All About The Glycemic Index
Here is a quick informative guide with some frequently asked questions regarding how to use the glycemic index:
Glycemic Index = ranking of carbohydrates on a scale from 0-100. This index was created to help manage and prevent diabetes by ranking food based on the amount of time it takes glucose to get into the bloodstream.
What are we ranking? -how high they raise blood sugar levels after eating
High GI foods have a quick digestion rate and result in fluctuations in blood sugar levels (big spike and big fall) sometimes can result in hyperglycemia (feeling of low blood sugar)
Low GI foods have slow digestion and absorption with a steady rise and fall of blood sugar and insulin levels.
Why does this matter? -Low GI foods are shown to benefit weight control because they deliver more sustainable energy while helping to control appetite and keep you satisfied longer. Given this information you can decide what foods are right for you at what times. This is especially good for nutrient timing around workouts.
This index is a great guide but has a few faults. IT DOES NOT show the nutritional value/density of food which is something we always want to be aware of. For example on this index chocolate has a lower GI than oatmeal.. oatmeal has a higher food density, lower sugar, and more fiber than chocolate. Obvious choice here will be the oatmeal.
Factors that affect the glycemic index of foods (don't kill the messenger here):
Cooking methods -How you cook your food matters. For example, sweet potato's GI is 3x higher when baked compared to being quickly boiled or steamed. Cooking and heating food for prolonged periods raise the GI. The longer you cook it the higher it becomes.
This is a result of the gelatinization of the starch content. We still want to cook food just enough to make nutrients bioavailable. Processed foods take this to a whole other level of extreme with instant mashed potatoes, oatmeals, cornflakes, puffed rice etc. they use binding agents such as "modified starches" or "dextrinized starches" to keep everything together. If you need a chemical to hold your food together maybe you shouldn't eat it...
How long the food has been in storage -Ripeness of a fruit or vegetable also plays a role in the GI. Green bananas have a GI of about 40. Once they are ripe it rises to about 65. This goes along with potatoes as well. Foods that have been sitting in storage for months have a higher GI than the freshly-harvested ones. This is one reason why buying seasonal fruits and vegetable from local sources is important.
Nutrient Density -High fiber carbohydrates slow down the digestion rate making them great choices for sustainable energy and moving things along the GI track. Fiber is not digestible in the human body so it will slow down the rate of absorption of food.
Is it in its whole form? -Particle size: when starchy foods are grinded up (oat flour, rice flour, wheat) they become finer and more refined. This means they lose a lot of their fibers, proteins, and micronutrients which contribute to raining the GI. So if you are reading the ingredients of a food and think you are making a healthy choice because it uses "brown rice flour" think again. Flour don't have the same reaction in our bodies as their whole forms do.
So what do I eat?
Foods that are in their whole form or closet to their whole form are ALWAYS best. Large food particles will be more intact, less refined, and slower to digest.
Examples would be steel-cut oats, yams, non-starchy vegetables, and whole fruits are all low. Medium GI examples include quick oats and brown/wild/basmati rice.
As always, It is best to be informed on what you are eating and how it affect your body so you can make better choices day by day! :-)