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.
Mystery solved!
References:
Murphy, S. (2011, September 28). Lecture given in Neurobiology, BIOS E-50, Harvard University, Cambridge, MA.