Some commonly consumed foods are fortified with calcium, such as calcium-fortified orange juice, and can be a major source of calcium. Lactose intolerance is a condition where an individual cannot digest lactose, the main sugar in milk. Lactose is a disaccharide composed of two single sugars glucose and galactose. Lactose is normally digested in the small intestine by lactase, an enzyme that breaks lactose into the smaller sugars, glucose and galactose, which can be absorbed by the small intestine. If there is not enough lactase, the undigested lactose moves into the large intestine and is fermented by bacteria naturally found in the large intestine.
Most infants produce the enzyme lactase at birth, but the amount tends to decrease by adulthood.
The incidence of lactose intolerance varies for different populations. Symptoms of Lactose Intolerance Symptoms of lactose intolerance include abdominal cramps, bloating, intestinal gas, diarrhea, and nausea. The severity of symptoms depends on the amount of lactose consumed and the degree of lactose intolerance. Symptoms may appear any time from 5 minutes to several hours after eating lactose contained in foods and beverages. Lactose intolerance is not a food allergy.