Turmeric, and more specifically its primary active constituent known as curcumin, has been used extensively in ancient and modern times for its medicinal qualities.1,2 It was used as a traditional remedy in Chinese and Indian ayurvedic medicine for more than 2,000 years,3 and the authors of a textbook on bioactive foods indicate that “the use of turmeric in Indian folk medicine is one of a veritable panacea, apparently efficacious for conditions that we would nowadays classify in the realm of infectious, inflammatory, metabolic and immunological diseases.”4 Furthermore, research on the modern, evidence-based uses of curcumin is extensive, and includes studies demonstrating a wide spectrum of biological actions. These include anti-inflammatory, antioxidant, anti-carcinogenic, anti-mutagenic, anticoagulant, anti-fertility, anti-diabetic, antibacterial, antifungal, antiprotozoal, antiviral, anti-fibrotic, anti-venom, antiulcer, hypotensive and cholesterol-lowering activities.5 The focus of this article is on curcumin’s benefits for cardiovascular health—and specifically for endothelial dysfunction.
The endothelium is the tissue that lines the interior surface of blood vessels (and lymphatic vessels). Normal functions of the endothelium include mediation of coagulation, platelet adhesion, immune function and control of volume and electrolyte content of the intravascular and extravascular spaces. In vascular diseases, endothelial dysfunction is a disorder broadly defined as an imbalance between vasodilating and vasoconstricting substances produced by (or acting on) the endothelium.6 Endothelial dysfunction can result from and/or contribute to several disease processes, including hypertension (high blood pressure), hypercholesterolaemia, diabetes, septic shock and Behcet’s disease (a rare autoimmune disorder causing blood vessel inflammation).7
Maintaining healthy endothelial function is of vital importance for supporting cardiovascular health, so measuring endothelial function is a good reflection of cardiovascular health. When blood flow increases through a vessel, the vessel dilates. This phenomenon is referred to as flow-mediated dilatation (FMD). FMD is a sensitive measure of endothelial function and serves as a predictive marker of cardiovascular risk. Therefore, improvements in endothelial function, as measured by FMD, are indicative of a reduced cardiovascular risk.8 Supple-mentation with curcumin is one way to help promote healthy endothelial function via FMD.
Preliminary Research With Curcumin
Excess fructose consumption is a risk factor for metabolic syndrome, causing hyperuricemia (excess of uric acid) and endothelial dysfunction in the kidneys. In a study with fructose-fed rats, curcumin lowered uric acid levels, and appeared to ameliorate endothelial dysfunction in the kidneys.9
Likewise, in a randomized, controlled crossover study,10 14 healthy male subjects were given a single serving of curry meal (a natural source of curcumin) or spice-free control meal, to determine if it would improve endothelial function. Before and one hour after consumption, fasting and postprandial FMD responses were measured. According to the results, curry meal increased FMD from 5.2 ± 2.5 percent to 6.6 ± 2.0 percent (P = 0.001), whereas the control meal decreased FMD from 5.8 ± 2.4 percent to 5.1 ± 2.3 percent (P = 0.039). The postprandial FMD after the curry meal was significantly higher than after the control meal (P = 0.002). The researchers concluded that, “consumption of curry ameliorates postprandial endothelial function in healthy male subjects and may be beneficial for improving cardiovascular health.”
Of course, a study in rats, and a study on a single serving of curry is not enough to definitively demonstrate that curcumin is effective for improving endothelial function. However, a well-designed and executed human study on curcumin has shown just that.
Before proceeding to a discussion of the human study on curcumin and endothelial function, it is important and relevant to first address the fact that curcumin has relatively poor biovailability—with 40 to 75 percent of curcumin passing through the digestive tract unchanged in animal research.11 Also, blood concentrations of curcumin are low and tissue distribution is limited following oral dosing due to its fast metabolic turnover in the liver and intestinal wall.12-20 Even upon intake of doses as high as 10 or 12 g curcumin, maximum plasma curcumin concentrations in humans, remain in the low nanomolar range (<160 nmol/L).21
There are, however, a few different commercial curcumin extracts that are supported by research showing better bioavailability vs. regular curcumin. One such extract, whose effects on endothelial dysfunction will be discussed below, is CurcuWIN, a novel curcumin formulation from OmniActive Health Technologies containing 20 percent curcuminoids. A recent human study22 showed that the absorption of total curcuminoids in the blood of this water-dispersible form of curcumin was 45.9-fold higher than normal curcumin.
Curcumin’s Effect on Endothelial Dysfunction
A double-blind, randomized, placebo controlled parallel study23 was conducted to examine the effect of differing doses of curcumin on FMD, and consequently on endothelial dysfunction. Researchers from Texas Christian University (USA), Massey University (New Zealand), and Increnovo, LLC (USA) recruited 59 moderately trained men and women to participate.
Subjects were assigned to placebo, 50 mg, or 200 mg curcumin (from 250 and 1,000 mg CurcuWIN, respectively), for eight weeks. The results of this study were originally presented at the Experimental Biology 2016 Meeting in San Diego, and subsequently published in the Journal of Nutrition and Metabolism.
Results showed that 200 mg of curcumin produced a dose-mediated improvement in endothelial function as measured by FMD. The outcome was a clinically significant 3.0 percent increase, relative to placebo (p=0.020). Those in the placebo group had a decrease in FMD. Consequently, the improvement in FMD with the 200 mg dose of curcumin represented a 37 percent increase over placebo.
The researchers concluded that eight weeks of 200 mg oral curcumin supplementation resulted in a clinically significant improvement in endothelial function as measured by FMD in apparently healthy adults. Not only does this suggest that oral curcumin supplementation may present a simple lifestyle strategy for decreasing the risk of cardiovascular diseases, but other research suggests that for every 1 percent increase in FMD, there is a 9 to 17 percent decrease in cardiovascular disease.24 Therefore, daily supplementation with 1,000 mg CurcuWIN (providing 200 mg of curcumin) had a clinically meaningful impact on potentially reducing cardiovascular risk by 15 to 50 percent in healthy individuals.
Curcumin has been used extensively in ancient and modern times for its medicinal qualities, with research demonstrating a wide range of biological effects. A particular benefit of curcumin supplementation is protection against, and improvement of endothelial dysfunction through an increase in FMD. CurcuWIN, which has been shown to have 45.9-fold higher bioavailability vs. standard curcumin, has also demonstrated a significant increase in FMD vs. placebo in clinical study. This increase in FMD could potentially reduce cardiovascular risk by 15 to 50 percent in healthy individuals. VR
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Gene Bruno, MS, MHS, the dean of academics for Huntington College of Health Sciences, is a nutritionist, herbalist, writer and educator. For more than 30 years he has educated and trained natural product retailers and health care professionals, has researched and formulated natural products for dozens of dietary supplement companies, and has written articles on nutrition, herbal medicine, nutraceuticals and integrative health issues for trade, consumer magazines and peer-reviewed publications. He can be reached at firstname.lastname@example.org.