What is a common effect of lactose intolerance?

Lactose intolerance is a condition where an individual has difficulty digesting lactose, a sugar found in milk and dairy products. This difficulty is due to a deficiency in lactase, the enzyme responsible for breaking down lactose in the digestive system. When lactose is consumed, it can lead to various gastrointestinal symptoms, the most common being diarrhea and bloating.

When lactose is not properly broken down, it ferments in the intestine, leading to symptoms such as gas, cramps, and watery stools. This reaction occurs because undigested lactose draws water into the intestines and can also be fermented by bacteria, producing gas. Therefore, experiencing diarrhea and bloating after consuming dairy is a hallmark effect of lactose intolerance, making it the correct answer.

The other options do not align with the typical symptoms associated with lactose intolerance. Increased energy levels and improved digestion would suggest that lactose is being adequately processed, which is not the case for individuals with lactose intolerance. Similarly, while some individuals may experience a loss of appetite when they associate dairy with discomfort, this is not a direct effect of lactose intolerance itself.