Saturday, July 11, 2015

Glycaemic Load


The next book I chose to read was The Glycemic Load Diabetes Solution by Rob Thompson, MD.

The Glycaemic Index (GI) is a measure of how badly a food makes your blood sugar spike, compared to pure sugar which has a GI of 100. The Glycaemic Load (GL) takes quantity into account. For example, watermelon quite a high GI of 72. But that is calculated on someone eating enough watermelon to get 50 grams of carbohydrate from it. Watermelon isn't all carbohydrate. In fact 100g of watermelon has only 5g of carbohydrate, so it has a glycaemic load of 3.6 (72 x 5/100), which isn't much at all. You'd have to eat a whole kilogram of watermelon to get the 50g of actual carbohydrate used in the study. Similarly carrots have a high GI, but not many people eat 7 large carrots in one sitting. One carrot is fine, and will not make your blood sugar spike to that extent.

Some researchers say a much more important indicator is the Insulin Index, which studies the person's insulin response to the food -- i.e. how much insulin is released. This is correlated to, but not the same as, the level of blood glucose. You still release some insulin for non-carbohydrate foods like meat, which doesn't have a GI number. But this is much more difficult to test for.

The GI was determined by getting quite a small group of subjects (usually 10) to eat the food (seven large carrots doesn't sound fun), and then the results of the blood tests were averaged. I assume there was quite a wide variation, for starters anyone with diabetes or insulin resistance is going to have a much more dramatic result. And also Tim and I were discussing this last night and there is no indication anywhere whether the result is linear. By which I mean, is eating two doughnuts twice as bad as eating one? Is eating ten all at once, ten times as bad? Or is it only six times as bad, or maybe twenty times as bad? I have no idea, and I don't know if it has been studied. But at least all these tables of foods give eaters a way of comparing one food to another in terms of how likely they are to cause a undesirable insulin response.

Back to the book, which I'm a third of the way through and really enjoying. Dr Thompson explains about diabetes, GI and GL, why it's hard to lose weight when you are producing too much insulin etc. His contribution to GL is to give tables of foods in "normal" servings sizes rather than per 100g. So a sandwich includes two slices of bread. A can of fizzy drink is given as the GL for a whole can, not for 100 mL. One that confused me was his serving size of Life Savers (a small lolly, almost pure sugar) as one piece. Who eats one piece? Anyway, knowing the GL for a whole serve is quite useful; but they are US serves, which are large. He comments that the original GL table had a slice of Australian bread weighing 30g but he weighed the ones his wife brought home from the supermarket and they averaged 42g, so keep that in mind if you don't live in the US. I also like to be able to compare things of the same weight, which is hard when they are in serving sizes. But GL tables are available elsewhere anyway, and the serving size tables are quite handy.

The main theme of his book is that if you are diabetic or insulin resistant you have to avoid starchy foods. Wheat, rice, potato. He writes a bit about the chemical make-up of starch. It is processed by the body differently to other carbohydrate foods like fruit and non-starchy vegetables and even sugar. He isn't against sugar in small quantities, because although sugar has a high GI, a square of chocolate or half a teaspoon of sugar in a cup of tea has a low GL. Serving size is important! And even pure sugar requires a certain amount of processing by the body before it is absorbed. NB sugary drinks are a separate and much more evil case because they contain so much sugar... this doesn't contradict my previous comment about tea because half a teaspoon in tea is very different to 12 teaspoons or whatever it is in a cola or fruit juice). Anyway, but starch is absorbed almost instantly and provokes a disproportionately high insulin response which is very bad.

I haven't finished the book but the take-away thoughts so far are:
* Avoid starchy foods, and sugary drinks. (Can have a small amount.)
* Pay attention to the GL of other carbohydrate foods, and moderate your serving size accordingly.
* Exercise (even gentle exercise like walking greatly improves insulin response)

I really like his writing style, he has some cute things to say like Evian (an expensive brand of bottled water) being the word "na├»ve" backwards. I am well aware that I like this book partly because it aligns with things I already believe. It focuses on carbs rather than fat, but isn't totally anti-carb. It gives easy rules for managing pre-diabetes (and avoiding full-blown diabetes) without having to give up chocolate. Or fruit. Not that giving up bread or potatoes is an easy ask! Not at all! And of course flour is in nearly every processed snack: biscuits, cake etc, so like any diet I think is reasonable, it calls for an extreme reduction in processed food. I will keep reading for his plan on how to give up this tasteless yet somehow appealing substance called starch.

Report card:
Diet: Good.
Exercise: Poor.
Water: Ok.
Sleep: Ok.
Mental health: Good.

1 comment:

  1. Lots of good information! Solid report card too, yay.