Twins have long been used as test subjects, with the idea first proposed by British polymath Francis Galton in 1875.
The first descriptions of the method, however, first appeared in 1924, according to the National Library of Medicine. Even NASA conducted an experiment using retired astronauts Scott and Mark Kelly, who are identical twins.
Now, a recently published study from Stanford University, which observed 22 pairs of healthy, adult, identical twins, is offering insights into the health effects of a meat-free vs. meat-filled diet.
One twin in each pair ate meals free of animal products (vegan), while the other was omnivorous, consuming both animals and plants, for eight weeks.
“Increasing evidence suggests that, compared with an omnivorous diet, a vegan diet confers potential cardiovascular benefits from improved diet quality (ie, higher consumption of vegetables, legumes, fruits, whole grains, nuts, and seeds),” the study authors wrote.
The researchers compared cholesterol, sugar and insulin levels, body weight, and other indications of cardiovascular health.
The vegan twins lost more weight, lowered their LDL (bad) cholesterol and showed lower insulin levels than their omnivorous siblings.
“The findings from this trial suggest that a healthy plant-based diet offers a significant protective cardiometabolic advantage compared with a healthy omnivorous diet,” the researchers wrote in their study, published Nov. 30 in the journal JAMA Network.