European elder (Sambucus nigra), also known as black elder and elderberry, is thought to be beneficial for the prevention and treatment of influenza and upper respiratory infections, though researchers are still debating which stage of infection it is most effective in and what the exact mechanisms of action are that lend elderberry its anti-viral effects. Sambucus canadensis (American elder) is a fast-growing, deciduous North American shrub with blooms and berries similar to Sambucus nigra. Elder flower extracts are also used to treat colds and flu. Only European elder berries will be discussed in this review.

Torabian et al1 studied the mechanism of action of elderberry and its principal anthocyanin component, cyanidin 3-glucoside, on influenza virus infectivity in an in vitro study published in the Journal of Functional Foods. Pasteurized whole-elderberry extract, as well as the isolated bioactive component cyanidin 3-glucoside, were tested at various doses in the study. The effect of these extracts at various doses on influenza virus activity at various stages of infection was the primary outcome investigated.

Elderberry had an inhibitory effect at all stages of influenza infection, but it was significantly stronger in the late stage than in the early stage; smaller concentrations (higher dilutions) of elderberry had partial or no inhibitory effect in the early phase, but those same concentrations had a significant inhibitory effect in the late phase. Furthermore, elderberry’s antiviral effectiveness against influenza was highest when it was administered before, during, and after infection, rather than just during infection. Elderberry’s antiviral efficacy on influenza is confirmed by a number of methods of action, including reducing virus entrance into cells, modifying the post-infectious phase, and limiting viral transmission to other cells, according to the study. Elderberry also increases the production of IL-6, IL-8, and TNF, suggesting that it has an indirect effect on the body’s viral immunological response. Elderberry, but not its main bioactive ingredient, cyanidin 3-glucoside, was found to have this effect.

Although no human clinical trials on elderberry for influenza prevention have been published, black elderberry extract has previously been found to inhibit human influenza A (H1N1) infection in vitro by binding to H1N1 virions and limiting the viruses’ capacity to infect host cells.

2 Elderberry was found to be effective against 10 strains of influenza virus in the same investigation, and its efficacy was compared favourably to the anti-influenza actions of oseltamivir (Tamiflu) and amantadine.

Torabian et al. released their mechanistic investigation, which was detailed above, almost simultaneously with the first meta-analysis of four randomised controlled trials on the effects of elderberry supplementation on acute upper respiratory symptoms.

3 Three studies (Zakay-Rones 1995,4 2004;5 Tiralongo 20166) looked at the entire length of time that upper respiratory symptoms lasted. Another study, Kong 20097, assessed symptoms across six symptom scales during the course of a 48-hour intervention. In the meta-analysis, 89 people in the elderberry group and 91 people in the control group took part (total 180). Three trials looked at the effects of elderberry treatment on confirmed instances of influenza or patients with symptoms that were consistent with an influenza infection. The effects of elderberry on symptoms associated with the common cold were investigated in the other trial.

Elderberry had a big effect size (ES) of 1.717 (P0.001), indicating that it significantly reduced the duration of upper respiratory symptoms. The efficacy of elderberry supplementation on upper respiratory symptoms was not affected by flu vaccination status, which was controlled for. Although the effect on cold symptoms is still within the criterion for a medium effect, elderberry appears to diminish symptoms caused by influenza virus (ES: 2.074) significantly more effectively than upper respiratory symptoms caused by the common cold (ES: 0.662).

Although the Tiralongo experiment on elderberry’s effect on common cold symptoms in air travellers failed to attain statistical significance, the amount of 90—135 mg of anthocyanins per day was significantly lower than that utilised in the Zackay-Rones studies (1,900 mg daily).

8 Kong utilised a 175 mg extract four times a day for two days in his study. This illustrates the large range of elderberry extracts available commercially.

These findings provide an alternative to using antibiotics to treat upper respiratory symptoms caused by viral infections, as well as a possible safer option to prescription medications for common colds and influenza. Elderberry appears to be most beneficial when administered before and throughout infection, albeit in the early stages of infection, a larger dose may be necessary to achieve considerable anti-viral activity.

*A word on safety: elderberries contain cyanogenic glycosides (such as sambunigrin), which are degraded in the gastrointestinal system to hydrogen cyanide.

9 Poisoning and hospitalisation have occurred in the United States after consuming undercooked elderberry products. 10 Smaller doses of these glycosides do not usually require hospitalisation, although they can cause nausea, vomiting, and diarrhoea in some people, especially youngsters. 11

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