Curcumin, the natural pigment that gives the spice turmeric its yellow colour, has come under the scientific spotlight in recent years, with studies investigating its potential benefits for reducing cholesterol levels, improving cardiovascular health, and fighting cancer.
However it is recommended that consumers wishing to make use of curcumin's properties consume it in supplement form rather than eating more curries, which tend to be rather high in fat in their Western form.
The new study, published on-line ahead of print in the Journal of Nutritional Biochemistry (doi: 10.1016/j.jnutbio.2006.03.007), reports a possible mechanism to explain the ability of this spice extract to reduce cholesterol levels.
The intention of the work, said the researchers, was "to understand the molecular basis for the hypocholesterolemic effects."
High cholesterol levels, hypercholesterolaemia, have a long association with many diseases, particularly cardiovascular disease (CVD), the cause of almost 50 per cent of deaths in Europe, and reported to cost the EU economy an estimated €169bn ($202bn) per year.
Lead researcher Norbert Nass and colleagues from the Martin Luther University in Germany investigated the effect of different doses of curcumin, ranging from two to 50 micromoles, at the genetic of human liver cells.
The specific targets studies were LDL-receptor mRNA, which affects uptake of LDL-cholesterol from the plasma; liver X receptor (LXR), a receptor that binds various oxidized cholesterol derivatives; and retinoic acid receptor (RXR) which forms dimers with LXR as well as activating several genes reportedly involved in cholesterol metabolism.
The researchers report that addition of curcumin results in "an up to sevenfold, concentration-dependent increase in LDL-receptor mRNA", an observation which "should result in a higher net uptake of LDL-cholesterol from plasma."
The effect was reported to be significant at concentrations higher than 10 micromoles and the curcumin was not toxic to the liver cells.
Expression of the LXR and RXR was also increased, and activation occurred even at the low doses (two to 10 micromoles).
"The observed activation of LXR and RXR that occurred at concentrations that can be reached by oral consumption of curcumin holds for a contribution of nuclear receptors to the hypocholesterolemic effect of curcumin," concluded the researchers.