How Carb-Containing Food Affects Blood Sugar Compared to Table Sugar

According to Dr. David Unwin, a UK general practitioner (family doctor) and published researcher whose practice focuses on helping people put their diabetes and pre-diabetes into remission,  blood sugar (glycemic) response to carbohydrate containing foods is what matters in both diabetes and obesity, and is even more than the absolute amount of carbohydrate in those foods. For Dr. Unwin, the challenge was to represent the effect of high Glycemic Index (GI) foods on people’s blood sugar in terms that could be easily understood. This article is about some of the infographics that Dr. Unwin has developed to help people more easily understand the concept of Glycemic Load*. 

*Note: I think it is important to cover a range of ways that credible individuals view important concepts. Dr. Unwin’s view of blood sugar response as it relates to Glycemic Load (GL) is only one of the ways that glycemic response is understood. The most obvious limitation is that GI measures blood sugar response as if the food is eaten alone, which rarely occurs.

UPDATE (May 14, 2019) Findings of a lack of reliability in Glycemic Index values is outlined in the next article, which can be accessed by clicking here.

In two earlier articles, I explained what the Glycemic Index (GI) and Glycemic Load (GL) are, as well as the challenges with using them.

In short, the Glycemic Index (GI) ranks the carbohydrate content of food in terms of their effect on blood sugar compared to a meal of pure glucose (which is counted as 100).

Using the Glycemic Index often causes confusion because it fails to compensate for the density of each carbohydrate in a particular portion of food. That is why Glycemic Load (GL) was created, which is given as grams of glucose for a specified portion of a food. The problem is, most people have no understanding of glucose and it’s metabolic effects and as Dr. David Unwin, a General Practitioner explained in the paper below (1), many healthcare professionals also have misconceptions about the effect of food-based carbohydrates on blood sugar, as compared to glucose.

Blood Sugar Response as a Patient tool

Dr. Unwin thought that in order to best use Glycemic Load to explain blood sugar response, that it would be more helpful for patients with pre-diabetes or diabetes to be able to understand the effect on blood sugar of eating specific by comparing them to the more familiar sugar, ordinary table sugar.  Dr. Unwin developed some infographics that explain glycemic response in comparison to one (4 g) teaspoon of table sugar.

While table sugar is made up of both glucose and fructose, patients are able to understand the table sugar analogy without being confused by what glucose is (the standard used in the Glycemic Index and Glycemic Load). 

Glycemic Load translated to Blood Sugar Response as a tool for Healthcare Practioners

Dr. Unwin’s and his colleagues had noted that healthcare professionals were making decisions based on Glycemic Index (GI) and assumed that carbohydrate-based foods have a lower GI than table sugar, which is not necessarily the case.

For example, the GI of table sugar is 65, but foods such as basmati rice (GI 69), whole wheat bread (GI 74) and baked potato (GI 86) have higher GIs. This incorrect assumption about many carb-based foods by healthcare professional affected food choices being recommended by them and which were then adopted by their patients, adversely impacting their blood sugar levels.

While Dr. Unwin expressed that health practitioners would be better to refer to Glycemic Load (GL) which takes into account the carbohydrate content of the food in terms of a likely portion size for that food, the concept of GL is not easily understood by their patients. That is where Dr. Unwin’s infographics may play a role.

Blood Sugar Response – a tool for people with diabetes and pre-diabetes

Below is one of the infographics developed by Dr. Unwin to explain Glycemic Index in terms of standard serving sizes (i.e. Glycemic Load) with a corresponding explanation of how that quantity of common foods affects blood sugar compared to one (4g) teaspoon of ordinary table sugar.

Infographic for health professionals to show how the glycemic index helps inform dietary choices.

In the infographic below, I’ve taken just 3 of the foods above and represented these three foods (1) visually (2) in imperial quantities and (3) in metric quantities.

Visual representation, imperial and metric portion sizes of 3 foods (Joy Y. Kiddie, MSc, RD)

In my experience people rarely eat the common portion size of foods, whether it is the recommended portion size listed in national food guides or in the Glycemic Index.

Common Portion Sizes rather than Normal Portion Sizes

As a Dietitian, I’ve come to realize that while the standard portion for cooked rice is given as a 1 cup (150 g) serving, many people eat more than 1 cup of rice at a time. In fact, the standard portion of rice in the old Canada’s Food Guide (which had recommended portions) was 1/2 cup (125 ml), which is half this amount!

The standard portion of spaghetti in the old Canada’s Food Guide was 1/2 cup (125 ml) which is half the amount listed in the GI portions and one has to ask how many people really limit their servings to 1 cups of spaghetti?  It is my experience that most people who are not restricting portions often eat 2 cups of spaghetti or more; which raises blood sugar as much as 13.2 tsp of sugar; and that is not yet counting the sauce that goes on the spaghetti!

Some adults eat only 3 small boiled baby potatoes at a time too but even if they do, that raises blood sugar as much as 9.1 tsp of table sugar!

Below are some other infographics developed by Dr. Unwin that demonstrate ordinary foods in terms of their effect on blood sugar compared to a teaspoons (4g) of ordinary table sugar.

I find the similarity between white bread and brown bread interesting. Not much difference, and if one makes a sandwich or 2 pieces of toast for breakfast, whether its white or brown bread, it raises blood sugar as much as 6- 1/2  and 7- 1/2 tsp of sugar…and that is before putting anything on the bread! 

Infographic for health professionals to show how bread products affect blood sugar (Dr. Unwin, from Public Health Collaborative

Below is an infographic for servings of cereal, but again how many people limit themselves to 30g (1/2 cup) of cereal for breakfast? In my experience, most adults eat 1 cup of cereal as a serving, often more.

Infographic for health professionals to show how cereal products affect blood sugar (Dr. Unwin, from Public Health Collaborative

Below is one of Dr. Unwin’s infographics with respect to fruit.

Again, the serving size here is much smaller than what is a “usual” serving in my experience.  For example, most people I’ve worked with eat a whole large banana, which is double this serving (and has the same blood glucose response as 11- 1/2 tsp of sugar).

Th fruit infographic below will also help explain why I recommend berries such as strawberries in 1/2 cup servings (which only affect blood glucose as much as a little over a tsp of table sugar).

Infographic for health professionals to show how various fruit affect blood sugar (Dr. Unwin, from Public Health Collaborative

Some final thoughts…

As mentioned above, there are different views regarding how different carb-containing foods impact blood glucose levels. Dr. Unwin’s infographics are certainly helpful for people to better understand the concept of Glycemic Load.

If you have been recently diagnosed as having pre-diabetes or as having type 2 diabetes (T2D) and would like to work on reversing the symptoms by adopting a low carbohydrate lifestyle, I can help.

You can learn more about my services including individual hourly appointments and sessions as well as packages above under the Services tab or in the Shop.

If you have questions, please feel free to send me a note using the Contact Me form above and I will reply as soon as I can.

To your good health!


About Dr. Unwin

Dr. David Unwin, MD, is a UK general practitioner (family doctor) known for pioneering a low-carb approach to managing diabetes in the UK who won the prestigious NHS Innovator of the Year award in 2016 for his work with diabetes patients. He serves as medical advisor to the Low Carb Program which is an online platform approved by the NHS and aimed and helping individuals put type 2 diabetes and prediabetes into remission.

In 2017-2018, Dr. Unwin’s practice saved £57,000 ($99,445 CDN / $74,077 USD) on drugs for type 2 diabetes, hypertension and other conditions by offering patients a dietary alternative to medications.

In 2018, Dr. Unwin was named the 9th most influential General Practitioner (GP) in the UK by GP magazine and has written several peer-reviewed papers related to low-carbohydrate diets.

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LEGAL NOTICE: The contents of this blog, including text, images and cited statistics as well as all other material contained here (the ”content”) are for information purposes only.  The content is not intended to be a substitute for professional advice, medical diagnosis and/or treatment and is not suitable for self-administration without the knowledge of your physician and regular monitoring by your physician. Do not disregard medical advice and always consult your physician with any questions you may have regarding a medical condition or before implementing anything  you have read or heard in our content.


Unwin D, Haslam D, Livesey G. It is the glycaemic response to, not the carbohydrate content of food that matters in diabetes and obesity: The glycaemic index revisited. Journal of Insulin Resistance. 2016;1(1), a8.