Concern
10 plain-language articles on longevity & aging — the physiology, the compounds researched for it, and what the evidence actually shows.
10 articles
The Bryan Johnson "Don't Die" phenomenon — what the protocol actually does and what it doesn't
In February 2023, a photograph of Bryan Johnson standing shirtless next to his 17-year-old son and his 70-year-old father circulated widely across social media. The premise was that Johnson, then 45, had biomarker readings suggesting his biological age was younger than his chronological age — and the photograph was offered as evidence of some kind of metabolic convergence across three generations. People reacted the way people react when something is simultaneously compelling and uncomfortable: they shared it while expressing ambivalence about whether they were supposed to find it inspiring or disturbing. Both responses were tracking something real.
Cellular senescence in deeper detail — the biology, biomarkers, and intervention frontier
A cell under severe stress faces a choice. It can repair the damage and carry on. It can trigger apoptosis — the orderly self-destruction program that eliminates compromised cells cleanly. Or it can do something else: it can stop dividing, enlarge, change its behavior, and stay. This third option is cellular senescence, and for decades it was understood primarily as a tumor suppression mechanism — a way of permanently halting cells that might otherwise accumulate mutations and turn cancerous. That understanding was correct as far as it went. What took longer to recognize was the cost.
The David Sinclair NAD+ story — hype, evidence, honest assessment
In the late 1990s, a graduate student named David Sinclair was working in Lenny Guarente's lab at MIT, trying to understand why yeast cells age. The answer his experiments pointed toward involved a protein called Sir2 — Silent Information Regulator 2. In yeast, Sir2 controlled whether certain genomic regions were transcriptionally active or silenced, and its activity appeared to be linked to lifespan. When you increased Sir2 expression in yeast, the cells lived longer. When you inhibited it, they lived less long. Sinclair went on to characterize Sir2 and its mammalian cousins, the sirtuins, as what he would eventually describe as a master regulatory system of aging — a set of molecular sensors that respond to cellular stress and energy status and govern whether cells survive, repair themselves, or succumb to aging-associated dysfunction.
Epigenetic clocks — Horvath, GrimAge, and what biological age tests actually measure
You spit in a tube, seal it, mail it off, and eight weeks later a number arrives: your biological age. Maybe the report says 38.2. You're 44 chronologically. A minor celebration. Or it says 47.6, and you spend the next week wondering what exactly you've been doing to yourself. The number has a quality of authority that a cholesterol panel carries — it arrives formatted, annotated, compared to a reference range, delivered by a company with a clean website and peer-reviewed citations in the footer. The question worth asking before you do anything with it is what the number actually measures, how confident you should be in it, and what the science behind it can and cannot honestly tell you.
Gene expression and tissue specificity — why the same genome makes different cells
In 1962, a British developmental biologist named John Gurdon did something that shouldn't have been possible according to the consensus of the day. He took the nucleus of a fully differentiated intestinal cell from an adult frog, transplanted it into an enucleated frog egg, and watched it develop into a functioning tadpole. The experiment was technically difficult, widely doubted, and conceptually unsettling, because it implied something that the field hadn't fully accepted: differentiated cells don't lose genetic information when they specialize. The intestinal cell's nucleus contained everything needed to build a complete organism. Every cell type, throughout the frog's body, carried the full complement of genetic instructions. They just used different parts of it.
NAD+ vs NMN vs NR — the precursor conversation
You're standing in the supplement aisle — or the online equivalent of it, scrolling through a longevity stack that someone recommended on a podcast — and there are three things that look related: NAD+, NMN, and NR. They're all described as "NAD+ support." They're all priced somewhere between expensive and extremely expensive. They're all backed by citations to researchers whose names you half-recognize. And the differences between them are explained, in every product description you've read, in a way that somehow makes it less clear what you should actually be taking, not more.
Proteostasis — the quality-control network that keeps proteins from killing cells
A protein begins life as a featureless string. The ribosome reads the genetic code and links amino acids one by one into a linear chain, and that chain, in itself, does nothing — it is a sentence with no meaning until it folds. Folding is where a protein becomes a machine: the chain collapses, in milliseconds to seconds, into a precise three-dimensional shape, and that shape is the function. An enzyme's pocket that grips its target, an antibody's arms that clamp an antigen, the channel in a membrane protein that lets ions through — all of it is folded geometry. Christian Anfinsen won a Nobel Prize for showing, in the 1960s, that a protein's sequence contains the instructions for its own folded shape. But Anfinsen worked with purified proteins in a test tube. Inside a living cell, folding has to happen in a chaotic, crowded environment, at speed, on tens of thousands of different proteins at once, with new chains pouring off ribosomes every second and old proteins constantly being damaged. The fact that this works at all, reliably, for decades, is one of the quiet miracles of cellular life, and the system that makes it work is called proteostasis.
The senescent cell story — what makes cells 'zombie cells'
You cut your hand and it heals. The skin closes, the inflammation resolves, the scar fades over months. At no point do you consciously manage this — your body runs an intricate repair sequence without your input, and if you're young and healthy, the outcome is essentially complete restoration. What you don't see is the cellular machinery underneath that sequence: cells dividing to replace damaged ones, immune cells clearing debris, signaling molecules coordinating the whole operation with timing measured in hours. And somewhere in that process, certain cells that have served their purpose — that have divided as many times as they safely can, or that have accumulated damage that makes further division risky — enter a state from which they will not emerge. They stop dividing and stay stopped. They are still alive. They will not come back.
Sirtuins — the longevity proteins and what they actually do
In the late 1990s, a yeast cell in Leonard Guarente's lab at MIT quietly upended the assumption that lifespan was a fixed parameter. The gene in question was Sir2 — Silent Information Regulator 2 — and when researchers added extra copies of it to yeast, the cells lived longer. When they deleted it, the cells died sooner. Nobody had expected a single gene to move the lifespan needle in either direction. The question the experiment opened wasn't just "what does Sir2 do" but something more unsettling: if a gene could regulate how long a cell lives, what exactly is the machinery of aging, and how close to the surface is it?
The unfolded protein response — how the cell handles its own folding crises
In the late 1980s, a cell biologist named Mary-Jane Gething and her colleague Joe Sambrook were studying how a viral protein folds inside cells when they noticed something that did not fit. When they forced cells to accumulate a misfolded protein in a compartment called the endoplasmic reticulum, the cells responded by ramping up production of a particular set of helper proteins — as if the cell had detected the folding problem and was calling for reinforcements. The cell, in other words, was monitoring the quality of its own protein folding and reacting when that quality slipped. Over the following decade, laboratories led by researchers including Peter Walter and Kazutoshi Mori would work out the machinery behind that reaction and give it a name: the unfolded protein response. It turned out to be one of the most important quality-control systems a cell possesses, and its failure runs through some of the most feared diseases in medicine.