1.1 Introduction
Lactose is the carbohydrate naturally found in all kinds of milk, including human milk; it can also be used as an ingredient in some foods.
Lactose intolerance is the inability of the body to digest lactose. To digest lactose the body contains the enzyme lactase. Lactase splits the lactose into two smaller sugars which are glucose and galactose .These smaller sugars are then absorbed by the body to provide energy.
When a person doesn't have enough of the lactase enzymes to breakdown all of the lactose, they are said to have lactose maldigestion. The under digested lactose passes through the small intestine to the colon. in the colon, natural bacteria ferment the lactose and produce acids and gas. This combination of events can cause the symptoms of lactose intolerance, which may include abdominal pain, bloating or diarrhea.
Lactose intolerance is not the same as milk or dairy allergies are caused by a reaction to a food by immune system, causing symptoms such as a rash, wheezing and itching.
If you are allergic to something, even a tiny particle can be enough to trigger reaction, while most people with lactose intolerance can still consume small amounts of lactose without experiencing any problems, although this varies from person to person.
Rates of lactose intolerance can differ significantly between different ethnic groups. For example, it is thought that only one in 50 people of Northern European descent have some degree of lactose intolerance, where as most people of Chinese descent have the condition.
This may be because people from places where there has historically been no ready access to milk, such as Africa or East Asia, may not have evolved the ability to digest lactose as there was no significant benefit in being able to do so.
In the UK, lactose intolerance is more common in people of Asian or African-Caribbean descent.
Lactose intolerance can develop at any age.Many cases first develop in people aged 20 to 40, although babies and young children can also be affected.
Depending on the underlying reason why the body does not produce enough lactase; lactose intolerance may be temporary or permanent.
Most cases that develop in adults are inherited from parents and tend to be lifelong, but cases in young children are often caused by an infection in the digestive system and may only last for a few weeks.
Most mammals normally cease to produce lactase, becoming lactose intolerance after weaning.
In some cases, people may choose to use lactase enzyme supplements, however, these may not completely relieve symptoms and it is difficult to determine the effective dose. Enzyme supplements should be an adjustment not a substitute for dietary reaction. If milk is able to be tolerated in small amounts, enzyme supplements are unnecessary. Low-lactose milk is generally not necessary unless large quantities of milk are consumed or in the rare case of non-tolerance to even small amounts of milk.
1.2 Types of Lactase Deficiency
1. Primary lactose deficiency:
Is the most common reason for lactose intolerance (sometimes referred to as adult or late onset lactose intolerance).lactose concentrations are at their greatest shortly after birth and rapidly decline after the usual age of weaning. The timing and rate of this decline is genetically determined. Primary lactase deficiency has a higher prevalence in those ethnic/geographical groups whose ancestors did not drink milk as a nutrient. Onset of primary lactase deficiency is typically subtle and progressive over several year, however acute development is possible. The age of onset varies among ethnic populations, but it would be uncommon to be seen before two or three years of age (or before four or five years of age in European children). Lactose intolerance may not become clinically evident until late adolescence.
2. Secondary lactase deficiency (acquired):
Is transitory and can occur as the result of any gastro-intestinal illness that alters the nature of the gut mucosa. This is common in children with rotaviral (and other infectious) diarrhea. Crptosporidiosis and other parasitic infections of the proximal small intestine often lead to lactose malabsorption.
This may occur with coeliac disease, crohn's disease and immune-related illnesses such as HIV .In addition, drugs such as tetracycline and methotrexate can cause villous atropy, resulting in secondary lactase deficiency .Alcoho is known to inhibit lactase and other enzymes, initiating or worsening lactose intolerance.
3. Congenital lactase deficiency (alactasia):
This is the life-long absence of lactase. This is an extremely rare condition that is apparent at birth, with the development of persistent diarrhea soon after milk is introduced. Children with alactasia have otherwise normal intestinal mucosa. This condition has diagnosed in less than 50people world-wide.
4. Developmental lactase deficiency (neonatal):
This occurs in premature infants. This condition is usually temporary and rapidly improves as the intestine mucosa matures. Lactase and other disaccharides are deficient until after 3-4 of week's gestation.
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