How does willow bark act in rheumatic diseases?
In natural medicine willow bark tea has long been a remedy for pain and inflammation. One of the active substances in willow bark is acetylsalicylic acid which is said to be effective in treating rheumatic diseases. Abbreviated as ASA, this substance has been commercially formulated and is better known as Aspirin ®.
The willow (Salix sp.) is a widely used tree species in Europe, Asia and North America. It prefers to grow in moist locations, usually alongside streams and river banks. Since ancient times, people have used the bark as a remedy for a range of aliments. As an antipyretic, it is an effective medicine for reducing pain and inflammation associated with gout and rheumatism.
Botanically, there are about 400 different species of willow. These include small dwarf shrubs through to trees 30 feet tall. The various willow species are distinguished by their leaves, some of which can be very narrow, while others are almost circular.
Typically there are hairs on the undersides of the leaves. Particularly noticeable on most pasture species are their hairy flowers. Willow is very flexible and is often used for braiding into baskets and other objects.
Famous compounds of willow bark
Willow bark (Latin: Salicis cortex) contains several active chemicals from the group of compounds known as salicylalkohols. This compound is the basis for ASPIRIN. Depending on the willow species, the average content of these substances range from 1.5 to 11%. One particular salicylalkohol called salicin plays a major role in pain management.
In the liver it’s converted into salicylic acid. Salicylic acid inhibits specific enzymes (cyclooxygenases, COX 2), which are responsible for the formation of inflammatory prostaglandins1. When present in the body, salicylic acid can offer up to eight hours of pain relief.
Anti-inflammatory and analgesic effects of willow bark extract
Willow bark offers a combination of analgesic, antipyretic and anti-inflammatory effects. These active compounds are just as effective as other COX2 inhibiting painkillers that are commonly used in osteoarthritis pain therapy.
In a cohort study from 2008, researchers investigated the influence of willow bark extract on pain perception in patients with osteoarthritis2.
A total of 90 patients received willow bark extract, 41 more participants were given a standard pain treatment, and eight were treated with a combination therapy. After three to six weeks doctors determined the efficacy and safety of willow bark extract. This included a physical examination of the participants, plus querying the intensity of pain and joint stiffness.
Results revealed that joint symptoms improved significantly. After 6 weeks, the effects of the willow bark extract corresponded with those of a conventional therapy. In addition, the willow bark group suffered no side effects.
The researchers concluded from their results that willow bark extract is well suited in the treatment of mild to moderate osteoarthritis. In addition, willow bark could serve as an alternative treatment for osteoarthritis pain without the side effects of conventional painkillers.
Animal study shows anti-inflammatory effects of willow bark
In a study on rats, willow bark extract protected the cartilage in damaged joints from further inflammatory degradation. The Indian scientists published their results in 2011 on the effect of willow bark extract on inflammatory markers and free radicals in the articular cartilage3. For this study, rats were treated with collagen to trigger an autoimmune response against cartilage tissue.
Rodents treated with willow bark extract showed a strong inflammatory response as inflammation markers were only formed in small amounts. Also, the formation of free radicals as a result of joint inflammation decreased. The scientists showed that willow bark extract is applicable as anti-inflammatories in rheumatic diseases.
Use and side effects of willow bark
The effects of willow bark extract seem not to come only from salicylic acid, but also as a result of polyphenols. These are important phytochemicals that appear to reduce inflammation.
Any observed side effects are generally harmless. In the case of adverse reactions, the negative side effects should stop as soon as the treatment is discontinued.
It’s important to note that while ASA or Aspirin ® has a blood-thinning effect; this is not observed in willow bark. This can be an advantage or disadvantage, depending on the patient.
Any potential cartilage-building effects of willow bark have not been recorded. The extract should therefore be part of a comprehensive approach to supplement the diet.
Tips for buying willow bark extract
The selection of willow bark extract available is not particularly large. Typically, the extract is presented in capsules, coated tablets or powder. Capsules or pills offer better dosing and are more hygienic than powder.
- Kayyal et al., 2005. Mechanisms Involved in the anti-inflammatory effect of a Standardized willow bark extract. Arzneimittelforschung 55 (11), 677-87
- Beer & Wegener., 2008. Willow bark extract (salicis cortex) for gonarthrosis and coxarthrosis-results of a cohort study with a control group. Phytomedicine 15 (11), 907-13; doi: 10.1016/j.phymed.2008.07.010
- Sharma et al., 2011. Amelioration of collagen-induced arthritis by Salix nigra bark extract via suppression of pro-inflammatory cytokines and oxidative stress. Food Chem Toxicol 49 (12), 3395-406; doi: 10.1016/j.fct.2011.08.013