BACKGROUND:Hedgerows that were white with ice only a few months ago are now white with hawthorn blossoms, also called the Maythorn. The mild weather has brought the blossoms earlier and in abundance.
A member of the Crataegus genus, hawthorn has a long history of medicinal use. The first-century Greek physician Dioscorides recommended it for heart conditions. In Germany and other countries, a standardised extract of hawthorn leaves and flowers has long been available on prescription for mild heart failure. Called WS 1442, it is found in the most popular hawthorn products.
EVIDENCE FROM STUDIES
Laboratory and animal studies have shown that hawthorn extracts contain several compounds that affect the blood and the heart. Extracts have a high flavonoid content, which gives them potent antioxidant activity. Other compounds have been found to dilate blood vessels, reduce blood pressure, lower cholesterol levels and have other actions that enhance cardiac activity.
A Cochrane systematic review was published in 2008 and concluded that hawthorn extracts were beneficial for chronic heart failure when used in addition to conventional treatments. These conclusions were based on 14 double-blind, randomised controlled trials published in the preceding years.
The patients in these studies had relatively mild symptoms and overall had about a 10 per cent improvement in their ability to tolerate exercise when they added hawthorn extract to their conventional medicines. However, all these studies involved relatively few patients as research subjects and were of short duration.
Since that review, three studies have been published which have cast doubt on the effectiveness and safety of hawthorn for the treatment of heart failure. All three used WS 1442, which was also used in most of the earlier studies examined in the Cochrane review. One of the newer studies, called the SPICE trial, enrolled 2,681 patients with mild to moderate heart failure who were receiving conventional cardiac medications.
After taking hawthorn or placebo for two years, the primary outcome measured showed no significant difference between the groups. The outcome measured here was a combination of features such as time before a cardiac event, heart-related hospitalisation, cardiac death. All of these are clinically objective measurements, unlike the earlier, short-term studies which measured outcomes such as exercise capacity and subjective symptoms. However, one sub-group of patients did have significantly fewer sudden cardiac deaths in the hawthorn group, suggesting that hawthorn may be beneficial for some patients.
PROBLEMATIC ASPECTS
In general, hawthorn causes few side effects. Sometimes dizziness and gastrointestinal problems occur, but tend to be mild and short-lived. Given the evidence that hawthorn can have cardiac effects, it may interfere with other heart medications, but this has not been examined in research. It has been suggested that that patients with heart failure should be carefully monitored if they take hawthorn.
RECOMMENDATIONS
Earlier evidence from smaller, shorter studies suggested that taking hawthorn provides additional benefits for patients with mild to moderate heart failure receiving conventional therapy. More recent and larger studies have raised questions about these early results.
Part of the discrepancy may be because the earlier studies did not closely monitor the other medications patients were taking. The recent studies have done this and suggest that hawthorn may not provide additional benefits. Hawthorn may benefit specific patients, particularly those at higher risk of sudden cardiac death.
Given these recent findings, anyone with concerns about a heart condition should consult a doctor before taking hawthorn. Since almost all the research has been conducted with heart failure patients with mild to moderate symptoms, those with more serious heart problems should not rely on hawthorn.
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.
