Plant-based nutrition has been pulled in two directions over the past few years. On one side, an increasingly loud chorus arguing that seed oils are dangerous, that animal protein is the only protein that matters, and that nutrition epidemiology is junk science. On the other, a quieter group of researchers continuing to do the careful, painstaking work of cohort studies, randomised trials, and biomarker validation. In this episode, I sit down with Dr Andrea Glenn, an Assistant Professor at New York University and Visiting Scientist at the Harvard T.H. Chan School of Public Health, to look at what that careful body of evidence actually says.
What I really wanted from this conversation was a grown-up account of the data. Andrea trained as a registered dietitian, completed her PhD at the University of Toronto with Dr David Jenkins, and now leads work on plant-forward dietary patterns and cardiometabolic disease using both cohort and clinical trial methods. We dig into the Portfolio Diet she helped score in the major Harvard cohorts, the recent papers on plant versus animal protein, the butter versus plant oils debate, and the methodological pushback against people who dismiss food frequency questionnaires without ever reading one. Throughout, she does the thing the social media nutrition space rarely does, which is hold the evidence up to the light and let it speak.
What We Cover:
- The 30-year analysis from the Nurses’ Health Studies and Health Professionals Follow-up Study showing a higher plant-to-animal protein ratio is associated with lower cardiovascular and coronary heart disease risk, with the strongest benefit at higher protein densities of around 20 per cent of calories
- Why the protein conversation has been almost entirely about quantity, and what gets missed when food source, food matrix, and accompanying nutrients are stripped out of the picture
- A defence of nutrition epidemiology, including how food frequency questionnaires are designed, validated, and updated, and why trans fat regulation is the cleanest counter-example to the claim that observational research protects industry
- The history and design of the Portfolio Diet, from the original metabolic ward studies showing roughly 30 per cent LDL-C reductions comparable to a low-dose statin, to the 2018 meta-analysis showing 17 per cent LDL reductions in free-living trials
- The new CHEAP trial recruiting around 1,100 statin-treated patients across Ontario, designed to test whether the Portfolio Diet on top of standard care can deliver a meaningful additional reduction in cardiovascular events
- The 2024 JAMA Internal Medicine paper from the Harvard cohorts showing the highest butter intake associated with around 15 per cent higher all-cause mortality, while the highest plant oil intake was associated with around 16 per cent lower all-cause mortality
- Why “low-carb” is not one diet, with animal-based low-carbohydrate patterns linked to up to 44 per cent higher type 2 diabetes risk while healthy plant-based low-carbohydrate patterns were associated with 16 per cent lower risk
- The 2026 American Heart Association dietary guidance, how it differs from the latest US Dietary Guidelines, and the practical takeaways for legumes, nuts, plant oils, and replacing saturated fat sensibly
The signal across this body of work is consistent and unsexy. It is not about a single hero food or a single villain, but about an overall pattern that prioritises legumes, nuts, whole grains, viscous fibre, plant oils, and modest amounts of higher-quality animal foods. That is a less marketable story than “butter is back,” and it happens to be where the strongest evidence sits.
To follow more of Dr Andrea Glenn’s work, find her on Instagram at instagram.com/andrea.glenn.rd, on X at x.com/andreaglennrd, and on LinkedIn at linkedin.com/in/andrea-glennrd.
- Intro (00:00)
- Plant vs Animal Protein Ratio and Heart Disease (01:17)
- Does Total Protein Amount Also Affect CVD Risk? (05:33)
- Why Nutrition Epidemiology Critics Often Get It Wrong (11:00)
- Where Epidemiology Fits in the Evidence Hierarchy (17:28)
- Sensitivity Analyses: How Scientists Test Their Results (22:16)
- What It’s Like Doing Science at Harvard (28:55)
- The Portfolio Diet: Origins and the Science Behind It (32:21)
- The CHEAP Trial: Testing Portfolio Diet Long-Term (41:03)
- Portfolio Diet in Cohort Studies: What the Data Shows (50:24)
- Unsaturated Fats: Are They Inherently Heart-Protective? (56:16)
- Phytosterol Supplements: LDL Benefits vs Safety Questions (01:00:06)
- Butter vs Plant Oils: What Mortality Data Actually Shows (01:06:57)
- Plant vs Animal MUFAs and Type 2 Diabetes Risk (01:12:11)
- Low-Carb Diet Quality and Diabetes Risk: New Data (01:15:37)
- 2026 AHA Dietary Guidelines: Key Differences Explained (01:20:23)
- Portfolio Diet’s Potential to Reduce Disease Burden (01:26:35)
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More about Andrea Glenn
Andrea J. Glenn, MSc, RD, PhD, is an Assistant Professor in the Department of Nutrition and Food Studies at New York University and a Visiting Scientist in the Department of Nutrition at the Harvard T.H. Chan School of Public Health. Her main research focus is on plant-forward dietary patterns and plant-based protein in the prevention and management of cardiometabolic disease using both epidemiological and clinical trial data. Her work also advances dietary assessment methods through the identification of novel biomarkers of dietary intake and nutritional status using metabolomics. More recently, she has been studying the impact of Food is Medicine initiatives on health outcomes, including blood pressure. Her work has been featured in major media outlets such as The New York Times, The Washington Post, and National Geographic.
