Curcumin or Boswellia: what's the difference

Curcumin and boswellia extract are two plant substances most often offered as a “natural alternative” to anti-inflammatory drugs. Both have a long history in the traditional medicine of India, but chemically and pharmacologically they are different. Our editorial team explains what exactly distinguishes curcumin from boswellic acids and what of this is confirmed by research.

Origin and active compounds

Curcumin is the main polyphenol of the rhizome of turmeric (Curcuma longa), a plant of the ginger family. It is what gives the spice its bright yellow colour. Together with related compounds — demethoxycurcumin and bisdemethoxycurcumin — it forms the group of curcuminoids. In ordinary powdered turmeric there is relatively little of them, so supplements contain standardised extracts.

Boswellia is a resin (olibanum, frankincense) of trees of the genusBoswellia, most oftenBoswellia serrata(Indian frankincense). The active components are considered to be pentacyclic triterpenes — boswellic acids. The most studied of them are 11-keto-β-boswellic acid (KBA) and its acetylated form AKBA.

So the first difference is chemical: curcumin is a diketone polyphenol, whereas boswellic acids are triterpenoids, structurally closer to steroid skeletons. Accordingly, their behaviour in the body is different too.

The second difference is standardisation. For curcumin the percentage of curcuminoids is usually stated (often 95%), and for boswellia the content of boswellic acids overall or specifically AKBA. Without these data it is almost impossible to compare products with each other.

Mechanisms of anti-inflammatory action

In laboratory studies curcumin acts on an extraordinarily large number of targets: it inhibits the activation of the transcription factor NF-κB, reduces the production of pro-inflammatory cytokines (TNF-α, IL-1, IL-6), modulates cyclooxygenase-2 and acts as an antioxidant. Such “pleiotropy” is both an advantage and a reason for scepticism.

The review by Nelson and colleagues (2017) in the Journal of Medicinal Chemistry drew attention to the fact that curcumin is chemically unstable and often gives false-positive results in laboratory tests, so many effects found “in the test tube” may have no clinical significance. This does not cancel the clinical trials, but calls for caution in interpreting mechanisms.

Boswellic acids have a more specific known target — the enzyme 5-lipoxygenase (5-LOX), which is responsible for the synthesis of leukotrienes. Leukotrienes are mediators of inflammation that take part, in particular, in asthma and inflammatory processes in the joints. AKBA is considered the most active inhibitor of 5-LOX among the boswellic acids.

Thus, one can conditionally say that boswellia acts mainly on the “leukotriene” branch of inflammation, whereas curcumin acts more broadly, on the signalling pathways that regulate inflammatory genes. Neither substance inhibits COX the way classic non-steroidal anti-inflammatory drugs do.

The bioavailability problem

The biggest practical problem with curcumin is its low bioavailability. It dissolves poorly in water, is weakly absorbed, and is rapidly metabolised in the liver and intestine with the formation of glucuronides and sulphates. The review by Anand and colleagues (2007) describes these limitations as the main obstacle to clinical use.

The classic study by Shoba and colleagues (1998) showed that simultaneous intake of piperine (an alkaloid of black pepper) in humans sharply raised the level of curcumin in the blood — the authors reported an approximately twentyfold increase in bioavailability. Since then many special forms have appeared: phospholipid complexes, nanoparticles, micellar forms.

The bioavailability of boswellic acids is also limited, especially for AKBA. Absorption is better when taken with food that contains fat. Some extracts enrich AKBA or use phospholipid forms to raise the concentration of active compounds in the blood.

For the consumer this means that the dose of “raw” extract says little about actual exposure. Products should be compared by form and standardisation, not just by milligrams on the label.

What clinical trials show

For curcumin the most research is in osteoarthritis. The meta-analysis by Daily and colleagues (2016) concluded that turmeric extracts and curcumin can reduce pain in arthritis, but the authors emphasised the small number and size of the studies and the risk of bias. The review by Hewlings and Kalman (2017) also describes moderate effects in inflammatory and metabolic conditions.

For boswellia, the randomised study by Kimmatkar and colleagues (2003) showed a reduction in pain and swelling in the knees of patients with osteoarthritis. Sengupta and colleagues (2008) studied an AKBA-enriched extract and also reported an improvement in symptoms. Most studies are small, and some were funded by extract manufacturers.

In major osteoarthritis clinical guidelines (ACR, OARSI), neither curcumin nor boswellia is part of the standard recommendations: the evidence is so far insufficient for that level.

Safety and interactions

Curcumin is usually well tolerated in studies, with digestive upset being the most common. At the same time, the LiverTox database of the US National Institutes of Health describes cases of liver injury linked to turmeric supplements, especially highly bioavailable forms and products with piperine. People with liver disease should be careful.

Curcumin can enhance the effect of anticoagulants and antiplatelet agents, and piperine affects the metabolism of many drugs through liver enzymes. People with gallstone disease are also advised to refrain, since turmeric stimulates contraction of the gallbladder.

Boswellia usually causes mild gastrointestinal symptoms — heartburn, nausea, diarrhoea. There are few data on long-term safety, as well as on interactions, so while taking medication, especially anticoagulants, it is worth consulting a doctor.

Both supplements are not recommended during pregnancy and breastfeeding because of a lack of data, and before planned surgery they are usually discontinued.

Editorial conclusions

Curcumin and boswellia are different plant substances: a polyphenol with a broad but mainly lab-described spectrum of action, and triterpene acids with a more specific target — 5-lipoxygenase.

Both have bioavailability problems, so the form and standardisation of the product matter more than the milligram figure.

The clinical data for both are encouraging but limited by small studies, and these substances are not yet part of the standard guidelines.

For the practical choice, read our article “Curcumin vs Boswellia: what to choose and for whom”, as well as pieces on piperine and bioavailability and on the safety of plant supplements for the liver.

References

1. Hewlings SJ, Kalman DS. Curcumin: a review of its effects on human health. Foods. 2017;6(10):92.
2. Anand P, Kunnumakkara AB, Newman RA, et al. Bioavailability of curcumin: problems and promises. Mol Pharm. 2007;4(6):807–818.
3. Shoba G, Joy D, Joseph T, et al. Influence of piperine on the pharmacokinetics of curcumin in animals and human volunteers. Planta Med. 1998;64(4):353–356.
4. Nelson KM, Dahlin JL, Bisson J, et al. The essential medicinal chemistry of curcumin. J Med Chem. 2017;60(5):1620–1637.
5. Daily JW, Yang M, Park S. Efficacy of turmeric extracts and curcumin for alleviating the symptoms of joint arthritis: a systematic review and meta-analysis of randomized clinical trials. J Med Food. 2016;19(8):717–729.
6. Kimmatkar N, Thawani V, Hingorani L, et al. 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.
7. 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.
8. Ammon HPT. Boswellic acids in chronic inflammatory diseases. Planta Med. 2006;72(12):1100–1116.