Blue cheese is a general term for cheeses, such as Roquefort, Stilton, and Gorgonzola, characterized by the presence of blue-green mold cultures introduced during the aging process. The complex composition and fermentation of these cheeses give them a distinct flavor profile. For some people, consuming blue cheese can lead to digestive discomfort, including diarrhea. The causes range from common issues like dietary intolerance to the unique biological components of the cheese and, in rare instances, food safety concerns.
Compositional Factors Affecting Digestion
Blue cheese is typically produced with a high concentration of milk fat, which can directly influence digestive response. High-fat foods take a longer time to digest because they require more bile and pancreatic enzymes for breakdown in the small intestine. When large amounts of undigested fat move into the colon, they can draw excess water into the bowel through an osmotic effect, resulting in loose stools or diarrhea. This inherent richness can make blue cheese a common trigger for individuals sensitive to high-fat meals, especially when consumed in large portions.
The manufacturing process of blue cheese involves fermentation and aging, which greatly reduces the presence of lactose, the milk sugar that causes issues for intolerant individuals. The bacteria and mold convert most of the lactose into lactic acid during the aging period. Consequently, blue cheeses are often considered naturally low in lactose, with some varieties containing levels below the detectable limit.
However, blue cheeses are not entirely lactose-free, typically containing very low residual amounts that can range up to 2.5%. For people with moderate to severe lactose intolerance, even these trace amounts can be sufficient to trigger symptoms. When residual lactose is not fully broken down due to insufficient lactase enzyme, it ferments rapidly in the large intestine.
This fermentation process produces gas and irritant acids, which collectively cause cramping and osmotic diarrhea. The specific amount of residual lactose is highly variable, influenced by the aging time and moisture content of the cheese variety. Ultimately, digestive tolerance depends on the individual’s sensitivity to these remaining milk components and the quantity of cheese consumed.
The Unique Role of Penicillium Mold
The characteristic flavor and texture of blue cheese come from the specific fungus, typically Penicillium roqueforti, which is introduced into the cheese paste. This mold actively breaks down proteins and fats through enzymatic action, releasing a variety of unique compounds known as secondary metabolites. These mold-derived compounds are responsible for the sharp, pungent taste but can sometimes act as gut irritants for sensitive consumers.
One such group of metabolites includes mycotoxins, such as roquefortine C and mycophenolic acid, which are produced by P. roqueforti. While the average concentrations of these compounds found in blue cheese are generally considered safe, some individuals might react to them. For example, mycophenolic acid has been associated with gastrointestinal side effects, including abdominal pain and diarrhea, when used in immunosuppressive therapies.
Fermented and aged products, including blue cheese, also contain naturally higher levels of biogenic amines, such as histamine and tyramine. These amines are formed when microorganisms break down amino acids during the ripening process. Histamine, in particular, can be found in high concentrations in some cheeses, with reported levels varying widely.
In people who have a reduced capacity to metabolize these compounds, consuming high concentrations of histamine can lead to a systemic response that mimics an allergic reaction. This response, sometimes called histamine intolerance, can manifest as gastrointestinal complaints, including nausea, flushing, and diarrhea. Tyramine is another biogenic amine that can accumulate in blue cheese and contribute to digestive upset.
Food Safety Concerns and Pathogens
The most serious, though least common, cause of diarrhea from blue cheese involves food safety issues related to bacterial contamination. Blue cheeses are classified as soft, mold-ripened varieties, which sometimes present a higher risk environment for certain pathogens compared to hard cheeses. This is partly because the mold growth reduces acidity in the cheese’s interior, creating conditions that can support the growth of harmful bacteria.
A primary concern is the bacterium Listeria monocytogenes, which can contaminate the cheese at various stages, including from raw milk, the brine solution, or during processing and handling. Listeriosis, the illness caused by this bacterium, is severe for vulnerable populations, such as pregnant women, the elderly, and those with weakened immune systems. The needling process used to introduce the Penicillium mold can also inadvertently introduce contaminants into the center of the cheese.
Risk assessments indicate that the frequency of contracting listeriosis from blue cheese is very low for the general population. However, experts advise vulnerable individuals to avoid soft, mold-ripened cheeses unless they are certain the cheese was made with pasteurized milk. The severity of infection, which includes symptoms like diarrhea, fever, and muscle aches, is considered high.
Beyond specific pathogens, general spoilage or improper storage can introduce other bacteria that cause acute food poisoning. Symptoms of food poisoning often appear quickly and include nausea, vomiting, and diarrhea. If diarrhea is persistent, bloody, or accompanied by a high fever or signs of severe dehydration, such as little to no urine output, medical attention should be sought immediately.