In November 2023, a randomized control trial delving into different types of diets and their impacts on cholesterol levels was published in the JAMA Network Open. Specifically, it dissected the effects of vegan diets versus omnivorous diets on LDL (low-density lipoprotein) — touted as “bad” cholesterol.
The randomized clinical trial from the lab of Christopher D. Gardner explored the different metabolic effects of the two aforementioned diets on 22 sets of identical twins, which helped reduce genetic variability and provided genuinely solid data. One twin from each set was assigned a vegan diet or omnivore diet for eight weeks. The scientists measured a handful of health markers, including LDL cholesterol. (1)
On Dec. 6, 2023, Dr. Layne Norton shared his analysis of the study’s findings on his YouTube channel. Check it out below:
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Cardiometabolic Effects of Omnivorous Vs. Vegan Diets
After eight weeks, those on the omnivorous diets saw no real change in biomarkers. However, those on the vegan diets “saw a reduction in LDL cholesterol by about 14 mg/dl…a reduction of fasting insulin…and bodyweight by about a kilo and a half.”
HDL (high-density lipoprotein) cholesterol — touted as the good kind of cholesterol — was also reduced. However, Dr. Norton mentioned HDL is more of a complete metabolic biomarker that is not directly related to heart disease and other risks (unlike LDL cholesterol).
Results Breakdown
While vegan diets appear superior in lowering “bad” cholesterol and improving other biomarkers, Dr. Norton isn’t surprised by the results. The twin participants on the vegan diet ate about 200 fewer calories than the omnivore diet group. Spread that across eight weeks, a 200-calorie deficit could result in a kilo and a half in weight loss.
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Those given vegan diets weren’t told to eat less – both diets were structured for maintenance — but it was a natural occurrence, possibly due to vegan diets comprised of higher-satiety foods. That said, the body weight reduction wasn’t enough to cause the reduction in LDL and fasting insulin levels.
During the first four weeks of the study, those on the vegan diet consumed less saturated fats and about 15-20 percent more polyunsaturated fatty acids (PUFAs). This swap from saturated to polyunsaturated should lower LDL, regardless of the other factors. In the final four weeks, the difference was more drastic. Reducing saturated fat intake is the most significant change one can make to one’s diet to positively affect their LDL cholesterol levels.
Another potential influential factor is the increase in dietary fiber featured in the vegan diet. The twins adhering to the vegan diet consumed 33 percent more fiber, which has been shown to decrease LDL and improve insulin sensitivity. Trimethylamine N-oxide (TMAO), a metabolite that has been shown to increase cardiovascular risk, is also affected by fiber and saturated fat. In short, consuming more fiber, fewer saturated fats, and more PUFAs are related to the improved biomarkers.
Dr. Layne Norton’s Takeaways
Dr. Norton found it unfortunate that this trial misinterpreted vegan diets as “better” than omnivorous diets.
It isn’t that the vegan diet is somehow magical or that meat has some inherent component to it that causes an increase in these risk factors.
The energy deficit, less saturated fat consumption, and more polyunsaturated fat and fiber consumption are the keys to a more sustainable diet and a healthier lifestyle.
Norton suggested that an omnivorous diet that is low in saturated fats, comprised of high-quality sources of lean meat, and provides enough daily fiber would likely lead to similar positive biomarker outcomes. While it might be easier to achieve that nutritional breakdown via a vegan diet, one can still eat meat and achieve proper nutrition.
Reference
Landry, M. J., Ward, C. P., Cunanan, K. M., Durand, L. R., Perelman, D., Robinson, J. L., Hennings, T., Koh, L., Dant, C., Zeitlin, A., Ebel, E. R., Sonnenburg, E. D., Sonnenburg, J. L., & Gardner, C. D. (2023). Cardiometabolic Effects of Omnivorous vs Vegan Diets in Identical Twins: A Randomized Clinical Trial. JAMA network open, 6(11), e2344457. https://doi.org/10.1001/jamanetworkopen.2023.44457
Featured image via Shutterstock/Tatjana Baibakova
