DOES IT WORK?Elderberry and the flu
ELDERBERRIES ARE the fruit of several different elder shrubs from the Sambucus genus. Ripe elderberries have been used for centuries in cooking and to makes juices and elderberry wine.
Herbal remedies have traditionally been made from extracts of the flowers. These remedies were most commonly recommended as diuretics and laxatives. Many other uses have been reported, ranging from the treatment of measles, diabetes, cancer and toothaches to repelling insects.
More recently, however, the berries have been used, extracted and recommended for the treatment of the flu and other viral infections. The European elderberry, Sambucus nigra, is the species most commonly used for this remedy. A syrup made from this extract contains a component called sambucol which has antiviral activity.
Evidence from studies
A number of laboratory studies have shown that sambucol is active against a number of different strains of the flu virus.
A recent study used serum from healthy volunteers to examine the extract’s effect on the immune system.
Sambucol stimulated the immune system to a greater degree than other immunostimulants commonly used for these comparisons. Other tests found that the extract also has good antioxidant properties, but this is probably unrelated to its effects on viruses. While the laboratory studies are promising, controlled studies in humans are needed to determine how well the remedy might work and if it is safe.
The Israeli company which developed Sambucol syrup has sponsored two controlled clinical trials in patients with influenza A or B. Both were relatively small studies, with fewer than 30 participants in one and 60 in the other. Patients were given either Sambucol or placebo syrup within 48 hours of developing flu symptoms.
Most of those receiving the elderberry syrup had significant improvements in their symptoms within two-three days. Among those taking the placebo syrup, very few showed early improvements and their symptoms generally lasted seven-eight days, which is commonly how long flu symptoms last without any treatment. On average, the flu symptoms lasted about half as long in those taking sambucol compared with those taking the placebo.
Problematic aspects
Adverse effects have not been reported in the studies published on elderberry syrup. Unripe berries and other parts of the shrub can cause nausea, vomiting or diarrhoea. The plant contains compounds which can release cyanide in the body. While large quantities would need to be consumed to cause harm, no part of the plant should be consumed other than the ripe berries. Some species of the elder shrub are more toxic than others.
Children in some countries have used the hollow stems of elder shrubs as peashooters and developed symptoms of cyanide poisoning. These concerns apply to the raw plant material, not extracts made from elderberries.
Recommendations
While very little research has been published on elderberry extracts, what is available suggests that sambucol syrup helps to relieve flu symptoms.
Given the recognition that antibiotics are of little value against viral infections and should not be used to treat the flu, sambucol may be beneficial for some people with influenza.
Sambucol syrup appears to work via both direct antiviral activity and by stimulating the body’s immune system. Whether or not other elderberry extracts have the same activity remains to be seen.
In both of the studies using sambucol syrup, patients took one tablespoonful four times a day for five days. Studies have not been published on whether or not this is the optimal dose.
The studies have been conducted for only one week, so the long-term effects of taking the syrup are not known. If the flu symptoms do not improve after a week, or if the person is weakened by other illnesses or conditions, a visit to the GP is in order.
- 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