Editorial NexoScience
Cutting back on butter, cheese and fatty cuts of meat will not necessarily add a single year to your life. According to the most comprehensive review of the evidence gathered so far, it will very likely lower your odds of having a heart attack or another cardiovascular event linked to plaque buildup, just not by as much as decades of public health messaging implied.
A team from Peru’s Instituto de Investigación Nutricional pooled 21 previous meta-analyses covering both randomized trials and long-term cohort studies, drawing on more than 480,000 participants across the strongest datasets, to settle a question that cardiology guidelines have answered with more confidence than the raw data actually supports.
The clearest signal comes from controlled trials, and it points to real protection. In the highest-quality randomized evidence, drawn from 15 trials and more than 56,000 participants followed for up to nine years, people who reduced their saturated fat intake had 21% fewer combined cardiovascular events than those who kept eating as before. That same trial data also showed measurable drops in total cholesterol, LDL cholesterol, body weight and body mass index in the low-fat group.
But that same evidence found no effect on how long people actually lived. All-cause mortality, cardiovascular mortality and cancer deaths were statistically identical between the groups that cut saturated fat and the groups that did not, in trials that ran up to nine years. The researchers note that nine years may simply be too short a window to capture a mortality difference, since heart disease that starts at 45 often does not kill until decades later.
The picture gets murkier once you leave the lab for the real world. Across 18 cohort studies tracking hundreds of thousands of people for as long as three decades, higher saturated fat intake was linked to a 10% relative increase in coronary heart disease mortality and a 51% relative increase in breast cancer mortality. Yet those same long-term datasets found no significant difference in all-cause or cardiovascular mortality either, and counterintuitively linked higher saturated fat intake with a lower rate of stroke, a pattern the authors could not fully explain and flagged as needing further research.
Correlation is doing a lot of the work in that second half of the story. Cohort studies compare people who happen to eat differently, not people randomly assigned to a diet, so factors like income, overall diet quality or exercise habits can quietly ride along with saturated fat intake and shape the outcome. Tellingly, the review’s own quality tool rated the vast majority of those cohort meta-analyses as “critically low” confidence, while the randomized trial evidence for cardiovascular events was graded moderate to high.
None of this hands saturated fat a clean bill of health, but it does undercut the idea that cutting it is a guaranteed way to live longer. The authors conclude that reducing saturated fat probably does reduce cardiovascular events, but has little or no measurable effect on death from any cause, and argue that blanket dietary limits should give way to advice tailored to a person’s actual health status, income and existing risk factors.
Source: A. Aramburu et al., “Effect of reducing saturated fat intake on cardiovascular disease in adults: an umbrella review,” Frontiers in Public Health (2024). DOI: 10.3389/fpubh.2024.1396576
