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 traditional Indian medicine, but chemically and pharmacologically they are different. The editors explain what exactly distinguishes curcumin from boswellic acids and what of this is supported 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 color. 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 standardized extracts.

Boswellia is a resin (olibanum, frankincense) of trees of the genusBoswellia, most oftenBoswellia serrata(Indian frankincense). Its 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 behavior in the body differs as well.

The second difference is standardization. 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 one another.

Mechanisms of anti-inflammatory action

In laboratory studies curcumin affects an enormous number of targets: it suppresses 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 skepticism.

A review by Nelson and colleagues (2017) in the Journal of Medicinal Chemistry drew attention to the fact that curcumin is chemically unstable and often produces false-positive results in laboratory assays, so many effects found "in the test tube" may have no clinical significance. This does not negate clinical studies, but it 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 involved, among other things, 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 loosely say that boswellia acts mainly on the "leukotriene" branch of inflammation, while curcumin acts more broadly, on the signaling pathways that regulate inflammatory genes. Neither substance suppresses COX the way classic non-steroidal anti-inflammatory drugs do.

The bioavailability problem

The biggest practical problem with curcumin is its low bioavailability. It is poorly soluble in water, poorly absorbed, and rapidly metabolized in the liver and intestine to form glucuronides and sulfates. A 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 co-administration of piperine (an alkaloid of black pepper) in humans sharply increased blood levels of curcumin - the authors reported roughly a twentyfold increase in bioavailability. Since then many special formulations have appeared: phospholipid complexes, nanoparticles, micellar forms.

Boswellic acids also have limited bioavailability, especially AKBA. Absorption is better when taken with food that contains fat. Some extracts are enriched with AKBA or use phospholipid forms to increase the concentration of active compounds in the blood.

For the consumer this means that the dose of "raw" extract says little about the actual exposure. Products are better compared by form and standardization, not just by milligrams on the label.

What clinical studies show

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

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

In the major clinical guidelines for osteoarthritis (ACR, OARSI), neither curcumin nor boswellia is among the standard recommendations: the evidence is not yet sufficient for that level.

Safety and interactions

Curcumin is usually well tolerated in studies, with digestive disturbances most commonly observed. At the same time, the LiverTox database of the US National Institutes of Health describes cases of liver injury associated with turmeric supplements, especially with highly bioavailable forms and products containing piperine. People with liver disease should be cautious.

Curcumin may enhance the action 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, diarrhea. There is little data on long-term safety, as well as on interactions, so when taking medications, especially anticoagulants, it is worth consulting a doctor.

Both supplements are not recommended during pregnancy and breastfeeding due to 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 largely lab-described range of action, and triterpene acids with a more specific target - 5-lipoxygenase.

Both have bioavailability problems, so the form and standardization 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 standard guidelines.

For a practical choice, read our article "Curcumin vs Boswellia: Which to Choose and for Whom," as well as our materials 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.