Does it work?

Can caraway help to ease dyspepsia?

BACKGROUND

Indigestion, heartburn and stomach pain are common ailments that come and go for many. For others, they linger and are chronically problematic. For about one-third of those with lasting symptoms, an underlying cause such as an ulcer or dietary intolerance will be diagnosed. But for the majority of those whose symptoms last three months or longer, medical tests reveal little about the underlying causes. In such cases, the condition is called functional dyspepsia. Numerous factors can be involved, often with several combining to contribute to the problem. In many cases, control of symptoms is the best that can be offered. Various pharmaceuticals are available, but herbs and food supplements are also recommended. One of these is caraway.

The caraway plant looks similar to the above-ground parts of a carrot. Caraway fruits are used in cooking, sometimes (incorrectly) called caraway seeds. They have an anise-like odour and flavour which comes from their oil. Caraway oil is used as a flavouring agent in pharmaceutical products, foods and some liqueurs. The fruits contain 2 to 7 per cent oil, which is the active medicinal agent. Preparations are available containing the plant parts or purified as caraway oil.

EVIDENCE FROM STUDIES

More than half of caraway oil is composed of carvone, also found in spearmint oil. Animal tests have shown that this relaxes the smooth muscle of the digestive tract. Although controlled studies have not been conducted on caraway itself, several studies have examined its effectiveness in combination with peppermint oil. The combination is believed to provide greater relief from dyspepsia and other gastrointestinal ailments.

One product containing caraway oil and peppermint oil was compared in a randomised controlled trial to cisapride. This pharmaceutical has since been taken off the market because of its side effects, but at the time was recommended for dyspepsia. The herbal combination was as effective as cisapride. Several other trials were conducted on the mixture and found it to be effective and safe.

Another combination herbal product called STW 5 or Iberogast contains caraway and peppermint oils, along with seven other herbs. It was first manufactured in Germany more than 40 years ago and has been studied in a few clinical trials. These have consistently shown that Iberogast relieves dyspepsia symptoms better than placebo and with similar effectiveness to pharmaceuticals.

PROBLEMATIC ASPECTS

Very few adverse effects have been reported for Iberogast. Ironically, caraway oil can cause a burning sensation in the chest, belching and nausea – the very symptoms it is recommended to treat. Some preliminary evidence exists that caraway might reduce blood sugar levels. People with diabetes should monitor their blood sugar levels carefully when using caraway. Concerns have been expressed that caraway might affect uterine smooth muscle and cause problems during pregnancy.

RECOMMENDATIONS

Functional dyspepsia is a complex condition, probably involving several different causes. Dietary and other lifestyle factors should be considered as ways to relieve symptoms. While pharmaceuticals are available which target the mechanisms underlying each symptom, Iberogast represents an alternative strategy. Each herb in this product has been demonstrated to impact a different contributory factor to the symptoms. The manufacturers have also taken the time to have the product’s effectiveness and safety tested.

Although direct comparisons with conventional treatments have been conducted infrequently, the evidence favours the use of Iberogast for functional dyspepsia. Caraway oil probably contributes to this effectiveness, especially in combination with peppermint oil, but no trials have been published on caraway’s use alone for dyspepsia.

Dónal OMathúna 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