Sweets and Sugary Drink's Affect on The Gut Flora
We often hear that sugar from candy and soft drinks is not healthy, but how exactly does it affect your gut health and what is the science behind it?
What Is Sugar?
Sugar is found in all foods that contain carbohydrates, including vegetables, fruits, grains, and dairy products, even green vegetables such as broccoli contain sugar. However, there are many types of sugars that differ in sweetness, calorie content, and, most importantly, how they interact with the body.
All carbohydrates are made up of sugar molecules. They can be “simple” or “complex” depending on how many sugar molecules are linked together and whether the chains are straight or branched. This ultimately determines how easily they are digested and absorbed.
Simple vs. Complex Carbohydrates
Simple carbohydrates have a basic structure made of one or two sugar molecules. Naturally occurring milk sugar (lactose) and refined white sugar (sucrose) are examples of simple carbohydrates. These are the most common sugars added to ultra-processed foods, cakes, and sweets.
Complex carbohydrates consist of longer chains, usually made of three or more linked sugar molecules. They take longer to break down and digest, providing energy over a longer period. Starch and glycogen are natural complex carbohydrates that our bodies can digest. Dietary fibers such as cellulose, inulin, beta-glucan, and resistant starch can only be partially digested by the gut microbiome.
How Does Carbs Affect Our Health?
When we eat foods containing digestible carbohydrates, they are broken down into individual sugar molecules that enter the bloodstream. As blood sugar rises, the pancreas releases insulin, which helps cells take up sugar for energy or storage. As cells absorb sugar, blood sugar levels fall again, maintaining normal energy balance.
A diet high in sugar damages this blood sugar regulation system. When too much sugar enters the bloodstream, insulin gradually becomes less effective, increasing the risk of insulin resistance - a precursor to type 2 diabetes and a common condition in people who are overweight.
This condition can be prevented with proper dietary and lifestyle choices.
In addition, a diet dominated by simple sugars leaves little room for nutrient-rich foods that are essential for overall health and for supporting the gut microbiome. These include foods containing fiber, polyphenols, and other compounds that nourish gut bacteria.
How Does Sugar Affect the Gut Microbiome?
We know that diet shapes the gut flora, so it is no surprise that a diet high in simple sugars can have negative effects on this ecosystem.
High intake of simple sugars has been shown to reduce microbial diversity and lower levels of short-chain fatty acids (SCFAs), which are crucial for gut health.
One study also suggests that fructose and glucose, consumed in large amounts in the Western diet, reduce levels of Bacteroides thetaiotaomicron, a beneficial bacteria known for helping limit pathogen growth and support gut health.
Some studies also indicate that high sugar and low fiber intake may promote intestinal inflammation.
Which Foods Contain Simple Carbohydrates and What Are the Better Alternatives?
Fruits and vegetables contain simple carbohydrates, but they are also rich in vitamins, minerals, and fiber, making them essential for a healthy diet and a healthy gut flora.
Milk and dairy products contain lactose, another simple carbohydrate. Although these foods do not contain fiber, they are rich in protein, calcium, and vitamin D.
The simple carbohydrates that should be avoided are mainly found in ultra-processed foods and products with added sugar, such as candy, sugary drinks, syrups, table sugar, fruit juice from concentrate, baked goods, and industrial breakfast cereals.
Whenever possible:
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Choose whole fruit instead of fruit juice.
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Choose whole-grain products (rice, bread, cereals, etc.).
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Don’t forget legumes - beans, lentils, and dried peas are excellent sources of complex carbohydrates.
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Add fruit and berries to meals instead of sugar or syrup to get fiber and vitamins along with sweetness.
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Keep a handful of nuts or a piece of dark chocolate on hand to satisfy sweet cravings.
It’s okay to treat yourself occasionally - balance matters. But remember that your food choices have a powerful impact on both your body and your gut flora. Make sure you provide the right nutrients to support a healthy gut ecosystem.
Do you want a look into your personal gut flora and see your gut health, then you can get insight with a gut microbiome test from Unseen Bio.
If you want to dive deeper into the gut microbiome, then listen to our podcast "Mikrobiomet" (The Microbiome), where we explore everything science knows about gut health and the microbiome together with a broad range of microbiome experts.
You can also read more about different foods impact on the gut microbiome in our other articles.
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By Cecilia Clausen (Clinical Dietitian)
