Is it im­por­tant to choose low GI foods?

Ask Dr Libby

Waiheke Marketplace - - Out & About -

Q: What are your thoughts on gly­caemic in­dex (GI) please? How im­por­tant is it to choose low GI foods? Kin­d­est, San­dra A: The gly­caemic in­dex (GI) is a scale based on how quickly the glu­cose from the food will hit the blood­stream. Es­sen­tially, the faster it gets to the blood­stream, the higher it ap­pears on the in­dex. Low GI is con­sid­ered to be a score of 55 or less.

How­ever, the GI does not take into ac­count the amount of car­bo­hy­drate in a food in com­par­i­son to the other macronu­tri­ents (pro­tein and fat), mi­cronu­tri­ents (vi­ta­mins and min­er­als) or how much you con­sume in one sit­ting.

The to­tal amount of car­bo­hy­drate that we con­sume has the great­est im­pact on our blood-glu­cose lev­els, and how much in­sulin is re­quired. In­sulin is a hor­mone that en­ables glu­cose to move from the blood­stream into our cells, so that it can be used for en­ergy and so that our blood-glu­cose lev­els are kept within the nor­mal range. How­ever, it is also a body-fat­pro­mot­ing hor­mone.

An­other cat­e­gori­sa­tion you might be fa­mil­iar with is gly­caemic load (GL). It is a bet­ter in­di­ca­tor of how a car­bo­hy­drate food will af­fect blood glu­cose lev­els. GL con­sid­ers the ac­tual amount of car­bo­hy­drate you eat in a sit­ting. For ex­am­ple, pump­kin is con­sid­ered a high GI food, but it is high in fi­bre, water, vi­ta­mins, min­er­als and pro­tec­tive phy­tonu­tri­ents, which al­ters the way it is di­gested and pro­motes ex­cel­lent health. The GL of a serve of pump­kin is low (a good thing).

I highly doubt that the GI would have be­come a way of as­sess­ing car­bo­hy­drates if pro­cessed foods didn’t ex­ist. When we ap­ply th­ese sci­en­tific mea­sure­ments to real life, we be­gin to see how they fail to take into ac­count the way that other things we con­sume along­side car­bo­hy­drates might af­fect the way our body re­sponds to them, as well as the nu­tri­tional value that par­tic­u­lar foods of­fer us.

Both GI and GL are af­fected by the pro­tein, fat and fi­bre con­tent of a meal, as they all slow down the re­lease of glu­cose into the blood and hence the re­quire­ment for in­sulin – so when com­bined with pro­tein, fat and fi­bre, a high- GI food is un­likely to reach our blood­stream in the same way.

Con­sider a piece of choco­late cake that you might buy from a bak­ery – many of them are low GI (due to their poor-qual­ity fat con­tent) and, if we chose ‘‘healthy’’ foods this way, they would be a ‘‘good’’ op­tion. Yet they con­tain high lev­els of re­fined sug­ars, poor-qual­ity fats, vir­tu­ally no nu­tri­ents and are high GL. In other words, the GI can be highly mis­lead­ing if that is all you use to guide your car­bo­hy­drate choices.

It has also been shown that the way a par­tic­u­lar food or meal is metabolised and how it im­pacts blood glu­cose lev­els can vary sig­nif­i­cantly from per­son to per­son. So the GI value of a food may not even be an ac­cu­rate in­di­ca­tion of how it will im­pact your blood glu­cose lev­els.

It’s no won­der peo­ple feel con­fused and over­whelmed at times about di­etary in­for­ma­tion! For­tu­nately, we stop need­ing con­cepts like this when we sim­ply eat whole, real foods. So rather than fo­cus­ing on the GI, I’d en­cour­age you to em­brace the state­ment ‘‘just eat real food’’.

Just us­ing a gly­caemic in­dex can be mis­lead­ing. A piece of choco­late cake could be low on the GI scale, yet have a high gly­caemic load.

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