If we compare carbohydrates vs sugars, do you know which is worse? To answer this question I will try to explain based upon the glycemic index and glycemic load of some foods. There are a lot of factors that can determine if carbs are worse than sugar. For example, if you are eating vegetables that have carbs in them, they will not be nearly as bad as carbs found in a donut.
The information I used for this chart is from www.glycemicindex.com by the University of Sydney.
This is the process that they used to come up with these numbers: “Following the international standard method, the GI (Glycemic Index) value of a food is determined by feeding 10 or more healthy people a portion of the food containing 50 grams of digestible (available) carbohydrate and then measuring the effect on their blood glucose levels over the next two hours. For each person, the area under their two-hour blood glucose response (glucose AUC) for this food is then measured.
On a separate occasion, the same 10 people consume an equal-carbohydrate portion of the sugar glucose (the reference food) and their two-hour blood glucose response is also measured. A GI value for the test food is then calculated for each person by dividing their glucose AUC for the test food by their glucose AUC for the reference food. The final GI value for the test food is the average GI value for the 10 people.
The GI of foods has important implications for the food industry. Terms such as complex carbohydrates and simple sugars are now recognized as having little nutritional or physiological significance. The WHO/FAO (World Health Organization/Food and Agriculture Organization of the United Nations) recommend that these terms be removed and replaced with the total carbohydrate content of the food and its GI value.”
I chose some random foods below to show the impact that they will have on your blood sugar levels so that we can compare. There is a range because there are a lot of factors that need to be considered when comparing these foods. For example, what variety of food is being tested (a Granny Smith apple will be different from a Red Delicious), how they were cooked or prepared, how ripe the food is, was it dried and several others that will affect the numbers below. Here are some charts (SupplementalTable1, and SupplementalTable2) for common foods put out by The American Journal of Clinical Nutrition published 2021 that are pretty good. Please check out these charts or do a simple search to determine the glycemic load of the foods you eat.
How carbs affect your blood sugar
The purpose of the chart below is for general comparison between carbohydrates vs sugars. It also helps to generalize the complex relationship between carbs and how they affect your blood sugar.
| Food | Glycemic Index (Range) | Carbs per gram | Glycemic Load |
| Popcorn | 51-89 | 10-14 | 6-10 |
| Potatoes | 49-111 | 18-45 | 15-33 |
| Bread | 18-104 | 0-68 | 0-28 |
| Pasta | 22-92 | 0-50 | 3-37 |
| Corn | 46-132 | 14-28 | 6-20 |
| Banana | 30-70 | 20-27 | 6-16 |
| Orange | 31-51 | 10-11 | 3-6 |
| Apple | 28-44 | 16-30 | 4-11 |
| Apricot | 30-64 | 9-30 | 3-10 |
| Orange Juice | 46-57 | 18-26 | 11-15 |
| Chocolate | 23-49 | 14-31 | 5-14 |
| Rice milk | 79-92 | 22-32 | 17-29 |
| Honey | 32-87 | 15-21 | 6-18 |
| Sucrose (Table sugar) | 48-110 | 10 | 6-11 |
| Fructose (Fruit sugar) | 20-23 | 10 | 2 |
| Glucose (Simple sugar) | 93-114 | 10 | 10-11 |
| Lactose (Milk sugar) | 46 | 10 | 5 |
As you can see, I chose 5 carb foods: Popcorn, potatoes, bread, pasta, and corn.
4 fruits: Banana, Orange, apple, and apricot.
4 commonly eaten sugary foods: Orange juice, chocolate, rice milk and honey.
To finish it off, I have the four most common sugars: Sucrose, Fructose, Glucose, and Lactose.
To understand this simple chart, let me explain some of the terms. The glycemic index is a number that shows how fast your body converts carbs into usable form of glucose (sugar). As you can see from the chart, the number of carbs does not necessarily reflect a similar glycemic index number.
There are a number of reasons why the number of carbs do not directly affect the glycemic index (GI) number. For example, the amount of fiber in a food will slow down the process of converting carbs to sugar. This means that if you eat carb loaded foods that are also high in fiber, they will have a lower GI number. The scale used for GI is if the food is 55 or below, it is considered a low GI food, 56-69 medium, 70 or above high.
Another important term is glycemic load (GL). The glycemic load is a number given to foods that
estimates how much a food will affect a persons blood glucose levels. The scale is based on the premise that 1 glycemic load is equivalent to consuming 1 gram of glucose. It is basically a scale to determine how each gram of carbohydrates raises blood glucose levels. It also takes into consideration the quality and quantity of carbs. This is a great tool to compare how foods will affect your blood glucose. The scale for glycemic load is: if the GL is 10 or below, it is considered to be a low GL food, 11-19 medium, and 20 or above is high.
The formula for calculating GL is: GL = (Glycemic index number X number of carbs) / 100
When on a keto diet, you would ideally want both the GI and GL to be in the low categories.
So, lets start comparing how these foods compare. To do this, lets use the 4 sugars as our basis.
The sugars had a range of GI of 20-114 and a GL of 2-11.
The sugary foods had a range of GI 23-92 and a GL of 6-29.
By looking at the GI ranges, we can see that the numbers are relatively similar. The difference becomes apparent when you look at the GL ranges. Those sugary foods have a much higher GL than straight sugar. The low end is not bad, but the top range is definitely in the high range for GL.
The sugars had a range of GI of 20-114 and a GL of 2-11.
The fruits had a range of GI 28-70 and a GL of 3-16.
The GI for the fruits is a fair bit lower than sugar. This is in part to the fact that they have more fructose which is harder for the body to break down. Fructose by itself has a range of 20-23 in comparison. The fruits also have other sugars in them, which is why the GI number is higher. The glycemic load of fruits is still higher than we want on a keto diet, but it is more comparable to eating straight sugar.
The sugars had a range of GI of 20-114 and a GL of 2-11.
The carb foods had a range of 18-111 and a GL of 0-37.
The GI for these carbs are almost identical. The huge difference is the glycemic load. Sugar tops out at 11, where as the carbs go all the way up to 37. That is extremely high. Simply put, the carbs will have a greater impact on your body than eating straight sugar. Weird, right?
If you want to read why many consider sugar to be a drug that is as addictive as cocaine, check out my blog here.
The time it takes carbs to affect blood sugar
To understand how long it takes your body to break down carbs and be able to absorb/use them, we need a basic understanding of how that works. Carbohydrates come in two basic forms, sugars and starches or simple and complex. If you want to learn more about carbohydrates, here is a link to Harvard that explains them well. Simple carbohydrates are sugars that are either monosaccharides or disaccharides (sugars that have 1 or 3 molecules). Complex carbohydrates have 3 or more sugar molecules (polysaccharides or oligosaccharides)
In order for your body to be able to utilize carbohydrates, they need to be in a single sugar form (1 molecule). For example single sugars (monosaccharides) like glucose can be absorbed rapidly because it is already in a usable form. A sugar that has two or more sugar molecules linked together (disaccharide, polysaccharide or oligosaccharides), our body would need to break those sugar molecules apart before we can use them. The extra step of separating those sugar molecules via digestion will slow down how quickly our body can absorb the sugars. So the more steps involved in breaking carbs down into simple sugars, the slower those sugars will be ready to be used in the body.
Fiber will slow down the absorption of sugars. Which is one of the reasons that foods like white potatoes have such a high glycemic index because they do not contain much fiber. Foods that have highly processed grains where the bran and germ was removed will also increase the glycemic index because of the removal of the fiber (example: white bread).
After you eat a carbohydrate, they will be broken down some in the stomach and then travel down to your small intestine. The small intestine is where most of the digestion of carbohydrates takes place. To overly simplify things, once your small intestine has broken carbohydrates down into simple sugars, your small intestine will absorb those sugars and put them into your blood stream. So how quickly your small intestine can break down carbohydrates into simple sugars affects the glycemic index of the foods. If your small intestine can quickly break down the sugars, then it will have a high glycemic index. On the other hand, if your small intestine has to work harder to break down the carbohydrates into simple sugars, then it will have a lower glycemic index.
Note, galactose and fructose are metabolized further in the liver in order to convert them into glucose.
I think that it is important for you to understand that there are different types of carbohydrates. There are simple carbs and “complex” carbs. The term complex refers to carbs made up of 3 or more molecule chains of sugar linked together. Simple carbs only have 1 or 2 molecules of sugar combined. This will have a fairly large affect on how our bodies metabolize carbs. Don’t get drawn into the misconception that the complex carbs take longer to digest and there for have a lower impact on your blood sugar. There are complex carbs that have a high glycemic index and there are other complex carbs that have a low glycemic index.
Complex carbohydrates that have a high glycemic index are digested relatively quickly. They can raise your blood sugar in about 15 minutes after consumption. Some examples of complex carbs that have a high glycemic index are potatoes, white breads and white rice.
Complex carbohydrates that have a low glycemic index do take longer for the body to break down. 
While your body can start extracting sugars from these carbohydrates in 15 – 30 minutes, but it will be in much smaller amounts. These carbs will still raise your blood sugar, but because of the time that it takes for your body to break them down, you will not get the same spike that you would with sugars or carbohydrates that have a high glycemic index. Some examples of complex carbohydrates with a low glycemic index are nuts, non-starchy vegetables and dairy.
If you want help with calculating how many carbs you can eat daily, check out my blog here.
Fun facts
- A meal containing protein and fat causes the sugars to be absorbed at a slower rate as compared to being consumed by themselves.
- Dietary fibre is a type of carbohydrate that the body can not digest. It is instead fermented by the body by colonic gut bacteria, and passes relatively untouched through your body.
- There are foods that will actually help lower your blood sugar, and you can read about them here.
Hopefully my chart above and my explanations help clear up some misconceptions about the debate over carbohydrates vs sugar. Everyone knows that eating sugar is bad for you. Not everyone realizes that eating carbs can actually have a greater impact on your blood sugar. I am not saying that all foods with carbs are horrible and that they will spike your blood sugar. You do need to be selective about what carbs you eat though.
Do your research. For example, some beans are high in carbs, but are also high in fiber so will have a lower GI and GL. They are a healthier way of getting some carbs. There are several other carb foods that we can eat on a keto diet (in moderation) and not get kicked out of keto. The key to getting healthier is knowing what you are eating and how it will affect your body and choosing not to eat those foods that are not beneficial.
