Why do people with low blood sugar avoid eating sugar? My Neurobiology professor, Shawn Murphy, M.D., PhD, offered a really simple explanation in today’s lecture:
It’s all about how insulin (a hormone produced at the pancreas) responds to sugar. Typically, cells in your muscle, liver, etc. will try to consume as much sugar as they can – without depriving your brain of the sugar it needs. (Your mitochondria uses sugar/glucose to generate ATP – which, to keep things simple, gives your brain energy to do what it needs to do.) Insulin production is triggered by ingesting sugar. Your body’s cells use this production as a signal to start grabbing up as much sugar as they can. So, when you eat a lot of (simple) sugars, your body produces a lot of insulin – signaling to cells in your muscle, liver, etc. that there’s a ton of sugar ripe for the picking. However, this doesn’t leave enough sugar for your brain (and remember, your brain needs ATP – which uses sugar/glucose for fuel). So you actually end up having low blood sugar, even though you just ate a bunch of it.
This is why it’s important to eat complex carbs (such as whole wheat bread) instead of simple carbs (like white bread or candy). Complex carbs take a lot longer to break down, which helps pace the body’s release of insulin, so that enough sugar gets saved for your brain.
Murphy, S. (2011, September 28). Lecture given in Neurobiology, BIOS E-50, Harvard University, Cambridge, MA.