For some people, eating more than several hours apart causes a fluctuating sugar level in the blood and brain. Significant dips in blood glucose can cause physical symptoms such as tremulousness, racing heart, weakness and fatigue. Some of these symptoms will be interpreted in your brain as anxiety, others as low mood overall. When you feel lousy it makes you irritable. So, for those people who do have sugar shifts it is helpful to eat to maintain a stable level in order to maintain even mood. Similarly dehydration can make you feel weak, tired, shaky and can even interfere with cognition. This is particularly an issue for older people who are more likely to get dehydrated in these summer months, not realize it and make not only their mood, but also their thinking worse. A little dementia can be much worse with dehydration.

Your Brain and Food - On the Couch with Gail Saltz, M.D. | A Mental Health Blog at iVillage.com