Amid the speculation as to which fats are the “good” or “bad,” some in the scientific community have speculated that it may not be as vital to focus on one type of fat as much as the effects of excessive macronutrients in the diet. This could be in part due to the propensity that such studies have on persuading the public to replace one eliminated fat with sugars or other simple carbohydrate foods, which could be problematic. However, decades of research suggest that different types of fat have different effects on the body, such as serum cholesterol levels, for example, as well-known metric assessed for cardiovascular risk.
In a Cochrane Library meta-analysis, saturated fat, found at high concentrations in animal products such as red meat, poultry, butter, and eggs, was a loser, signifying a big win for plant-based diets, insofar as cardiovascular benefits go.
Prior to this study, saturated fat reductions were well-linked to lower serum cholesterol, but effects on other intermediate outcomes are less clear. It’s also unclear which type of replacement (polyunsaturated fat, monounsaturated fat, carbohydrate, or protein) is most optimal for cardiovascular outcomes in replacing excessive saturated fat.
The meta-analysis extracted 15 randomized controlled trials from the Cochrane Database which used a variety of interventions aimed at reducing saturated fat, amassing results from a pool of 59,000 trial participants.
“Meta-regression suggested that greater reductions in saturated fat (reflected in greater reductions in serum cholesterol) resulted in greater reductions in risk of CVD events, explaining most heterogeneity between trials,” researchers wrote. “The number needed to treat for an additional beneficial outcome (NNTB) was 56 in primary prevention trials, so 56 people need to reduce their saturated fat intake for about four years for one person to avoid experiencing a CVD event. In secondary prevention trials [which took place in patients who’ve already experienced a cardiovascular event] the NNTB was 32.”
While the evidence suggested that reducing saturated fat intake for at least two years causes a potentially important reduction in combined cardiovascular events, researchers found moderate-quality evidence that it had little to no effect on reducing all-cause mortality, and determined that evidence suggesting it had little or no effect on non-fatal myocardial infarction or CHD mortality was of low quality. There was no evidence that saturated fat reductions had any harmful effects.
“People who are currently healthy appear to benefit as much as those at increased risk of heart disease or stroke, (people with high blood pressure, high serum cholesterol, or diabetes, for example) and people who have already had heart disease or stroke. There was no difference in effect between men and women,” researchers wrote.