Study
A self-selected vegan diet reduces skeletal muscle mass in healthy older adults: a randomized controlled trial.
Among healthy adults aged 65 or older, a self-selected vegan diet reduced protein intake and muscle mass over 12 weeks; adding resistance exercise mitigated the loss.
Jacintha Domić and colleagues randomized 72 healthy adults aged 65 years or older to a self-selected vegan diet, a habitual omnivorous diet, or a vegan diet combined with resistance exercise for 12 weeks. The study used MRI, DXA, deuterium oxide, and muscle-protein-synthesis measures. The vegan group consumed about 19 to 28 grams less protein per day than the omnivore group across study weeks. Compared with omnivores, vegan participants lost about 0.61 litres of muscle volume and 1.15 kg of appendicular lean mass. Muscle-protein synthesis was lower in the vegan group, at 1.09 versus 1.27 percent per day. Resistance exercise mitigated the losses in the combined group. The trial does not show that all vegan diets cause muscle loss. It tested self-selected diets in older adults and did not impose a matched protein prescription. It does show that protein quantity and resistance training matter when older adults change to a vegan pattern. For longevity, preserving muscle and function is a relevant outcome. The study supports individualized protein planning rather than a universal diet rule.
A self-selected vegan diet reduced skeletal muscle mass in healthy older adults, which was mitigated by resistance exercise.
The trial was short, small, and based on self-selected diets. Protein intake was not matched across arms. The result should not be generalized to well-planned, high-protein vegan diets or to younger adults.