The Importance of Method Selection in Determining Product Integrity for Nutrition Research

Reporting completeness of nutrition and diet-related randomised controlled trials protocols

BACKGROUND AND AIMS

There is a need to consolidate reporting guidance for nutrition randomised controlled trial (RCT) protocols. The reporting completeness in nutrition RCT protocols and study characteristics associated with adherence to SPIRIT and TIDieR reporting guidelines are unknown. We, therefore, assessed reporting completeness and its potential predictors in a random sample of published nutrition and diet-related RCT protocols.

METHODS

We conducted a meta-research study of 200 nutrition and diet-related RCT protocols published in 2019 and 2021 (aiming to consider periods before and after the start of the COVID pandemic). Data extraction included bibliometric information, general study characteristics, compliance with 122 questions corresponding to items and subitems in the SPIRIT and TIDieR checklists combined, and mention to these reporting guidelines in the publications. We calculated the proportion of protocols reporting each item and the frequency of items reported for each protocol. We investigated associations between selected publication aspects and reporting completeness using linear regression analysis.

RESULTS

The majority of protocols included adults and elderly as their study population (n = 73; 36.5%), supplementation as intervention (n = 96; 48.0%), placebo as comparator (n = 89; 44.5%), and evaluated clinical status as the outcome (n = 80; 40.0%). Most protocols described a parallel RCT (n = 188; 94.0%) with a superiority framework (n = 141; 70.5%). Overall reporting completeness was 52.0% (SD = 10.8%). Adherence to SPIRIT items ranged from 0% (n = 0) (data collection methods) to 98.5% (n = 197) (eligibility criteria). Adherence to TIDieR items ranged from 5.5% (n = 11) (materials used in the intervention) to 98.5% (n = 197) (description of the intervention). The multivariable regression analysis suggests that a higher number of authors [β = 0.53 (95%CI: 0.28-0.78)], most recent published protocols [β = 3.19 (95%CI: 0.24-6.14)], request of reporting guideline checklist during the submission process by the journal [β = 6.50 (95%CI: 2.56-10.43)] and mention of SPIRIT by the authors [β = 5.15 (95%CI: 2.44-7.86)] are related to higher reporting completeness scores.

CONCLUSIONS

Reporting completeness in a random sample of 200 diet or nutrition-related RCT protocols was low. Number of authors, year of publication, self-reported adherence to SPIRIT, and journals' endorsement of reporting guidelines seem to be positively associated with reporting completeness in nutrition and diet-related RCT protocols.

Safety considerations for dietary supplement manufacturers in the United States

Due to significant dietary supplement use in the US, product manufacturers must understand the importance of implementing a robust approach to establishing safety for all ingredients, including dietary ingredients, components, and finished dietary supplement products. Different regulatory pathways exist by which the safety of dietary ingredients can be established, and thus allowed to be marketed in a dietary supplement. For individual dietary ingredients, safety information may come from a variety of sources including history of safe use, presence of the ingredient in foods, and/or non-clinical and clinical data. On occasion safety data gaps are identified for a specific ingredient, particularly those of botanical origin. Modern toxicological methods and models can prove helpful in satisfying data gaps and are presented in this review. For finished dietary supplement products, issues potentially impacting safety to consider include claims, product labeling, overages, contaminants, residual solvents, heavy metals, packaging, and product stability. In addition, a safety assessment does not end once a product is marketed. It is important that manufacturers actively monitor and record the occurrence of adverse events reported in association with the use of their products, in accordance with the law. Herein, we provide a comprehensive overview of considerations for assessing dietary supplement safety.

Detecting and Profiling of Milk Thistle Metabolites in Food Supplements: A Safety-Oriented Approach by Advanced Analytics

Milk thistle (Silybum marianum (L.) Gaertn.) is among the top-selling botanicals used as a supportive treatment for liver diseases. Silymarin, a mixture of unique flavonolignan metabolites, is the main bioactive component of milk thistle. The biological activities of silymarin have been well described in the literature, and its use is considered safe and well-tolerated in appropriate doses. However, commercial preparations do not always contain the recommended concentrations of silymarin, failing to provide the expected therapeutic effect. While the poor quality of raw material may explain the low concentrations of silymarin, its deliberate removal is suspected to be an adulteration. Toxic contaminants and foreign matters were also detected in milk thistle preparations, raising serious health concerns. Standard methods for determination of silymarin components include thin-layer chromatography (TLC), high-performance thin-layer chromatography (HPTLC), and high-performance liquid chromatography (HPLC) with various detectors, but nuclear magnetic resonance (NMR) and ultra-high-performance liquid chromatography (UHPLC) have also been applied. This review surveys the extraction techniques of main milk thistle metabolites and the quality, efficacy, and safety of the derived food supplements. Advanced analytical authentication approaches are discussed with a focus on DNA barcoding and metabarcoding to complement orthogonal chemical characterization and fingerprinting of herbal products.

Have safety and efficacy assessments of bioactives come of age?

This article describes why the safety and efficacy assessment of non-nutrient bioactives for reducing chronic disease risk is so complicated, especially for dietary supplements and traditional medicines. Scientists, regulators, and the public have different and sometimes opposing perspectives about bioactives. Drug, food, and traditional medicine models used for bioactive safety assessment are based on different assumptions and use different processes. Efficacy assessment is seldom based on clinical trials of boactives' effects in reducing chronic disease risk. It usually consists of application of quality assurance measures and evaluation of label claims and commercial speech about ingredients or products to ensure conformity to regulations. Harmonization of safety and efficacy assessment on a global basis is difficult because of differences within and between regulatory systems. The recommendations provided may open the way for bioactives to play a larger health role in the future, fill gaps in data needed for crafting authoritative dietary guidance on intakes, and speed harmonization of global standards.

Analytical strategies to determine the labelling accuracy and economically-motivated adulteration of "natural" dietary supplements in the marketplace: Turmeric case study

Turmeric has faced authenticity issues as instances of economic-adulterations to reduce the cost. We used carbon-14 and HPLC analyses as complementary methods to verify "all-natural" label claims of commercial dietary supplements containing turmeric ingredients. A high percentage of curcumin-to-curcuminoids value was used as an indicator to imply the presence of synthetic curcumin. However, using the HPLC method alone did not provide direct evidence of curcuminoids' natural origin, whereas using only the carbon-14 method cannot test for potency label claims and determine which constituent(s) contain ¹⁴C radiocarbon. By analyzing results from both methods, a significant correlation between the percentage of curcumin-to-curcuminoids and % biobased carbon (Pearson's r = -0.875, p < 0.001) indicated that synthetic curcumin was greatly attributed to determined synthetic ingredients. Only four out of the 14 samples analyzed supported authentic label claims. This orthogonal testing strategy showed its potential for the quality control of turmeric products.

The Importance of Reference Materials and Method Validation for Advancing Research on the Health Effects of Dietary Supplements and Other Natural Products

Insufficient assessment of the identity and chemical composition of complex natural products, including botanicals, herbal remedies, and dietary supplements, hinders reproducible research and limits understanding mechanism(s) of action and health outcomes, which in turn impede improvements in clinical practice and advances in public health. This review describes available analytical resources and good methodological practices that support natural product characterization and strengthen the knowledge gained for designing and interpreting safety and efficacy investigations. The practice of validating analytical methods demonstrates that measurements of constituents of interest are reproducible and appropriate for the sample (e.g., plant material, phytochemical extract, and biological specimen). In particular, the utilization of matrix-based reference materials enables researchers to assess the accuracy, precision, and sensitivity of analytical measurements of natural product constituents, including dietary ingredients and their metabolites. Select case studies are presented where the careful application of these resources and practices has enhanced experimental rigor and benefited research on dietary supplement health effects.

Determination of Curcuminoids in Turmeric Dietary Supplements by HPLC-DAD: Multi-laboratory Study Through the NIH-ODS/NIST Quality Assurance Program

Background

Turmeric is a medicinal herb containing curcuminoids, used as quality markers in dietary supplements. In 2016, an AOAC First Action Official Method^SM was adopted for quantitation of curcuminoids and requires multi-laboratory reproducibility data for Final Action status.

Objective

To collect reproducibility data for the quantitation of curcuminoids in dietary supplements through the National Institutes of Health Office of Dietary Supplements/National Institute of Standards and Technology Quality Assurance Program (QAP).

Method

Laboratories that participated in the QAP by following the Official Methods of Analysis^SM Method 2016.16, submitted data for ten turmeric products. The data were analyzed for mean, repeatability, and reproducibility standard deviations, repeatability, and reproducibility.

Results

The initial data collection resulted in insufficient replicates (five) for each test sample to determine reproducibility, therefore laboratories were provided additional materials resulting in an incremental data approach. For homogenous products, reproducibility for curcumin ranged from 3.4 to 10.3%, bisdemethoxycurcumin with reproducibility ranging from 6.4 to 14.8%, and demethoxycurcumin ranging from 5.6 to 9.9%. The method was unsuitable for the quantitation of curcuminoids in complex smoothie products, products containing microbeads, or tinctures based on interlaboratory variances. Recommendations were provided for future multi-laboratory studies performed through QAPs and incremental approaches.

Conclusions

Method 2016.16 is suitable for the quantitation of curcuminoids and should be adopted for Final Action status for single and multi-ingredient dietary supplements containing dried roots, dried powders/extracts in bulk material, capsules, and softgels.

Highlights

Reproducibility for Method 2016.16 was collected through a non-traditional incremental data multi-laboratory study. The method is suitable for quantitation of curcuminoids in most common dietary supplements.

Rapid and Economic Determination of 13 Steviol Glycosides in Market-Available Food, Dietary Supplements, and Ingredients: Single-Laboratory Validation of an HPLC Method

Steviol glycosides, obtained from leaves of Stevia rebaudiana Bertoni (stevia) or produced via bioconversion and biosynthesis, are diterpenes used by the food/dietary supplement industry as zero-calorie sweeteners derived from natural sources. JECFA 2017 is the most updated international standardized method but it runs for 80 min per sample with suboptimal separations on several critical pairs for its high-performance liquid chromatography-ultraviolet (HPLC-UV) determination. We developed and validated a rapid and economic HPLC-UV method using the superficially porous particle column to determine 13 steviol glycosides (stevioside, dulcoside A, rubusoside, steviobioside, and rebaudioside A-F, I, M, and N). Baseline separation with a minimum resolution of 1.5 for 13 steviol glycosides was achieved within only 14 min of separation time. The hydrocarbon stationary phase with additional steric interactions from the isobutyl side chains on the C18 ligand was shown to be an important contributor to chromatographic selectivity of several critical pairs of steviol glycosides. The method was proven to perform suitably on columns from three different manufacturers and two HPLC instruments. The method was further used to perform a single-lab validation on eight food and supplement products with multiple matrices. The results ranged from 0.05% w/w rebaudioside A for a hard-candy finished product to 100.8% w/w purity for a rebaudioside M raw ingredient. The validation test results showed that the method was linear, suitable, specific, accurate, and precise. The method is therefore suitable to be considered as a new industrial standard for quality control analysis for stevia products.

Selection and characterization of botanical natural products for research studies: a NaPDI center recommended approach

Covering: up to the end of 2018 Dietary supplements, which include botanical (plant-based) natural products, constitute a multi-billion-dollar industry in the US. Regulation and quality control for this industry is an ongoing challenge. While there is general agreement that rigorous scientific studies are needed to evaluate the safety and efficacy of botanical natural products used by consumers, researchers conducting such studies face a unique set of challenges. Botanical natural products are inherently complex mixtures, with composition that differs depending on myriad factors including variability in genetics, cultivation conditions, and processing methods. Unfortunately, many studies of botanical natural products are carried out with poorly characterized study material, such that the results are irreproducible and difficult to interpret. This review provides recommended approaches for addressing the critical questions that researchers must address prior to in vitro or in vivo (including clinical) evaluation of botanical natural products. We describe selection and authentication of botanical material and identification of key biologically active compounds, and compare state-of-the-art methodologies such as untargeted metabolomics with more traditional targeted methods of characterization. The topics are chosen to be of maximal relevance to researchers, and are reviewed critically with commentary as to which approaches are most practical and useful and what common pitfalls should be avoided.

Integrated analytical assets aid botanical authenticity and adulteration management

This article reviews and develops a perspective for the meaning of authenticity in the context of quality assessment of botanical materials and the challenges associated with discerning adulterations vs. contaminations vs. impurities. Authentic botanicals are by definition non-adulterated, a mutually exclusive relationship that is confirmed through the application of a multilayered set of analytical methods designed to validate the (chemo)taxonomic identity of a botanical and certify that it is devoid of any adulteration. In practice, the ever-increasing sophistication in the process of intentional adulteration, as well as the growing number of botanicals entering the market, altogether necessitate a constant adaptation and reinforcement of authentication methods with new approaches, especially new technologies. This article summarizes the set of analytical methods - classical and contemporary - that can be employed in the authentication of botanicals. Particular emphasis is placed on the application of untargeted metabolomics and chemometrics. An NMR-based untargeted metabolomic model is proposed as a rapid, systematic, and complementary screening for the discrimination of authentic vs. potentially adulterated botanicals. Such analytical model can help advance the evaluation of botanical integrity in natural product research.

Challenges in Developing Analytically Validated Laboratory-Derived Dietary Supplement Databases

The Dietary Supplement Label Database (DSLD) is sponsored by the Office of Dietary Supplements (ODS) and the National Library of Medicine (NLM). It provides a searchable, free database of the contents of ∼65,000 supplement labels. A companion database of analytically verified product labels [the Dietary Supplement Ingredient Database (DSID)] was created by ODS, NLM, and the USDA. There are considerable challenges to populating both databases, but the DSID faces unique analytic chemistry challenges. This article describes the challenges to creating analytically verified marketplace surveys of dietary supplement (DS) product content claims for inclusion in public databases. Nutritionists and public health scientists require information on actual exposures to DS constituents because labeled content may not match labeled product content. Analytic verification of composition of DSs provides a link to actual exposure. A public database of analytically derived DS content was developed to provide more accurate estimates of dietary intake in population-based epidemiologic studies. The DSID has conducted surveys of several types of vitamin- and mineral-containing DSs. Results showing label content claims as analytically derived values are available in the current DSID. A recent pilot project explored the feasibility of adding botanical DS products to the DSID. Candidates for future botanical DSID studies will be based on sales volume, potential public health impacts, and the availability of validated analytic methods and reference materials. Databases like DSID and the DSLD are essential for researchers and clinicians to evaluate dietary ingredient intakes in population-based epidemiologic studies. Together, these databases provide a picture of the DS marketplace. The DSID provides an analytic survey of marketed DSs. However, selection of future botanical supplements for DSID evaluation involves analytic challenges. Even when appropriate resources are available, method selection and data evaluation are resource- and time-consuming.

Dietary Supplements: Regulatory Challenges and Research Resources

Many of the scientific and regulatory challenges that exist in research on the safety, quality and efficacy of dietary supplements are common to all countries as the marketplace for them becomes increasingly global. This article summarizes some of the challenges in supplement science and provides a case study of research at the Office of Dietary Supplements at the National Institutes of Health, USA, along with some resources it has developed that are available to all scientists. It includes examples of some of the regulatory challenges faced and some resources for those who wish to learn more about them.

Methods for the Chemical Analysis of β-N-Methylamino-L-A lanine: What Is Known and What Remains to Be Determined

β-N-Methylamino-L-alanine (BMAA) is a non-canonical amino acid implicated as a cause for amyotrophic lateral sclerosis/parkinsonism dementia complex and potentially other neurodegenerative diseases. As interest in this molecule has increased, there has been a proliferation of methods along with a plethora of opinions as to the superiority of some methods over others. We analyzed the literature with reference to BMAA and its naturally occurring isomers, N-(2-aminoethyl) glycine (AEG) and 2,4 diaminobutyric acid (DAB). A comparison of methods, results, and critiques reveal that a single method has been approved by the AOAC but several different methods provide comparable BMAA quantification concentrations in similar tissues. We also describe a productive way to move forward as technology improves and changes.

Leaner and greener analysis of cannabinoids

There is an explosion in the number of labs analyzing cannabinoids in marijuana (Cannabis sativa L., Cannabaceae) but existing methods are inefficient, require expert analysts, and use large volumes of potentially environmentally damaging solvents. The objective of this work was to develop and validate an accurate method for analyzing cannabinoids in cannabis raw materials and finished products that is more efficient and uses fewer toxic solvents. An HPLC-DAD method was developed for eight cannabinoids in cannabis flowers and oils using a statistically guided optimization plan based on the principles of green chemistry. A single-laboratory validation determined the linearity, selectivity, accuracy, repeatability, intermediate precision, limit of detection, and limit of quantitation of the method. Amounts of individual cannabinoids above the limit of quantitation in the flowers ranged from 0.02 to 14.9% w/w, with repeatability ranging from 0.78 to 10.08% relative standard deviation. The intermediate precision determined using HorRat ratios ranged from 0.3 to 2.0. The LOQs for individual cannabinoids in flowers ranged from 0.02 to 0.17% w/w. This is a significant improvement over previous methods and is suitable for a wide range of applications including regulatory compliance, clinical studies, direct patient medical services, and commercial suppliers.