What is elderberry — and can it really help fight viruses?

Among the plethora of natural wellness products out there, elderberry in particular has generated a ton of buzz on social media. People have long relied on it as a cold and flu remedy, and now some claim it can fight COVID-19. An analysis by market research company IRI found that elderberry supplement sales in the first week of March skyrocketed 415% compared to same time in 2019, the New York Times reports. But can elderberry really treat the cold, flu, or coronavirus?

First, a mini-medical ethnobotany lesson: Elderberry is an umbrella term for varieties of the flowering Sambucus tree, the most common being Sambucus nigra, or black elderberry. Its use as a health remedy dates at least as far back as the time of Hippocrates, per the New York Times. Today, brands sell the berries in everything from capsules and syrups, to tinctures and teas. Raw and unripe berries, as well as the stems, and leaves, and other parts of the plant harbor a toxic substance that can trigger severe diarrhea, nausea and vomiting if you don't prepare them properly, according to the National Center for Complementary and Integrative health. The National Library of Medicine notes that cooked berries don't pose this danger.

Some even go so far as to call elderberry an antiviral, but we can't make that claim with certainty in the absence of rigorous, controlled studies that actually demonstrate this ability.

Elderberry supplements are often marketed as immune enhancing, David Cennimo, an infectious disease specialist and assistant professor at Rutgers New Jersey Medical School, tells Mic. This could explain elderberry’s purported cold- and flu-fighting properties. But as far as scientific evidence, “I haven’t seen anything showing that shows it increases immune activity,” he says.

Still, people who tout the herbal supplement cling to the minimal positive findings that do exist. Some even go so far as to call it an antiviral, but we can't make that claim with certainty in the absence of rigorous, controlled studies that actually demonstrate this ability. For example, A study of 312 air travelers found that cold symptoms didn’t last as long among those who took elderberry syrup as they did in those who took a placebo, per the Cleveland Clinic’s blog, Health Essentials. The sample size was small, though, Irina Todorov, an integrative medicine physician at Cleveland Clinic, told the blog, which prevents us from drawing definitive conclusions from it.

Proponents of elderberry as a flu remedy also theorize that it prevents the flu virus from binding to target cells, Cennimo says. But he notes that most data on this proposed mechanism comes from lab studies, which “can show plausibility, but not guaranteed efficacy.” One recent review of previously-published studies cited some clinical trials, but he points out that they were small and didn’t demonstrate many benefits.

Ideally, elderberry would be tested in a large clinical trial like any other drug, comparing two groups of, say, 500 people, matched across characteristics, Cennimo says. One group would take elderberry, and the other wouldn’t. “Without studies like that, it’s hard to understand if it’s effective.” When there isn't a control group, we can't rule out whether exercise, a healthy diet, or other factors might also explain the results.

The theories used to support elderberry as a cold and flu remedy don’t really back its use as a COVID-19 treatment, Cennimo tells Mic. In fact, its purported immune-enhancing properties may even backfire against the disease. Since people with weakened immune systems have a higher risk of not only novel coronavirus infection, but COVID-19-related complications, it seems logical to assume that taking elderberry would reduce your risk of infection and boost the chances that your immune system will fight off the infection if you do get one.

But Cennimo notes that there’s growing data on patients who seem to have an exaggerated immune response to infection with the virus, a phenomenon known as cytokine release syndrome. In these patients, the New York Times explains, the immune system continues attacking the virus way after it ceases to present a risk and keeps pumping out molecules called cytokines that send signals to mount a response. In fighting a nonexistent threat, the cytokines damage various organs and may ultimately kill the patient. So if you have cytokine release syndrome in particular, you'll want to avoid elderberry.

That’s why studies have begun to investigate immune modulators, like tocilizumab, for critically ill people in the midst of this storm as a means to dial back their immune response, he says. Likewise, it seems that patients in ongoing studies who get steroids — broad-acting immune suppression agents — early in the course of infection may fare worse, since these drugs could dampen the immune response too much. But they might help later, when it’s on overdrive. If these dynamics really are at play, “could strengthening your immune system with elderberry actually hurt you in the end?” Cennimo wonders.

“Take if it makes you happy, and don’t lose sleep over it either way.”

Cennimo hasn’t seen any evidence to back the theory that elderberry blocks virus-target cell binding for SARS-type viruses like the novel coronavirus. Plus, “the receptors are completely different, so I doubt it would be accurate anyway,” he says.

Overall, he believes elderberry is “unlikely to have such a significant immune effect that it would be beneficial or detrimental.” In other words, it probably won’t help you, but it’s not likely hurt you, either. “Take if it makes you happy, and don’t lose sleep over it either way.”

Of course, elderberry is not a substitute for the flu shot, Health Essentials points out. By the same token, it doesn’t remove the need for social distancing, hand-washing, or other measures known to prevent COVID-19, Cennimo says. Whether or not you’re taking elderberry, if you feel ill and your symptoms are progressing, you still need to seek medical attention (but call your doctor beforehand, rather than sauntering in and risking exposing others, CNN recommends). If you want to try to this folk remedy, have at it, but don’t neglect to take steps that’ve been proven to keep you from getting sick.