Feta cheese is a brined white cheese traditionally made from sheep’s milk or a blend of sheep and goat’s milk, known for its tangy flavor and crumbly texture. While feta offers nutritional benefits, its consumption can lead to gastrointestinal distress, including diarrhea, for several reasons. These causes stem from the cheese’s natural composition and potential issues related to food safety and handling. Understanding the mechanisms involved, such as carbohydrate malabsorption and the effects of high fat and salt content, can help consumers determine the source of their discomfort.
Lactose Intolerance and Feta Cheese
Diarrhea and other digestive issues following dairy consumption are frequently traced back to lactose intolerance. This is the body’s inability to fully digest lactose, the natural sugar found in milk, due to a deficiency in the enzyme lactase. When undigested lactose reaches the large intestine, it draws water into the bowel through an osmotic effect and is fermented by gut bacteria.
Feta cheese is generally considered a low-lactose food, making it more tolerable for many sensitive individuals. The cheesemaking process, which involves culturing and aging, allows bacterial cultures to break down much of the lactose. This significantly reduces the lactose content compared to fresh milk, which contains about 4.8% lactose.
Most feta varieties contain a small residual amount of lactose, often ranging from nearly zero to about 1.5%. Highly sensitive individuals may still experience symptoms if they consume a large portion. The undigested sugar causes osmotic diarrhea by pulling excess water into the colon, resulting in loose stools. Fermentation of residual lactose also releases gases, leading to bloating and abdominal cramping.
High Fat Content and Salt Effects
Beyond lactose, the intrinsic composition of feta cheese, particularly its fat and salt levels, can independently trigger digestive upset. Feta is a relatively high-fat cheese, with a typical one-ounce serving containing between 5.3 and 8.1 grams of fat. Consuming a large quantity of any high-fat food can overwhelm the small intestine’s capacity to produce enough bile and digestive enzymes to properly absorb the fat.
When excess fat remains undigested, it passes into the large intestine, a condition known as steatorrhea, which often manifests as loose or greasy stools. This unabsorbed fat increases the motility of the colon, speeding up the transit time of waste and reducing the time available for water reabsorption. This increase in gut movement contributes directly to the development of diarrhea.
Feta cheese is also notoriously high in sodium because it is traditionally preserved in a salty brine solution. A one-ounce serving can contain over 300 milligrams of sodium. This high concentration of salt can lead to an osmotic effect within the digestive tract. The sodium draws water from the body’s tissues into the intestinal lumen, increasing the volume of fluid in the colon and resulting in watery diarrhea.
Food Safety Concerns and Contamination Risks
When diarrhea is sudden, severe, and accompanied by symptoms like nausea or fever, the cause is often an external contaminant rather than a digestive sensitivity. Soft, brined cheeses like feta are sometimes implicated in foodborne illnesses, particularly if made from unpasteurized milk. Pasteurization kills harmful bacteria, and its absence increases the risk of contamination.
The primary concern with unpasteurized feta is Listeria monocytogenes, a bacterium that causes listeriosis. In healthy adults, listeriosis often begins with milder, flu-like symptoms, including nausea, fever, abdominal pain, and diarrhea. This bacterium is concerning because it is hardy and can survive and grow at refrigeration temperatures, and it is also resistant to salt and acidity.
Even feta made with pasteurized milk can become contaminated through improper handling, such as cross-contamination during slicing or packaging. Consumers should always check the label to ensure the feta was made with pasteurized milk, especially those who are pregnant or have weakened immune systems. Proper storage and adherence to expiration dates also limit the growth of potential spoilage organisms.