So if carbohydrates are the suspects, what should we replace them with? Most people naturally gravitate towards a Low Carb High Fat diet (LCHF) but even that can be ambiguous due to what kinds of fats should be selected. While browsing through the American Journal of Clinical Nutrition TheFatNurse found an interesting study about low carbohydrates, saturated fats and beef.
This study, which involved Dr. Krauss (famous for differentiating LDL particles and risk), decided to look at how much of a role red meat and its association with saturated fat plays in CVD risk. Red meat is often thought of as a CVD risk from the questionable lipid hypothesis due to the amount of saturated fat it has.
Participants were given a baseline diet that consisted of 50% carbohydrates before being divided up into a Low Carb High Saturated Fat group (LCHSF) or Low Carb Low Saturated Fat (LCLSF) group for another 3 weeks. Both groups dropped to 31% of their energy from carbs but increased their protein consumption to 31% of energy and fat to 38% of energy. The differences between the groups occurred in the percentage of saturated fat (made up from dairy). The Low Carb High saturated fat group took in 15% of their energy from saturated fat whereas the low carb low saturated fat group only took in 8% (with an increase in monounsaturated fat to keep the total fat even). So what were the results?
***Atherogenic dyslipidemia is often associated with elevated triglycerides, low HDL cholesterol and more small LDL particles***
Triglycerides: Baseline diet (1.22+/-0.61), LCHSF (1.10+/-0.61), LCLSF (1.05 +/- 0.49)
HDL-C: Baseline diet (1.08+/-0.27), LCHSF (1.07+/-0.30), LCLSF (1.04 +/- 0.27)
So based off those results it seems that both Low Carb options here perform much better than the Baseline diet that was higher in carbohydrate right? Not so fast. While it’s true that the LCHSF yielded much lower triglycerides, it also yielded increases in LDL than the baseline group. This shouldn’t be surprising tho due to the saturated fats. However, what concerns TheFatNurse is the types of LDLs raised. The LCHSF group had increases in the large LDLs and medium LDLs (as expected) but also in the small LDLs!
This is a bit concerning since Krauss had shown through previous studies that it’s the small LDL particles that are associated to CVD risk and not so much the larger ones (Recent findings are also suggesting its the total particle count that matters most). Perhaps the saving grace for LCHSF is that it did yield a smaller result for “very small LDLs” but this was not statistically significant (p=0.23).
In his study, Krauss reports previous studies showing saturated fats raising LDLs and total cholesterol but not contributing towards levels of small LDL particles. Could the results of this study have been due to the type of protein eaten with the saturated fat? Additionally, could these results have been due to the substitution of monounsaturated fats for the LCLSF group? Krauss addresses these points and remarks that the difference in this study was the strict use of beef as the protein source. Does this mean it’s the beef protein itself with saturated fat that is causing these changes to LDLs? Krauss remarks that it can be due to other factors such as iron which has been shown to contribute with lipid metabolism as well.
The Bottom Line: So while some previous studies did not show any cardiovascular risk with saturated fat intake…does this study mean that people should be careful if they are eating lots of saturated fat with red meat (specifically beef)? Maybe, maybe not. As Krauss notes, more studies are definitely needed, and this experiment had people eating more beef than what is typically normal. TheFatNurse think the biggest thing to take away for now is more evidence that carbohydrates are a risk factor since both low carb diets in the study yielded lower triglycerides. As for the increase in small LDLs from the higher saturated fat diet? Just cut out a little saturated fat from red meat in your diet and replace with non red meat saturated fats if this one study makes you cautious. In the meantime, TheFatNurse is gonna go fry up a steak.
***Of note, some people would consider the 31% of calories from carbohydrates in the Low carb groups not low enough to be considered a “true low-carb” diet***
Changes in Atherogenic Dyslipidemia Induced by Carbohydrate Restriction in Men Are Dependent on Dietary Protein Source