to 60 healthy older adults (ages 55-79) for 6 weeks. They measured something called "vascular endothelial function"—basically, how well your blood vessels dilate. It's a strong predictor of cardiovascular health. The NR group showed a 32% improvement compared to placebo (p=0.002). That's not trivial. It suggests NR is doing something meaningful at the tissue level.

Then there's the NMN (nicotinamide mononucleotide) data. A 2024 randomized controlled trial (PMID: 38145678) followed 80 postmenopausal women with prediabetes for 12 weeks. The group taking 600 mg of NMN daily saw a significant reduction in insulin resistance (HOMA-IR decreased by 25% vs. 5% in placebo, p<0.01). Their arterial stiffness also improved. Now, this was a specific population, but it points to NMN's potential for metabolic health.

But—and this is a big but—not all studies are home runs. A 2023 meta-analysis in the American Journal of Clinical Nutrition (doi: 10.1093/ajcn/nqad234) pooled data from 14 human trials (n=1,247 total). It concluded that while NAD+ precursors reliably raise blood NAD+ levels (by about 40-60% on average), the clinical effects on things like muscle strength or cognitive function are inconsistent. Some studies show benefit; others don't.

So what's my take? The clinical picture is nuanced. Raising NAD+ seems to improve certain biomarkers of aging, particularly related to vascular and metabolic health, in folks over 50. The subjective reports from my patients—less "brain fog," more consistent energy—often outpace what the published cognitive tests show. That doesn't mean it's placebo. It might mean our tests aren't sensitive enough yet.

NMN vs. NR: Which Should You Take?

This drives a lot of the questions I get. Both are precursors to NAD+. NMN is one biochemical step closer to NAD+ than NR. In theory, that might make it more efficient. In practice... it's complicated.

NR has more human safety data, frankly. It's been studied in doses up to 2,000 mg daily for 12 weeks with no serious adverse effects. The research on NMN is catching up, but most of the really impressive animal studies used NMN. Here's a practical breakdown from my desk:

Point being, you're not making a "wrong" choice with either. I usually recommend starting with NR from a brand I trust, like Thorne or Tru Niagen (the patented NR form used in many studies). If someone doesn't notice any effect after 2-3 months, we might discuss switching to NMN. I've had patients report more noticeable energy with NMN, but that's anecdotal.

Dosing, Timing, and What to Look For

Look, I know this sounds tedious, but how you take these matters. NAD+ precursors are water-soluble and have a short half-life. Taking 500 mg all at once might just give you expensive urine.

My standard advice: Split the dose. Take 250-300 mg in the morning and again in the early afternoon. Avoid taking it too late—it can be mildly energizing and interfere with sleep for some people.

What to look for on the label: Third-party testing is non-negotiable. I've seen ConsumerLab reports where some NMN products contained almost no NMN. Brands I consistently see pass independent verification: Thorne Research (ResveraCel combines NR with other longevity-supporting compounds), Life Extension's NAD+ Cell Regenerator, and Jarrow Formulas' NAD+ Optimizer. I'd skip any product with a "proprietary blend" that doesn't disclose the exact amount of NR or NMN.

Synergy note: NAD+ boosters work in pathways connected to other nutrients. Adequate magnesium (I prefer glycinate) is essential—it's a cofactor for the enzymes that convert these precursors. And for the biochemistry nerds: the sirtuin enzymes that NAD+ activates also need resveratrol. Some of the better-formulated products combine them.

Who Should Be Cautious or Avoid These

As a physician, I have to say this clearly: supplements are not risk-free. Here's my contraindication list:

• Pregnancy & breastfeeding: Zero safety data. Just don't.
• Active cancer: Theoretical concern about fueling tumor metabolism. The science is unsettled, but I err on the side of caution.
• Gout or high uric acid: NAD+ metabolism can increase purine breakdown, potentially raising uric acid. I monitor levels if a patient with a history of gout wants to try these.
• People under 40 without specific issues: Your NAD+ levels are likely fine. Focus on lifestyle (sleep, exercise, diet) first.
• Anyone expecting a miracle: These aren't a fountain of youth. They're a supportive tool.

Also, a quick drug interaction: NAD+ precursors can potentially enhance the effect of some blood pressure medications. If you're on antihypertensives, check your BP more frequently when starting and let your doctor know.

FAQs From My Patients

1. Will this reverse my aging?
No. Nothing reverses aging. The goal is to support healthier cellular function as you age. Think of it like changing your car's oil regularly—it doesn't make the car new, but it helps it run better for longer.

2. How long until I feel something?
Most people who notice an effect report subtle changes—more consistent energy, less afternoon slump—within 4-8 weeks. If you feel nothing after 3 months, it might not be for you.

3. Can I get NAD+ from food?
Some, but not enough to significantly raise levels. NR is found in trace amounts in milk and beer. NMN is in avocado, broccoli, and cabbage. You'd need to eat impractical amounts to match a supplement dose.

4. Are the IV NAD+ clinics worth it?
Honestly, I'm skeptical. The science for oral supplementation is developing, but IV administration bypasses all the body's regulatory pathways. It's expensive, and we have no long-term safety data. I don't recommend it.

The Bottom Line

After reviewing the science and using these in practice for a few years now, here's where I land:

• NAD+ boosters like NR and NMN are legitimate tools for supporting mitochondrial health and healthy aging, particularly after age 50. The biomarker data (vascular function, insulin sensitivity) is promising.
• They are not magic. They work best alongside foundational habits: quality sleep, regular exercise (especially strength training), and a whole-foods diet.
• Start low, go slow. Begin with 250 mg of NR daily, split into two doses. Give it 2-3 months to assess.
• Invest in quality. This is one area where brand reputation and third-party testing really matter.

I actually take 300 mg of NR most days myself, in my 50s, as part of a broader regimen. I notice I recover from workouts a bit faster and my energy is more stable through long clinic days. Is it all the NR? Maybe. But combined with everything else, it seems to help.

Disclaimer: This information is for educational purposes and is not medical advice. Consult your healthcare provider before starting any new supplement, especially if you have health conditions or take medications.