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Does sugar cause diabetes?

When someone reaches for their 3rd or 4th dessert at a family dinner, I have often heard things like, “calm down, you’ll become diabetic!” Or, it’ll be the person being offered a second serving of cake and saying “no, I don’t want to become diabetic.” But is there any truth to this?

What is diabetes?

First off, a quick explanation of what diabetes is. There are two types: type 1 and type 2. Type 1 diabetes is definitely not caused by sugar intake, or diet at all. It’s generally due to genetic reasons – it’s an autoimmune reaction (the body attacking itself by mistake) that destroys the cells in the pancreas that make insulin, called beta cells.

And what’s insulin’s main role? It’s to transport glucose (from carbohydrate-containing food) from the blood to the cells. In people without diabetes, insulin is released when we eat food with carbs in it, then the glucose from the food is transported into our cells. In people with diabetes, it’s not that simple.

If there’s not enough insulin available, like in the case of type 1 diabetes, it means that cells aren’t being fed, and blood glucose (AKA blood sugar) is high (since glucose isn’t being transported into cells). This means increased hunger and thirst, headaches, frequent urination, fatigue, etc. If this goes on too long, it can lead to the nervous system malfunctioning, the peripheral circulatory system failing, the kidneys failing… and death. Thus, people with type 1 diabetes must have insulin injections to ensure that the energy from their food is being properly transported to their cells and feeding their bodies.

Type 2 diabetes has similar symptoms and dangers; however, its cause and etiology are different. What happens is that instead of the body not producing much insulin, the person’s cells are resistant to insulin (AKA insulin resistance). Therefore, the glucose from food isn’t fully being transported into the cells – causing high blood sugar. People with type 2 diabetes can control their condition with diet and exercise, but often times, they need medication to help. Sometimes, they need insulin too, as their beta cells eventually lose some of their insulin-producing function as well.

So, what causes type 2 diabetes?

There are many, many reasons why someone may become type 2 diabetic. And the reasons are highly interconnected – there isn’t one sole cause to it. Some of the different things that can increase the risk of insulin resistance and hence developing type 2 diabetes include:

· distribution of body fat

· genetics/family history of diabetes

· ethnicity

· being of older age

· low levels of physical activity

· low dietary fibre intake

· PCOS (polycystic ovary syndrome)

· high blood pressure

· chronic stress

· sleep deprivation (1)

This isn't even the complete list. Type 2 diabetes is incredibly multifactorial, combining genetic, environmental and lifestyle factors. So, can diabetes be blamed on sugar? Nope.

One common thought behind “sugar causes diabetes” is that consuming sugar increases blood sugar, and high blood sugar is a symptom of diabetes. But as I explained previously, it’s the diabetes itself that causes the inability of sugar, or glucose, to properly enter cells and thus keeping it in the blood.

Another argument is that eating high-sugar foods releases too much insulin, causing our cells to become insulin resistant. However, there is absolutely no evidence for this being true (1). Insulin secretion following food consumption, including sugar, is normal and does not cause insulin resistance. High-carbohydrate diets have actually been linked to enhanced insulin sensitivity in normal individuals (2)!

We may also be thinking that sugar intake has increased within the past few years due to, for one, increased availability of highly processed and sugary foods. And, although diabetes incidence has increased within the past few years, sugar intake has actually been declining ever since 1999 in Canada and the US.

Data source: Statistics Canada, CANSIM. Adjusted for waste using updated USDA Loss-Adjusted Food Availability.

Now, this is not all to say that sugar isn’t at all related to causing diabetes. As stated previously, distribution of body fat may cause insulin resistance. That is, however, the distribution of fat and not just fat itself. Increased visceral fat (around the organs) has the most harmful impact on insulin resistance (3), followed by subcutaneous fat (beneath the skin) around the abdomen. Other locations of subcutaneous fat, such as the hips and thighs, may even be protective (4).

Where we store fat is up to our genetics and some lifestyle factors, like lack of exercise, poor sleep quality, lack of dietary fibre and chronic stress, which are all positively associated with fat being stored viscerally (1). Increasing overall body weight can also increase visceral fat, which is where sugar comes into play. If someone consumes enough sugar every day in such a way that it increases caloric consumption higher than calorie expenditure, then it can contribute to weight gain. If that weight is stored viscerally, then it can contribute to insulin resistance. But in almost all cases, it’s not that simple.

Does being at a higher weight necessarily cause diabetes?

If being at a higher weight caused diabetes, then “obese” people would necessarily have diabetes, and diabetes trends would follow obesity trends. But, that isn’t the case. There are many countries that have low rates of obesity, yet high rates of diabetes such as the Philippines, Romania, France, Bangladesh and Georgia (5,6). As another example, while Sri Lanka's diabetes prevalence rate increased from 3% in 2000 to 11% in 2010, obesity prevalence remained at 0.1% during the same period. On the other hand, diabetes prevalence in New Zealand fell from 8% in 2000 to 5% in 2010, while obesity rates increased from 23% to 34% during the same period. Pakistan and Iceland have shown similar declines in diabetes incidence despite rising obesity rates (7).

Sugar itself cannot cause diabetes.

An excess of sugar causing an excess of calories and thus a gain in (visceral) body fat can contribute to it… But so can an excess of any type of food. Now, this blog post isn’t a recommendation for you to eat all the sugar in the world and have no repercussions. There are other negative effects that come from consuming an excess of added sugar, like cavities, or potentially an increased risk of heart disease. However, if you have 3 donuts on one day because they’re really good and you haven’t had them in a long time, go for it. If you want a cookie every day, that’s totally fine. It sure as heck won’t give you diabetes.

Works cited

1. Wolrich, Joshua. Food Isn’t Medicine. Vermillion London, 2021.

2. Wolever, T.M. Dietary carbohydrates and insulin action in humans. British Journal of Nutrition 83 (2000) S97–102.

3. Hardy, OT. et al. What causes the insulin resistance underlying obesity. Current Opinion in Endocrinology Diabetes and Obesity 19 (2012) 81–87.

4. Stefan, N. et al. Causes, characteristics, and consequences of metabolically unhealthy normal weight in humans. Cell Metabolism 26 (2017) 292–300.

5. International Diabetes Federation (2011) IDF Diabetes Atlas.

6. World Health Organization (2012) Global database on body mass index.

7. Basu, S. et al. The Relationship of Sugar to Population-Level Diabetes Prevalence: An Econometric Analysis of Repeated Cross-Sectional Data. Plos One (2013).


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