The glycemic index can be used to help manage chronic conditions like heart disease, obesity, and even epilepsy, not just diabetes. If you’ve been diagnosed with diabetes or prediabetes, your healthcare provider may recommend you use the glycemic index as a tool for dietary planning.
But what is the glycemic index? How exactly can it help you with your health? What qualifies as a low-glycemic versus high-glycemic food? What does the evidence say about the index’s usefulness?
What Is the Glycemic Index?
The glycemic index is a number assigned to carbohydrates on a scale of 0 to 100 based on how much they raise blood sugar levels after being eaten. Foods with lower GI values don’t cause big spikes in blood sugar, while those with higher values do. The GI scale is calibrated with pure glucose assigned the value of 100.
The GI scale is a medical device used to measure the glycemic index of a food. It was developed by two physicians, David Jenkins and Thomas Wolever, in 1981. The assigned values were determined by how a set amount of glucose raised blood sugar levels in study participants over the course of two hours.
The test is simple: 10 or more people are given a certain food, and then their glucose levels are monitored for the next two hours to see how high it gets. A cohort of people is fed pure glucose sugar to see how it compares to the previous group. An apple is given a sugar ranking of 50 if it causes blood sugar levels to rise by half as much as pure sugar would. This means that the pretzel’s effect on blood sugar is nearly the same as that of sugar. And so on.
However, you might be thinking, what about volume? If you eat more of a food, it will raise your blood sugar levels more than if you eat less of the same food. Are they comparing two different things that are not alike, or are they comparing two things that are very different?
Well, it’s complicated. Jenkins and Wolever tried to account for portion size by making the test portions the same size. However, they did not compare equal volumes or equal weights. They decided that each test food must contain 50 grams of carbohydrates instead of some other amount.
How useful is this, really? In reality, people don’t usually eat foods in the exact amount that would be equivalent to 50 grams of carbohydrates.
Limitations of the Glycemic Index System
The variables that can impact the GI of a food are: -How the food is prepared -The type of food -The Ripeness of the food -Individual variance A less ripe banana has a lower glycemic index than a more ripe banana. How you cook food can affect its score.
Take the lovely potato as an example. Baked potato wedges have a lower glycemic index than mashed potatoes; they are both prepared from the same vegetable.
Glycemic index charts and databases take into account some of the differences between foods, but not all of them. Also, the testing method for establishing a food’s GI isn’t realistic. What was the last meal you ate? It probably included a combination of different foods, like a salad with nuts and dressing, or peanut butter on apple slices.
In order to accurately test a food’s glycemic index, it must be done on an empty stomach. However, this also means that the Glycemic Index should not be considered an exact science when applying it to daily eating habits. The testing method requires the subject to eat 50 grams of the food’s carbohydrate. However, this method presents some challenges. Again, this doesn’t represent reality.
However, highly processed foods like a white bagel or sugary soda or cereal have large amounts of carbs in small portions, so it might not take long to eat a 50-gram serving. This encourages overeating and can quickly raise blood sugar levels.” In other words, eating a lot of processed carbs at once can cause blood sugar levels to spike. But the glycemic index ranking of 64 for beets is a little misleading since beets have just 13 grams of carbs per cup; we would need to consume nearly 4 cups of beets in order to cause that spike in blood sugar levels.
Glycemic Index is not the most effective way to discover how a food will affects blood sugar. If you looked only at the glycemic index (GI) of raw pineapple, you might think it was a food to be cautious of since it has a moderately high GI of 58. A half inch thick slice of watermelon contains about 7 grams of carbohydrates, which means that eating a few slices probably won’t cause your blood sugar to spike. The Glycemic Load (GL) is a useful tool when considering foods like pineapple.
The Difference Between Glycemic Load & Glycemic Index
That’s why the glycemic load (or GL) was created. The GL is used in nutrition research and dietary advice to factor in the quantity of carbohydrates in addition to the quality. Glycemic load measures how much a typical serving of a food impacts blood sugar, rather than just the amount of carbohydrates in the food.
The glycemic load (GL) is different from the glycemic index (GI), but you may see both numbers when looking up a food. This is because both are used to measure the quality of carbohydrates in a food. The GL considers how much of the food people typically eat and its impact on blood sugar levels. Some experts believe that the Glycemic Load (GL) provides a more realistic picture of how foods affect blood sugar.
What’s heavier a ton of feathers or a ton of lead? The answer is a little counterintuitive if you’re just thinking of the relative weights of feathers and lead. A tonne of lead can easily fit into a carry-on bag, whereas it would take around 1,000 queen-size bed comforters to make up a tonne of feathers.
When it comes to the glycemic index, foods that are high in water and fiber are not as impactful as processed carbs. In other words, you would need to eat twice as many apples as you would cookies to consume the same amount of carbohydrates.
Calculating Glycemic Load
The GI of food can be used to calculate the GL by multiplying the GI by the amount of carbohydrates in the food and dividing by 100.
Geometric mean ratio of glycaemic responses (GR) is used to calculate the quality of the carbohydrates in a given food. GR is calculated by dividing the carbohydrate in a food by the GL of that food.
Here’s an example. Sweet raw cherries have a GI of 62. The glycemic load of a cup of pitted cherries can be calculated by first determining the number of carbohydrate grams present in the cup. You can find the nutritional information for various foods online at sites such as NutritionData.self.com. If you look at the nutritional information for cherries, you’ll find that one cup contains 25 grams of carbohydrates. Now, you can plug the two variables into the equation to find out the GL:
GL = (62 x 25) ÷ 100 = 15.5
What does the number actually mean when you calculate it? The following is a recommendation from the Glycemic Index Foundation for optimal health and blood sugar levels. They recommend keeping your daily glycemic load under 100. A cup of pitted cherries is still within your daily limit of 100 GL points, leaving you with 84.5 more GL points for the day.
The GL index is actually more relevant to how we consume food, even though the GI is more widely used.
What They Mean for You
So what can GI and GL tell you? The GI is a way of measuring how fast-acting vs. slow-acting carbohydrates are in terms of their impact on blood sugar.
There are many factors that can affect how quickly a particular food will raise your blood sugar levels. GI numbers can differ for foods with the same carbohydrate content. The type of carbohydrate, the cooking method, the chemical and physical properties, the fiber, protein, fat, and acid content all affect how the food is metabolized.
Cooking or processing foods generally makes their GI higher. If you cook food before you eat it, your body will spend less time digesting it. For example, the GI of mashed potatoes is higher than the GI of a baked potato, which is also higher than the GI of a raw, untouched potato. However, it is not recommended to eat raw potatoes to lower your GI. The American Diabetes Association states that pasta cooked al dente has a marginally lower glycemic index than pasta that has been cooked longer.
One could think of this as taking a match to a pound of wood. If the wood is in one piece, it may not catch fire. If the wood has been turned into a pound of crinkled newspaper, it could ignite more quickly. Same substance, but differently processed.
The GI of fruits also increases as they ripen. A green banana has a lower impact on your blood sugar than a ripe banana that’s starting to develop brown spots. The ripeness of a banana affects its flavor, with ripe bananas being sweeter than green ones. The tendency to prefer foods that give us a big sugar spike is an evolutionary adaptation that can be traced back to a time when food insecurity and famine were more common. In a world where food is more readily available, this tendency can be a hindrance to maintaining a healthy weight.
Can You Benefit from Using the Glycemic Index?
No matter what your level of healthiness is, the GI can help you pick foods that will fit in with your health goals.
Glycemic Index and Chronic Disease
This system has the potential to help reduce your risk for chronic diseases since it typically promotes less-processed food choices, which research has shown generally leads to weight loss. Although the jury is still out on whether or not a low GI diet can improve your health, research suggests it is worth looking into.
The evidence surrounding the impact of a low GI diet on multiple health markers is inconclusive; some studies suggest there may be a positive impact while other studies suggest there may not be an impact. The GI system can provide useful information, even though the evidence is mixed.
For example, if you want to learn which foods are high in carbohydrates, you can look up the GI of different foods.
Diabetes and Glycemic Index
You should avoid highly processed foods. They are detrimental to your health unless you eat them in moderation. If you have diabetes, your body doesn’t process sugar as it should. If you eat a lot of foods with a high glycemic index, you could be at risk for hyperglycemia.
The glycemic index (GI) can help you better understand how many carbs are in the foods you regularly eat. But it may be simpler to directly count the carbohydrates in your meals for the purposes of managing your blood sugar. While basic carb counting is a method for monitoring changes in blood sugar, you might want to stick with what is currently working.
How to Incorporate GI and GL Into a Healthy Lifestyle
To use GI and GL daily:
- Begin by assessing the foods you typically consume. If oatmeal is one of your staples, familiarize yourself with its GI information by using a glycemic index list or database.
- To balance your blood sugar, aim to eat foods that are low to moderate on the glycemic index.
- Pair high-GI foods with healthy proteins, fats, and fiber. For example, eat mashed potatoes (GI 83) with boiled carrots (GI 39) and roasted turkey. The pairing method will slow your body’s digestion of all the carbohydrates in your meal. You can also easily swap out high-GI foods for low-GI ones:
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