Key Question: When you eat a meal, what happens to all that energy?
Before we get stuck in, a big thank you to my new friend and researcher of all things insulin for helping craft this one. On a side note, if you are looking for a new favorite hormone, you won't go far wrong with insulin... Anyway, lets crack on and learn about blood sugar! This is an important topic to have an awareness of, with current worldwide trends for metabolic diseases. Hopefully it's a useful 5 min article with some great nuggets of science!! Enjoy!!
Does your body love that KitKat as much as you do? The answer is probably yes. Sugars (or carbohydates) are one of your body’s main energy sources. What begins as a KitKat can eventually ends up as food for your muscles. So let’s talk about what happens in between.
When you eat a snack or meal, your stomach digests it by breaking down any carbohydrates into glucose (a fancy name for sugar) and releases it into the bloodstream. Glucose is a universal energy currency in your body: many of your tissues want it, many of your tissues need it (especially your brain) and some tissues (the main ones are the liver and muscle) can store it for later.
Glucose travels through the bloodstream to reach the tissues in your body. One of the most important tissues that glucose reaches is the pancreas, where it signals the release of the hormone insulin. Insulin is like the traffic controller of glucose: it tells the tissues that glucose is available and instructs the tissues to prepare for its arrival. One of the tissues that insulin communicates with is skeletal muscle. Your skeletal muscles are huge energy burners: they do a lot of work to move and stabilize your body and they can use glucose to do it.
Insulin is released by the pancreas into the bloodstream where it travels to skeletal muscle and permits the muscle to take glucose from your blood. This is important: it could be catastrophic if your muscles constantly drained glucose from your blood during between-meal periods (aka: fasting), because your blood sugar would fall critically low and you could experience the consequences of hypoglycaemia (like seizures, for example). Insulin’s job is to tell the muscle that the blood glucose level is high enough that the muscle can take some of the glucose for itself. As a small side note, insulin also tells the liver to stop releasing sugar into the blood and tells the adipose (fat) tissue to stop releasing fat. These things happen when we are fasting to supply energy to the body, but are not needed after we have eaten.
Glucose needs a ‘door’ to enter the muscle. These ‘doors’ are called glucose transporters. In between meals, the insulin-responsive muscle glucose transporter (GLUT4) is stored inside cells where it cannot permit glucose uptake from the blood. In response to insulin, GLUT4 is moved to the surface of muscle cells and several doors are therefore opened and glucose from the blood can be taken up into the muscle. This process is regulated to match your nutrient status (mainly the availability of glucose), so that the GLUT4 doors are at the surface of the muscle cell when blood glucose is high.
In the case of type 2 diabetes insulin can still be released from the pancreas and reach the muscle, but GLUT4 remains inside the muscle cells (and therefore, less doors are opened). As a result, the sugar remains in the blood: this is why one of the hallmark signs of diabetes is high blood sugar. While we don’t fully understand why or how skeletal muscle stops responding to insulin in diabetic patients, many research efforts are endeavouring to solve this problem in efforts to develop new diabetic therapies.
So why did I bother reading this?
1. Well hopefully you’ve learnt some new science and that's cool!! What we’ve talked about will also be useful for understanding exercise and diet studies that have measured blood insulin (e.g. click here for research around breakfast timing and exercise).
2. Making healthy lifestyle choices such as being physically active and not eating too much sugar means your skeletal muscle will stay more responsive to insulin (that GLUT4 part) and you can control your blood sugar levels better.
3. On the flip side, being sedentary and having a bad diet in the long-term can result in high blood sugar levels.
The take home message: in the world of hormones, insulin is sweet. One of its (many) jobs is to help us control our blood sugar. So next time you eat a KitKat, spare a thought for insulin.
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