The common cold is usually a minor illness that is self-limiting. It resolves in a week or so with or without treatment. Unless you are chronically ill or debilitated, it is unlikely to have serious consequences; but it can cause plenty of misery and days lost from work. Science has made great progress in other areas, but it has found no cure for the common cold. Antibiotics are useless. For prevention, the best science can offer is handwashing. There are medications that can provide some temporary relief from symptoms like fever, congestion, runny nose, and cough, but they do nothing to shorten the duration of the illness.
In desperation, many people have resorted to herbal remedies, folk remedies, and supplements like zinc, Vitamin C, and Echinacea. These supplements have all been studied, with inconsistent results that have not verified their effectiveness. Zinc may shorten the duration of a cold by a day, but it can cause permanent loss of smell and the appropriate dosage and schedule have not been established. Linus Pauling advocated large doses of Vitamin C, but the results of controlled studies have been disappointing. Studies of Echinacea have shown little or no benefit. But there’s another dietary supplement that is supported by more convincing evidence: preparations of flowers and berries from the black elder tree. Elderberry remedies have been used for centuries and are popular in Europe. Various formulations of black elderberry extract are marketed under the brand name Sambucol. They include syrups, gummies, pills, chewable pills, pediatric, and homeopathic (!) versions. They advertise that it provides strong immune system support and is safe to take every day.
Black elderberry is a nutritious fruit with high concentrations of anthocyanins; it has twice as much antioxidant capacity as blueberries and significantly more than cranberries. A multitude of beneficial health effects have been claimed for it since the time of Hippocrates, who reportedly called it a medicine chest. Sambucol carries the usual FDA disclaimer that it is not intended to diagnose, treat, cure, or prevent any disease; but it is commonly used for prevention and treatment of colds and flu. There is speculation about why it might work, but the mechanism of action is not actually known.
Placebo-controlled studies
In contrast to many supplements on the market, there are studies that used the same brand, Sambucol; and randomized, placebo-controlled, double blind studies have been done.
Sambucol was tested in a placebo-controlled double blind study during an outbreak of influenza in a kibbutz in Israel. Hemagglutination inhibition titers to influenza B were higher in the treatment group, and there was significantly more symptom improvement in the treatment group than in the controls (93.3% significantly improved in 2 days compared to 91.7% in 6 days).
In a randomized, double-blind, placebo-controlled study in Norway, 60 patients with influenza-like symptoms were given an elderberry extract or a placebo; self-rating of symptoms indicated that symptoms were relieved 4 days earlier in those taking elderberry.
In 2016 in Australia, a randomized, double blind placebo-controlled study found that elderberry reduced cold duration and symptoms in air travelers. They recruited 325 volunteers who were planning an overseas trip with a minimum 7-hour flight. Subjects were randomized to receive either a standardized elderberry extract (Iprona, a brand from Italy) or a placebo. They were instructed to take the pills from 10 days before flying to 5 days after arriving at their destination. Symptoms were self-reported in a diary, with subjects recording each day whether they believed they had a cold or were experiencing rhinorrhea. An exit poll asked participants to guess whether they were in the elderberry or the placebo group; it confirmed the success of blinding. Elderberry did nothing to prevent colds, but those in the elderberry group reported a 2-day shorter duration of the cold (4.75 days vs. 6.88 days) and lower symptom severity (21 vs 34).
Other studies and reviews
A standardized elderberry extract (Rubini) inhibited bacteria and influenza virus in an in vitro study.
A 2014 review found “no animal- or human studies of safety of elderberry in pregnancy” and advised pregnant women not to use it.
A 2019 article in The Medical Letter concluded, “There is no acceptable evidence to date that elderberry is effective for prevention or treatment of influenza and its safety is unclear”.
A 2017 review evaluated the state of current research. They found evidence that elderberry extract has antiviral and antimicrobial properties but said that a lack of studies made clinical recommendations impractical.
Adverse effects
While standardized elderberry extracts are generally recognized as safe (GRAS) by the FDA, homemade preparations may be poisonous. The commercial preparations have not been tested in long-term studies or in pregnancy, and precautions are advised. Prolonged use (more than 12 weeks) or use during pregnancy and breastfeeding are not advised; and patients with autoimmune diseases are advised to avoid elderberry because stimulating the immune system might be expected to make symptoms worse.
Prospective customers may be discouraged by a recent report of acute pancreatitis attributed to Sambucol. The report didn’t mention whether he still had cold symptoms. It seems to me a cold would be preferable to pancreatitis.
What is missing?
We still lack a really good study. I’d like to see one that not only uses the same product and is large, randomized, double-blind, and placebo-controlled; but that relies on objective diagnosis rather than self-reporting of symptoms, and one that recruits the typical purchasers of Sambucol and tests the product as actually used in practice.
Conclusion: Promising, but questions remain
The research on elderberry for colds and flu is promising, but better evidence is needed. Surely there are compounds in elderberry extract that are not needed and could even be harmful. We need to know more about the mechanism of action and the possibility of pancreatitis. We need to know more about safety in pregnancy and breastfeeding and with long-term use. We need to know which products are the best standardized, with accurate labeling and absence of contaminants. The best-case scenario would be isolation of the active ingredient or ingredients and scientific development of a specific drug with good enough evidence to gain FDA approval. Meanwhile, since there is no cure for the common cold, elderberry might be worth trying…if you’re not worried about the possibility of pancreatitis.