White willow bark is harvested from the dried bark of young branches or twigs of the trees, usually in early spring or autumn. It belongs to the willow family1. Historical records show that white willow bark has been used for thousands of years in ancient China, Egypt, Greece and South Asia, to relieve headaches, reduce fever, lessen muscle ache and pain and to support various other illnesses.2 Indeed, anecdotal accounts of willow bark extract being used as a medicine have occurred since written records began, in the time of Hippocrates (400BC) when physicians advised their patients to chew the bark to reduce fever and inflammation.3
Today, white willow bark is used widely for a range of health conditions due to its anti-inflammatory, antipyretic and analgesic properties, which are associated, at least in part, with its salicin content. Yet, willow bark has also been shown to have at least eleven other related salicylate compounds, which are all thought to contribute to its beneficial properties.9
Salicylic acid and aspirin
Chemically, the bark contains polyphenols, and notably salicylic glycosides, of which salicin is of particular interest, given that pharmacokinetically, when digested, the pharmacologically active salicylic acid is formed4.
Many people believe that Willow was the original source of aspirin, however it was actually another plant, Meadowsweet – once called Spiraea ulmaria – that formed the original basis for the drug, with its salicylic acid – at that time, called spiric acid – having an acetyl group added to it, to synthesize Aspirin as we know it today; acetylsalicylic acid5.
Whole extract benefit of white willow bark
Whilst until recent years, salicylic acid was considered to be the main active principle in white willow bark, modern lab analysis informs us that the salicin and salicin-related content of willow bark cannot fully explain its clinical efficacy, especially given that white willow only contains a low level of salicin11. Comprehensive analysis of white willow has identified the presence of several other compounds, including flavonoids and polyphenols such as catechin and ampelopsin, which are known to possess high antioxidant and free radical scavenging activity. These other constituents may exhibit antioxidant, antiseptic and immune-enhancing properties.9
White willow bark evidence overview
Whilst having a long history of use for health, relatively few human and animal studies have been published that confirm anecdotal observations. A small number of clinical studies have been conducted that support the use of willow bark extracts in chronic lower back and joint pain and osteoarthritis. Willow bark extracts also are widely used in sports performance and weight loss products presumably because of anti-inflammatory and analgesic activities, although no human studies have been published that specifically and directly document beneficial effects10.
White willow bark shown to be effective at reducing osteoarthritis pain
Oral analgesic medication, especially non-steroidal anti-inflammatory drugs (NSAIDS) are commonly prescribed for the treatment of pain. While the analgesic, anti-inflammatory and antipyretic properties of NSAIDs are well documented, so are the potential adverse side effects of long-term use such as gastrointestinal toxicities, cardiovascular risks, renal injuries, and hepatotoxicity as well as hypertension and other minor disorders10.
Several studies show that willow is more effective at reducing pain from osteoarthritis than placebo. In a small study of people with osteoarthritis of the neck or lower back, those who received willow bark experienced significant improvement in symptoms compared to those who received placebo. A similar study of 78 people hospitalized with osteoarthritis of the knee or hip joint found that people who received willow bark had significant pain relief compared to those who received placebo12.
Delayed onset muscle soreness, post resistance training
A recent US pilot study looked into the effect of white willow bark for delayed onset muscle soreness, following resistance training. The basis for this study was to assess the anti-inflammatory and analgesic properties and effectiveness of an agent similar to aspirin, but without the adverse gastrointestinal effects associated with said medication, and on healthy college-age adults without medical diagnoses such as arthritis, and rheumatic pain. A double blind, placebo controlled RCT of 25 participants showed that white willow bark decreased subjective pain and soreness more than the placebo group. A pronounced lower rating in muscle discomfort and soreness was also reported 24-72 hours following exercise in the group taking the willow bark16.
Rheumatoid arthritis and white willow bark
Whilst having a strong tradition as an antirheumatic, there has been little recent clinical research on its use for rheumatoid arthritis. A small-scale study showed that daily use of willow extract for six weeks resulted in a mean reduction of pain by 15%, in comparison to 4% in the placebo group14. However there remains a strong specific traditional indication of using the herb for rheumatoid arthritis13.
No human trials have been located, assessing the antipyretic, fever-reducing actions of white willow bark, however one animal trial noted a significant reduction in temperature six hours after administration of a willow bark extract, compared with the control group, attributing the antipyretic effect to the salicin content, which is metabolically transformed in the body into an antipyretic agent15.
White willow bark safety
It is relatively well-know that aspirin has antiplatelet properties6 which is due to the presence of the acetyl group, but salicylic acid itself lacks the antiplatelet action, and therefore white willow bark in its whole form is not considered to pose an antiplatelet risk4. Consequently, this also means that white willow is not a substitute for the cardiovascular uses of aspirin4. However, many sources still advise caution when using aspirin and willow bark concomitantly, stating it may potentiate the effect of anticoagulant medication6.
- Salicylate allergy: Those with an allergy or hypersensitivity to salicylates should avoid the use of willow bark6.
- Aspirin allergy: Those with an allergy to Aspirin should avoid the use of willow bark6.
- Pregnancy: Willow bark should be avoided in pregnancy7.
- Breastfeeding: Willow bark is strongly discouraged during breastfeeding8.
- Gastrointestinal sensitivity: Due to the presence of tannins, there is some risk of gastrointestinal irritation for those with constipation and iron deficiency anaemia13.
References available upon request
If you have questions regarding the topics that have been raised, or any other health matters, please do contact our team of Nutritional Therapists.
Last updated on 29th June 2023 by cytoffice