Does eating too much sugar really cause diabetes?
People with diabetes have high blood sugar, but does that mean eating too much sugar can cause diabetes?
Sugar in your diet doesn’t directly cause type 2 diabetes — but eating too much sugar can contribute to risk factors for type 2 diabetes.
Drinks like sodas with lots of added sugar are linked to an increased risk of diabetes. But sugar is only part of the picture when it comes to diabetes risk. Other factors include your age, weight, family history, and how active you are.
At ZOE, we run the world’s largest ongoing scientific study of nutrition, with over 20,000 participants so far.
Our results show that everyone responds differently to foods. While one person might experience a large blood sugar spike after eating a particular food, another may have a more moderate response.
You can take a free quiz to learn more about your unique blood sugar responses to foods.
Your body releases insulin when you eat. This hormone helps to move glucose out of your blood and into your cells.
Diabetes occurs when your body can’t make enough insulin or your cells don’t respond to it effectively. This means that glucose stays in the blood, causing high blood sugar levels.
Over time, raised blood sugar can damage your body and increase your risk of many other health conditions, including heart disease, stroke, kidney disease, and vision loss.
There are several different types of diabetes, but two main types are:
Type 1 diabetes: Your immune system destroys the cells that make insulin. Because your body can’t produce insulin, you need to take it every day. Type 1 diabetes often appears early in life and is not related to diet or lifestyle factors, so you can’t get it from eating too much sugar.
Type 2 diabetes: Your body can’t produce or use insulin efficiently, leading to high levels of blood sugar. Type 2 diabetes usually takes some time to develop and is strongly influenced by your diet and other lifestyle factors.
overweight or obesity
higher than normal blood sugar (prediabetes)
a history of heart disease or contributing factors
a history of gestational diabetes (during pregnancy)
given birth to a baby who weighed over 9 pounds
a family history of diabetes
low levels of physical activity
Being aged 45 or older also increases your risk of developing type 2 diabetes.
What happens to sugar in the body?
When you think about sugar, you’re probably thinking of “table sugar,” the type added to coffee and tea or used in baking.
But there are several types of sugar, and they have different effects on your body.
The scientific name for table sugar is sucrose. Sucrose is a disaccharide, meaning it’s made of two simple sugars: glucose and fructose.
When you eat sucrose, the glucose goes directly into your bloodstream to be used for energy. Alternatively, it can be stored in your muscles or as fat.
Before fructose can be used as energy, most passes through your liver, where it’s turned into glucose and fat.
If you eat too much fructose, this process can lead to fatty deposits in your liver, unhealthy levels of blood fats called triglycerides, and excess uric acid, all of which are linked to an increased risk of diabetes.
The most common sources of fructose are:
Sucrose, which comes from sugar cane or sugar beet.
High-fructose corn syrup (HFCS), which is a blend of fructose and glucose made from corn starch.
Sucrose, fructose, and glucose also occur naturally in fruits and vegetables but usually in relatively smaller amounts, and fruits and vegetables generally are good sources of other beneficial substances, such as fiber and minerals.
Many processed foods like soft drinks and desserts contain added sugars in larger, more concentrated amounts.
The World Health Organization call these “free sugars.” More specifically, they are sugars “added to foods and beverages by the manufacturer, cook or consumer, and sugars naturally present in honey, syrups, fruit juices, and fruit juice concentrates.”
Free sugars in fruit juices have been released from the cells of fruits or vegetables by processing, meaning they can be absorbed easily, raising your blood sugar quickly.
The sugars in “natural” syrups like honey and agave are also free sugars.
Does sugar increase diabetes risk?
Eating sugar doesn’t increase your risk of type 1 diabetes, because it’s not caused by lifestyle factors, such as diet. But when it comes to type 2 diabetes, things are a bit more complicated.
Regularly eating lots of sugar can contribute to overweight, which is a risk factor for type 2 diabetes.
Several large-scale studies did show that people who regularly consume drinks like soda, which contain added sucrose and fructose, have a significantly higher risk of developing type 2 diabetes.
Researchers looking at eight studies, including more than 286,000 participants, found that higher consumption of drinks with added sugar was associated with a 30% higher risk of developing type 2 diabetes.
Another review of studies found that consuming one serving each day of added-sugar drinks increased people’s risk of diabetes by between 13% and 18%.
These and other studies also showed that the risk was greater even when differences in BMI or weight were accounted for.
The American Diabetes Association recommends that you “avoid drinking sugar-sweetened beverages and switch to water whenever possible to help prevent type 2 diabetes.”
What is the mechanism behind sugar and diabetes risk?
We’ve already seen that overweight or obesity are risk factors for type 2 diabetes and that eating too much sugar may contribute to this.
We've also mentioned that eating fructose can lead to the production of uric acid. Some scientists have linked this to insulin resistance. Insulin resistance is when your cells don’t respond appropriately to insulin; it is a risk factor for diabetes.
But there are other ways the sugar in your diet could increase your risk of diabetes, especially when it comes to fructose.
In one study, two groups of people with overweight or obesity drank sweetened drinks containing either glucose or fructose, which made up 25% of their daily calorie intake.
After 10 weeks, participants had gained similar amounts of weight, and those who had consumed drinks containing glucose saw an almost 10% increase in their triglyceride levels.
But those who had consumed the fructose drinks experienced a whole range of changes linked to a greater risk of type 2 diabetes.
These included increases in:
fatty acid production, which is linked to fatty liver disease
Glucose, the sugar that enters your bloodstream after you eat or drink, also has a part to play in diabetes risk.
That’s because sugary foods and drinks — as well as refined carbohydrates like white bread and pasta — can cause larger “spikes” and “crashes” in blood sugar.
In the hours after a meal, these crashes can lead to low energy and increased hunger, especially cravings for more sugar.
Although foods high in refined carbs and free sugars are more likely to lead to sizable rises and dips in blood sugar, at ZOE, we know that everyone responds differently to food.
You can take ZOE’s free quiz to learn more about how your body responds to sugar.
Should you stop eating fruit?
Fruit contains fructose, which — in large amounts — is linked to a number of risk factors for type 2 diabetes. Does that mean you should cut fruit out of your diet?
In a word, no.
Firstly, there’s much less fructose in fresh fruit than in many processed foods and drinks. While a 20-ounce serving of soda could contain around 40 grams or more of fructose, a granny smith apple only has around 6 g of fructose per every 100 g of apple.
Another important factor is how the different compounds in food interact. This is called the food matrix.
For instance, the fructose in soda is free sugar, so it’s absorbed into your blood very quickly. However, when you eat an apple, your body has to break down the cells to get to the sugar. The fiber in an apple slows your digestion, so the fructose is released much more slowly.
In fact, a recent large-scale study showed that eating more fruit is associated with a significantly lower risk of developing type 2 diabetes.
How about fruit juices with added sugar?
Juicing fruit releases the fructose and removes a lot of the fiber, so the fructose is likely to be absorbed more quickly. But studies looking at a possible link between drinking fruit juice without added sugar and the risk of type 2 diabetes have either not found one or have been inconclusive.
Nevertheless, some researchers still suggest that fruit juice is unlikely to be a healthy alternative to sodas for reducing diabetes risk.
Artificial sweeteners and diabetes
Manufacturers often add artificial sweeteners like saccharin, aspartame, and sucralose to diet foods and drinks as a replacement for sugar.
And a larger, longer-term study showed drinking diet sodas might be related to a higher risk of type 2 diabetes.
On the other hand, other studies have found no link between artificial sweeteners and diabetes, and some researchers say many of those that did find links lack clear evidence to suggest this association. So, it’s clear that scientists need to carry out more research.
One study observed some early evidence that artificial sweeteners can cause glucose intolerance by altering the gut microbiome.
At ZOE, our scientists are working to understand how gut bacteria influence metabolic diseases, such as diabetes.
If you’d like to know more about your personal gut microbiome, you can take this free quiz.
Tips to reduce sugar intake in the diet
Reducing the amount of added sugar in your diet could have a whole host of health benefits, including reducing some risk factors for type 2 diabetes.
If you’re looking for ways to eat less sugar, try:
Adding less sugar to food and drinks, such as tea, coffee, and cereal.
Swapping sugary soda for water.
Switching sugar for fruit: Add banana or berries to your breakfast oatmeal or use unsweetened applesauce instead of sugar in recipes.
Looking at labels: Learn to understand food labeling and choose products with less added sugar.
Finding other ways to add flavor: Swap sugar for vanilla or fruit extracts, or use spices like cinnamon or nutmeg.
The relationship between diabetes and sugar is far from simple.
Eating too much sugar is not linked to type 1 diabetes, and it doesn’t directly cause type 2 diabetes — but it can increase your risk of developing it.
Studies have shown that people who regularly consume drinks that contain added sucrose and fructose, like soda, have a greater risk of developing type 2 diabetes.
A high sugar intake may also lead to you taking in more calories than your body needs, which can contribute to overweight or obesity. These are risk factors for type 2 diabetes.
Eating large amounts of added fructose is linked to a range of other health conditions associated with type 2 diabetes.
However, whole fruits and vegetables that contain lower concentrations of fructose and lots of fiber can actually reduce your risk of type 2 diabetes.
At ZOE, we know that everyone’s responses to foods are different.
The ZOE at-home test can tell you about your personal blood sugar and blood fat responses, as well as the makeup of your gut microbiome.
With the ZOE program, you get personalized nutrition advice to find the best foods for you. Take a free quiz to find out more.
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