Echinacea, Elderberry, Garlic and Mushrooms for Immunity

Overview

Echinacea, elderberry, garlic and medicinal mushrooms are often sold for "immune support". This page asks what human research shows for colds and respiratory infections, and where the evidence stops. Herb and mushroom profiles live in their own sections: echinacea, elderberry, garlic and mushrooms. Evidence labels: promising but limited, mixed, insufficient evidence, preclinical, or "Proper evidence not found".

The NHS says there is little evidence that supplements such as vitamin C, echinacea or garlic prevent colds or help you get better more quickly. [1]

Summary table

Echinacea

NCCIH says taking echinacea may slightly reduce your chances of catching a cold, and it is unclear whether it can shorten one. [2] The Cochrane review of 24 trials (4,631 participants) could not pool results because products differed so much in species, plant parts and extraction. None of the 12 prevention comparisons reporting colds found a statistically significant difference, though pooling after the fact suggested a 10% to 20% relative risk reduction. Only one of seven treatment trials reporting cold duration showed a significant effect. [6] Because products are so different, a result for one extract does not transfer to another. [6]

Safety. Some people have allergic reactions, which may be severe; the most common side effects are digestive. Some children in a trial developed rashes. There is conflicting evidence about interactions with liver-metabolized drugs, and theoretical reasons to suspect interaction with immunosuppressants. [2] It belongs to a plant family with sunflowers, daisies and ragweed. [2]

Elderberry

NCCIH says a small number of studies evaluated elderberry for colds, flu and other upper respiratory infections, and preliminary research suggests it may relieve symptoms. [3] A 2019 meta-analysis of randomized trials covering only 180 participants reported a large reduction in upper respiratory symptoms. [7] The small total sample means the result should be treated as preliminary. Elderberry has been promoted for COVID-19 but there is no good evidence for it. [3]

Safety. Raw or unripe elderberries and other parts of the elder tree (leaves, stem) contain poisonous cyanide-producing substances that can cause nausea, vomiting and severe diarrhea; cooking removes the toxin. Little is known about use in pregnancy or breastfeeding. [3] See plant and mushroom poisoning.

Garlic

NCCIH notes garlic supplements are promoted as immune boosters during cold and flu season, but very little research exists; a 2022 review found only two studies suggesting possible benefit, both small and weak. [4] The Cochrane review found only one qualifying trial (146 participants, 12 weeks), which reported fewer colds with a garlic supplement, and concluded the evidence is insufficient. [5] Most garlic research is on cholesterol, not infection. [4]

Safety. Supplements may increase bleeding risk, which matters with blood thinners, aspirin or before surgery. Side effects include breath and body odor, abdominal pain, gas and nausea. Fresh raw garlic on the skin can cause burns. [4] See supplements before surgery.

Mushrooms and beta-glucans

Proper evidence not found for medicinal mushrooms preventing or shortening colds in healthy people. What we checked and found:

• Reishi (Ganoderma lucidum). A Cochrane review of five trials in people with cancer found some increases in immune-cell percentages (CD3, CD4, CD8) when reishi was added to treatment, but trial quality was generally unsatisfying, and the authors did not find sufficient evidence to justify it as first-line cancer treatment. [8] That is a different population and outcome from infection prevention in healthy people. Label: insufficient evidence for infection outcomes.
• Turkey tail (Trametes versicolor). A small randomized trial of 24 healthy volunteers found its polysaccharopeptide changed gut microbiome composition. [9] That is a gut bacteria measure, not an infection outcome.
• Beta-glucans. A meta-analysis of 13 trials found yeast beta-glucan reduced upper respiratory infections in healthy people, but the authors warn of high heterogeneity and few studies. [10] This is yeast, not mushroom, beta-glucan, so it should not be assumed to apply to mushroom products.

Lab and animal findings on mushroom compounds are preclinical and are not evidence of fewer infections. Mushroom profile pages: Mushrooms hub, mushroom research and mushroom safety.

Safety and when to get help

Natural does not mean safe: see natural does not mean safe and medication interactions. If you take immunosuppressants, have an autoimmune condition, are pregnant, or have an allergy to daisy-family plants, ask a clinician first. [2] See immunodeficiency and autoimmune conditions and immune safety. If you have a high temperature for more than 3 days, worsening symptoms, or chest pain or breathlessness, do not rely on a herb; seek care. [1]