However, for the inverse association between PDF and risk of death from neurological diseases, limited support comes from intervention studies where the Paleolithic diet — sometimes modified — has increased cognitive function, hippocampal volume, and serum brain-derived neurotrophic factor levels, and reduced fatigue and increased quality of life, exercise capacity, and hand and leg function in patients with multiple sclerosis [44–46]. This evidence concerns the gene BDNF and nervous system disorder.