Excessive sugar consumption may increase risk for diseases by altering the gut microbiome. What’s the connection between sugar and gut health? We’ll show you and give you steps you can take to maintain a diet that keeps your sugar intake in check and promotes a healthy gastrointestinal tract.
Diets high in excess sugar have long been associated with a negative impact on health.
The typical Western Diet, which is high in overall sugar, refined sugar, and processed foods, is repeatedly linked to the development of chronic diseases, particularly cardiovascular diseases and Type 2 Diabetes.
The harmful impact of excessive sugar may be explained by its effects on the gut microbiome, affecting the makeup of the microorganism species and the gut’s functionality. This impairment of the GI tract contributes to metabolic disturbances such as increased inflammation.
We’re going to dive into what sugars are and how to spot them in foods, the potential short and long-term implications of a high-sugar diet on gut health, and recommendations for dietary patterns which keep sugar intake to a reasonable level.
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The science of sugar from an RDN
Sugars are defined as sweet-tasting carbohydrates which the body can use for energy. Like all carbohydrates, sugars contain 4 calories per gram.
Simple sugars are divided into two primary categories: monosaccharides, which consist of one sugar molecule, and disaccharides, which contain two sugar molecules.
Monosaccharides include glucose, fructose, and galactose.
Disaccharides include sucrose, better known as table sugar, which is made up of one glucose molecule and one fructose molecule, lactose, which contains one galactose molecule and one glucose molecule, and maltose, which is two glucose molecules bound together.
Why type of sugar matters
During digestion, disaccharide sugars are broken down into monosaccharide forms.
Glucose is the body’s preferred form of energy and is metabolized in a straightforward manner.
Fructose and galactose have another step. They must be converted into glucose by the liver to be used as a fuel source.
Glucose and fructose occur naturally in carbohydrate foods like fruits, vegetables, and whole grains.
Lactose is well known as the sugar contained in milk and dairy products.
However, sugars can also be added into processed foods. This typically involves manipulating the sugar’s form which can affect how they are digested and utilized by the body.
Research has indicated that excessive intake of added sugars increases risk for many serious health conditions.
The Many Names of Added Sugar
Added sugars, also known as free sugars, refer to the sugars added to the food by the manufacturer as well as sugars from altered fruits and vegetables like juices or pureed forms like applesauce.
Added sugars are widely found in many food products and can be incorporated in a variety of types, including simple sugars, solid or granulated sugars, and liquid or syrup sugars.
There are at least 61 different names for sugar which appear on the ingredient lists of nutrition facts labels. Many of these names end in the suffix “ose” (such as maltose, dextrose, and sucrose), while others may not be as easy to identify.
A famous example of added sugar is the manipulation of fructose to make high fructose corn syrup, a frequent ingredient in condiments like ketchup and beverages like sodas and fruit drinks.
Some common names for added sugars include the following:
- High-fructose corn syrup (may be abbreviated as “HFCS”)
- Agave nectar/syrup
- Barley malt
- Beet sugar
- Brown sugar
- Cane sugar
- Fruit juice
- Fruit juice concentrate
- Golden syrup
- Malt syrup
- Rice syrup
The average American consumes roughly 17 teaspoons of added sugars per day, primarily from processed foods and beverages. For reference, the American Heart Association recommends no more than 6 teaspoons of added sugar daily for women and no more than 9 teaspoons per day for men.
High sugar diets, particularly ones high in added sugars, are linked to weight gain, even increased incidence of obesity, metabolic disease and effecting overall health. But what is it about these sugars that may be to blame?
Sugar and the gut microbiome
The gut microbiome
The digestive tract, especially the large intestine, is home to trillions of microorganism species like bacteria. When the gut microbiota which offer health benefits to the human body (like immune system and digestive support) are plentiful, the gut microbiome is in a symbiotic, mutually advantageous, relationship with its host.
By contrast, when diversity of gut microbes is reduced and infectious bacteria outnumber the beneficial bacteria, this is known as dysbiosis, a state which lays the groundwork for the development of disease.
Diet plays a significant role in the makeup of the gut microbiome, particularly if beneficial microbiota have enough fuel to dominate over pathogenic ones.
Diet impact on gut microbiome
The “good” gut bacteria are nourished by prebiotic carbohydrates such as the oligosaccharides found in fruits, vegetables, and legumes. A relatively new study refers to these carbohydrates as microbiota accessible carbohydrates (MAC).
Low-MAC diets are associated with decreases in gut bacteria species, reduction in overall microbial diversity, and subsequent metabolic dysfunction. In animal studies, diets which were deficient in proper fiber intake resulted in increased inflammation and exposure to disease-causing pathogens.
It is especially problematic when diets which are low in MAC are also higher in simple and refined sugars.
A study by Redondo-Useros et al indicated that excessive intake of fructose can impair the liver through altering gut microbiome composition and allowing pro-inflammatory bacteria to grow and thrive.
The authors also noted that compromised microbiome integrity is seen in individuals with Type 2 Diabetes.
Sugar intake may also impair the functionality of the gut. A 2018 study by Do et al found that mice who were fed high-glucose and high-fructose diets had gut inflammation which caused the intestinal tight junction proteins to become loose and the intestinal walls to become permeable.
In this hyperpermeable state, toxins and pathogens are more easily able to pass through the gut, a phenomenon known as “leaky gut syndrome”.
Additionally, Moriconi et al in Frontiers in Endocrinology found that a lack of dietary fiber in a high protein/low carbohydrate dietary pattern also showed negative microbiome shifts towards inflammation.
What About Artificial Sweeteners?
Artificial sweeteners are frequently used as sugar substitutes as many have little or no calories. They were previously believed to have a negligible impact on gut composition.
However, recent studies have indicated that artificial sweeteners may cause changes in the gut microbiome, and not necessarily for the better.
Sweeteners have differences in their chemical structure which affects how they are absorbed in the gastrointestinal tract. Let’s take a closer look at the commonly found sugar substitutes like sugar alcohols and non-caloric sweeteners.
The most common low-calorie sweeteners are sugar alcohols, which include sorbitol, mannitol, and xylitol.
They are typically suggested as sugar alternatives for patients with diabetes as they have the potential to improve insulin resistance and glycemic control.
While certain sugar alcohols, particularly xylitol, may produce some beneficial effects on gut bacteria, regular consumption of these sweeteners may cause gastrointestinal discomfort.
Sorbitol is poorly absorbed in the small intestine and converted into gas and short chain fatty acids in the colon. Sugar alcohols are also osmotic (which means they pull water into the gut) and can have laxative effects at high doses.
Sugar alcohols are not recommended for individuals with irritable bowel syndrome (IBS) or inflammatory bowel diseases (IBD), especially in chewing gum as there can be increased intestinal motility even without having a laxative effect.
No Calorie Sweeteners
Non-calorie sweeteners, such as saccharin, aspartame, acesulfame-K, sucralose, and stevia rebaudiana, have the potential to increase sugar absorption during a meal. Most of these sweeteners are absorbed in the small intestine (only about 30% reach the large intestine).
A study on mice found that saccharin caused glucose intolerance, inhibited the growth of good bacteria strains, and created a dysbiotic state in the gut. Germ-free mice who received fecal transplants from saccharin-fed animals also experienced impaired glucose tolerance. However, it is worth noting that the saccharin doses were notably higher than the typical human daily consumption.
Some no-calorie artificial sweeteners may impair gut microbiome composition. Though stevia rebaudiana demonstrated positive effects on glucose control and blood pressure in rat studies, it was also found to inhibit Lactobacillus reuteri, which is a probiotic strain.
Excessive use of non-caloric artificial sweeteners can alter the microbiome and impede the body’s ability to tolerate glucose. The American Heart Association and the American Diabetes Association both recommend limiting use of sweeteners due to a lack of long-term positive impacts on heart health, diabetes, and maintaining a healthy weight.
*NOTE: Due to its high content of phenylalanine, aspartame is contraindicated for individuals with the metabolic condition phenylketonuria (PKU).
Sugars occur naturally in many whole foods, but added sugars are much more of a health concern. Given how widespread added sugars are in processed and refined foods, it is easy to consume too much sugar on a daily basis.
Keep added sugar intake to no more than 25 grams per day for women (100 calories total), and no more than 37.5 grams per day for men (150 calories total). When buying packaged foods, be sure to check the nutrition facts label for the added sugar amount as well as the list of ingredients to spot added sugar names.
Research indicates that high sugar diets, particularly when paired with insufficient intake of MAC carbohydrates, cause undesirable changes to the gut microbiome like promoting the growth of pro-inflammatory bacteria.
Excess sugar may also lead to functional gut issues like hyperpermeability in the intestinal walls allowing toxins and pathogens to “leak” through and cause infection.
While artificial sweeteners may be a good choice for some, they may have negative effects on gut bacteria and/or cause gastrointestinal distress. It is best to avoid excessive intake, while those with IBS or IBD should avoid sugar alcohols.
Diets that are rich in whole, unprocessed foods and fiber are particularly beneficial for the human gut. It is important to focus on foods with naturally occurring sugars and complex MAC carbohydrates like fruits and vegetables.
Making natural sugar substitutes for refined sugar can be beneficial, though should be done in moderation. Substituting honey for refined sugar or using dates or maple syrup to sweeten your treats can be an alternate way to satiate your sweet tooth, while not going so overboard on refined sugars.
This Gluten Free Almond Pulp Granola Recipe is made with nuts and dates and perfectly sweet.
Smoothies can also be a great way to satisfy your sweet tooth by utilizing whole fruits and healthy add ins. We have an extensive smoothie ingredient list written by an RDN to give you some ideas for delicious, healthy smoothies.
If your gut has been damaged by excessive amounts of dietary sugar, following a diet high in whole, unprocessed foods and fiber is the best way to get back on track. Adding a daily probiotic supplement can also be helpful in rebuilding your healthy gut microbiome.
All included information is not intended to treat or diagnose any disease or medical condition. Always consult your healthcare provider for medical questions and before beginning or changing any dietary or supplementation regimen.