Short for the Glycemic Index.
Okay, maybe you’ve heard of it.
Maybe you haven’t.
But the weight loss industry is currently abuzz about your Glycemic Index; on the cover of a recent diet book The New Glucose Revolution, it’s even being touted as ‘the dietary solution for lifelong health.’
So what’s the real truth?
Let’s begin at the beginning.
The Glycemic Index was conceived in 1981 by a scientist named David Jenkins at the University of Toronto. It was initially developed as a tool for the dietary management of type 1 diabetes; Jenkins was investigating the impact of different carbohydrates on blood sugar levels.
The Glycemic Index (GI) ranks carbohydrate-containing food based on how quickly they elevate blood sugar levels. High GI values are associated with carbohydrates that are quickly ingested, spiking blood sugar levels. Conversely, a low GI value is given to carbohydrates that are slowly digested, releasing glucose gradually into the bloodstream. Most refined carbohydrate-rich foods have a high GI while non-starchy vegetables, fruits and legumes tend to have a low GI.
While an interesting concept, the Glycemic Index remains both problematic and incomplete in terms of giving us real nutritional guidance.
To begin with, the GI is highly variable and somewhat unreliable. A number of factors influence the GI value including the physical structure of the carbohydrate, how the food is processed and prepared and the presence of other nutrients in the food (protein, fat). Complicating matters more, the GI can vary between individuals and even fluctuate in the same individual.
Secondly, the GI is incomplete as an assessment tool. When choosing the best foods to eat, it is essential to consider its nutrients rather than evaluating it solely on its GI. Some high GI foods are brimming over with nutrients while some low GI foods are poor in nutritional value. A potato chip enjoys a lower GI but is devoid of nutritional value while a baked potato with its higher GI is packed with healthful nutrients.
Probably the biggest flaw with the GI is it assesses carbohydrates in isolation. The reality is that most of the time carbohydrates are consumed within the context of a ‘mixed meal’ alongside proteins and fats. This is extremely important because proteins and fats also have a direct effect on the blood glucose response and GI.
Several studies clearly demonstrate that when you add protein to a meal containing carbohydrates, the blood sugar may decrease but your insulin response spikes dramatically. In other words, the presence of protein exponentially increases the insulin spike compared to what it would be if the carbohydrate had been ingested on its own. (The same is true when you mix fat with carbohydrates).
What’s more, some protein- and fat-rich foods release as much insulin as carbohydrate-rich foods (and meat protein alone may induce insulin secretion as high as pure glucose.) This is all the more important given the fact that high insulin levels are linked to a number of diseases including obesity, metabolic syndrome, and type 2 diabetes.
Ample evidence exists showing that a plant-based diet—i.e. a diet that is 100% free of animal protein–naturally optimizes blood sugar levels and enjoys a relatively low daily insulin secretion (despite its high consumption of carbohydrates.)
Not convinced? David Jenkins (the man who invented the GI in the first place!) himself eats a whole food plant-based diet. He explains that plant-based eaters are thinner, have lower cholesterol and blood pressure levels, a reduced risk of coronary heart disease, type 2 diabetes and lower cancer rates.
So maybe it’s time to stop worrying about a food’s GI count. And simply start digging into all the whole grains, fruits and vegetables, beans and lentils, nuts and seeds with their great wealth of enriching nutrients.