Dear readers,
I have a version of this conversation almost every week.
A patient comes in six months into GLP-1 therapy. She’s down twenty-eight pounds, her A1c has moved from 5.9 to 5.4, and she has done exactly what I asked her to do, which is eat considerably more protein than she used to, because the entire point of medical weight loss done well is that you lose fat and keep muscle. She is proud of the work she’s put in, and she should be.
Then we pull her labs and her LDL is fifteen points higher than it was last spring.
She asks the obvious question, which is whether the protein did this. For years the honest answer was a shrug dressed up in confident language. Nutrition science has largely assumed that protein is neutral for blood lipids, that fat and carbohydrate are where the action is and protein is a bystander. That assumption is why nearly every heart-health recommendation you have ever read talks endlessly about saturated fat and sugar while saying almost nothing about protein.
A review published this July in Nutrients by Kevin Maki and colleagues argues that the assumption is wrong, and that it was wrong for a reason worth understanding.
Why we got it wrong
The error turns out to be arithmetic rather than biology.
Most of what we believed came from observational studies, but if you hold calories constant and someone eats more protein, they are by definition eating less of something else. So when a large cohort study reports that protein has no relationship to cardiovascular risk, what it is often reporting is a blur: the effect of adding protein tangled up with the effect of removing whatever that protein displaced, averaged across thousands of people who displaced very different things.
Controlled feeding trials, where investigators provide the food and deliberately swap one macronutrient for another, untangle that. The picture they produce is not neutral at all.
In the OmniHeart trial, researchers fed 164 adults three versions of a heart-healthy diet, and the version that shifted ten percent of daily energy from carbohydrate to protein outperformed the higher-carbohydrate version on both non-HDL cholesterol and triglycerides. Maki’s own group later replaced sixteen percent of energy from refined starch and added sugar with a combination of egg protein and unsaturated fat, and found that triglycerides fell about eighteen percent compared with two percent on the refined-carbohydrate arm, ApoB fell nearly twelve percent, and LDL particles became larger rather than small and dense.
Here is the practical takeaway, and it is the one I would want you to leave with: the benefit of eating more protein depends enormously on what the protein replaces. If your extra protein is displacing bread, crackers, and afternoon granola bars, your ApoB is likely to improve. If it is displacing olive oil, nuts, and salmon, you may have traded sideways or slightly downward. Protein is a lever, and every lever has a fulcrum.
Plant versus animal, said carefully
Across 112 randomized trials, swapping one to two daily servings of plant protein for animal protein lowered LDL by roughly 6 mg/dL and ApoB by roughly 5 mg/dL, which works out to about three to four percent.
That is a real effect and a small one. It is not a statin, and it will not rescue someone with an ApoB of 130 and a family history of early heart attack. Anyone selling you soy as a cardiovascular intervention on the strength of these numbers is overselling.
Small effects do stack, though. The National Lipid Association’s portfolio approach, which combines swapping saturated fat for unsaturated fat, adding viscous fiber and plant sterols, including about thirty grams a day of plant protein, and losing five percent of body weight where there is excess adiposity, lands somewhere around twelve to fifteen percent LDL reduction under real-world conditions. That is low-dose statin territory achieved entirely through food, which matters a great deal for the patient who has declined a statin or who wants to do everything possible alongside one.
My favorite detail in the whole review comes from a head-to-head trial of 25 grams a day of soy protein versus 25 grams a day of milk protein. Both lowered atherogenic lipoproteins, but soy did considerably more, dropping ApoB nearly ten percent against about two percent for milk. The investigators had predicted that soy worked by increasing bile acid excretion, so they measured bile acid excretion, and it hadn’t changed. The effect is real and we still don’t know the mechanism. I appreciate a paper willing to say that out loud.
On red meat, I’ll give you the honest version rather than the comfortable one. Trials comparing red meat to white meat have repeatedly failed to find any lipid difference between them. But in one carefully controlled crossover study, LDL and ApoB were higher on both meat diets compared with a non-meat protein diet, and this held whether the background diet was high or low in saturated fat. The meaningful divide was not red versus white but meat versus not-meat. So if you are choosing between a steak and a chicken breast, that is probably not the choice steering your cardiovascular trajectory, whereas choosing either one over lentils, beans, tofu, or nuts appears to matter somewhat. The clearest targets for reduction remain exactly what they have always been: processed meat, refined starch, and added sugar.
The tension this resolves
Here is why I spent this much time on a fairly technical lipid review.
Longevity medicine is the discipline of managing two clocks at once. The first is atherosclerosis, and its currency is cumulative lifetime exposure to ApoB-containing particles. The second is sarcopenia, the slow loss of skeletal muscle that predicts frailty, falls, insulin resistance, and loss of independence more powerfully than almost anything else we measure in aging adults.
For a long time those two clocks appeared to be in conflict. Protecting muscle requires eating well above the old RDA of 0.8 g/kg, which was never a target for thriving but a floor set to prevent outright deficiency. The 2025–2030 Dietary Guidelines, released this January, finally raised the recommendation to 1.2 to 1.6 g/kg. The uncomfortable question has always been whether meeting that number came at a cardiovascular cost.
This review’s answer is that it doesn’t, provided the protein displaces refined carbohydrate and saturated fat rather than displacing unsaturated fat and fiber, and provided a reasonable share of it comes from plants.
For patients on semaglutide or tirzepatide, that matters enormously. Protecting lean mass isn’t optional, because it is the difference between losing fat and losing the metabolic machinery you will need for the next thirty years. Appetite suppression makes protein targets genuinely hard to hit, which makes it tempting to hit them with whatever is easiest, usually a bar or a shake. What this review suggests is that the composition of that strategy is not lipid-neutral.
It matters for my hormone optimization patients as well. Lipids shift adversely through the menopause transition, and protein requirements rise with age because older muscle responds less efficiently to the same amino acid load. The people who most need to increase their protein are frequently the same people watching their LDL drift upward for entirely separate reasons, and knowing that those two goals are compatible rather than opposed changes what I feel comfortable recommending.
What I’d temper
The review devotes a section to food-derived peptides that appear to competitively inhibit HMG-CoA reductase, the same enzyme statins target, and to regulate ApoB100 expression at the surface of the liver cell. The mechanisms are elegant. The authors then say the thing I want every peptide discussion to include, which is that this is cell and animal data, that oral bioavailability is poor, and that human trials have not been done.
I use peptides in my practice and I am transparent with every patient about the fact that many of them lack large human trials. I don’t think the absence of phase 3 data automatically disqualifies a well-characterized compound with a plausible mechanism and an acceptable safety profile, so long as the patient understands exactly where the evidence stands. But that transparency has to run in both directions, and the lipid-lowering peptide story is mechanistically beautiful and clinically unproven. I am watching it closely. I am not building treatment plans on it.
Two other caveats belong here. This is a narrative review rather than a systematic one, meaning there was no pre-registered protocol and the studies were selected by expert judgment. And the authors’ institution discloses research funding from the National Cattlemen’s Beef Association and the National Dairy Council. I don’t think that invalidates the work, since the disclosure is complete and the plant-protein findings actually cut against those funders’ interests, but you should read the red meat section with that context in mind and I would be failing you not to mention it.
What to actually do
If you take nothing else from this, take these five things.
Eat more protein than you think you need, and keep eating it. For most adults that means somewhere between 1.2 and 1.6 grams per kilogram of body weight per day, which for a 160-pound person works out to roughly 87 to 116 grams. If you are actively losing weight, on a GLP-1, or over fifty, you belong at the higher end of that range rather than the lower one.
Pay attention to what the protein is pushing off your plate. This is the single highest-leverage question in the entire review. Protein that replaces bread, crackers, sweetened yogurt, pasta, and afternoon snack bars will very likely improve your ApoB. Protein that crowds out olive oil, avocado, nuts, and fatty fish will not. Before you add a protein source, notice what it is taking the place of.
Make roughly a third to a half of your protein plant-based, without becoming a vegetarian. Lentils, black beans, chickpeas, tofu, tempeh, edamame, almonds, walnuts, and pumpkin seeds are the workhorses here. Thirty grams a day of plant protein, which is about a cup and a half of lentils or two servings of tofu, is the amount used in the studies that showed benefit. You do not need to eliminate animal protein to get this effect.
Keep the animal protein you eat minimally processed. Fish, eggs, poultry, unprocessed cuts of red meat, Greek yogurt, and whey are all reasonable. Deli meat, bacon, sausage, and hot dogs are the category where the evidence is genuinely unfavorable and where I would spend your restriction budget.
Ask your physician for an ApoB, not just an LDL. If you have insulin resistance, elevated triglycerides, or a family history of early cardiovascular disease, LDL alone can look reassuring while particle number tells a very different story. And if your LDL rises during a period of rapid weight loss, don’t panic and don’t assume the protein caused it. Fat mobilization can transiently raise cholesterol during active weight loss and it usually settles, but that is worth confirming with a repeat panel rather than guessing.
Longevity medicine tends to get discussed as though it were a collection of exotic interventions. It isn’t. It is mostly the unglamorous work of managing the small number of variables that actually determine how the next thirty years go, and food is still the highest-leverage tool we have. We have simply been giving incomplete instructions about a third of the plate for a very long time.
Reach out to our office at 703-866-4144 or schedule a free introductory call with us and let’s get you sorted the right way.
Best wishes,
Dr. Gajer
The Gajer Practice – The Science of Health, The Art of Transformation
