Longevity Latest • Issue 02
Longevity Latest
The Evidence-Based Edge on Living Longer and Better
NMN vs NR vs niacin: the NAD+ showdown. Berberine under the Spotlight. A viral age-reversal study debunked. Three interventions graded, zero affiliate links. 🧬 |
👋 Welcome to Longevity Latest
Welcome back. This week we’re tackling the question that dominated our inbox after Issue 01: should you be spending £150 a month on NAD+ precursors, or is there a cheaper alternative hiding in the vitamin aisle?
We put NMN, NR, and plain niacin head-to-head. We grade each one. We let the evidence talk. The answer involves a 90-year-old vitamin and some uncomfortable truths about marketing.
In this issue:
🔬 Top 3 — NMN, NR, and niacin graded on our A–F scale
💡 Spotlight — Berberine: the over-the-counter AMPK activator
🚨 Hype Check — That viral “biological age reversal” study
🥦 Superfood — Walnuts and the omega-3 mortality data
🔍 Deep Dive — Sirtuins and NAD+: why “more” isn’t always better
⚙️ Biohacking — Time-restricted eating: what the largest trial found
🔬 Top 3 Interventions Under the Microscope
1. Nicotinamide Mononucleotide (NMN)
Evidence Grade: D Pre-clinical only
What it is. NMN is a direct precursor to NAD+, the coenzyme essential for energy metabolism, DNA repair, and sirtuin activation. It’s marketed as the premium NAD+ booster at £100–£200/month for 250–500 mg/day.
Human evidence. A 2024 meta-analysis (Zhang et al., Crit Rev Food Sci Nutr; 12 RCTs, n=513; PMID: 39116016) found NMN reliably raises blood NAD+ but clinically relevant outcomes — fasting glucose, insulin resistance, lipid profiles — were not significantly different from placebo. Five of twelve studies had high risk of bias. A 2025 systematic review (J Cachexia Sarcopenia Muscle) found no significant improvements in muscle mass, grip strength, or gait speed. A January 2026 head-to-head trial (Christen et al., Nature Metabolism) showed NMN and NR both doubled circulating NAD+ over 14 days, with neither demonstrating clinical superiority.
Cautions. Well-tolerated at 250–1,200 mg/day in trials up to 12 weeks. No long-term safety data. Quality control is poor — independent testing shows significant potency variability between brands.
Takeaway. NMN raises a biomarker. That’s not the same as improving health. No published RCT has shown meaningful clinical benefits in healthy adults. At £150/month, you’re paying for a surrogate endpoint change. Evidence Grade D: pre-clinical promise, insufficient human outcomes.
🧪 Personal note: I took NMN (500 mg/day) for four months last year. Blood NAD+ went up. My hs-CRP, fasting glucose, and HRV didn’t budge. The most expensive placebo effect I’ve purchased. I stopped. |
2. Nicotinamide Riboside (NR)
Evidence Grade: B Promising human data
What it is. NR enters cells via the NRK pathway and converts to NMN intracellularly before becoming NAD+. Available as Niagen® (ChromaDex) at £40–£70/month. Unlike NMN, NR has a more established safety record from larger clinical trials.
Human evidence. The NICE trial (Nature Communications, 2024; n=90) showed NR at 1,000 mg/day meaningfully improved 6-minute walk distance in peripheral artery disease — one of the few NAD+ precursor trials with a functional clinical outcome. NR-SAFE (Nature Communications, 2023; n=20) demonstrated safety at 3,000 mg/day in Parkinson’s patients with significant NAD+ augmentation. A small MCI trial (Orr et al., GeroScience, 2024; n=20; PMID: 37994989) found modest epigenetic age reductions, though cognition was unchanged.
Cautions. Well-tolerated up to 3,000 mg/day. No flushing. ChromaDex funds much of the NR research — always worth noting when evaluating results.
Takeaway. NR has the strongest clinical trial record of any NAD+ precursor. The NICE trial’s functional outcome data puts it a clear step ahead of NMN, at roughly half the price. Evidence Grade B: promising human data from multiple trials, though most are small or disease-specific.
🧪 Personal note: I switched from NMN to NR (500 mg/day) three months ago. Too early for conclusions, but the trial evidence is materially stronger. I’ll report back once I have six months of biomarker data. |
3. Niacin (Nicotinic Acid / Vitamin B3)
Evidence Grade: B- Established metabolic data, longevity data lacking
What it is. Plain niacin — the original vitamin B3 — is the oldest and cheapest NAD+ precursor. It boosts NAD+ via the Preiss-Handler pathway and has been used clinically for six decades. Cost: approximately £0.03/day for 500 mg.
Human evidence. Pirinen et al. (Cell Metabolism, 2020; n=30; PMID: 32386566) showed niacin at 750–1,000 mg/day increased blood NAD+ up to 8-fold, with improvements in muscle strength and mitochondrial biogenesis. Liver fat decreased up to 50% in patients. Decades of cardiovascular data confirm it raises HDL and lowers triglycerides. However, a 2017 Cochrane review found niacin did not reduce overall mortality when added to statin therapy. The Christen et al. 2026 trial found NR and NMN work via gut-bacteria-mediated conversion to nicotinic acid — the expensive precursors may ultimately use the same pathway as plain niacin.
Cautions. Flushing (warmth, redness, itching) is the major barrier. Start at 100 mg and titrate up. Extended-release formulations reduce flushing but carry liver toxicity risk. Nicotinamide (niacinamide) avoids the flush but inhibits sirtuins at high concentrations — potentially counterproductive for longevity.
Takeaway. The unglamorous workhorse. Longest clinical track record, strongest metabolic data, lowest cost. Evidence Grade B-: robust metabolic and cardiovascular data, but direct longevity evidence is lacking — keeping it a notch below NR’s functional outcome results.
🧪 Personal note: I’ve added niacin 250 mg/day alongside NR. The flush lasts about 20 minutes — mild facial warmth I’ve mostly adapted to. At this price, the cost of experimentation is essentially zero. |
💡 Spotlight Treatment: Berberine
Berberine activates the same metabolic switch as metformin, costs £15/month over the counter, and has one-fiftieth of the clinical evidence. Here’s the honest case. |
Berberine is a plant alkaloid from barberry and goldenseal, used in traditional Chinese medicine for centuries to treat gastrointestinal infections. In the longevity community, it has gained traction as a natural metformin alternative — available without prescription, activating many of the same pathways, and at a fraction of the cost.
✅ The Case For
Berberine activates AMPK through multiple routes without directly inhibiting mitochondrial Complex I — theoretically more exercise-compatible than metformin. A meta-analysis (Guo et al., Oxid Med Cell Longev, 2021; PMID: 34956436; 20 RCTs) found berberine at 900–2,400 mg/day significantly reduced fasting glucose, HbA1c, and triglycerides in type 2 diabetes, with effects comparable to metformin. It also lowers LDL cholesterol. Over-the-counter at £10–20/month.
❌ The Case Against
Oral bioavailability under 1% versus metformin’s 50–60%. Only 34 completed clinical trials versus 1,600+ for metformin. No human longevity trials. Supplement quality is inconsistent — one study found 60% of products failed potency standards.
Bottom Line
⚠️ Promising but premature. If you’re on metformin, no reason to switch. If you’re not eligible and want AMPK activation, berberine is reasonable — but buy third-party tested and manage expectations. |
🚨 Hype Check: That Viral “Age Reversal” Study
Nine men. No placebo group. A surrogate endpoint. And it’s been shared as “proof” that ageing is reversible. |
The Hype. The TRIIM trial (Fahy et al., Aging Cell, 2019; PMID: 31496122) treated participants with growth hormone, DHEA, and metformin for 12 months. Four epigenetic clocks showed an average 2.5-year reduction in biological age. Influencers are sharing this as proof that age reversal is here. The Evidence. Nine white men, aged 51–65, no placebo control. Epigenetic clocks measure DNA methylation as a proxy for biological age — not ageing itself. The authors acknowledged this limitation. A 2022 review (Johnson et al., Aging Cell; PMID: 35778957) noted these clocks exhibit technical noise and that youthful methylation can be induced without genuine rejuvenation. Why it’s misleading. Growth hormone is associated with increased cancer risk, insulin resistance, and joint pain. The sponsor (Intervene Immune) sells age-reversal services commercially. TRIIM-X remains ongoing. Our verdict. Wait for placebo-controlled replication. Do not inject growth hormone based on a nine-person uncontrolled trial. The science of epigenetic ageing is real — the hype is running years ahead of it. |
🥦 Superfood Spotlight: Walnuts
The richest tree nut source of plant-based omega-3, with mortality data from over 118,000 people. And they cost about £0.15 each. |
Walnuts are the highest tree nut source of alpha-linolenic acid (ALA), a plant-based omega-3, and among the richest food sources of polyphenols. They feature prominently in Mediterranean diet patterns and are a daily staple in several Blue Zone populations, particularly Sardinia and Ikaria, where nut consumption is a consistent dietary marker among the longest-lived cohorts.
The Nurses’ Health Study (Guasch-Ferré et al., Nutrients, 2019; n>118,000) found consuming walnuts five or more times weekly was associated with significantly lower all-cause mortality. A 2021 RCT meta-analysis confirmed walnut consumption improves endothelial function and lowers LDL. Their ellagitannins support gut microbiome diversity — itself an emerging longevity biomarker.
Practical serving: 30g daily (7–8 halves). Add to porridge or salads. Store in the fridge — polyunsaturated fats oxidise quickly. Calorie-dense (~185 kcal/30g). Tree nut allergy is a contraindication.
🔍 Deep Dive: Sirtuins and NAD+ Metabolism
Your cells have seven repair enzymes that depend entirely on NAD+ to function. They’re called sirtuins, and they sit at the crossroads of every longevity pathway we cover — DNA repair, mitochondrial biogenesis, inflammatory control. When NAD+ declines with age, sirtuin activity falls with it. But not all precursors activate sirtuins equally. One common form of B3 actually inhibits them at high doses. And the Christen et al. 2026 trial suggests NR and NMN may ultimately work through the same pathway as plain niacin. If you read one thing about NAD+ biology this year, make it this. 🔍 Read the full Deep Dive: Sirtuins and NAD+ Metabolism → [link] |
⚙️ Biohacking Corner: Time-Restricted Eating
The largest trial of time-restricted eating found no benefit over calorie matching. But the nuance matters. |
A 2022 NEJM trial (Liu et al.; n=139; 12 months; PMID: 35443107) compared calorie restriction alone versus restriction within a 16:8 window. Both groups lost similar weight with comparable metabolic improvements. The time restriction conferred no additional benefit. This was the study that quieted much of the intermittent fasting community — and it deserves a closer look.
However, Sutton et al. (Cell Metabolism, 2018; crossover, n=8) found that even without calorie reduction, a 6-hour window improved insulin sensitivity and blood pressure in men with prediabetes. Timing may matter most for those with existing metabolic dysfunction.
Three evidence-based takeaways:
1. Metabolically healthy? A strict 16:8 window is unlikely to beat calorie control alone. Don’t force it.
2. Insulin resistant? Time-restricted eating may offer genuine benefits beyond calorie restriction.
3. Either way: A consistent 12-hour overnight fast (7pm–7am) is well-supported. Avoid eating within 2–3 hours of bedtime.
🧪 Personal note: I eat within a roughly 10-hour window most days. The biggest change after reviewing this data wasn’t the window — it was front-loading calories to breakfast and lunch. |
📊 Reader Pulse
This week’s question: Are you currently taking any NAD+ precursor? Which one and why? Hit reply in one sentence — we’ll share the anonymised results in Issue 03. From Issue 01: We asked about your longest-running intervention. Responses are still coming in — full breakdown in Issue 03. Keep them coming. |
👋 See You Next Week
Next week in Issue 03: We’re grading rapamycin, spermidine, and quercetin — three compounds targeting autophagy, the cellular recycling system that declines with age. Quercetin goes under the Spotlight as a potential senolytic. And the Hype Check tackles a popular “telomere lengthening” supplement that costs £100 per bottle. You’ll want to read that one before you buy it.
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Stay curious and stay healthy!
— The Longevity Latest Team
Medical Disclaimer
Longevity Latest is for informational and educational purposes only. Nothing in this newsletter constitutes medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before starting any new supplement, medication, or health protocol. Personal notes reflect individual experience and are not presented as evidence. Interventions graded in this newsletter reflect our assessment of the published evidence and do not constitute personal recommendations.
© 2026 Longevity Latest Newsletter
The Evidence-Based Edge on Living Longer and Better