What Are Curcuminoids and What Do They Do?
An overview of the science of curcuminoids, the active compounds in turmeric, examining their biological properties and factors affecting their use.
Curcuminoids are natural compounds in the turmeric plant, a spice long used in cooking and traditional medicine. As the plant’s primary active ingredients, they are the focus of significant research for their biological properties. This article explores the identity of these compounds, their health characteristics, factors influencing their absorption, and their common uses and safety profile.
Defining Curcuminoids and Their Natural Origin
Curcuminoids are polyphenolic compounds sourced from the rhizome of the Curcuma longa plant, which is ground to produce turmeric. These compounds give turmeric its characteristic bright color and are its main bioactive components. While other Curcuma species contain them, Curcuma longa is the most common commercial source.
The term “curcuminoids” refers to a mixture of three compounds: curcumin, demethoxycurcumin, and bisdemethoxycurcumin. Curcumin is the most abundant, making up about 77% of the curcuminoid content in turmeric extracts. Demethoxycurcumin constitutes around 17% of the mixture, and bisdemethoxycurcumin is the least prevalent at 3%.
Each of these three curcuminoids shares a similar chemical structure, and their minor structural differences contribute to their distinct biological activities. Although curcumin is the most studied, research into the specific properties of the other two compounds is growing.
Principal Health-Associated Properties
The health properties of curcuminoids are primarily linked to their antioxidant and anti-inflammatory activities. As antioxidants, these compounds can neutralize damaging free radicals. This action is linked to their chemical structure, which allows them to donate electrons to stabilize these reactive molecules and mitigate cellular stress.
Their anti-inflammatory effects are mediated through interaction with multiple molecular targets. Curcumin inhibits the activity of enzymes like cyclooxygenase-2 (COX-2) and lipoxygenase (LOX). Both of these enzymes are involved in producing pro-inflammatory substances in the body.
Curcuminoids also influence the activity of transcription factors, which are proteins that regulate gene expression. One of the most studied is nuclear factor-kappa B (NF-κB), a protein that controls genes involved in the inflammatory response. By inhibiting NF-κB activation, curcuminoids can down-regulate the production of inflammatory mediators. Research also explores their role in neuroprotective functions and metabolic health.
Bioavailability and Absorption Factors
A significant challenge with curcuminoids is their low bioavailability, meaning only a small fraction enters the bloodstream when consumed orally. This is due to poor water solubility and rapid metabolism in the liver and intestinal wall. The body quickly converts curcuminoids into other compounds through a process called glucuronidation and eliminates them.
To enhance absorption, one common method is combining curcuminoids with piperine, an alkaloid from black pepper. Piperine inhibits the glucuronidation process, slowing the breakdown and elimination of curcumin. This combination can significantly increase its serum concentrations.
Another approach is to formulate curcuminoids with lipids or phospholipids. This improves their absorption through the lymphatic system, bypassing initial liver metabolism. Advanced delivery systems, such as nanoparticles, micelles, and phytosome complexes, are also used to encapsulate curcuminoids, protecting them from degradation and increasing their uptake.
Common Applications and Safety Aspects
Curcuminoids are widely used as the active components in turmeric spice, as a food-coloring agent, and in dietary supplements. Certain preparations have Generally Recognized As Safe (GRAS) status for use as additives in foods and beverages. As supplements, they are available in capsules, tablets, and powders, often in formulations designed to enhance bioavailability.
Curcuminoids are well-tolerated by most people, especially at levels found in food. High-dose supplementation may cause mild side effects, such as nausea or diarrhea. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) established an acceptable daily intake (ADI) for curcumin at 3 mg per kg of body weight per day.
Potential interactions with certain medications exist. Because they can affect platelet aggregation, they may increase the risk of bleeding when taken with anticoagulant or antiplatelet drugs. Anyone with existing health conditions or taking prescription medications should consult a healthcare professional before starting curcuminoid supplements.