Vegan vs omnivore diet

Executive summary

* The research group that brought us the DIETFITS and KETO-MED trials has published the results from its latest randomised controlled trial.

* This trial involved 22 sets of identical twins (44 people). One of each twin was randomly allocated to an 8-week (whole foods) vegan diet and the other to an 8-week (whole foods) omnivore diet.

* The participants may have been identical twins, but they weren't identical in characteristics. These differences were not adjusted for. Some baseline food intakes were also quite different between the two groups – notably grains and plant-based protein.

* The diet was provided by the researchers for the first four weeks and then participants provided their own food for the second four weeks.

* The main outcome of interest was the change in LDL-cholesterol. Cholesterol did fall in the vegan group relative to the omnivore group, but it would, because the consumption of plant sterols increased in the vegan group.

* In the food delivery phase, the vegan group were given an average of 345 calories fewer than baseline and nearly 200 fewer than the omnivore group. This calorie gap was largely maintained during the self-delivery phase.

* The vegan group lost a reported 1.9kg over the 8 weeks (the raw data showed the loss to be 1.4kg). Fasting insulin was reported to be 2.9 μIU/mL lower in the vegan group than the omnivore group. Both could easily be explained by the calorie (and protein) inequalities introduced in the trial.

* The paper claimed that vitamin B12 intake did not suffer. It was noticeably higher in those assigned to the vegan group at baseline and vitamin B12 intake did not drop to zero during the trial, indicating that fortified foods were being consumed.