what is lactose

What is Lactose?

Lactose is the form of sugar that is found in milk and dairy products. It is a disaccharide, which means it is made up of two monosaccharides, or simple sugars (carbohydrates). The monosaccharides that join to form lactose are glucose and galactose, both of which are important carbohydrates in the human body.

Why is Lactose Bad?

Lactose ingestion can harm and cause extreme discomfort to people that are lactose intolerant.

Lactose Related Disorder

Lactose Intolerance

• Primary
• Secondary
• Congenital

What is Lactose Intolerance?

Lactose Intolerance is the inability to digest the sugar in milk, lactose. This inability results from a shortage or lack of the enzyme lactase, which is normally produced in the small intestine. Lactase breaks down the milk sugar lactose, so the body can easily digest it. When there is not enough lactase to digest the amount of lactose consumed, the lactose does not get broken down where it should and makes it all the way to the colon where it is then fermented and broken down by intestinal bacteria into short-chain fatty acids and gas. Once this happens your body will begin to react and cause nausea, gas, cramps, loose stool, diarrhea, bloating and vomiting. Symptoms tend to occur anywhere from thirty minutes to two hours after eating or drinking foods containing lactose. One's severity of symptoms and tolerance levels varies person to person. As an infant, your body produced a large amount of lactase, which broke down lactose from your mother's milk. However, many people lose the ability to break down lactose in adulthood. In fact, about 75% of the world's adult population is unable to break down lactose.

Primary Lactose Intolerance

This is the most common type of lactose intolerance. People who develop primary lactose intolerance start life producing plenty of lactase, a necessity for infants, who get all their nutrition from milk. As children replace milk with other foods, their lactase production normally decreases, but remains high enough to digest the amount of dairy in a typical adult diet. In primary lactose intolerance, lactase production falls off sharply, making milk products difficult to digest by adulthood. Primary lactose intolerance is genetically determined, occurring in a large proportion of people with African, Asian or Hispanic ancestry. The condition is also common among those of Mediterranean or Southern European descent.

Secondary Lactose Intolerance

This form of lactose intolerance occurs when your small intestine decreases lactase production after an illness, injury or surgery involving your small intestine. Among the diseases associated with secondary lactose intolerance are celiac disease, bacterial overgrowth and Crohn's disease. Treatment of the underlying disorder may restore lactase levels and improve signs and symptoms, though it can take time.

Congenital or Developmental Lactose Intolerance

It's possible, but rare, for babies to be born with lactose intolerance caused by a complete absence of lactase activity. This disorder is passed from generation to generation in a pattern of inheritance called autosomal recessive, meaning that both the mother and the father must pass on the same gene variant for a child to be affected. Premature infants may also have lactose intolerance because of an insufficient lactase level.

Lactose Intolerance Related Conditions

• Nausea
• Gas
• Cramps
• Loose Stool
• Diarrhea
• Bloating
• Vomiting

Risk Factors

Factors that can make you or your child more prone to lactose intolerance include:

• Increasing age; Lactose intolerance usually appears in adulthood, the condition is uncommon in babies and young children.

• Ethnicity; Lactose intolerance is most common in people of African, Asian, Hispanic and American Indian descent, (Believed to be because of the eating history of their ancestral line)

• Premature birth; Infants born prematurely may have reduced levels of lactase because the small intestine doesn't develop lactase-producing cells until late in the third trimester.

• Diseases Affecting The Small Intestine; Small intestine problems that can cause lactose intolerance include bacterial overgrowth, celiac disease and Crohn's disease.

• Certain Cancer Treatments; If you have received radiation therapy for cancer in your abdomen or have intestinal complications from chemotherapy, you have an increased risk of lactose intolerance.


Your doctor may suspect lactose intolerance based on your symptoms and your response to reducing the amount of dairy foods in your diet. Your doctor can confirm the diagnosis by conducting one or more of the following tests:

• Lactose tolerance test; The lactose tolerance test gauges your body's reaction to a liquid that contains high levels of lactose. Two hours after drinking the liquid, you'll undergo blood tests to measure the amount of glucose in your bloodstream. If your glucose level doesn't rise, it means your body isn't properly digesting and absorbing the lactose-filled drink.

• Hydrogen breath test; This test also requires you to drink a liquid that contains high levels of lactose. Then your doctor measures the amount of hydrogen in your breath at regular intervals. Normally, very little hydrogen is detectable. However, if your body doesn't digest the lactose, it will ferment in the colon, releasing hydrogen and other gases, which are absorbed by your intestines and eventually exhaled. Larger than normal amounts of exhaled hydrogen measured during a breath test indicate that you aren't fully digesting and absorbing lactose.

• Stool acidity test; For infants and children who can't undergo other tests, a stool acidity test may be used. The fermenting of undigested lactose creates lactic acid and other acids that can be detected in a stool sample.


There's currently no way to boost your body's production of lactase. But you can avoid the discomfort of lactose intolerance by avoiding lactose completely or by consuming or adding a lactose enzyme into your meal. Once you have ingested lactose, you cannot treat your symptoms, including your stool. Treatment includes purchasing lactose-free dairy products, lactase enzyme supplements or eliminating cow's milk from your diet. Lactose-free dairy products add lactase to the milk during the manufacturing process to eliminate lactose. A lactase enzyme taken as directed prevents most digestive symptoms associated with lactose intolerance. People with mild lactose intolerance can tolerate a small amount of lactose and do not need to avoid it altogether.

Vitamin and Mineral Supplements

Having to avoid lactose can lead to nutritional deficiencies. Vitamins and supplements are usually taken in pill form. If your digestive tract has trouble absorbing vitamins, your doctor may give them by injection. You need to be sure that the vitamins and supplements are lactose free. You may need to supplement your levels of;

• Vitamin D
• Calcium

Sources of Lactose?

• Milk
• Whey
• Caseinates
• Nougat
• Cheese
• Milk by-products
• Casein
• Dry Milk Solids
• Lactose
• Butter
• Curds
• Nonfat Dry Milk
• Dry Milk Powder

Common Foods that Contain lactose

(must be verified by reading the label or checking with the manufacturer/kitchen staff)

  • Milk
  • Yogurt
  • Cream
  • Butter
  • Ice Cream
  • Cheese
  • (Any food that contains any ingredient on the sources of lactose list)


(must be verified by reading the label or checking with the manufacturer/kitchen staff)

  • Bread
  • Baked Goods
  • Pancake Mixes
  • Ready-to-Eat Breakfast Cereals
  • Instant Soups
  • Candy
  • Cookies
  • Salad Dressings
  • Deli Meats
  • Drink Mixes
  • Margarine
  • Frozen Potato Foods
  • (Any food that contains any ingredient on the sources of lactose list)

Digestion Process of Lactose

Because disaccharides like lactose are relatively large molecules, they cannot be absorbed by the small intestine. Before lactose can be absorbed, it must be broken down into the smaller monosaccharides. In order to do this, the small intestine produces an enzyme called lactase. The job of lactase is to attach itself to the lactose molecule and hydrolyze it into glucose and galactose. These smaller molecules can easily be absorbed by the intestines and enter the blood stream. When the small intestine is deficient in the enzyme lactase, it causes lactose intolerance. In rare cases, babies can even be born without the presence of lactase in the intestines. However, most cases of lactose intolerance develop later in life due to a gradual loss of lactase activity. Without the presence of lactase, lactose remains intact and moves on to the colon. In the colon it is fermented by intestinal bacteria, causing bloating, gas and diarrhea. These abdominal side effects are the classic symptoms of lactose intolerance.