Sour cream is a dairy product made by fermenting pasteurized cream with lactic acid bacteria, known for its rich texture and tangy flavor. While consuming sour cream in moderation is usually fine, it can cause diarrhea due to its dairy composition, high fat content, or external contamination. Understanding these causes helps determine why this fermented food might lead to gastrointestinal distress.
Lactose Intolerance and Dairy Sensitivity
The most common trigger for dairy-induced diarrhea is the body’s inability to fully process lactose, the milk sugar. Proper digestion requires the small intestine to produce the enzyme lactase, which breaks lactose down into simpler sugars for absorption. Many adults produce insufficient lactase, a condition resulting in lactose malabsorption.
While fermentation converts some lactose into lactic acid during sour cream production, it does not eliminate all milk sugar. A typical two-tablespoon serving contains 1 to 2 grams of lactose, which can still cause a reaction in sensitive individuals. When this undigested lactose reaches the large intestine, gut bacteria rapidly ferment it. This fermentation creates gases and short-chain fatty acids, leading to symptoms like bloating and abdominal discomfort.
The unabsorbed lactose and its byproducts also create an osmotic effect in the colon. This draws water from the body into the bowel, swelling the stool volume. This influx of fluid results in the watery, loose consistency characteristic of osmotic diarrhea. The severity of the reaction depends on the amount of lactase a person produces and the quantity of sour cream consumed.
The Digestive Impact of High Fat Content
Even for individuals who properly digest lactose, the high fat concentration in sour cream can cause digestive issues. Regular sour cream is a high-fat food, often containing 18% to 20% milkfat, or about 5 to 6 grams of fat per two-tablespoon serving. High fat content naturally slows down gastric emptying to allow sufficient time for fat digestion.
If a person consumes a large quantity of sour cream, especially within an already high-fat meal, the digestive system may become overwhelmed. The small intestine relies on bile from the liver and lipase enzymes from the pancreas to break down these lipids. When the amount of fat exceeds the system’s capacity, it passes through the small intestine undigested.
This failure of fat absorption, known as malabsorption, results in undigested lipids continuing into the colon. The presence of excessive undigested fat in the large intestine is called steatorrhea, which creates stools that are greasy, foul-smelling, and bulky. This high-fat content disrupts normal bowel function and leads to an increased urge for defecation and loose stools.
Bacterial Contamination and Food Safety
A separate cause of diarrhea is the presence of harmful external bacteria, indicating a food safety issue. Sour cream is perishable; although its acidity inhibits some spoilage organisms, it is susceptible to contamination from pathogens. Improper handling or temperature abuse allows these harmful microorganisms to multiply rapidly.
Sour cream should not be left at room temperature for more than two hours, as this allows bacteria to enter the temperature danger zone. Consuming spoiled sour cream can lead to acute gastroenteritis, or food poisoning. Symptoms include acute diarrhea, stomach cramps, and nausea, caused by pathogenic bacteria like Salmonella or E. coli, or the toxins they produce.
Visible signs that sour cream is unsafe include mold, significant discoloration (such as yellow or green tint), or an excessively rancid smell. While some liquid separation is normal, a chunky or curdled texture combined with an off-odor suggests harmful bacterial growth and signals that the product should be discarded immediately.