Microbiome Diet ~ 4.3 Harmful Foods - Sweets and Sweetened Drinks

In addition to "dangerous" foods, such as alcohol and artificial sweeteners , sugar from candy and soft drinks can also affect our gut health. In what way is this? And what are the science and concepts behind it?

This is part 4.3 of the articles about the Microbiome Diet. Read part 4.2 here: Microbiome Diet 4.2: Harmful Foods - Artificial Sweeteners .

What is sugar?

Sugar is found in all foods that contain carbohydrates, including vegetables, fruits, grains and dairy products - even green vegetables like broccoli contain sugar. But there are many types of sugars that differ in their sweetness level, calorie content and, most importantly, how they interact with our bodies.

All carbohydrates are made up of sugar molecules. They can be "simple" or "complex" depending on how many molecules are connected and whether the chain they form is straight or branched. This ultimately determines how easily our bodies digest and absorb them.

Simple vs. complex carbohydrates

Simple carbohydrates have a very basic structure, consisting of one or two sugar molecules . Natural milk sugar (lactose) and refined white sugar (sucrose) are simple carbohydrates. These are the most common types of sugar added to ultra-processed foods, but also in cakes and other sweets that we eat.

Complex carbohydrates are longer chains, usually made up of three or more linked sugar molecules. They take longer to break down and digest. This way, they are able to provide energy over a longer period of time. Starch and glycogen are examples of complex carbohydrates found in nature that our bodies can digest. Dietary fibers such as cellulose, inulin, beta-glucan or resistant starch can only be partially digested by our gut microbiome.

How do simple carbohydrates affect our overall health?

When we eat foods that contain digestible carbohydrates, our bodies break them down into individual sugar molecules that enter our bloodstream. As the amount of sugar in our blood increases, the pancreas produces insulin, a hormone that causes cells to take up this sugar for energy production or storage. As cells take up the sugar in the blood, the levels in the bloodstream begin to fall. In this way, our bodies ensure that they have normal levels of energy to carry out our daily tasks.

A diet high in sugar damages our mechanism that regulates blood sugar levels. When too many sugar molecules enter the bloodstream directly, the effectiveness of insulin slowly decreases. We then risk developing a condition called "insulin resistance," often a precursor to type 2 diabetes and frequently found in obese people.

Although this is a serious condition, it can be prevented if we make the right food (and lifestyle) choices.

Also, if our diet is packed with foods that contain simple sugars, there is little room left for nutrient-rich foods that we need to satisfy our body's complex nutritional needs, and also to support our gut microbiome.

This includes foods that contain dietary fiber , polyphenols and all the molecules that feed our gut bacteria.

How does sugar affect the gut microbiome?

We know how diet shapes the composition of the gut microbiome, so it's no surprise to learn that a diet high in simple sugars can negatively impact this ecosystem.

In fact, it has been shown that high amounts of simple sugars in the diet can reduce microbial diversity and lead to lower levels of short-chain fatty acids (SCFAs), a beneficial compound for our gut health.

Another interesting study suggests that fructose and glucose, present in large amounts in the Western diet, decrease levels of Bacteroides thetaiotaomicron . A well-studied beneficial bacterium, known for its potential ability to limit the growth of pathogens and maintain good intestinal health.

There are also some studies that show that Intake of simple sugars and low fiber content can potentially lead to inflammation in the gut.

Which foods contain simple carbohydrates and what are the alternatives?

Fruits and vegetables contain simple carbohydrates, but they are also rich in vitamins, minerals and dietary fiber, making them indispensable for a healthy diet and for supporting good bacteria.

Milk and dairy products contain lactose, which is also a type of simple carbohydrate. Although these foods do not contain fiber, they are rich in protein, calcium, and vitamin D.

Simple carbohydrates to avoid are typically found in ultra-processed foods or those with added sugar. For example, candy, sugary drinks, syrups, table sugar, fruit juices from concentrate, baked goods, or industrially produced breakfast cereals.


So when possible:

1. Try consuming whole fruits instead of fruit juice.

2. Choose whole grain products (rice, bread, breakfast cereals, etc.).

3. Don't forget the legumes - beans, lentils and dried peas, excellent sources of complex carbohydrates.

4. Add fruits and berries to your meals instead of sugar and syrup. That way you also get healthy fiber and vitamins, not just pure sugar.

5. Make sure you always have a handful of nuts or a piece of dark chocolate on hand to satisfy your sweet tooth.

Final comment

It's okay to indulge once in a while and balance is important. But remember that your food choices can have a big impact on your body and your gut microbiome. Make sure you're getting the right nutrients to maintain a healthy gut microbiome.

Author: Cecilia Clausen (Clinical Dietitian)