A market and risk assessment of 125 turmeric supplements available in Australia, Germany, India, UK, and USA

Abstract

Historically prominent in Ayurvedic cultures, turmeric (Curcuma longa), or "Haldi," is renowned for its anti-inflammatory and antioxidant effects, mainly due to its active compounds, curcuminoids. Due to the increasing use of turmeric supplements, this study critically examined 125 preparations across the UK, USA, India, Australia, and Germany and evaluated their compliance with evidence-based recommendations. Results reveal significant regulatory and labeling inconsistencies across countries, with 34% of preparations failing to disclose the active curcuminoid content. This lack of dosage regulation is especially concerning when considering the ongoing research into advanced delivery systems-such as nanoparticles, liposomes, micelles, and phospholipid complexes-which significantly enhance curcumin's absorption. Curcumin, a hydrophobic compound, undergoes rapid metabolism in the liver through Phase I and II detoxification pathways, particularly via cytochrome P450 enzymes and UDP-glucuronosyltransferase enzymes. This results in limited bioavailability, as curcumin is rapidly converted to water-soluble metabolites and excreted, reducing its effectiveness at therapeutic doses. However, through modern formulation technologies, curcumin can potentially not only alter drug metabolism, but its antioxidant action via Nrf2 activation can shift to pro-oxidant effects at high doses, causing oxidative stress and the accumulation of reactive metabolites. Emerging evidence suggests chronic low-dose use may lead to gastrointestinal, hepatic, or renal toxicity, yet turmeric preparations, falling within the scope of food law, lack the stringent controls applied to pharmaceuticals and are generally assumed safe. This study highlights the need for transparent labeling, clear dosage guidelines, and an understanding of curcumin's metabolic profile to guide consumers in maximizing benefits while mitigating risks. Furthermore, it aims to assist healthcare professionals in making informed recommendations regarding curcumin supplementation. Further research must include long-term clinical trials and potential standardization of curcumin supplement formulations.

Keywords: Curcuma longa; Bioavailability; Curcuminoids; Detoxification; Drug metabolism; Labeling; Nanoparticles; Oxidative stress; Pro-oxidant; Regulation; Safety; Supplement; Therapeutic doses; Toxicity; Turmeric.