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.

Fig. 1

Diagram showing curcumin properties. Adapted from Sohn et al. (2021). The diagram employs a color-coded scheme to summarize the pharmacological properties of curcumin: blue represents its anti-oxidative effects, red denotes anti-inflammatory actions, yellow highlights anti-carcinogenic mechanisms, and green encompasses its anti-microbial functions (including anti-biofilm and bactericidal activity)

Fig. 2

Time trend of publications for “Curcumin Supplements” on PubMed.gov (accessed on 17.08.2024) https://pubmed.ncbi.nlm.nih.gov/?term=curcumin+supplement

Fig. 3

Time trend of publications for “Turmeric Supplements” on pubmed.gov (accessed on 17.08.2024) https://pubmed.ncbi.nlm.nih.gov/?term=turmeric+supplement)

Fig. 4

Google search interest since 2004 for “turmeric supplements.” The vertical axis indicates search interest relative to the peak value on the chart for a specific region and time period. A value of 100 represents the highest popularity for the term. A value of 50 means the term is half as popular as the peak. A score of 0 indicates insufficient data for the term. https://trends.google.com/trends/explore?date=all&q=Turmeric%20supplements&hl=en-US (accessed on 17.08.2024)

Fig. 5

Types of turmeric. Graph showing the frequency of types of turmeric used in supplements in each country. Information is presented in a grouped column diagram, and each country is color-coded

Fig. 6

Turmeric effect enhancing substance. Representation of the number of preparations containing a TEES. Information is shown in a bar chart and is color-coded to represent each country

Fig. 7

Specified curcuminoid amount per unit (SCA) (mg). Analysis of the specified curcuminoid amount per unit in milligrams. This is represented in a grouped column diagram, showing each country in a different color. The x-axis shows range categories from < 10 to 1000 mg

Fig. 8

Maximum daily dose (MDD) (mg). Representation of the MDD in a box and whiskers chart. The box extends from the 25th to 75th percentiles, and the median is indicated by the line within the box. The average is denoted by a “ + ”, and the whiskers mark the maximum and minimum values. The dots represent individual values

Fig. 9

Cost of maximum daily dose (CMDD) (€). Graphic representation of the CMDD (€) as a scatter dot graph. The dots show individual data. The bar corresponds to the median, and the “ + ” indicates the mean. The whiskers correspond to the minimum and maximum value. The countries are color-coded

Fig. 10

Comparison of advertising benefits. Graphical representation of the number of times a benefit was mentioned in the preparations. The information is presented in a stacked bar chart with each bar showing the number of times a benefit was mentioned per category. The bar is then divided into sections showing the number of times a benefit was mentioned in each country. Each country is represented by a color shown in the top right of the diagram

Fig. 11

Dosage form. Graphical representation of dosage forms of preparations. Information presented in a grouped column chart

Fig. 12

Flowchart showing study review selection and analysis