> Randomized controlled trials do not show a step-function threshold (e.g. “below X% energy from saturated fat, risk disappears”). Instead, they show: • Progressive reductions in coronary events as saturated fat is lowered and replaced with polyunsaturated fat (PUFA). • Risk reduction tracks the amount of replacement, not merely crossing a cutoff.
In other words: risk ↓ smoothly as saturated fat ↓ (when replaced appropriately).
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2. Magnitude of reduction seen in RCTs
Meta-analyses of classic RCTs (LA Veterans Study, Oslo Diet-Heart, Finnish Mental Hospital, etc.) show: • ~2–3% absolute reduction in coronary events • ~10–30% relative reduction • Achieved when: • Saturated fat is reduced from roughly 15–20% of total energy → ~8–10% • And replaced primarily with PUFA, not refined carbohydrates
Key quantitative finding (Mozaffarian et al., PLOS Med 2010; Cochrane 2020):
For every 5% of energy replacement of saturated fat with PUFA → ~10% reduction in coronary events
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3. Why guidelines converge on <10% (and often <7%)
Because RCTs didn’t test ultra-low saturated fat intakes (e.g. 2–3%), guideline thresholds are pragmatic extrapolations, not mechanistic breakpoints: • <10% energy: roughly the lowest level consistently achieved in long-term RCTs • <7% energy (AHA): extrapolated from LDL-cholesterol lowering and event reduction curves
These are policy targets, not RCT-defined thresholds.