What Is Lactose Intolerance (Lactase Deficiency)? What Causes Lactose Intolerance?

People with lactose intolerance or lactase deficiency cannot metabolize lactose properly; they lack lactase, an enzyme required in the digestive system to break down lactose. Patients typically experience a bloating, flatulence, and diarrhea after drinking milk. Lactose is a sugar that is found most notably in milk.

At least three-quarters of adults show decreased lactase activity as they get older. Lactose intolerance is less common in northern than southern Europe; it is more common in Africa and Asia than in Europe.

According to Medilexicon's medical dictionary:

Lactose intolerance is a disorder characterized by abdominal cramps and diarrhea after consumption of food that contains lactose (milk, ice cream); believed to reflect a deficiency of intestinal lactase; may appear first in young adults who had tolerated milk well as infants.

Symptoms can range from some mild discomfort to severe, depending on how much lactase they produce and the extent of their consumption of milk and other dairy products.

What is Lactose?

Lactose, which has a formula C₁₂H₂₂O₁₁, is a sugar that is found in the milk of mammals; it makes up around 2% to 8% of milk. It was discovered by Fabriccio Bartoletti in 1619, and later identified as a sugar by carl Wilhelm Scheele in 1780.

The human body uses the enzyme lactase to break down lactose into galactose and glucose - which is then absorbed into the bloodstream.

What are the signs and symptoms of lactose intolerance?

A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor detect. For example, pain may be a symptom while a rash may be a sign.

Typically, a person with lactose intolerance will experience symptoms after consuming milk or some dairy product that contains lactose. Symptoms may include:

• flatulence - a buildup of excessive gas in the intestinal tract; this can lead to farting and burping.
• Diarrhea - an hour or two after consuming lactose the individual can suddenly become desperate to go to the toilet.
• Bloated feeling
• Stomachache and abdominal pains
• Tummy rumbles
• Nausea
• Dehydration - if symptoms are severe

What are the causes of lactose intolerance?

Lactose is a type of sugar found in milk. Lactase is a protein, an enzyme that is produced in the small intestine - it breaks down lactose. Individuals with lactose intolerance do not produce enough lactase.

People with adequate amounts of lactase can break down lactose into glucose and galactose (a type of sugar) which are then absorbed into the bloodstream. In people with low levels of lactase, the lactose is not broken down and does not absorb into the bloodstream, instead it moves into the large intestine (colon). Bacteria in the colon react to the lactose, triggering symptoms.

Four main types of lactose deficiency

Primary lactase deficiency - genetically inherited. It is the most common type and usually develops when the patient is under 20 years of age. As soon as the individual's diet includes less milk, lactase production drops. In most cases, this occurs when the baby is weaned from milk to solids. Although lactase levels may drop at such an early age, it may be a few years before lactose intolerance symptoms develop.

Secondary lactase deficiency - there is a problem with the small intestine that results in inadequate amounts of lactase production. Possible causes are intestinal surgery, Crohn's disease, ulcerative colitis, chemotherapy, celiac disease and gastroenteritis. If the underlying condition is chronic (long-term), the resultant lactose intolerance tends to be long-term too.

Congenital lactase deficiency - the person is born with a genetic mutation which means they produce very little lactase (or none at all). The condition is inherited from the patient's parents.

Familial lactase deficiency - lactase production is fine, but it does not do the job. It does not break down the lactase into glucose and galactose so that it can be absorbed into the bloodstream. This condition is also inherited from the parents.

What are the risk factors of lactose intolerance?

A risk factor is something which increases the likelihood of developing a condition or disease. For example, obesity significantly raises the risk of developing diabetes type 2. Therefore, obesity is a risk factor for diabetes type 2.

Age- older people are more likely to have lactose intolerance than babies or young children.

Ancestry - northern Europeans are less likely to suffer from lactose intolerance than southern Europeans. People from all non-European (non-Caucasian) ancestries are more likely to develop lactose intolerance compared to people from southern Europe.

Radiation therapy (radiotherapy) - people who have received radiotherapy in their abdomen have a higher risk of subsequently developing lactose intolerance.

Being born prematurely - children who were born at full term will never have lactose intolerance symptoms until they are 3 years of age or more. Premature babies may have symptoms earlier.

How is lactose intolerance diagnosed?

Most people will visit their GP (general practitioner, primary care physician first) if they have lactose intolerance type symptoms. Ideally, before the visit, keeping a food diary and writing down when symptoms appear and how severe they are may help the doctor reach a diagnosis.

The doctor may advise the patient to try a lactose free diet for a couple of weeks, to see if symptoms improve. If they do, the individual most likely suffers from lactose intolerance.

Hydrogen breath test - the patient fasts overnight and then has a lactose solution the following morning. Hydrogen concentrations in exhaled air are measured. If levels are very high, the patient probably has lactose intolerance.

Lactose tolerance test - the patient consumes a lactose solution before a blood sample is taken to measure glucose levels. If glucose levels have not risen, it means the lactose has not been broken down into glucose and galactose, which in normal cases would have gone into the bloodstream. A milk tolerance test is the same, just that the patient's drink is milk instead of a lactose solution.

Stool sample - lactose tolerance tests and hydrogen breathe tests are not suitable for babies and very young children. So the doctor may have a stool sample tested. If levels of acetate and other fatty acids are high, the child is probably lactose intolerant.

Underlying disease/condition - if the doctor suspects there may be an underlying cause, such as celiac disease, a small bowel biopsy may be ordered; a tissue sample of the small intestinal lining is taken. This is a surgical procedure.

What are the treatment options for lactose intolerance?

There are many people who insist that lactose intolerance in people who are no longer being bottle fed or breast fed is not an undesirable condition, but a natural state of a human being. We are the only mammals that carry on drinking milk after babyhood.

People who live in countries where the non-baby human diet contains very little lactose, lactose intolerance does not require treatment - in fact, many lactose-intolerant people will be unaware of it.

If the patient has an underlying condition/disease, it is important that he/she has it under control - this means adhering/complying to their treatment plan.

The simplest way to avoid having the symptoms if you are lactose intolerant, is to avoid lactose. If symptoms are mild, it might be a question of trial an error until you find your lactose threshold.

Any product that contains lactose will have the ingredient listed on its label.

The US NIH (National Institutes of Health), wrote:

Dietary control of lactose intolerance depends on people learning through trial and error how much lactose they can handle.

Products containing lactose

Most milk and milk products have lactose in them. Many processed foods have milk and milk products added to them. If you are lactose intolerant, check the labels carefully in these types of foods:
(list source: National Institutes of Health, USA):

• bread and other baked goods
• candies
• instant potatoes, soups, and breakfast drinks
• liquid and powdered milk-based meal replacements
• margarine
• non-dairy liquid and powdered coffee creamers
• non-dairy whipped toppings
• potato chips, corn chips, and other processed snacks
• processed breakfast cereals
• processed breakfast foods such as doughnuts, frozen waffles and pancakes, toaster pastries, and sweet rolls
• processed meats, such as bacon, sausage, hot dogs, and lunch meats
• protein powders and bars
• salad dressings
• waffles, pancakes, biscuits, cookies, and mixes to make them

Any product with milk, lactose, whey, curds, milk by-products, dry milk solids or non-fat dry milk powder listed in their labeling (ingredients) will have lactose in them.

Some medications, such as birth control pills and stomach acid medications have lactose in them. Patients with severe lactose intolerance should tell their doctor or pharmacist.

What are the complications of lactose intolerance?

If a person comes from a dairy-friendly society and tries to avoid lactose-containing products, he/she will have to make sure their move does not result in malnutrition. Milk contains calcium, proteins, vitamins A, B12 and D - all important nutrients for good health.

If you are embarking on a change of diet, make sure you ask your doctor or a qualified dietician/nutritionist what you should do.

Calcium is found in seaweeds, nuts and seeds, blackstrap molasses, beans, oranges, figs, quinoa, amaranth, collard greens, okra, rutabaga, broccoli, dandelion leaves, kale, and fortified products such as orange juice and soy milk

Vitamin A can be found in carrots, broccoli, sweet potatoes, cod liver oil, liver, spinach, pumkin, cantaloupe melon, egg, apricot, papaya, mango, and peas.

Vitamin D levels can be enhanced by exposure to natural sunlight, consuming fatty fish, eggs, fish liver oils, and some fortified soy milks and other fortified products.

Lactose free milk - this does exist. If you suffer from severe symptoms, make sure the lactose levels are zero, and not just reduced.