Small Intestinal Bacterial Overgrowth (SIBO) is defined by an abnormal increase in bacteria within the small intestine, which naturally should have a low microbial count. These excess bacteria consume and process food before the body can fully absorb it. This confirms that sugar and other fermentable carbohydrates worsen SIBO symptoms by providing fuel for this misplaced microbial population. Managing the resulting digestive distress requires understanding how these bacteria interact with the food we eat.
How Bacteria Metabolize Sugars
The underlying issue in SIBO is bacteria feeding on carbohydrates intended for human absorption. When these microorganisms encounter undigested sugars, they rapidly break them down through anaerobic fermentation. This metabolic activity generates gaseous byproducts that cause SIBO symptoms. The principal gases produced are hydrogen and methane, which can be measured on a diagnostic breath test. Hydrogen is produced by bacteria, while methane is generated by archaea, which feed on hydrogen gas. The production of these gases is directly linked to the amount of fermentable carbohydrate consumed.
Highly Fermentable Carbohydrates That Exacerbate SIBO
The term “sugar” in SIBO is broader than table sugar, encompassing fermentable short-chain carbohydrates known as FODMAPs. These compounds are poorly absorbed by the human small intestine, making them available for bacterial consumption. FODMAP stands for:
- Fermentable Oligosaccharides (found in wheat, garlic, and onions)
- Disaccharides (such as lactose in dairy products)
- Monosaccharides (fructose, especially in high-fructose corn syrup, honey, and some fruits)
- Polyols (sugar alcohols like sorbitol and xylitol)
Reducing the intake of these specific compounds is a central strategy for managing SIBO symptoms.
Physical Consequences of Sugar Fermentation
The uncomfortable physical consequences of SIBO result directly from gas production during bacterial fermentation. Hydrogen and methane gases accumulate rapidly, increasing internal pressure. This buildup causes severe abdominal bloating and visible distension, often reported as the most bothersome symptom. The pressure stretching the intestinal walls also leads to abdominal pain and cramping. The type of gas influences bowel habits: hydrogen production is often associated with diarrhea, while methane production is linked to constipation (sometimes called Intestinal Methanogen Overgrowth or IMO). Excessive burping and flatulence are also common as the body attempts to expel the accumulated gases.
Dietary Strategies for Limiting Problematic Sugars
Managing SIBO symptoms through diet centers on restricting the highly fermentable carbohydrates that feed the overgrowth. The most recognized therapeutic approach is the low-FODMAP diet, which involves a temporary reduction of these problematic sugars. This diet aims to reduce the bacterial fuel source sufficiently to alleviate gas-related symptoms. The protocol has two main phases: a strict elimination phase (typically two to six weeks) followed by a reintroduction phase. High-FODMAP foods are systematically reintroduced to identify specific triggers and tolerance levels. This diet is not intended to be a long-term solution, as prolonged restriction may negatively affect beneficial gut flora.