Does reducing saturated fat actually prevent heart attacks?For decades, saturated fat from foods like butter, red meat, cheese, coconut oil, and full-fat dairy has been treated as something to reduce. But the new USDA/HHS dietary guidelines and the inverted food pyramid have made the message a lot less clear.In part two of this series, we look into three of the major randomized controlled trials behind the meta-anlayses: the Minnesota Coronary Experiment, the Sydney Diet Heart Study, and the LA Veterans Trial. Along the way, we also discuss relative risk vs absolute risk, what an ideal saturated-fat trial would look like, why these old trials are so hard to interpret, and how issues like trans fats, adherence, short duration, and missing data complicate the conclusions.Hopefully, there’s also something useful here about how to think through studies, evidence, and nutrition claims when the answer is not as clean as it first seems.This is the second in a series of videos on the subject. Slides:https://www.jsdatascience.com/saturated_fat_meta-analyses_RCTs/Papers:Steen et al. 2025 https://pubmed.ncbi.nlm.nih.gov/41397264/Yamada et al. 2025 https://pubmed.ncbi.nlm.nih.gov/40416032/Frantz et al. 1989 https://pubmed.ncbi.nlm.nih.gov/2643423/Ramsden et al. 2016 https://pubmed.ncbi.nlm.nih.gov/27071971/Woodhill et al. 1978 https://pubmed.ncbi.nlm.nih.gov/727035/Ramsden et al. 2013 https://pubmed.ncbi.nlm.nih.gov/23386268/Dayton et al. 1968 https://pubmed.ncbi.nlm.nih.gov/4176868/Dayton et al. 1969 https://www.ahajournals.org/doi/10.1161/01.cir.40.1s2.ii-1Wilkins et al. 2012 https://pubmed.ncbi.nlm.nih.gov/23117780/

Does cutting saturated fat actually prevent heart attacks?For decades, saturated fat from foods like butter, red meat, cheese, coconut oil, and full-fat dairy has been treated as something to reduce. But the new USDA/HHS dietary guidelines and the inverted food pyramid have made the message a lot less clear.In this episode, Calvin and John look closely at two 2025 meta analyses of randomized controlled trials: Yamada 2025 and Steen 2025. One says there is no clear benefit to reducing saturated fat. The other says there may be a benefit, but mostly depending on your cardiovascular risk and what you replace saturated fat with.We don’t just read the abstracts. We go deep into the studies, recreate some of the charts, check the reported metrics, look at the forest plots, compare odds ratios and risk ratios, and dig into where the conclusions seem strong, weak, or a little too confident.Hopefully, there’s also something useful here about how to think through studies, evidence, and nutrition claims when the answer is not as clean as it first seems.

In this episode, we look at how Americans die at different ages using U.S. mortality data from the CDC. John walks through an interactive mortality data tool he built with multiple interactive charts showing broad causes of death by overall rank, age at death, and over time, along with detailed subcauses.The charts have filters for sex, age range, time period, and metric. We discuss the patterns that stand out and why the tool is useful.