Lactose intolerance

Lactose

Lactose is a natural sugar found in milk. It is also known as milk sugar. As well as being a good source of energy, lactose helps the body to absorb a number of minerals, such as calcium and magnesium.

In order for lactose to work effectively, it first has to be broken down into two simpler sugars - glucose and galactose. Once lactose has been broken down, it can pass from the gut into the bloodstream.

Lactose is found in the milk of mammals, and it is also added to many foods including:

• dairy products, such as cream, cheese, and yoghurt,
• ice cream,
• salad cream and mayonnaise,
• biscuits,
• chocolate,
• boiled sweets,
• cakes, and
• peanut butter.

Lactose intolerance

Lactose intolerance is the inability of your body to breakdown lactose. The problem is usually caused by a lack of a substance known as lactase. Lactase is an enzyme (a protein that causes a chemical reaction to occur) that is normally produced in your small intestine. The lactase breaks down lactose into the sugars, glucose and galactose.

If your body produces very little, or no, lactase, it will be unable to break down the lactose in your system. The unabsorbed lactose passes through your stomach and into your large bowel. Bacteria in your large bowel ferment (react to) the lactose, producing fatty acids, such as acetate, and gases, such as hydrogen and methane. This can cause symptoms such as stomach bloating and flatulence (wind).

The symptoms of lactose intolerance can be similar to those of other conditions, such as irritable bowel syndrome (IBS) and milk protein intolerance. Due to the similarities, these conditions can sometimes be confused.

The main symptoms of lactose intolerance include:

• wind (flatulence),
• diarrhoea,
• bloated stomach,
• stomach pains,
• loose stools (faeces),
• stomach gurgling (borborygmi),
• nausea, and
• stomach cramps.

If you are lactose intolerant, the amount of lactase your body produces will affect when you begin to experience symptoms, and the severity of those symptoms. This is because your body's digestive system can only tolerate certain amounts of lactose. For example, if your body produces a moderate amount of lactase, you may experience mild symptoms. However, if your body produces a very small amount of lactase, or none at all, your symptoms are likely to be more severe.

Lactose intolerance is usually the result of a lactase deficiency. The main types of lactase deficiency are outlined below.

Primary lactase deficiency

Primary lactase deficiency is the most common form of lactose intolerance. The condition is genetically inherited (it runs in families). Primary lactase deficiency often develops between 5-20 years of age. It develops when your lactase production decreases as a result of your diet becoming less reliant on milk and dairy. However, the reasons for this are unclear.

Secondary lactase deficiency

Secondary lactase deficiency is a form of lactose intolerance that can be caused by illness, injury, medication or surgery to your small intestine. Conditions that can cause secondary lactase deficiency include:

• coeliac disease (inflamed small intestine caused by sensitivity to gluten),
• gastroenteritis (inflammatory condition of the intestines),
• Crohn's disease (disease of the small intestine), and
• ulcerative colitis (a serious disease of the bowel).

Treatments that can cause secondary lactase deficiency include:

• chemotherapy, and
• long courses of antibiotics.

Conditions and treatments, such as those above, can cause a decrease in lactase production. Sometimes, the deficiency is temporary, but if it is caused by a long-term condition, it may be permanent.

Congenital lactase deficiency

Congenital lactase deficiency is a rare condition that runs in families. A faulty gene results in little or no lactase being produced. The faulty gene is passed on from both your mother and father. This is known as an autosomal recessive trait.

Familial lactase deficiency

Familial lactase deficiency is similar to congenital lactase deficiency. However, with this type of lactase deficiency, you body is able to produce a substantial amount of lactase but it is unable to break down lactose properly. As with congenital lactase deficiency, the faulty gene responsible for the production of lactase is passed on from both mother and father.

As the symptoms of lactose intolerance and irritable bowel syndrome (IBS) are similar, misdiagnosis can sometimes occur.

If you think you have lactose intolerance, you should visit your GP. Before seeing your GP, observe the foods that you eat and the reaction that you have to them. Tell your GP if you notice any patterns, or if there are any foods that you seem particularly sensitive to.

Your GP may suggest further tests to find out how much (if any) lactase your body is producing and what might be causing lactose intolerance.

Lactose tolerance test

In a lactose tolerance test, you will be given a drink of lactose solution followed by a blood sugar test. If the lactose is not completely broken down, your blood sugar levels will either rise slowly, or not at all. This is because your body is unable to break down the lactose into sugar.

Milk tolerance test

In a milk tolerance test, you will be given a glass of milk (about 500ml) and afterwards, your blood sugar levels will be tested. If your blood sugar levels do not rise, you may be lactose intolerant.

Breath hydrogen test

In a breath hydrogen test, you will be given a drink of lactose solution after you have fasted (not eaten) overnight. The concentration of hydrogen (measured in parts per million) in your breath is then measured using a breath test. If your breath contains a large amount of hydrogen (more than 20 parts per million above your baseline) you are likely to be lactose intolerant. The baseline is the amount of hydrogen that is present in your breath before drinking the lactose solution.

Small bowel biopsy

In a small bowel biopsy, a sample of your small intestinal lining is taken using an endoscopy (an instrument with a narrow flexible telescope attached). The amount of lactase is then measured. If the sample only contains a small amount of lactase, lactose intolerance is likely. Due to the invasive nature of a small bowel biopsy, the procedure is rarely carried out to diagnose lactose intolerance. However, it may be carried out to confirm whether or not your symptoms are being caused by another condition, such as coeliac disease.

Stool acidity test

The stool acidity test is often used to check babies and young children for lactose intolerance. This is because large doses of lactose, such as those given in the lactose and breath hydrogen test, are dangerous for young children. Also, young children are more likely to develop dehydration caused by diarrhoea.

Stool samples (faeces) are taken and the amount of acid in them is measured. If the baby or child is lactose intolerant, there will be a high amount of fatty acid, such as acetate, present. This is created by the reaction between bacteria in the colon and the undigested lactose.

Treatment for lactose intolerance depends on how sensitive you are to foods that contain lactose.

Mildly sensitive

If you are mildly lactose intolerant, paying close attention to your diet and carefully monitoring what you eat may be all that is needed to avoid the symptoms. Drinking milk as part of a meal, rather than on its own, will help improve the absorption process within your digestive system.

Substitute fresh dairy products with fermented ones (products that have been broken down by substances, such as yeast, bacteria or other micro-organisms). Fermented dairy products include:

• probiotic yoghurts,
• probiotic milk,
• sour cream,
• cottage cheese and,
• hard cheeses, such as Edam and Cheddar.

As well as the above dairy products, non-dairy products, such as soya milk, are also good alternatives. However, it is important that you try not to eliminate dairy products completely from your diet as they provide important nutrients. Also, if you decide to experiment with what you can and cannot eat, make sure that you introduce new foods gradually rather than all at once. This will help you to get used to any foods you may be sensitive to.

Lactase enzyme in liquid form (usually as drops) can be taken before a meal or added to milk. This can be very effective in helping your digestive system to digest the lactose in the meal. You can also take lactase pills (lactase enzyme capsules) before a meal. Both lactase enzyme drops and capsules are available from most health foods shops.

Very sensitive

If you are sensitive to foods containing lactose, you need to be aware of the foods that cause the problem, and avoid them. When buying food products, check the labels for the nutritional information. See the prevention section for a list of common foods that may contain lactose.

Missing out on the nutrients provided by milk and products containing lactose can lead to deficiencies in calcium and other important minerals. Therefore, if you are very sensitive to foods containing lactose, you should talk to your GP about your diet. You may need to have regular bone mineral density checks.

If you are unable to eat most dairy products, there are other ways you can stock up on calcium. For example, you can include foods such as:

• broccoli,
• soya milk
• horseradish,
• watercress,
• red kidney beans,
• soya beans,
• cabbage,
• peas,
• celery,
• parsnips, and
• fish containing edible bones, for example sardines

It is very important for young children to have certain essential nutrients in their diet, such as calcium, for healthy growth and development. Therefore, if your child is extremely sensitive to lactose, you may need to seek advice from a from a dietitian (an expert on diet and nutrition) about what foods need to be included in their diet.

Dairy products, such as milk, are an important part of our diet. If consumed in line with the recommended daily allowance (RDA), dairy products provide us with our daily dose of calcium and other vitamins, such as vitamin D. For adults, the RDA for calcium is 700mg, and for vitamin D it is 5mg.

Lactose also enhances the body's absorption of a number of minerals including calcium, magnesium and zinc. These vitamins and minerals are important for the development of strong, healthy bones.

If you are lactose intolerant, it can be difficult for you to get your RDA of important vitamins and minerals, such as calcium and vitamin D. This may lead to an increased risk of:

• Osteopenia - a condition where you have an extremely low bone mineral density. If it is not treated, it can develop into osteoporosis.
• Osteoporosis - a condition that causes the bones to become thin and weak. If you have osteoporosis, your risk of getting fractures and broken bones is increased.
• Malnutrition - happens when your body is deprived of important nutrients that are essential for a healthy functioning body. If you are malnourished, wounds can take longer to heal, and you may start to feel tired or depressed.
• Weight loss - excessive weight loss can damage your health, and can lead to conditions such as osteoporosis.

Lactose intolerance cannot be prevented. However, the symptoms of the condition can be reduced by avoiding foods that contain lactose. These include:

• dairy products, such as cream, cheese, and yoghurt,
• ice cream,
• salad cream and mayonnaise,
• biscuits,
• chocolate,
• boiled sweets,
• cakes, and
• peanut butter.

Make sure that you check the ingredients of all food and drink carefully, as lactose is often a 'hidden ingredient'. It can also be found in some types of medication, so you should check with your GP, or pharmacist.