Glycemic Index, Glycemic Load and the changes in blood sugar levels
May 09, 2016
Glycemic Index is a measure of how much the blood sugar (i.e., glucose) increases after one eats a particular food. Pure glucose has a GI of 100, and all other meals are ranked concerning this. GI is a relative ranking of different foods and is useful in estimating how much sugar will the body have to deal with. There are a lot of junk articles online about GI; it is always a good idea to go to the research programs rather than use favorite media sources for information. For example, the University of Sydney’s website on GI is a good source of information on GI.
Glycemic Load is another number that factors in the recommended serving size. It is calculated by multiplying the GI with the recommended serving size. So it gives a much more realistic representation of how much increase in blood sugar one can expect after eating a particular food item. A high GI food item consumed in a small quantity would not increase the blood sugar level too much, whereas, a medium GI food eaten in large amounts during a meal would dump a whole lot more sugar than one would like.
Now one thing that neither of these two numbers capture is how soon the carbohydrates from the food reach the blood and increase blood sugar levels.
If one plots the blood sugar levels measured in an individual after eating a meal, it will increase up to a certain level and then begin to drop. GI is the area under the curve. Anyone who has studied college math (and remembers it!) will immediately recognize that the area can be the same for two curves with a very different rate of rising, or even different peak values. When we are trying to identify how our body is stressed during digestion and absorption of nutrients, the rate of change in blood sugar levels is a critical parameter.
And surprisingly, there is a simple number one can use to get a measure of this – the carbohydrates to fiber ratio. For convenience, let's call it the ‘C/F’ of a food. Digestive juices need to soften and move through the ingested fiber before they can get to the sugars. So a high fiber food item would have a slower release of sugars compared to the same thing with low fiber content. Based on this idea, the Harvard School of Public Health has promoted the 10:1 thumb rule to assess if a food item is a whole grain or not.
So let's see the comparative nutritional table for millets and do the math to calculate the C/F for each of the food items. And the resulting table is …
There are two main advantages of using C/F rather than GI when assessing how good a particular food item is.
It can be identified with just a simple division operation that a consumer can do looking at the nutritional label and does not need lab testing and trials.
It is a better reflection of how it affects a person concerned about diabetes and controlling blood sugar levels.
The first nutrition we derive from our cereals is the energy from its carbohydrate content. But this needs to be moderated to decrease its rate of release into the bloodstream. And this is achieved by having a good fiber content. The secondary nutritional components we derive are the minerals and essential fatty acids. Note that within a grain, carbohydrates are found in the endosperm, the inner (typically white) portion of the grain that forms a majority of its volume and mass. Fiber is mostly found in the bran, a thin protective layer around the grain also rich in minerals, essential fatty acids.
So looking at it beyond the labels and nutritional analysis, it is a relatively simple thing to remember when shopping for something to eat:
Has bran? Good
No bran? ~ Ok..!
I do advocate for people to move to whole grains, not just in millets, but also with paddy rice and wheat. And at the same time I recognize that as with everything else in life, one has to compromise when negotiating what food to eat. So if eating polished/semi polished millets will get your family to accept it. Do make the shift. Gradually shift towards products that still have the bran layer.