Elderberry for colds and flu: what the reviews missed, and what a later trial found

A bottle of elderberry syrup makes two promises easy to blur together: don’t get sick, and get better sooner if you do. The evidence doesn’t support the first promise. There’s a tentative signal for the second in older small trials, but a later trial in people with confirmed flu didn’t find a benefit. That’s a less catchy answer than the label might suggest, and a more useful one. Wieland et al., 2021; Macknin et al., 2020.

First, the prevention question

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One trial followed 312 air travelers taking an elderberry preparation or placebo. A defined cold developed in 12 of 154 people in the elderberry group and 17 of 158 in the placebo group. That difference wasn’t clear enough to establish prevention. The numbers point in a favorable direction, sure, but the uncertainty is wide enough to include no effect. Wieland et al., 2021.

Among the 29 travelers who did catch a cold, the elderberry group had a shorter-duration signal. It’s tempting to turn that into “elderberry saves two days.” Don’t. This was a small subset of an already modest trial, and the review rated the estimate very low certainty. Besides, a possible change in how long a cold lasts isn’t evidence that you won’t catch one in the first place. Wieland et al., 2021.

People have used elderberry for respiratory complaints for a long time. That’s part of why it’s familiar in the cold aisle, not proof that taking a syrup prevents flu. Lab work on elderberry compounds is interesting too (including influenza experiments), but a result in a dish can’t tell you whether a retail product changes the course of an infection in a person. NCCIH; Wieland et al., 2021.

Why the flu headlines sound more confident than the evidence

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A 2019 meta-analysis pooled treatment-related upper-respiratory symptoms from studies totaling 180 participants and reported a benefit. That’s the attractive headline. Yet pooling small studies doesn’t make their limitations disappear - particularly when the studies don’t measure exactly the same thing.

A 2021 systematic review took a harder look at trial quality. It included five respiratory prevention or treatment trials in its evidence set (not five clean tests of elderberry alone for flu). The authors graded the apparent elderberry-versus-placebo benefits as low or very-low certainty. Two older placebo-controlled influenza studies suggested faster improvement, but their estimates differed substantially from each other. I’d read that as a reason to run better trials, not as a promise that a sick person can bank on a particular number of days saved.

There’s also a timing snag. The 2021 review’s literature search closed before a relevant trial was published; publication years alone make it look as if the review must have considered everything available in 2020. It hadn’t. In the later-published randomized trial, 87 people with PCR-confirmed influenza received elderberry or placebo. Time until symptoms were none or mild averaged 5.3 days with elderberry and 4.9 days with placebo; complete resolution averaged 8.6 versus 8.7 days. Neither comparison showed a detected benefit. One small null trial can’t settle every possible formulation or patient group, but it belongs in any honest account of the older positive results. Wieland et al., 2021; Macknin et al., 2020.

And no, a study of an echinacea-plus-elderberry hot drink compared with oseltamivir doesn’t establish that elderberry alone works as well as a prescription antiviral. You can’t isolate elderberry’s effect from that combination. Wieland et al., 2021.

What the product on the shelf changes

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Even if a trial of one elderberry extract looked promising, would it tell you much about the gummy in your hand? Maybe not. Preparations, ingredients and study schedules differed; a combination product isn’t the same as a single-ingredient syrup. There’s no well-supported, universal elderberry dose to carry from these trials to every bottle. Check the full ingredient list rather than treating “elderberry” as a standardized product name. Wieland et al., 2021.

The FDA doesn’t approve dietary supplements for safety and effectiveness before they’re sold, though manufacturers do have applicable requirements. A quality seal or reassuring label isn’t evidence that a product prevents a cold or treats flu. So if you’re comparing products, start with what is actually in them - and don’t mistake a marketed claim for a clinical result. FDA supplement Q&A.

The safety details are less optional than the sales pitch

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The berries in a prepared supplement and the raw plant aren’t interchangeable. Raw or unripe elderberries, as well as leaves and stems, contain substances that can produce cyanide; eating them can cause nausea, vomiting and severe diarrhea. NCCIH says cooking eliminates the toxin, but that’s not a tested recipe for a foraged or homemade remedy. Don’t eat raw berries or other elder-tree parts, and don’t assume that a homemade preparation matches the product used in a clinical trial.

For pregnancy or breastfeeding, the problem is missing safety evidence, not demonstrated harm. NCCIH says little is known about using elderberry for health purposes in these circumstances; an older review of pregnancy evidence found no relevant elderberry safety studies through its search. Ask your clinician before taking a supplement rather than treating “natural” as a safety assessment. And if you take medicines, ask a clinician or pharmacist about the full product - NCCIH advises checking for herb-drug interactions, but the sources here don’t establish a particular elderberry-drug interaction. NCCIH.

Short trials reporting few serious problems don’t prove that regular use is harmless; adverse effects weren’t consistently monitored. For a child, or if you have a chronic condition or are immunocompromised, don’t extrapolate from these limited adult-focused findings. Get individualized advice instead. Wieland et al., 2021; NCCIH; CDC flu symptoms and risk groups.

If it might be flu, don’t wait on a syrup

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Flu care has a clock on it. The CDC recommends prompt medical advice when flu is suspected in someone at higher risk of complications (including pregnant people, older adults, young children and people with certain chronic illnesses), or when symptoms are severe or getting worse. Prescription antivirals work best when started early; an elderberry experiment shouldn’t delay an assessment or a prescribed treatment. Vaccination remains a flu prevention measure, not something elderberry has been shown to replace.

Trouble breathing, chest pain or pressure, confusion, dehydration or not urinating, or symptoms that improve and then worsen warrant urgent assessment. The CDC’s symptom and warning-sign guidance has separate adult and child details. A supplement’s apparent effect can’t tell you whether you have flu, COVID-19 or another illness; NCCIH says there’s no good evidence for using elderberry against COVID-19. NCCIH.

Bottom line

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If you’re an adult weighing elderberry for a cold, the clearest answer is that it hasn’t been shown to prevent one. An uncertain symptom-duration signal is worth studying, not promising. For flu, older favorable trials sit beside a later null trial in patients with confirmed infection. I wouldn’t count on an elderberry product to change the outcome - especially when getting timely care matters more. Wieland et al., 2021; Macknin et al., 2020; CDC flu treatment.