Following This Diet Improves Cholesterol, Says Unique New Study That Followed Identical Twins

Updated: Dec. 06, 2023

Researchers discovered this still-trending diet is clearly healthier...but it also fell short when it came to one important factor.

Maybe you’re brainstorming ways to clean up your eating habits ahead of the new year and have wondered how practical it would be to test out a plant-based diet. Now you might have more inspiration to give it a go: A clever new study just revealed a major benefit that can come from a diet that cuts down on animal products.

Research in recent years has highlighted the benefits of a vegan diet, which excludes any food that comes from an animal or animal product. Science has suggested veganism can contribute to heart health and weight loss, and that it improves other health values, potentially leading to a longer and healthier life.

To explore this further, researchers from Stanford University have conducted a unique study examining pairs of identical twins with an average age of 40 to analyze what would happen if one followed a vegan diet and the other didn’t. 

The study was published in the American Medical Association’s Nutrition, Obesity, and Exercise journal on November 30, 2023. It enlisted 22 sets of twins, randomly assigning one twin to follow a vegan diet and the other a healthy omnivore diet. Presumably, using twins for the study ensured that their diet, and not their genetics, influenced the health-related values the participants set out to measure. The twins adhered to their respective diets for eight weeks, with regular measurements of blood and other biomarkers, such as weight, blood sugar, and blood pressure monitored throughout the study.

What the researchers discovered was that in terms of certain markers of health—particularly cholesterol—a vegan diet appears to be better.

For the study, the vegan diet-assigned twins received breakfast, lunch, and dinner by delivery for four weeks and then followed a healthy vegan diet for the rest of the study. In contrast, the omnivore diet-assigned twins were instructed to eat a healthy diet for the duration of the study, emphasizing minimally processed foods and building a balanced meal with vegetables, starch, protein, and healthy fats. All of the participants in the group were relatively healthy and of average body mass index (BMI); in addition, none were underweight or suffering from high cholesterol.

Weight loss wasn’t discouraged, but it also wasn’t a focus of the study, and participants were told to eat until they were no longer hungry.

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Those who followed the vegan diet saw a significant reduction in LDL cholesterol numbers, showing a positive benefit to eating a vegan diet for those with cholesterol issues. In fact, as early as four weeks into the study, the vegan group was showing significant improvement in their cholesterol numbers. Fasting insulin also improved more with the vegan diet versus the omnivore diet.

Both the vegan and omnivore groups experienced weight loss, but the vegans experienced greater losses on average.

While a vegan diet led to better cholesterol numbers and greater weight loss, it did have its drawbacks. The biggest issue was that participants reported not being as satisfied with their diet, suggesting that following a vegan diet long-term might be difficult for people who don’t want to forgo all animal products. The twins who ate the omnivore diet were happier with their diets overall. (The omnivores also saw improved fasting insulin and LDL cholesterol levels.)

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Overall, the researchers weren’t convinced that a vegan approach was essential for heart health, suggesting that “cardiovascular benefits can be achieved with modest reductions in animal foods and increases in healthy plant-based foods compared with typical diets.” They emphasized that creating more barriers to healthy eating, as people might find with restrictive vegan diets, would be counterproductive.

So as you’re meal planning in the new year, the study indicates that a diet higher in plant foods with a relative reduction in foods from animals can be beneficial, but you don’t have to go all vegan if that’s not your thing.