The different SFAs vary in their effects on lipid levels; of note, stearic acid is generally excluded from the listings of cholesterol-raising saturated fats.[10,11] However, this thinking is the result of flawed logic, according to Dariush Mozaffarian, dean of the Friedman School of Nutrition Science and Policy at Tufts University in Boston, Massachusetts. “The US view on saturated fats is totally based on the effects on LDL-C, and that’s why we have dietary guidelines to lower our saturated fat intake and why stearic acid is given a free pass,” he noted in an interview with Medscape. SFAs are biologically complicated. “They don’t just affect LDL-C, they affect particle size, they affect HDL-C and triglycerides. It’s not clear which [ones] are better or worse if you look at all of those effects.”
In a meta-analysis of over 60 trials, higher intakes of saturated fat were associated with increases in both LDL-C and high-density lipoprotein cholesterol (HDL-C) and decreases in triglyceride levels, for a net neutral effect on the ratio of total cholesterol to HDL cholesterol. Although saturated fats increase LDL-C, they reduce the LDL particle number. Total LDL particle number quantifies the concentration of LDL particles in various lipid subfractions and is considered a stronger indicator of CV risk than traditional lipoprotein measures. As for stearic acid, the allegedly non-cholesterol-raising fat, while it appears to lower LDL-C relative to other SFAs, one analysis concluded that it raised LDL-C, lowered HDL-C, and increased the ratio of total to HDL cholesterol in comparison with unsaturated fatty acids. And this is one of the confounders of much nutrition research—observations about a given nutrient are highly dependent on what you compare it to.