Two APOE4 copies isn't a verdict, plus your brain's energy bill
Hi friend,
This month’s issue covers a lot of ground: how your brain makes and spends energy, how the fat in your blood talks to the fat in your brain, what ends up on your plate, and how you hold onto muscle as the years pass. We also took on the scariest headline a two-copy carrier can read and tried to give it honest proportions. Here is a quick taste of everything new on the site.
New deep dives
Is Alzheimer’s inevitable with two APOE4 copies? No. A population estimate puts the odds of dementia by age 85 near 60 percent, which means roughly two in five two-copy carriers reach 85 without it. A 2024 Nature Medicine paper got read as the opposite because it found three in four two-copy carriers already have a positive amyloid scan by 65, and closer to nine in ten by 80. But an abnormal scan is biology, not a diagnosis, and the gap between them is wide enough to live in. Read the full deep dive.
Brain energy failure, sex, and mitochondria. In cognitively healthy people ages 40 to 65, women’s brains already run a thinner energy reserve than men’s, and if you carry APOE4 it runs thinner still in the regions Alzheimer’s hits first. That comes from a 2023 PLOS ONE study of 209 healthy adults (80 percent women, 46 percent carriers) using a non-invasive fuel gauge for neurons. A lower reserve can mean less stored energy or higher demand drawing it down, and either way the cell has less buffer. This is midlife biology, decades before a memory test would flag anything. Read the full deep dive.
Diet, your metabolome, and APOE4. Closely following a Mediterranean diet was associated with about 35 percent lower dementia risk in two-copy carriers, the largest reduction of any genetic group, in an August 2025 Nature Medicine study of roughly 16,500 women. In plain terms, the highest-risk genotype got the most out of the same food. Because this is observational, read it as a strong association rather than proof, and the deep dive lays out the diet score, the hazard ratios, and how carriers compared with everyone else. For a carrier, it is a reason to look hard at what is on the plate. Read the full deep dive.
Meat, APOE4, and the Karolinska study. Among older Swedish adults, the carriers who ate the most meat developed dementia at roughly half the rate of those who ate the least (hazard ratio 0.45). Surprising, and worth reading carefully before you touch your shopping list. The carrier subgroup was small at 569 people, and the confidence interval ran almost to no effect at all (0.21 to 0.95), so treat it as a signal to watch rather than a reason to change dinner. It also sits awkwardly next to the Mediterranean finding above, which leaned toward fish and legumes, and holding both in your head at once is the honest way to read food research this early. The full deep dive explains why the analysis leaned on a competing-risk method to avoid overstating the odds. Read the full deep dive.
HDL, ApoA-I, and clearing amyloid from vessels. One copy of APOE4 roughly triples the odds of Alzheimer’s, taking a baseline near 10 percent up toward 30 percent. A big reason is not that e4 brains make more amyloid but that they clear it more slowly, and much of that clearing runs along the brain’s blood vessels. Researchers at the Autonomous University of Barcelona are showing that ApoA-I, the main protein in your HDL, helps pull amyloid out of vessel walls and arrives from the bloodstream rather than the brain. This is lab-model work, so read it as a clarified pathway rather than proof, but it links your peripheral lipid health to your brain’s plumbing. Read the full deep dive.
How APOE4 affects the brain. One gene variant moves Alzheimer’s risk more than almost any other, and the reason comes down to a job APOE does poorly: moving fat around a brain that is roughly 60 percent fat by dry weight. A 2022 Gladstone review sorts the damage into four overlapping pathways (slower amyloid cleanup, tau, inflammation, and overactive circuits), plus vascular and early-life threads. The honest headline is that most of this mechanism comes from mice and lab-grown neurons, not proof in living human brains, though the associations in people are strong. Each of those pathways ends at a system you can actually influence, which is the reason to keep reading. Read the full deep dive.
From the podcasts
Hussein Yassine on the brain’s energy crisis and omega-3 timing. USC lipid and Alzheimer’s researcher Hussein Yassine makes the case that APOE4 raises risk partly through a brain energy problem, and that omega-3 fats (specifically DHA) may help, but probably only at the right time of life. He gives the familiar relative-risk figures (roughly 12-fold for two copies, two to four-fold for one) while stressing these are relative, not certainty, and that most carriers age without the disease. In a Colombian study he cites, E4 plus diabetes carried much higher risk than either alone, while E4 in lean, metabolically healthy people added little. Peter Attia is candid that the science here is still frustratingly early. Read our summary.
Lyon, Boyle, and Cavaliere on strength, muscle, and protein. This roundtable is about the practical question longevity talk skips: how to build and keep muscle for decades without breaking yourself. For carriers, the thread that matters is metabolic, because muscle acts as a glucose reservoir and glucose handling bears on how you age. The speakers estimate only 5 to 15 percent of Americans do real resistance training, so most people are not doing this at all. Lyon’s muscle-first approach started with an anecdote about an early-Alzheimer’s-looking brain scan, which shaped her thinking but is not evidence that training prevents the disease. Read our summary.
John Kastelein on CETP inhibition, brain, and heart. CETP inhibition is a drug class known mostly for failing. Lipid researcher John Kastelein thinks it might still help an APOE4 carrier’s brain and heart at once, by keeping cholesterol on HDL and lowering LDL. The hinge is ApoA-I, the small main HDL protein that may slip into the brain. He is also a co-developer of the drug at the center of the episode, worth remembering when weighing his optimism. Along the way he grounds it in familial hypercholesterolemia (roughly 1 in 250 people), where a single causal gene mutation can be pinpointed in about 95 percent of the children who have it. Read our summary.
Isaacson and Rogen on personalizing prevention. Lauren Miller Rogen watched Alzheimer’s take her grandfather, grandmother, mother, and uncle, and Richard Isaacson runs a prevention clinic at Weill Cornell. Their sharpest example is a family one: Lauren’s mother and uncle were both APOE4/4, yet symptoms started about 15 years apart. Isaacson’s repeated message is that APOE4 is a risk factor, not a verdict, and that the truly deterministic genes (presenilin 1 and 2, and APP) are a different, far rarer category accounting for well under 1 percent of cases. He reframes Alzheimer’s as less one disease than an umbrella, and APOE4 as a road rather than a fixed destination. Read our summary.
Francisco Gonzalez-Lima on the vascular and metabolic hypothesis. To Francisco Gonzalez-Lima, a UT Austin neuroscientist, late-onset Alzheimer’s is fundamentally a brain energy failure, driven by chronically reduced blood flow and failing mitochondria, with amyloid as a downstream marker rather than the cause. It is a provocative minority view, so read it as one researcher’s hypothesis, not consensus. The reason it matters to carriers is that his levers (blood flow, blood pressure, blood sugar, metabolic health) are exactly the vascular and metabolic ones that come with the gene. We draw that connection; he does not single out APOE4. Read our summary.
Dave Feldman vs Peter Attia on low-carb and high LDL. If you carry APOE4 and eat low-carb, you have probably watched your LDL climb and wondered whether it matters. This is a two-sided argument about exactly that, and it does not land on “do not worry about it.” Dave Feldman, an engineer turned self-experimenter, proposes the “lipid energy model” and the “lean mass hyper-responder” (LDL 200 or higher, HDL 80 or higher, triglycerides 70 or lower), which he says spans genotypes including 3/4 and 4/4. The crux is whether a very high particle count is harmful when the rest of the panel looks pristine, a question that matters more for E4 carriers because the gene already raises both vascular and brain risk. Read our summary.
Tom Dayspring on brain cholesterol and lipid drugs. A worry many carriers share is that lowering LDL too far might starve the brain. Lipidologist Tom Dayspring takes that apart, and the established core of his argument is that the brain runs its own cholesterol economy, with the LDL particles in your blood too big to cross into it, so what floats in plasma has very little to do with what your neurons work with. He walks through the division of labor (oligodendrocytes make about 70 percent of brain cholesterol for myelin, astrocytes wrap it in ApoE for delivery) and puts the brain’s cholesterol content near 20 to 25 grams. The episode ends with an early but interesting story about a new drug class and APOE4 carriers. Read our summary.
Peter Attia on apoB, VO2 max, and exercise. This tour of Attia’s book Outlive circles two of his obsessions, apoB and VO2 max, that sit right where cardiovascular and Alzheimer’s risk overlap for carriers. On the most established ground, apoB counts the particles that actually drive plaque, and the causal link between high apoB and atherosclerosis is about as solid as cardiovascular biology gets. Because APOE4 is associated with higher circulating LDL, a carrier’s lipid picture often starts out worse. His very aggressive targets (like apoB toward 20 to 40 mg/dL) are his own judgment calls under what he calls “Medicine 3.0,” not settled science. Read our summary.
One thing to try this month
The food signals we covered this month do not all point the same way. The Mediterranean study leaned toward vegetables, olive oil, legumes, and fish, while the Swedish meat finding cut the other direction, and neither is strong enough to be a rule. If you want a low-stakes place to experiment, nudging one meal a day toward the Mediterranean pattern is a gentle thread to pull, and you can read exactly what each study found in the deep dives above before you decide anything.
Take care of yourself out there. You are not a genotype, you are a person with a lot of levers.
This newsletter is general education, not medical advice. Talk with your own clinician before making changes to your care.