Question: Do the blood vessels in the brain or going to the brain vasoconstrict when we are full from food so that the blood vessels in the stomach can vasodilate? Is this also the reason we ( or at least I ) feel sleepy sometimes after a big meal?

Emily Robinson answered on 17 Jun 2011:

Hi scorpius, I think this question is really good as I know exactly were you are coming from about getting sleepy after eating! But there is nothing to worry about when eating as yes blood is directed to the digestive tract once you have eaten but the body always prioritises blood going to the heart and brain before anything else, as they are so important! The reason you are sleepy after eating is not because of a lack of blood but instead it is because we release hormones to keep us alert (therefore wide awake to hunt and get food), but after eating these hormones are turned off for a while. So that is why you feel sleepy after eating. In some cultures it is normal to take a short nap after eating.