Does too much sugar cause diabetes? Nutrition myths busted, part 10 - The sugar edition

We’re back with another edition of nutrition myths, busted. There’s so many myths circulating so this is an ongoing series where I look into the science and give you the facts. This time, I’m going to be busting sugar myths.

The myths I’m going to cover today are:

‘Sugar causes diabetes’

‘Sugar feeds cancer cells’

‘Fruit is high in sugar and so is unhealthy’

Let’s dive right in…

Too much sugar causes diabetes – MYTH

When people say this, we first have to assume they're talking about type 2 diabetes (T2DM), as type 1 diabetes is an autoimmune condition that isn’t caused by any lifestyle factors. I think this idea that sugar causes diabetes comes from the fact that T2DM is a condition in which your body is not able to control its blood sugar levels and so if untreated, you’d have high blood sugars.

T2DM is actually caused by insulin resistance. Insulin is the hormone that our bodies release after consuming carbohydrates to bring our blood sugar levels back down. Insulin resistance means that your body doesn’t respond to this insulin as well it normally would.

Sugar in your bloodstream makes its way out of the blood by entering your body cells with insulin acting as a ‘key’ to the cell, to let the glucose in. So, if your body isn’t reacting to the ‘key’ and letting the sugar into your cells, then it will remain in your bloodstream and give a high reading. This means after every carbohydrate containing meal, you’ll have the same problem, and your cells won’t respond to insulin as well.

So, we know that insulin resistance causes T2DM, but what causes insulin resistance?

Now this is where things get technical. Insulin resistance can be caused by being overweight or obese. And typically, foods that are high in calories and contribute to obesity may also be high in sugar. So, there is an indirect link between sugar and T2DM, but it’s wrong to say that sugar causes diabetes. And you can still enjoy sugar as part of a healthy balanced diet and within a healthy body size without developing T2DM.

Sugar feeds cancer cells – MYTH

This myth is based on a misunderstanding of cell biology. It’s true that cancer cells use glucose i.e., sugar for energy and to reproduce. But it doesn’t mean that eating sugar will make cancer worse, or cause cancer to grow quicker. So, cutting out sugar or going on a low carbohydrate diet, isn’t going to treat cancer.

All of our cells need glucose for energy, and this, unfortunately, includes cancer cells. We get glucose from carbohydrate containing foods, and if we don’t eat any carbohydrates or sugar, our bodies can create glucose from proteins and fats. There’s also no way for our bodies to only provide glucose to our healthy cells and not the cancer cells. So, the idea that sugar feeds cancer cells is unhelpful, and avoiding sugar won’t help.

On the other hand, a diet high in excess sugar can contribute to obesity, and obesity can be a risk factor for developing cancer. But this doesn’t mean that eating sugar directly causes or fastens cancer.

Fruit is high in sugar and so is unhealthy - MYTH

I’ll start by saying that yes, fruit does contain sugar. These are naturally occurring within the fruit. As I described earlier, when we eat sugars, it causes our blood sugar levels to rise and then the body releases the hormone insulin to bring the sugar level back down. Excess added sugar can contribute to obesity, dental decay, and increased risk of diseases.

Fruit is also high in a type of sugar called fructose. Fructose doesn’t lead to a rise in our blood sugar levels as it’s quickly taken up by the liver. So, the effect of most fruits on our blood sugars is low.

Fruit also contains lots of fibre, which takes longer to digest and so delays the rise in blood sugar levels after consuming the fruit. And we can’t ignore the fact that fruit contain lots of essential vitamins and minerals that our bodies need to function.

If you are concerned about the sugar in fruit or have a health condition that affects your glucose metabolism, there are a few tips you can practice. You can pair fruit with a source of protein or fat to also down the digestion further. This could be apples and peanut butter, grapes and cheese or berries and yoghurt for example. Another way to manage this is to try to only have 1 portion of fruit at a time, as opposed to eating multiple portions at once to reduce the amount of natural sugar you're consuming at one time.

Fruits do contain sugar, but they also contain lots of fibre, vitamins, and minerals which are essential for our health. They absolutely can be part of a nutritious and balanced diet.

Key points:

• Type 2 diabetes is caused by insulin resistance, not eating too much sugar. Insulin resistance can be caused by being overweight or obese.
• Cancer cells do use sugar to function, but it doesn’t mean that sugar in your diet will feed the cancer cells and make it worse. Your body can make glucose, even if you avoid carbohydrate foods.
• Fruits do contain naturally occurring sugars, but also contain fibre, vitamins, and minerals which are beneficial to health. Fruit is not unhealthy.

I hope you enjoyed this blog post! If there’s any other myths you want me to bust, let me know.

References:

Insulin resistance: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6170977/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7547588/

Sugar and cancer: https://news.cancerresearchuk.org/2023/08/16/sugar-and-cancer-what-you-need-to-know/

Fructose https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2714385/

GI of fruits: https://www.sciencedirect.com/science/article/pii/S0002916522004944?via%3Dihub