Are There Fruits That Are Better For Diabetics? Lola Ng Webber Academy

In my project, I will be testing different fruits to determine which fruits contain the most and least amount of glucose.
Lola Ng
Grade 6


If a fruit is a “tropical” fruit, then it will have a higher glycemic index. If a fruit is a “berry” fruit, then it will have a lower glycemic index making it a safer choice for diabetics.



-Diabetes is a disease in which your body either can't produce insulin or can't properly use the insulin it produces. Insulin is a hormone produced by your pancreas.

-Insulin's role is to regulate the amount of glucose (sugar) in the blood. Blood sugar must be carefully regulated to ensure that the body functions properly. Too much blood sugar can cause damage to organs, blood vessels, and nerves. Your body also needs insulin in order to use sugar for energy.

-Eleven million Canadians are living with diabetes or prediabetes. About 422 million people worldwide have diabetes

(Michael Dansinger, December 06, 2020)

There are 2 types of Diabetes:

Type 1

Type 1 diabetes is an autoimmune disease and is also known as insulin-dependent diabetes. People with type 1 diabetes aren't able to produce their own insulin because their body is attacking the pancreas and therefore can’t regulate their blood sugar. Type 1 diabetes generally develops in childhood or adolescence, but can also develop in adulthood. People with type 1 need to inject insulin or use an insulin pump to ensure their bodies have the right amount of insulin. Roughly 10 percent of people living with diabetes have type 1 diabetes.

Type 2

People with type 2 diabetes can't properly use the insulin made by their bodies, or their bodies aren't able to produce enough insulin. Roughly 90 percent of people living with diabetes have type 2 diabetes.

Type 2 diabetes is most commonly developed in adulthood, although it can also occur in childhood. Type 2 diabetes can sometimes be managed with healthy eating and regular exercise alone, but may also require medications or insulin therapy. 

(World Health Organization, 2021)



Fruits are an excellent source of essential vitamins and minerals, and they are high in fiber. Fruits also provide a wide range of health-boosting antioxidants

Eating a diet high in fruits and vegetables can reduce a person’s risk of developing heart disease, cancer, inflammation, and diabetes. Citrus fruits and berries may be especially powerful for preventing disease. It is no wonder that the Canada Food Guide recommends 7 to 10 servings per day for adults

There are 7 families of fruit. These include: 

1. Apples & pears  2. citrus  3. stone fruit  4. tropical and exotic  5. berries  6. melons  7.Tomatoes & avocados.

Fruits have varying levels of sugar content

(Victoria State Government, 2020)



It is a common misconception that fruits only contain fructose and that sucrose is mainly added to foods during manufacturing. In fact, almost all fruits and vegetables naturally contain sucrose, as well as glucose and fructose, in varying amounts. 

Glucose (monosaccharide) is the most important simple sugar for your body as it is the primary source of energy for all organs and mechanisms, including brain activity. Your body can create glucose as it breaks down complex carbohydrates, and it is also present naturally in fruits. 

Fructose (monosaccharide) is a simple sugar found in all ripe fruits. it can also be processed into a crystal and used as an added sweetener.

Sucrose (disaccharide), also the name for table sugar, is a blend of glucose and fructose and is present in ripe fruits.

(Anna Barnwell, 2018)

Glucose is absorbed directly across the lining of the small intestine into your bloodstream, which delivers it to the cells in your body. It raises blood sugar more quickly than other sugars, which stimulates the release of insulin. Insulin is needed for glucose to enter your cells. Your body tightly controls your blood sugar levels. When they get too low, glycogen is broken down into glucose and released into your blood to be used for energy

Fructose is absorbed directly into your bloodstream from the small intestine. It raises blood sugar levels more gradually than glucose and does not appear to immediately impact insulin levels However, even though fructose doesn’t raise your blood sugar right away, it may have more long-term negative effects. Your liver has to convert fructose into glucose before your body can use it for energy. Eating large amounts of fructose on a high-calorie diet can raise blood triglyceride levels. Therefore, eating fructose and glucose together may harm your health more than eating them separately. This may explain why added sugars like high-fructose corn syrup are linked to various health issues.                                                                                          (Kathleen Pointer, 2017)

Because fruits are high in dietary fiber and fructose, they do not cause drastic changes in blood sugar levels. This makes many of them a low-glycemic-index food - the glycemic index being a measurement of how much carbohydrates affect blood sugar levels.


Manipulated variable: The manipulated variable is the different fruits I will be testing

Controlled variable: Using the same test strips, the same amount of time before observation.

Responding variable: The responding variable is how much glucose is in each fruit



  1. Take a sample of fruit (equivalent to the size of a blueberry) and mash fruit with spoon until liquid is produced
  2. Immediately place test strip on liquid
  3. Time for 30 seconds
  4. Observe change of colour and compare test strip to legend and record data
  5. Repeat with same fruit 2 more times
  6. Repeat above with other fruits


  • Diastix Reagent strips for Urinalysis/glucose
  • different types of fruits: apple, pear, raspberry, blueberry, peach, plum, banana, mango, mandarin, and grapefruit.
  • Stopwatch
  • Glass dish
  • spoon



The data collected shows that mango has the least amount of glucose while banana has the highest amount of glucose, even though they are both part of the tropical fruit family. All other fruits fell in a spectrum between these two. Berries (raspberry and blueberry) both showed consistently higher glucose numbers.


Diabetes is a disease that affects many Canadians and runs in my family as well. I originally started this experiment wanting to find out if there are fruits that are better suited for people predisposed to diabetes, and decided to find out which fruits contain the most glucose. 

My background consistently showed that fruits from the tropical family (mangos/bananas) contained the most sugar per unit. Whereas berries (blueberries/raspberries) contained the least per unit. 

Based on my research I hypothesized that bananas would contain the most amount of glucose and blueberries would contain the least.

My hypothesis was partially correct as bananas did score the highest on the glucose scale, but blueberries were also very high on the glucose scale.

My experiment showed that all fruits contain some amount of glucose, although they do range in content as shown below. 

Berry family had the highest average content at 1.96g/dL but was expected to be lower

The citrus family had the lowest average content at 0.88g/dL

Apple/Pear family (1.33g/dL) and stone fruits(1.00g/dL) fell in between the ranges

Tropical family (1.25g/dL) also fell in between the ranges but was expected to be higher

The results obtained from the experiment were consistent for the most part. 

Banana contained the most glucose as expected and the other fruit families (apple/pear/citrus/stone) all contained a lesser amount.

The inconsistent results were that of the berry family (contained a greater amount than expected) and mangoes (contained a lesser amount than expected)

Upon further investigation of my scientific question and review of my background information, I realized that there were inconsistencies 

I had endeavored to determine the content of glucose in fruits, which I had done correctly with my experiment. 

But, it was during the collection of background information that there were slight variances. I had searched the total amount of sugar content of fruit. This would include glucose, but also the other sugars, fructose, and sucrose in their calculations. I had only been looking at one sugar type (glucose), whereas the research showed the total amount of the 3 types of sugar contained in fruits (glucose, fructose, and sucrose)

I did more research after this discovery and found information on the sugar content, but specifically glucose in fruit as seen in this table.

As seen mangoes do

have a low glucose content, as was seen in my results too.

Berries actually have a higher glucose content than other fruits, which was also consistent with my results.

All fruits do contain different amounts of glucose, but we must also look at the amounts of fructose and sucrose as well to make a more informed decision. Although I did discover that mangos do contain the least amount of glucose in my results, they also contain some fructose and a large amount of sucrose making them one of the most sugary fruits. Berries, on the other hand, contained higher glucose amounts, but the overall sugar content is one of the lowest on a per weight basis.

In conclusion, when evaluating which fruits are best for people predisposed to diabetics, it is the total amount of sugars present that must be used and not simply glucose. As sucrose, fructose, and glucose all contribute to an increase in blood glucose.

Overall there is not really a need to avoid sugars that are naturally found in whole foods like fruits, as the nutrients, fiber, and water can help counter these negative effects. It ultimately comes down to moderation and avoiding added sugars in other treats.




Diabetics can use this information to make informed decisions on what fruits are more likely to spike their blood glucose and be healthier in controlling their blood sugar levels.

With the information I have gathered there could be genetic engineering in making super hybrid fruits. We could modify the fruits that have the most antioxidant potential and nutrients and combine them with fruits that have the lowest combined sugar content. For example, if we could somehow gather only the low glucose content of mangos and combine it with the low sucrose content of blueberries, you would have a fruit that has all the nutritional benefits and have the lowest potential total sugar amount.


Sources Of Error

Sources of error:

  -precise measuring of the volume/mass of fruit sample 

 - precise time elapsed when comparing fruit samples on diastix

 - ripeness of the fruits 

 - the consistency of the fruit liquid vs mash and ability to absorb on to diastix

 - does the amount of time the liquid sits affect the measurement?

What could have been done differently: 

- use a test that would accurately measure all sugars present in fruits

- consistency in obtaining the test samples. For example, berries were easy to obtain juice. Bananas and apples were very difficult

- would like to test different fruits (ie. avocado) and more exotic fruits (ie. dragon fruit/lychees)

Does the ripeness/seasonality of a fruit contribute to the sugar content?

Does dehydrated or frozen fruit have different amounts of sugar content vs fresh fruit?

Do locally sourced vs overseas/imported fruits have differing levels of sugar?

Do organic vs non-organic fruits have differing sugar levels?

Do natural sugar substitutes affect blood glucose (monk fruit/stevia)?





Works Cited

“Blood Glucose (Blood Sugar): How It's Made, How It's Used, Healthy Levels.” WebMD, WebMD,

“Data Blog.” Diabetes in Canada - Data Blog - Public Health Infobase | Public Health Agency of Canada, 20 Nov. 2019,

“Diabetes.” World Health Organization, World Health Organization,

“Fruit and Vegetables.” Better Health Channel,

Person. “What Is Glucose and What Does It Do?” Healthline, Healthline Media, 24 Mar. 2017,

“Secret Sugars: The 56 Different Names for Sugar.” Virta Health, 17 Jan. 2020, goes by a slew,e.g., Maltodextrin and dextrose).

“Types of Sugar in Ripe Fruits.” LIVESTRONG.COM, Leaf Group,

“Fruit Sugar Content.” Nomnomkids Reusable Food Pouches,


Thank you for helping me with my presentation:

  • Hubert Ng
  • Janet Summerscales
  • Jason Baillie
  • Lauren Au
  • Marlea Wang