Ask one twin to eat a diet that contains meat and dairy. Ask the other to eat only plant-based food. Which would you think is healthier? No need to answer, medical researchers know already, and you can see the results for yourself on Netflix (no, it’s not Twins, starring Arnold Schwarzenegger and Danny DeVito).
In an eight-week study of 22 pairs of twins by Stanford Medicine, one sibling was asked to consume a “healthy” diet that contained meat and dairy, while the other sibling was asked to tuck into only fruit, vegetables, nuts and pulses. Using genetically identical twins meant this was a diet study unencumbered by having to take account of participants’ sometimes wildly varying family backgrounds and lifestyles.
For the first four weeks of the study, which ran from May to July 2022, the twins were sent a specially prepared breakfast, lunch and dinner; after that they prepared their own meals, with a registered dietician on hand to offer advice.
And the results? Not only had the vegans’ levels of “bad” LDL cholesterol dropped, but their insulin levels – a marker of diabetes – were lower by a fifth and they had lost more weight than their omnivorous twin. The most surprising fact, however, was that their biological age – how old they were physiologically and metabolically – had also come down. The plant-based twin, in short, was now a little younger, which could mean living longer. And all of that in eight weeks.
Joint lead author, Christopher Gardner, Rehnborg Farquhar professor of medicine at the Stanford Prevention Research Centre, in Palo Alto, California, said the study provided “a groundbreaking way to assert that a vegan diet is healthier than the conventional omnivore diet”. And the fact that only one twin failed to make it to the end of their vegan journey proved anyone could do it.
“Our study used a generalisable diet that is accessible to anyone, because 21 out of the 22 vegans followed through with the diet,” said Gardner, who appears with the twins in a four-part Netflix series documenting his work, You Are What You Eat: A Twin Experiment. “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.
“Based on these results and thinking about longevity, most of us would benefit from going to a more plant-based diet.”