Aerobic cardio exercise increase glucose uptake into brain proven by studies. Studies has also proven that stutterers has a reduced glucose metabolism in brain this aerobic cardio exercise can help the brain. Had also read somewhere that you the no. 1 bottleneck of our brain is oxygen thus it could make sense that lack of glucose uptake and oxygen in brain is a major cause of stuttering There is also another theory on increasing gaba in the brain to decrease speech stuttering. But the brain has a blood brain barrier which is complex and not just simply by eating gaba to increase it