Reducing saturated fat intake shows mortality benefit, but only in high-risk individuals, review suggests

A systematic review of 17 randomized trials found that among high cardiovascular risk individuals, reducing saturated fat was linked to lower all-cause mortality and possible reductions in cardiovascular deaths, heart attacks, and strokes. Notably, the greatest benefit for preventing nonfatal heart attacks occurred when saturated fats were replaced with polyunsaturated fats (PUFA) rather than simply reducing them.

For people at low to intermediate cardiovascular risk, cutting or replacing saturated fat intake offered little or no benefit over five years.

Researchers reviewed trials involving 66,337 participants that compared the effect of reducing saturated fat intake or replacement with alternative nutrients such as PUFA on mortality and cardiovascular-related outcomes over at least two years.

The data show that overall, reducing saturated fat intake results in important reductions in total cholesterol and low-density lipoprotein cholesterol (LDL-C). For high-risk individuals, low to moderate certainty evidence showed that reducing saturated fat intake may have important benefits for all-cause mortality, cardiovascular mortality, nonfatal myocardial infarction (MI), and stroke.

In particular, replacing saturated fat with PUFA showed important absolute reductions in nonfatal MI risk. For low-risk individuals, absolute benefits were not important. These findings suggest that saturated fat reduction may be most relevant for high-risk populations, and that PUFA replacement could enhance benefits.

Wow, this is sure contrary to conventional knowledge. The excerpt points out several times that people without risk factors don't have to worry so much about saturated fats. So what are the risk factors?

Major Risk Factors for Coronary Heart Disease, Heart Attack, and Stroke
Coronary heart disease (also called coronary artery disease or CAD) involves plaque buildup in the arteries supplying the heart, which can lead to a heart attack (myocardial infarction). A stroke occurs when blood flow to the brain is blocked (ischemic) or interrupted by bleeding (hemorrhagic). These conditions share many risk factors due to common underlying processes like atherosclerosis, but some are more prominent for one than the others.

Risk factors fall into two categories: non-modifiable (cannot be changed) and modifiable (can be managed through lifestyle, medication, or treatment). Most major risks are modifiable, and addressing them can significantly lower the chances of these events.

Shared Major Risk Factors (Apply to All Three)
These are the most important and well-established factors, supported by organizations like the WHO, CDC, and American Heart Association:
* High blood pressure (hypertension) — The top modifiable risk factor; damages arteries and promotes plaque buildup.
* High blood cholesterol (especially high LDL/"bad" cholesterol) — Contributes to artery narrowing.
* Smoking/tobacco use — Damages blood vessels, raises blood pressure, and promotes clotting; even secondhand smoke increases risk.
* Diabetes — High blood sugar damages vessels; people with diabetes have 2–4 times higher risk.
* Obesity/overweight — Often linked to other risks like hypertension and diabetes.
* Physical inactivity — Increases weight, blood pressure, and cholesterol levels.
* Unhealthy diet (high in salt, saturated fats, sugars; low in fruits/vegetables) → Leads to obesity, hypertension, and high cholesterol.
* Harmful alcohol use — Can raise blood pressure and contribute to obesity. (I'm surprised that it is couched as "harmful." Many studies show that ANY alcohol use is harmful.)

These behavioral factors (diet, inactivity, smoking, alcohol) manifest as intermediate risks like elevated blood pressure, glucose, and lipids.

Non-Modifiable Risk Factors (Shared)
* Age → Risk rises significantly after age 45 for men and 55 for women (post-menopause).
* Family history → Early heart disease or stroke in close relatives increases risk.
* Sex → Men generally at higher risk earlier; women's risk rises after menopause.
* Ethnicity/race → Higher rates in certain groups (e.g., non-Hispanic Black, South Asian, Indigenous populations), often due to higher prevalence of modifiable risks.

Additional or More Specific Risks
* Atrial fibrillation (irregular heartbeat) — Strongly linked to stroke (increases risk 5-fold) due to clot formation; also raises heart attack risk.
* Previous heart disease or stroke/TIA — Greatly increases risk of recurrence.
* Stress, poverty, or air pollution — Emerging contributors, per WHO.

Less common:
* Certain conditions like sickle cell disease (for stroke) or drug use (e.g., cocaine for heart attack).

Controlling modifiable risks through quitting smoking, healthy eating, exercise, and medical management can prevent most cases.

“There were 17 eligible trials (66 337 participants). Risk stratified evidence provides low to moderate certainty that reducing saturated fat intake may result in a reduction in all-cause mortality (risk ratio [RR], 0.96 [95% CI, 0.88 to 1.06]), cardiovascular mortality (RR, 0.93 [CI, 0.77 to 1.11]), nonfatal myocardial infarction (MI) (RR, 0.86 [CI, 0.70 to 1.06]), and fatal and nonfatal stroke (RR, 0.83 [CI, 0.58 to 1.19])...

Data were limited on the replacement of saturated fat with monounsaturated fat or protein. Trials varied considerably in their efficacy in reducing saturated fat intake and in their replacement macronutrients and concomitant dietary interventions, and new trials are needed to clarify uncertainty.”

I believe their own abstract means they had ZERO statistically significant results. Other than, reviewing these other trials, “when replacing saturated fat with polyunsaturated fat for nonfatal MI (RR, 0.75 [CI, 0.58 to 0.99];” - and if that gap had opened to include 1.0 instead of 0.99, it would also be statistically insignificant!

Meanwhile, in a population study, one has no idea WHAT ELSE the people are eating, their health standards, etc. Arguably anyone who has replaced saturated fat with polyunsaturated fat would have “healthy user bias” since they are doing something intentional to improve their health - and thus likely to be doing OTHER THINGS as well to improve their health!

So yeah...this study is bullshit. Sorry.

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