Boswellia: what it is and how it works

Boswellia is the resin of the Boswellia serrata tree, also known as Indian frankincense. For centuries it was used in Ayurveda, and today standardized boswellia extracts are sold as supplements for joints and ligaments. The editorial team looked into what this resin is made of, how its active compounds work and how convincing the scientific evidence is.

What boswellia is

Indian frankincense (Boswellia serrata) is a deciduous tree of the Burseraceae family that grows in the dry mountainous regions of India and Pakistan. When its bark is cut, an aromatic sap is released that hardens in the air into light yellowish lumps. It is this oleo-gum-resin that is called Indian frankincense, or salai guggul, and it is the raw material for supplements.

Related species -Boswellia sacraandBoswellia carteriifrom the Arabian Peninsula and Africa - yield classic frankincense used in religious rituals. In sports nutrition and phytotherapy the Indian species is used most often, since it has the most accumulated clinical data and standardized extracts have been developed for it.

Raw resin consists of three main parts: an essential oil responsible for the aroma, a polysaccharide gum and a resin fraction. The pharmacological interest lies precisely in the resin part - it contains pentacyclic triterpenes, among which boswellic acids are considered the most important.

In Ayurvedic medicine the resin was used for joint pain, cough, skin diseases and digestive disorders. Modern science has focused primarily on its anti-inflammatory potential: since the late 1980s German and Indian researchers began to systematically study which molecular targets the resin's components act on.

For the consumer it is important to distinguish raw resin from a standardized extract. Raw resin has an unpredictable composition, whereas a manufacturer standardizes an extract by its content of boswellic acids - often at 65% and above - or separately by the content of the most active of them, AKBA.

Active compounds: boswellic acids

The six main boswellic acids are the most studied: α- and β-boswellic acids, their acetylated forms, as well as 11-keto-β-boswellic acid (KBA) and 3-O-acetyl-11-keto-β-boswellic acid (AKBA). It is the keto forms, and AKBA above all, that show the strongest biological activity in experiments.

The problem is that natural resin contains little AKBA - usually a few percent of the total amount of boswellic acids. That is why some modern patented extracts (for example, 5-Loxin and Aflapin) are specially enriched with AKBA to 20-30% in order to increase the pharmacological effect per unit of mass.

It should be remembered that boswellic acids are poorly absorbed from the intestine. Pharmacokinetic studies have shown that concentrations of KBA and especially AKBA in human plasma remain low, while β-boswellic acid reaches higher levels. This partly explains why in vitro results are not always transferable to humans.

Besides the acids, the resin contains other triterpenes and polysaccharides whose contribution to the overall effect is studied much less. Therefore some researchers believe that the action of the whole extract is not reduced to AKBA alone, and the choice between "full spectrum" and enriched forms is still under discussion.

Mechanism of action: how boswellia affects inflammation

The main target of boswellic acids is considered to be the enzyme 5-lipoxygenase (5-LOX). It initiates the synthesis of leukotrienes - lipid mediators that attract leukocytes to the site of inflammation, increase vascular permeability and sustain pain. Unlike classic NSAIDs, which block cyclooxygenases, AKBA acts on a different "branch" of arachidonic acid metabolism.

Interestingly, AKBA does not compete with the substrate at the enzyme's active site but binds to a separate regulatory region. This allosteric mechanism was described in the reviews by Ammon (2006) and Poeckel and Werz (2006). It was this feature that at one time made boswellia an attractive model for the development of new anti-inflammatory agents.

Later work showed that the list of targets is broader. In experiments boswellic acids affected the NF-κB signaling pathway, reduced the production of pro-inflammatory cytokines, inhibited the activity of leukocyte elastase and of the matrix metalloproteinases that destroy cartilage tissue. However, most of these data were obtained in cell cultures or in animals.

An important caveat: the concentrations at which boswellic acids inhibit enzymes in vitro often exceed those actually achieved in human blood. Therefore the editorial team advises treating marketing claims about "blocking inflammation" with caution - the clinical effect, if it exists, is moderate and develops gradually.

What clinical studies show

The most clinical data concern osteoarthritis of the knee. In the randomized double-blind study by Kimmatkar and colleagues (2003), patients who received boswellia extract reported reduced pain and swelling and increased range of motion compared with placebo. The study was small but became one of the frequently cited works.

Sengupta and colleagues (2008) tested the AKBA-enriched extract 5-Loxin in a 90-day study and also recorded improvement on the WOMAC index and, in the synovial fluid, a reduction in the level of matrix metalloproteinase-3. The systematic review and meta-analysis by Yu and colleagues (2020) concluded that boswellia and its extracts may reduce pain and stiffness in osteoarthritis, although the quality of the studies is uneven.

Besides joints, boswellia has been studied in bronchial asthma, inflammatory bowel diseases and brain edema after irradiation. For example, in Crohn's disease the H15 extract was compared with mesalazine (Gerhardt et al., 2001). The results are interesting but not convincing enough to replace standard therapy.

• Best evidence:osteoarthritis of the knee - reduction of pain and stiffness.
• Moderate data:inflammatory bowel diseases, bronchial asthma.
• Minimal data:sports injuries, recovery after training, gains in strength indicators.

For athletes the key point is that there are very few direct studies on healthy trained people. Thus, conclusions about benefits for recovery are so far extrapolated from osteoarthritis studies, and they should be treated as a hypothesis.

Safety and the place of boswellia in the diet

In clinical studies lasting up to several months, boswellia extracts were generally well tolerated. Mild gastrointestinal symptoms are most often described: heartburn, nausea, diarrhea. Allergic reactions also occur, and the literature describes isolated cases of liver injury associated with supplements containing boswellia.

The bioavailability of boswellic acids depends substantially on food: in the study by Sterk and colleagues (2004), taking the extract together with fatty food noticeably increased the acid concentrations in plasma. This is worth considering when choosing the time of administration.

Data on safety during pregnancy and breastfeeding are insufficient. There are also laboratory data on the effect of the resin's components on cytochrome P450 enzymes, so people taking drugs with a narrow therapeutic window should discuss the supplement with a doctor.

Boswellia is not on the WADA Prohibited List and is not a doping agent. However, as with any supplement, athletes undergoing doping control would be wise to choose products with independent certification in order to minimize the risk of contamination.

Editorial conclusions

Boswellia is the resin of the Indian frankincense tree, whose active components, the boswellic acids, inhibit 5-lipoxygenase and other links of the inflammatory response. This mechanism differs from the action of ordinary painkillers.

The most convincing clinical data concern osteoarthritis of the knee, where standardized extracts moderately reduce pain and stiffness. For sports recovery and injury prevention there is still little evidence.

The effect depends on the quality of the extract, the AKBA content and bioavailability, so the choice of product matters. The supplement is generally well tolerated but is not free of side effects and interactions.

If the topic interests you, the editorial team also recommends reading our materials "The benefits of Boswellia for athletes: the evidence base", "Side effects of Boswellia" and "Boswellia: dosage forms and which to choose".

References

1. Ammon HPT. Boswellic acids in chronic inflammatory diseases. Planta Med. 2006;72(12):1100–1116.
2. Poeckel D, Werz O. Boswellic acids: biological actions and molecular targets. Curr Med Chem. 2006;13(28):3359–3369.
3. Siddiqui MZ. Boswellia serrata, a potential antiinflammatory agent: an overview. Indian J Pharm Sci. 2011;73(3):255–261.
4. Kimmatkar N, Thawani V, Hingorani L, Khiyani R. Efficacy and tolerability of Boswellia serrata extract in treatment of osteoarthritis of knee – a randomized double blind placebo controlled trial. Phytomedicine. 2003;10(1):3–7.
5. Sengupta K, Alluri KV, Satish AR, et al. A double blind, randomized, placebo controlled study of the efficacy and safety of 5-Loxin for treatment of osteoarthritis of the knee. Arthritis Res Ther. 2008;10(4):R85.
6. Yu G, Xiang W, Zhang T, et al. Effectiveness of Boswellia and Boswellia extract for osteoarthritis patients: a systematic review and meta-analysis. BMC Complement Med Ther. 2020;20(1):225.
7. Gerhardt H, Seifert F, Buvari P, et al. Therapy of active Crohn disease with Boswellia serrata extract H 15. Z Gastroenterol. 2001;39(1):11–17.
8. Sterk V, Büchele B, Simmet T. Effect of food intake on the bioavailability of boswellic acids from a herbal preparation in healthy volunteers. Planta Med. 2004;70(12):1155–1160.