What research really tells us

Only few are the people who have not yet tried turmeric as a spice in cooking or supplemented their diet with curcumin. Curcumin is the most important and one of the most studied curcuminoids (polyphenols, naturally occurring plant-based chemicals) found in turmeric. Turmeric is a flowering plant of the ginger family known as Curcuma longa. The bright yellow spice has been used throughout Asia for centuries (as a cooking ingredients and a herbal medicine) and has recently been embraced by the West — a key ingredient in South Asian’s curries. Turmeric has an impressive list of health benefits and it is probably the most studied herb in the world, particularly curcumin.

Turmeric, Curcumin and Research 

Despite the wide array of use in alternative medicine throughout the centuries, studies have shown that this fat-soluble compound is poorly absorbed by the body, and so the therapeutic effect of curcumin is mostly targeting the gut. The content of curcumin in turmeric is around 3%, and so the actual ingested and absorbed dose is, therefore, minuscule. Supplementing with curcumin extract has thus been the preferred medium to increase the portion the body can absorb and use. However, further studies have revealed that it is still not enough to provide sufficient therapeutic effect — even in high dosages —, as curcumin is recognised as a foreign substance and is quickly glucuronidated. Glucuronidation is one of the most important reactions for the elimination of xenobiotics (foreign substances, often toxic) from the body — making them water-soluble, and so harmless and easily excretable. (1)

For decades, it was suggested to mix curcumin extract with piperine to increase the absorption in the gut. (2) Again, this has been shown by many studies to not increase plasma levels — the levels of 2 free curcumin travelling in the bloodstream, because the quicker curcumin is absorbed, the quicker it is glucuronidated. In fact, it is estimated that only 2% of curcumin is absorbed by the body and it may not be enough to provide any true therapeutic benefit. (3) With decades of research dedicated 3 to increasing the absorption of curcumin, we have discovered that attaching curcumin to a fatty substance increases its absorption and retention in its free state — the molecule the body can recognise and use. Various companies using different patented versions of fat-soluble curcumin are claiming to increase its absorption and extend its bioavailability, because curcumin is not absorbed by the gut lining and, therefore, glucuronidated, but instead is diverted to the lymphatic system and absorbed in the same way fat-soluble vitamins are.

Despite the best efforts, curcumin absorption is still far from being optimal and large peer-reviewed studies are still lacking to be objectively precise about the true rate of absorption and the concentration of curcumin in circulation. It is clear that the longer the body can retain higher levels of free curcumin the longer the effect of curcumin on the body.

Why studying curcumin is important

​​Biological activities of curcumin has been well-studied and curcumin displays antioxidant, antiinflammatory, antimicrobial and antiviral activity, among which its anticancer potential has been the most described and still remains under investigation. Curcumin has been reported to modulate growth factors, enzymes, transcription factors, inflammatory cytokines, and upregulate and downregulate proteins involved in the apoptotic process (programmed cell death) (4) — a key component mutated cells can override, and so 4 escape the immune system.

The therapeutic benefits of curcumin have been demonstrated in multiple chronic inflammatory diseases including arthritis, metabolic syndrome, liver disease, obesity and neurodegenerative diseases; however, over a third of all research is associated with cancer, because there is enough evidence to suggest that the disorder of inflammatory pathways play a key role in cancer development. (5) In its ability to interact with several immune mediators and address inflammatory 5 processed, curcumin is thus believed to have anticancer properties. (6,7,8,9,10)

Clinical use of curcumin is still under investigation, which may suggest that despite the very low level of absorption and concentration of free curcumin in the bloodstream, low concentration of free curcumin is still able to offer therapeutic effect, especially tumour regression and can be used alongside chemotherapy or radiotherapy — curcumin specifically exhibits cytostatic and cytotoxic effects against tumours of multiple origin, and is a remarkable immunomodulator. (11) A comprehensive systematic review also confirmed that curcumin reduces the side effects of chemotherapy or radiotherapy, resulting in improving patients’ quality of life. (12)

In vitro and In vivo, what’s the difference?

​​It is important to note that most of the evidence that supports the therapeutic potential of curcumin is mainly based on in vitro studies (outside a living tissue, i.e., inside a petri dish). As far as cancer is concerned, in vitro studies have demonstrated that cancer cells do not die unless they are exposed to curcumin in high concentrations for several hours, and this level of concentration is not achieved outside the gastrointestinal tract when curcumin is taken orally. (13) However, this may be extremely useful for colon cancer, mainly due in part to angiogenesis (development of new blood vessels) inhibition. (14)

As research increases, in vivo studies are showing promising results. It is suggested that injecting a water-soluble form of curcumin can offer targeted effect on the colon, especially as a part of a treatment for colorectal cancer, the third most common cause of cancer-related death worldwide, and without toxicity. (15)

What supplementing form of curcumin should I choose?

It is clear that not two supplements are the same, and when it comes to curcumin it could not be any more true. As a spice, teas or turmeric-based supplements, these offer very little curcumin, which may be poorly absorbed. It is still important to consider turmeric as a food as it is still shown to have localised effects on the gut. For example, turmeric can help soothe inflammatory disorders like inflammatory bowel syndrome (IBS) and ulcerative colitis; however, the effect highly depends on the purity of the food or supplement, as the processes involved may damage it and the more additives are added to the final product, the greater the risk of sensitivity. Which means that some supplements can generate the same symptoms they are supposed to offer relief from. It is, therefore, essential to carefully choose curcumin supplements. Only choose supplements from trusted sources. These must be in their purest forms (free of any additives and preservatives). Attention should also be given to the application, and so choosing the right form (or molecular structure) is essential. For example, turmeric as a spice, tea or supplements can be used for ailments related to the gut, but a form of curcumin attached to a fat molecule or protected inside a fat capsule (to increase absorption and the concentration of free curcumin in the blood) can be used for the anti-inflammatory benefits and antioxidant capabilities, or lower blood cholesterol and address dyslipidaemia — a leading risk factor for cardiovascular disease, also a common feature of obesity. (16,17,18)

To make sure you are taking the right supplement and use it correctly, always consult your health practitioner.

Sources:

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17: Ferguson, JJA. et al. (2018). Curcumin potentiates cholesterol-lowering effects of phytosterols in hypercholesterolaemic individuals. A randomised 17 controlled trial. Metabolism. 82, pp. 22–35. doi:10.1016/j.metabol.2017.12.009

18: Mohammadi, A. et al. (2013). Effects of supplementation with curcuminoids on dyslipidemia in obese patients: a randomized crossover trial. 18 Phytotherapy Research : PTR. 27(3), pp. 374-379. doi:10.1002/ptr.4715