Sulfide Production (H2S)

This marker assesses your microbiome's ability to produce Hydrogen Sulfide (H2S), a gas famous for its characteristic "rotten egg" smell. In tiny amounts, H2S acts as a necessary cellular messenger; however, when certain bacteria produce it in excess, it becomes a highly toxic gas that "suffocates" your gut cells, destroys the mucus barrier, and is one of the main drivers of chronic gut inflammation (especially in Ulcerative Colitis).

The sulfide that reaches your large intestine comes mainly from two sources: your diet (sulfur-rich amino acids present in red meat, eggs, and dairy, as well as preservative additives like sulfites in wines and processed foods) and your own mucus layer (which is "sulfated" to protect you).

In a healthy ecosystem, the production of this gas is minimal. However, diets very high in animal fats and proteins —and low in fiber— favor the overgrowth of a specific group of microorganisms known as Sulfate-Reducing Bacteria (SRB).

The most representative species in this group are Bilophila wadsworthia and Desulfovibrio. When these bacteria dominate, they use the sulfur from your food or degrade your own protective mucus layer to "breathe," releasing large amounts of H2S gas as toxic waste directly onto the delicate wall of your colon.

The chronic accumulation of H2S in the intestinal lumen has a very negative effect, often described as "cellular toxicity":

• "Suffocation" of Intestinal Cells: Your colon cells need butyrate for energy. H2S gas is biologically toxic because it blocks the cellular enzymes that process butyrate. Unable to use it, intestinal cells have decreased energy levels and weaken, breaking down the intestinal barrier.
• Ulcerative Colitis and Bleeding: There is a strong and proven clinical correlation between high levels of H2S (and sulfate-reducing bacteria) and the development of Ulcerative Colitis. The gas severely irritates the mucosa, causing micro-ulcers and bleeding.
• Digestive Symptoms (Gas and Pain): At an immediate clinical level, high production manifests as extremely foul-smelling flatulence. Furthermore, H2S acts on the nerves of the intestine, causing visceral hypersensitivity (normal gas is felt as painful cramps).
• DNA Damage: Being a highly reactive molecule, chronic excess H2S causes oxidative stress and damage to the DNA of colonic cells, statistically increasing the risk of mutations and colorectal cancer.

Sulfur toxicity evaluation is performed using Shotgun metagenomics, quantifying the genetic potential of the dissimilatory sulfate reduction pathway and sulfur amino acid metabolism.

Our bioinformatics pipeline maps the abundance of key genes such as dsrA and dsrB (dissimilatory sulfite reductases). At the taxonomic level, we assess the specific load of Sulfate-Reducing Bacteria (SRB), paying close attention to the genera Desulfovibrio, Desulfobulbus and the species Bilophila wadsworthia (whose growth is specifically stimulated by bile salts secreted when eating animal fats).

Normal or low levels indicate efficient protein digestion and an ecosystem where saccharolytic (healthy) fiber fermentation predominates, keeping SRBs in check. Conversely, a high level suggests a predominance of proteolytic fermentation (putrefaction) and a hostile intestinal environment. If the marker is high, a temporary restriction of high-sulfur animal proteins, drastic reduction of saturated fats, elimination of foods with sulfites (E220-E228), and a significant increase in prebiotics (such as GOS and FOS) to acidify the colon, which physically inhibits the growth of H2S-producing bacteria, are strongly recommended.