For most people, laxatives are only necessary as a short course to help them manage when some other factor or illness is making them constipated, or to prevent straining when they have a condition such as a hernia or haemorrhoids.

Occasionally, chronic factors interfere with normal bowel movements, such as damage to the nerves in the spinal cord, hypothyroidism or the use of medication that can cause constipation (including painkillers and some antidepressants). For these people, long-term use of laxatives may help.

Constipation is also often a problem in older age as the bowel becomes less efficient at moving contents through. Many elderly people need to take long-term laxatives.

What's important is choosing the right type of laxative, especially if it's being taken for months and months. Some are safer than others.

Risks of laxatives

One of the biggest problems with using certain laxatives long-term is that the body grows used to their effects and normal bowel action becomes dependent on the laxative.

This is especially true of those types that stimulate the bowel to contract and push, such as senna. If laxatives are stopped, the normal mechanism and activity of the bowel can no longer take over.

If used to excess, most laxatives can cause diarrhoea and may disrupt levels of salts in the body, which can be dangerous if extreme.

Risks of suddenly stopping

You may find it difficult to stop taking laxatives suddenly and could run the risk of becoming very constipated. But you're well advised to at least change from senna to a more gentle or natural laxative.

Senna works by stimulating the nerves in the bowel to contract the intestinal muscles and speed up the passage of food through the intestines, allowing less time for the liquid in the food to be reabsorbed back into the body, so keeping the faeces soft.

Many doctors regard senna as an old-fashioned approach to managing constipation and prefer other methods. (However, senna may be useful in old age when the gut seems to lose its ability to contract and push faeces along).

Stop your laxatives slowly and replace their action by other means.

Add bulk to your diet

A better approach is to modify your diet to increase the amount of bulk from plant fibre. Plants contain a combination of two types of fibre - soluble and insoluble. Neither is absorbed into the body but passes through the gut.

Soluble fibre, which contains chemicals known as gums and pectin, dissolves to form a gel that softens the hard motions of constipation.

Insoluble fibre soaks up water as it passes through the intestine (it holds up to 15 times its own weight in water). As it swells, it adds soft volume to faeces, which helps to send signals to the bowel to contract.

Sources of insoluble fibre include:

• Roughage foods, such as fruit and vegetables with skins, husks or peels on
• Cereals such as maize and oats
• Wheat bran (sprinkle on meals or look for cereals containing it)
• Leafy green vegetables
• Wholemeal bread and flour
• Brown rice
• Nuts and some legumes, such as haricot beans

Sources of soluble fibre include:

• Cereals such as oats and barley
• Fruit, especially apples, pears and strawberries
• Vegetables, especially legumes

Also make sure you drink plenty of water - at least three pints a day.

Other types of laxative

If diet alone isn't enough, ask your doctor for advice on other laxatives. There are several types to choose from, including:

• Bulk-forming laxatives - such as those based on a type of soluble fibre called isphagula or cellulose.
• Lactulose - a sugary solution that helps to draw water into the bowel and keep faeces soft. May cause stomach cramps and wind, but can be used long-term.
• Stool softeners - such as docusate, which acts like a detergent to trap dietary fat, then mixes it with the stool to make it softer

Just a final word of warning. Any new change in your bowel habit or the appearance of blood of mucus in the motions should be treated as a warning sign that there may be a problem that needs further investigation. Get advice from your doctor.

This article was last medically reviewed by Dr Trisha Macnair in December 2007