In clinical settings, a randomized controlled trial involving patients with Alzheimer’s disease showed that a multi-strain probiotic increased serum brain-derived neurotrophic factor (BDNF) by 36%, elevated antioxidant enzyme levels (SOD), and reduced oxidative markers like malondialdehyde (MDA) and protein carbonyl content [200]. Here, BDNF is linked to early-onset autosomal dominant Alzheimer disease.