The fact that eating less meat improves cardiovascular health is not a new revelation, but previous studies supporting this have often been hampered by confounding factors such as genetics, background and lifestyle. Now, scientists have removed many of those variables, with a study on identical twins, pitting a healthy omnivore diet against a healthy vegan one.
Stanford University recruited 22 sets of identical twins who had grown up together, and who reported similar present-day lifestyles, for this eight-week meal-plan-controlled trial, in an effort to provide more robust data to support the existing body of evidence.
“Not only did this study provide a groundbreaking way to assert that a vegan diet is healthier than the conventional omnivore diet, but the twins were also a riot to work with,” said Christopher Gardner, a professor of medicine at Stanford. “They dressed the same, they talked the same and they had a banter between them that you could have only if you spent an inordinate amount of time together.”
Of the sets of twins, with a mean age of 39.6 years, more than three quarters lived with their sibling at the time of the study. And 69% of the participants reported that they were very similar to their twin.
Over the course of eight weeks, twins were randomly selected to either follow a healthy plant-based diet or a healthy omnivorous diet, with a delivery service providing nutritionist-designed meals for the first month. After this stage, the participants prepared their own meals in line with their specific eating directives.
The participants were assessed before, during and after the trial, with bloodwork, weigh-ins, feces testing and more. Those on the vegan diet had the most significant change in low-density lipoprotein cholesterol (LDL-C), dropping from 110.7 mg/dL to 95.5 mg/dL (compared to 118.5 mg/dL to 116.1 mg/dL in the omnivores). Optimal range is below 100 mg/dL.
It's also worth noting that the twins in the study generally already had reasonably healthy LDL levels, with Gardner expecting a more drastic drop for those with poorer baseline measurements.
The vegans also experienced around a 20% drop in fasting insulin and lost an average of 4.2 lb (1.9 kg) more than their meat-eating counterparts.
“Based on these results and thinking about longevity, most of us would benefit from going to a more plant-based diet,” Gardner said.
Both diet plans featured vegetables, legumes and whole grains heavily, while omitting refined sugars and starches. The plant-based regimen, of course, omitted all animal products, including eggs and milk, while the omnivorous plan included fish, chicken, eggs, cheese and dairy.
At the end of the two months, 43 participants had completed the study, which the researchers point out shows how easy it is to learn to prepare healthy dishes, something required of the twins once the 21-meals-a-week deliveries ended after week four.
“Our study used a generalizable diet that is accessible to anyone, because 21 out of the 22 vegans followed through with the diet,” said Gardner. “This suggests that anyone who chooses a vegan diet can improve their long-term health in two months, with the most change seen in the first month.”
Interestingly, and what will be presented in a future study, the twins on the vegan diet also tested younger, giving them a biological age less than their chronological age.
“A vegan diet can confer additional benefits such as increased gut bacteria and the reduction of telomere loss, which slows aging in the body,” Gardner said.
And while the researchers know a study will unlikely make anyone adopt a plant-based diet full-time (one vegan twin remarked that she ate less because she didn't want more whole grains or vegetables), the primary takeaway from this study is how effective cutting back on saturated fats, increasing dietary fiber and losing weight is to improving cardiovascular health.
“What’s more important than going strictly vegan is including more plant-based foods into your diet,” said Gardner, someone who has been “mostly vegan” for 40 years. “Luckily, having fun with vegan multicultural foods like Indian masala, Asian stir-fry and African lentil-based dishes can be a great first step.”
The study was published in JAMA Network.
Source: Stanford University
