Study: Does Dietary Saturated Fat Effect Blood Lipids?

It’s the latest study in the low-carb vs. low-fat debate! Published about a week ago on PLOS One, some articles have boldly claimed that it “proves” that we don’t need to limit saturated fat in our diets, but rather carbs! So, how trustworthy is this information? Here’s what you need to know:

1. The funding. This study was funded by a few groups with a vested interest in the low-carb, high (saturated) fat recommendation–key example? The Beef Checkoff. While the researchers say that the funders had no say in the experimental set up or the decision to publish the data, we must still tread carefully. The researchers may unconsciously build a study that benefits the funders.

2. The premise. Basically, if you eat too many carbs, you will turn the leftovers into fat through de novo lipogenesis. The main fats produced are the saturated fat palmitate (16 carbons) and the monounsaturated fat palmitoleic acid (16 carbons, cis-double bond on carbon 7). High levels of these fats are indicative of heart disease and insulin sensitivity.  However, are high levels of these lipids in your blood caused by dietary fat? This study aims to find out (and actually show that carbohydrates are the real problem).

3. The hypothesis. Researchers expected blood plasma levels of saturated fats to remain largely the same when on a diet low in carbs and for palmitoleic acid to increase as carb intake increased.

4. The method. First and foremost when looking at this study we must remember that there were only 16 participants. This study far from “proves” anything–it barely shows anything statistically. However, it was a controlled study, and that is a point in its favor. While it is too small to really draw conclusions from, this study could offer some interesting insight into future research.

Additionally, participants were given food made by the research team to conform to six three-week diet stages, moving from a high saturated fat diet to a high carb diet (all while caloric intake and protein intake remained constant). In a smaller group, the study was conducted “backwards” –from high carb to high saturated fat, just in case there was a time lag that effected the study.

5. The results. This study found that saturated fat levels in the blood didn’t correlate with higher levels of blood lipid levels. However, they did find that palmitoleic acid increased as carb intake increased.

My takeaway. I think that this is an interesting study that has lots of potential. The method intrigues me, though if another (larger) study is done, I would be gunning for longer times on each of the diets as well as a larger sample of participants doing the study “backwards.” That would give the diets more time to have an effect and the significance of the data would surely increase if the study involved more people.

Of course, it would be ideal if other funders stepped forward–especially ones not vested in the outcome of the study!

All in all, I look forward to future research on this topic coming out with larger sample sizes especially. Being able to name the cause of high blood lipids is really important–even if it means I have to give up my pasta.


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