Introduction

Lactose intolerance is a common digestive problem where the body is unable to digest lactose, a type of sugar mainly found in milk and dairy products.

Symptoms of lactose intoleranceusually develop within a few hours of consuming foodor drink that contains lactose. They may include:

• Wind (wind)
• diarrhoea
• bloated stomach
• stomach cramps and pains
• stomach rumbling
• feeling sick

The severity of your symptoms and when they appear depends on the amount of lactose you've consumed.

Some people may still be able to drink a small glass of milk without triggering any symptoms, while others may not even be able to have milk in their tea or coffee.

When to seek medical advice

The symptoms of lactose intolerance can be similar to several other conditions, so it's important to see your GP for a diagnosis before removing milk and dairy products from your diet.

For example, the symptoms above can also be caused by:

• irritable bowel syndrome (IBS) a long-term disorder that affects the digestive system
• milk protein intolerance an adverse reaction to the protein in milk from cows (not the same as a milk allergy )

If your GP thinksyouhave lactose intolerance,they may suggest avoiding foods and drinks containing lactose for two weeks to see if your symptoms improve.

This breaks down lactose into two sugars called glucose and galactose, which can be easily absorbed into the bloodstream.

People withlactose intolerancedon't produce enough lactase, so lactose stays in the digestive system where it's fermented by bacteria. This leads to the production of various gases, which cause the symptoms associated with lactose intolerance.

Depending on the underlying reason why the body isn't producing enough lactase, lactose intolerance may be temporary or permanent. Most cases that develop in adults are inherited 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.

Many cases first develop in people aged 20 to 40, although babies and young children can also be affected.

Is it an allergy?

Lactoseintolerance isn't the same as a milk or dairy allergy. Food allergies are caused by your immune system reacting to a certain type of food. Thiscauses symptoms such asa rash, wheezing and itching.

If you're allergic to something, even a tiny particle can be enough to trigger a 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).

Treating lactose intolerance

There's no cure for lactose intolerance, but limiting your intake of food and drink containing lactose usually helps tocontrol the symptoms.

Depending on what dairy products you're able to eat, you may also require additional calcium and vitamin D supplements to keepyour bones strong and healthy. In some cases, your GP may refer you to a dietitian for further advice.

In addition to dietary changes, lactase substitutesmayalso be helpful. These aredrops or tablets you can take with your meals or drinks to improve your digestionof lactose.

Complications of lactose intolerance

Milk and other dairy products contain calcium, protein andvitamins such as A, B12 and D. Lactose also helps your body absorb a number of other minerals, such as magnesium and zinc. These vitamins and minerals are important for the development of strong, healthy bones.

If you're lactose intolerant, getting the right amount of important vitamins and minerals can prove difficult. This may lead to unhealthy weight loss andput you at increased risk of developing the following conditions:

• Osteopenia where you have a very low bone-mineral density. If osteopenia is not treated, it can develop into osteoporosis.
• Osteoporosis where your bones become thin and weak. If you have osteoporosis, your risk of getting fractures and broken bones is increased.
• Malnutrition when the food you eat doesn't give you the nutrients essential for a healthy functioning body. If you're malnourished, wounds can take longer to heal and you may start to feel tired or depressed.

If you're concerned that dietary restrictions are putting you at risk of complications, you may find it helpful to consult a dietitian. They can advise you on your diet and whether you require food supplements.

Your GP should be able to refer you to an NHS dietitian free of charge. Alternatively, you can contact a private dietician. The British Dietetic Association has information on how to find a private dietitian.

Blood

Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.

Enzymes

Enzymes are proteins that speed up and control chemical reactions, such as digestion, in the body.