Brain fog/headaches seems to be associated with poor brain blood supplies in some cases. (it is in my case, and the agravation after a meal may be consistent with a brain blood flow issue) "Blood supply to the brain was once considered an involuntary action regulated by the body and relatively unaffected by changes in blood pressure caused by exercise or exertion. However, previous studies have shown that the foot’s impact during running causes back-flowing waves through the arteries that sync with the runner’s heart rate and stride thus regulating blood circulation to the brain. In this new study, the research team examined the effects of walking, which involves a lighter foot impact than running." "The scientists found that walking resulted in a significant blood flow to the brain despite having a lighter foot impact. Walking produced larger pressure waves in the body which significantly increased the flow of blood to the brain. The blood flow was not as dramatic as seen while running but had greater effects than that seen during cycling, which has no foot impact at all. The new data suggests that the brain blood flow is very dynamic and depends on cyclic aortic pressures that interact with retrograde pressure pulses from foot impacts." "The scientists conclude that there is an optimising rhythm between brain blood flow and walking and that stride rates and foot impacts are within the normal range of our heart rate ( about 120 per minute). The foot’s impact while walking helps control and increase the amount of blood sent to the brain. More blood means more energy and more oxygen in the brain — and thus an enhanced sense of wellbeing."