DOES IT WORK?Senna and constipation
SENNA IS a herbal remedy whose popularity has not faded like some other herbs. It remains one of the more commonly used laxatives. A recent survey found that about one-in-three people in Ireland report being constipated occasionally or regularly.
The normal frequency of bowel movements varies considerably. When someone's usual frequency decreases, the symptoms of constipation can range from bloating and cramps, to headaches, tiredness and irritability.
The senna shrub (cassia senna) has long been used in traditional medicine in the Middle East and Africa. Some cultures have used it to eliminate intestinal worms, alleviate indigestion or haemorrhoids. Today, it is mostly used for constipation and to clear the bowels prior to surgery. Senna is regarded as more potent than another natural laxative, cascara sagrada.
Senna is often included in multi-herb products used for intestinal cramps or for dieting. However, the use of laxatives for weight loss is highly questionable and can be dangerous.
Evidence from studies
The leaves and fruit of senna contain compounds called anthraquinones. These occur in the plant in an inactive form. When they reach the intestines, bacteria act on them to release the active form which stimulates the intestines to contract more frequently.
The activated anthraquinones also cause electrolytes and water to be secreted into the intestines. All of these actions together facilitate bowel movements.
However, because the drugs have to travel through the stomach before being activated, the laxative effect may not be experienced until eight to 10 hours after taking senna. Additional tablets should not be taken during this time.
A number of randomised controlled trials have been conducted using senna. These have found that it is an effective, relatively safe laxative when used occasionally for constipation. A few studies have compared senna with other natural and manufactured laxatives, and found them similarly effective. Senna tends to be less expensive.
Problematic aspects
Occasional, short-term use of senna is not problematic for most people. A small number of people react badly to the remedy, worsening their abdominal discomfort. Senna should not be used by anyone with serious gastrointestinal problems or haemorrhoids.
Ongoing use of any laxative can lead to serious problems and this is the biggest danger with senna. Excessive use can cause dehydration and loss of electrolytes. This can lead to serious heart, liver, muscular and other problems.
Continuous use of laxatives can lead to a worsening of the original constipation. Laxatives should not be used as a way to lose weight because of these adverse effects.
Recommendations
Senna is an effective and relatively safe laxative when used occasionally. The usual recommendation is to take it for no more than seven days in a row.
When using senna, or any laxative, other factors influencing digestion should be addressed at the same time. A balanced diet rich in fibre should be consumed. Foods rich in fibre include wholegrain cereals and breads, potatoes with their skins, porridge, wholemeal pasta and brown rice.
Five or more portions of fruit and vegetable should be eaten each day. Adequate fluids should be consumed (1.5 to 2 litres per day). Digestion is also affected by exercise and stress. Therefore, getting the recommended 30 minutes of daily activity and finding enjoyable leisure activities will also help to keep everything regular.
If needed, senna will help to get things moving again, but the key to healthy digestion requires addressing all these lifestyle factors.
Dónal O'Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University