YAM Nutrition Sweet Potato Flour – Glycemic Index and Glycemic Load, Explained

Sweet potatoes are particularly popular with strength athletes. Today, many French bodybuilders and endurance athletes have added sweet potato flour, or the famous starch, to their diets. On this subject, we will return to the concepts of Glycemic Index and Glycemic Load in this article...

Very different from the potato, the sweet potato stands out from its distant cousin with its slightly sweet taste, which is so appreciated, but that's not all. Indeed, sweet potatoes are also a real nutritional treasure. They provide you with calcium, magnesium , potassium as well as trace elements such as manganese and copper, elements necessary for the proper functioning of the body. However, the first nutrient that sweet potatoes provide you with are Carbohydrates . For 100g of starch, we get 20 grams of carbohydrates in the form of glucose and fructose. For sweet potato flour, you get 70g of carbohydrates per 100g.

Is the amount of carbohydrates the only factor to consider when it comes to starchy foods?

Naturally, the answer to this question is no. As you know, when we talk about carbohydrate assimilation, we must take into account two factors: the glycemic index and the glycemic load .

The Glycemic Index (GI) represents the impact of a food on blood glucose levels 2 hours after ingestion, which is called blood sugar. The food will create an increase in blood sugar, this is called a peak. Then, insulin will play its storage role by lowering blood sugar. Thus, when eating a food with a high glycemic index (over 70), the blood sugar peak will be high. Conversely, this peak will be reduced with a food with a low glycemic index (less than 55). The GI scale is based on glucose, which gives the value 100. Be careful, however, not to confuse the glycemic index with the old notions of “slow sugar” and “fast sugar,” which no longer mean anything today.

But then, how do we determine the Glycemic Index of a food?

As you have understood, this notion of glycemic index can vary depending on the food itself, what it contains (presence or absence of fiber and other nutrients such as proteins and fats), packaging, cooking or lack of cooking... First of all, the type of carbohydrate present in the food in question will influence its GI. For example, fructose has a glycemic index of 20, which is low compared to glucose. The texture of the food will also be taken into account to determine its GI. For example, for potatoes, their glycemic index is high and varies depending on its food preparation method. A puree, for example, will have a very high GI. Indeed, when the texture is solid, it is less well absorbed than when it is liquid. Since puree is denser, the GI will be higher than steamed starch. Cooking and humidity will increase the gelatinization of starch, which will also raise the glycemic index. Also, be careful not to confuse the sweetness (the sensation of sweet taste) with the glycemic index of a given carbohydrate because there is no relationship between the two.

Glycemic load is more accurate than glycemic index

If the glycemic index informs us about the impact of a food on blood sugar, the glycemic load proves to be more adequate on the real influence of a meal on blood sugar since it takes into account the GI but also the amount of carbohydrates present in a food portion . From there, to know the glycemic load of a food, you simply need to take into account its GI which is multiplied by the quantity of carbohydrates it contains and divided by 100 to obtain a value.

CG = [GI x amount of carbohydrates in a portion of food (g)] /100

The table below gives you the correspondences:

High Glycemic Load	Greater than or equal to 20
Moderate Glycemic Load	Between 11 and 19
Low Glycemic Load	Less than 10

Let's take a concrete example, that of carrots and baguettes.

If you eat 200 grams of cooked carrots, you get 10 grams of carbohydrates. Carrots have a GI of 49. The calculation of their glycemic load will then be 49 x 10 divided by 100 or 4.9 . Less than 10, their glycemic load is therefore low. On the other hand, if you eat 100 grams of baguette, you take 56.6g of carbohydrates associated with a GI of 70. The glycemic load will be 70 x 56.6 divided by 100 or 39.62 . The glycemic load of the baguette is therefore very high because it is greater than 20.

Take the example of a sweet potato flour cake, once baked

What needs to be understood here is that if a food contains few carbohydrates per 100 grams (less than 5%), its glycemic load will be low most of the time, this is logical. But to return to our subject, the GI of the sweet potato is moderate for the starch itself (around 70 compared to 80 to 111 for the potato). Indeed, the sweet potato contains a starch mainly composed of amylose and not amylopectin. The latter gelatinizes easily unlike amylose. This allows us to obtain a lower GI of 49 for the sweet potato when cooked. For example, if you take 40 grams of sweet potato flour for a pastry, its glycemic load will then be 49 x 30 divided by 100, or 19.60 , once baked. The glycemic load of your pastry is still considered moderate, despite the high carbohydrate content of sweet potato flour (70%). Needless to say, under these conditions, nothing is more tempting than to start baking excellent desserts, even for those who suffer from diabetes!