RCT based evidence of beneficial health effects of vitamin D supplementation is still limited to a few health outcomes, such as fall and fracture risk [29] (at least when combined with calcium), upper respiratory infections [30], autoimmune disease [31], increased muscle strength [32], improved cognitive function in older adults with Alzheimer’s disease [33], reductions in migraine frequency and severity [34], positive effects on transferrin saturation and iron status [35], and on cardio-metabolic indicators in obese adults [36]. The gene discussed is TF; the disease is early-onset autosomal dominant Alzheimer disease.