There is a coenzyme inside every one of your dog's cells right now. It powers DNA repair, keeps the mitochondria running, and switches on a family of proteins that researchers have started calling longevity genes. It's called NAD+. And from the moment your dog is born, the supply is quietly falling.
I started paying attention to this topic the way most people do — sideways, slightly embarrassed. I had a bottle of NMN on the shelf. Basil (my dog, not me) was staring at it. And I found myself wondering whether anything I was taking for myself was relevant to him.
It turned out the answer was more interesting than I expected. The NAD+ research in dogs is limited, but the underlying biology is not. The mechanisms are well-established across mammals. And some of what researchers have learned translates — carefully, with appropriate caveats — into decisions you can make today about what goes in your dog's bowl.
NAD+ stands for nicotinamide adenine dinucleotide. It's a coenzyme — a molecule that helps enzymes do their jobs. The two things it's most important for are energy metabolism and DNA repair. Without adequate NAD+, cells can't efficiently convert food into usable energy, and they lose the ability to respond properly when DNA gets damaged.
That second function matters enormously for aging. DNA damage is constant — from normal metabolism, from environmental exposure, from simple replication errors. In a young, NAD+-replete cell, damage is detected quickly and repair mechanisms fire. In an NAD+-depleted cell, that response is sluggish. Damage accumulates. And damaged cells are among the primary drivers of two things we covered in earlier parts of this series: they either become senescent zombie cells (Part 4), or they lose mitochondrial function and begin contributing to systemic inflammation.
NAD+ is constantly cycling between two forms: NAD+ (oxidised) and NADH (reduced). When a cell burns glucose or fat for energy, NAD+ accepts electrons and becomes NADH. The mitochondria then use NADH to generate ATP — the cell's actual energy currency. The NAD+ is regenerated and the cycle continues. When total NAD+ levels fall, this entire energy-production cycle runs less efficiently. The dog gets less energy from the same food. Mitochondria begin to decline. And the enzymes that depend on NAD+ — particularly the sirtuins — slow down.
The connection between NAD+ and longevity research came largely through the discovery of sirtuins. These are a family of seven proteins (SIRT1 through SIRT7) that regulate an enormous range of cellular processes — inflammation, DNA repair, mitochondrial function, fat metabolism, stress response. They've been found in virtually every organism studied, from yeast to dogs to humans.
What makes sirtuins relevant here is that they are entirely dependent on NAD+ to function. They consume NAD+ as part of their mechanism. No NAD+, no sirtuin activity. And sirtuin activity, in research terms, is closely associated with the cellular maintenance functions that slow aging.
Regulates inflammation, stress response, and fat metabolism. Also involved in circadian rhythm and DNA damage response. The most studied sirtuin, particularly in caloric restriction research.
Lives inside the mitochondria. Protects against oxidative stress and maintains mitochondrial efficiency. Declines with age in parallel with NAD+ loss.
Specialises in DNA repair and telomere maintenance. Lower SIRT6 activity correlates with faster aging in animal models. Overexpression has extended lifespan in male mice.
SIRT1 activity suppresses mTOR signalling — the same pathway targeted by rapamycin (Part 2). Caloric restriction (Part 1) activates SIRT1 partly by raising NAD+:NADH ratios. The mechanisms connect.
This is the mechanism that makes caloric restriction interesting beyond just reducing calories. When you feed less, cells experience mild energy stress. NAD+ levels relative to NADH rise. Sirtuin activity increases. The cellular maintenance and repair functions that sirtuins regulate switch on more efficiently. The reason a slightly lean dog lives longer may partly come down to better sirtuin function driven by a more favourable NAD+ ratio.
NAD+ levels fall with age in all mammals studied — mice, rats, monkeys, humans, and by extension almost certainly dogs, though direct canine NAD+ decline data is limited. The decline appears to begin in early adulthood and accelerates through middle age. By the time a dog is genuinely old, NAD+ levels in some tissues may be half what they were in youth.
NMN (nicotinamide mononucleotide) and NR (nicotinamide riboside) are precursor molecules — the building blocks the body uses to make NAD+. The reason they've attracted such interest is that NAD+ itself doesn't absorb well when taken orally. NMN and NR do absorb, and the body converts them into NAD+ through established metabolic pathways.
The mouse research on NMN is genuinely compelling. Studies from Washington University and elsewhere have shown that NMN supplementation in aging mice restores NAD+ levels, improves mitochondrial function, increases physical endurance, and in some studies has extended lifespan. The David Sinclair lab at Harvard has published extensively on NR and NMN, and his own supplementation routine (which includes NMN) brought this topic into widespread public awareness.
In dogs, the picture is thinner. There are no large controlled trials on NMN in dogs. Some integrative veterinarians have started recommending NR or NMN for aging dogs, particularly large breeds, but this is clinical intuition extrapolated from mouse and human data — not dog-specific evidence. If you're considering supplementing your dog with NMN, it is a conversation to have with a vet familiar with the research, not something to do based on a bottle on your own shelf.
The biology is solid. NAD+ declines with age. Sirtuins need NAD+ to function. NMN raises NAD+ in mice and humans. These are not in serious scientific dispute. What is genuinely uncertain is whether giving a specific dose of NMN to your dog will meaningfully raise their NAD+ levels, and whether that translates to measurable health or longevity benefits in dogs specifically. Dogs metabolise things differently from mice. Doses that work in mice don't scale linearly to dogs. The gap between plausible mechanism and proven intervention in dogs is real, and worth being honest about.
NAD+ precursors exist in food. Niacin (vitamin B3) and its forms — nicotinamide, nicotinic acid — are the dietary building blocks of NAD+. A diet rich in niacin-dense proteins provides the raw material the body needs to maintain NAD+ synthesis through natural pathways.
This is not the same as taking 500mg of NMN a day. The amounts are different. But for a dog eating fresh, whole food with good niacin-dense proteins at every meal, the NAD+ precursor supply from diet is meaningfully better than a dog eating processed kibble, where heat treatment degrades B vitamins significantly.
One of the richest dietary sources of niacin (B3) available to dogs. 100g cooked chicken breast provides approximately 14mg niacin — well above the daily requirement for most dog sizes. A staple NAD+ precursor food.
Already in most homemade recipes — prioritise lean breast over thigh for higher niacin densityExceptionally high niacin content — roughly 14–18mg per 100g depending on species. Also provides omega-3 DHA and EPA. One of the best niacin-to-calorie foods available. Drain thoroughly, no brine or oil.
2–3 tablespoons a few times per week, mixed into mealsSimilar niacin profile to chicken, with slightly lower fat content. Excellent for dogs with pancreatitis risk or those on a lower-fat diet. Good rotation option for dogs that eat chicken daily.
Substitute for chicken in any recipe 2–3 times per weekGood niacin source alongside its omega-3 credentials. Wild-caught preferred. The combination of niacin for NAD+ precursor and DHA/EPA for anti-inflammatory support makes salmon one of the more complete longevity proteins for dogs.
80–120g cooked (medium dog) once or twice per weekDecent niacin content and a useful flavour addition. Check the label every time — xylitol is lethal to dogs and appears in many "natural" peanut butters. Smooth, unsalted, xylitol-free only.
Half a teaspoon as a topper or treat — it's calorie-dense, so don't overdo itGood source of niacin and riboflavin (B2), which supports the NADH-to-NAD+ recycling pathway. Also provide tryptophan, which the body can convert to NAD+ through the kynurenine pathway — a slower route but a real one.
1 egg (small dog), 1–2 eggs (large dog) 3–4 times per weekA dog eating fresh chicken, tuna, salmon and eggs regularly is getting meaningful dietary niacin — the primary NAD+ precursor available through food. A dog on ultra-processed kibble, where B vitamins have been degraded by extrusion temperatures and must be sprayed back on synthetically, is getting far less. Switching to homemade or fresh food is itself a meaningful step toward better NAD+ precursor supply. No supplement bottle required.
By this point in the series, the mechanisms are beginning to overlap and reinforce each other in ways that feel meaningful. Caloric restriction (Part 1) raises the NAD+:NADH ratio, which activates sirtuins, which suppresses mTOR — the same pathway rapamycin (Part 2) targets pharmaceutically. LOY (Part 3) reduces IGF-1 signalling in large breeds, which has knock-on effects on cellular stress and senescent cell accumulation. Zombie cells (Part 4) accumulate faster when DNA repair is slow — which happens when NAD+ is low.
These aren't separate levers. They're parts of the same underlying system. A dog that eats lean, eats fresh, and gets niacin-rich proteins alongside quercetin-rich foods is nudging multiple pathways simultaneously — not with drug-level force, but consistently, daily, across years. That's the argument for taking this seriously even when the dog-specific research is incomplete.
The shortest-lived breed — and what it might mean for NAD+
The Irish Wolfhound has an average lifespan of 6 to 8 years. It is, by most measures, the shortest-lived dog breed. An Irish Wolfhound that reaches 10 years is genuinely exceptional. A 10-year-old Chihuahua is barely middle-aged.
The size-lifespan relationship in dogs is one of the most striking biological patterns in mammals — larger bodies age faster, for reasons that involve IGF-1 (covered in Part 3), higher oxidative stress from larger metabolic loads, and very likely faster NAD+ decline. The mitochondria in a 70kg Irish Wolfhound are working harder, producing more reactive oxygen species, and creating more pressure on the NAD+-dependent repair systems than those in a 4kg Chihuahua.
For Irish Wolfhound owners, the entire longevity series applies with extra urgency. Lean body condition from an early age, a niacin-rich fresh food diet, regular quercetin-containing foods, and a vet willing to discuss emerging longevity research are all worth prioritising. The breed's biology makes every year count more.
Recommended proteins for Irish Wolfhounds: Lean chicken, turkey, salmon — all high in niacin, manageable in fat. Avoid very high-fat red meat as the primary daily protein given the breed's cardiac risk. Fish oil supplementation is particularly valuable for this breed.
The practical steps here don't require a supplement protocol. They require good food choices made consistently:
Prioritise niacin-rich proteins — chicken, tuna, turkey and salmon — as the backbone of your dog's diet. Rotate them rather than feeding one protein daily. Add eggs three or four times a week. Keep the diet fresh and minimally processed so B vitamins aren't degraded before they reach the bowl. Combine this with the quercetin-rich foods from Part 4 (apple, blueberries, broccoli) and the lean body condition from Part 1, and you're supporting multiple longevity pathways through diet alone.
If your dog is a large or giant breed, genuinely senior, or you're working with a vet who's familiar with the NAD+ research, then NMN or NR supplementation is a reasonable conversation to have. The mechanism is sound. The risk profile appears low. But go in with realistic expectations — this is supportive, not curative, and the dog-specific data is still catching up with the mouse research.
Sources: Yoshino et al. (2011) "Nicotinamide Mononucleotide, a Key NAD+ Intermediate, Treats the Pathophysiology of Diet- and Age-Induced Diabetes in Mice," Cell Metabolism; Rajman et al. (2018) "Therapeutic Potential of NAD-Boosting Molecules," Cell Metabolism; Gomes et al. (2013) "Declining NAD+ Induces a Pseudohypoxic State Disrupting Nuclear-Mitochondrial Communication during Aging," Cell; Guarente L. (2013) "Calorie restriction and sirtuins revisited," Genes & Development; Sinclair DA & Guarente L. (2014) "Small-molecule allosteric activators of sirtuins," Annual Review of Pharmacology and Toxicology.
Part 6 covers the largest scientific study of dog aging ever conducted — what they've found, how to enrol your dog, and what it means for longevity research in the next decade.
Read Part 6 →