Green Tea - Multiple Ingredient Study

Sampling Plan

A sampling plan was developed to identify representative products for purchase and analysis. The scope and variety of GT DS reported in NHANES 2009-2010 and the Dietary Supplement Label Database (DSLD; https://dsld.od.nih.gov/) were evaluated for information about GT composition, component levels and health claims. In addition, we conducted a detailed survey of GT products sold via various channels including local stores, the internet and multi-level marketing companies in 2013-14.

DS were purchased within a five-month timeframe in 2014-2015 from the three major sales channels: mass market retail (e.g., Walmart, CVS, Safeway, Target), natural and specialty retail (e.g., GNC, Whole Foods), and direct sales (products sold exclusively on-line or by multi-level marketers like Amway). The purchased products were in a variety of dosage forms (hard-shell capsules, caplets, tablets, soft gels, gummies and liquid-filled capsules).

Three DS were purchased in bulk for use as in-house control materials to monitor laboratory performance over time. Samples were repackaged and sent for laboratory analysis in defined batches.

Analytical Methods

Laboratories analyzed the sample sets using validated sample-handling protocols and appropriate methods to obtain analytical information about ingredient levels. For the catechin monomers, high-performance liquid chromatography (HPLC) using a reversed phase column with either ultraviolet absorbance (UV) or mass spectrometric (MS) detection was used. For caffeine, HPLC with UV detection was used. Samples were sent for retesting if there was a large discrepancy among lab results or to confirm unusually high or low values.

Quality control (QC) materials, including three certified reference materials (NIST® SRM® 3255 “Green Tea Extract”, 3254 “Green Tea Leaves” and 3256 “Green Tea Solid Oral dosage”) were analyzed with each batch of samples to evaluate the accuracy and precision of the laboratory methods. In addition, product duplicates and in-house control materials were included. The consistent results seen in the catechin and caffeine values for these quality control materials gave confidence in the results for these constituents in the commercial GT DS under study.

The percentage difference from the label claim was calculated for each analyzed constituent in each sample: % difference from label = ((analytical value – label value)/label value) × 100%. Laboratory data were reviewed and samples with unusually large % differences from label claims, high variability among lots of the same product, and/or samples from batches with QC results showing biased results were retested. The final laboratory data were sent to MAFCL’s consulting statistician for statistical analysis.

Statistical Analysis

Least squares means and standard deviations (SDs) were computed for each constituent in each product using a SAS mixed model procedure. Results for EGCG (the most prevalent catechin), total catechins (TC; the summed content of 7 individual catechins) and caffeine are reported as amount per serving (Appendix, Table 2), amount per day (Appendix, Table 3) and percentage difference from label, if applicable (Appendix, Table 4).

For many products, the label recommended more than one serving per day (1 serving per day, n=20; 2 servings per day, n=17; 3 servings per day, n=7). Therefore, the most useful comparison among these products is the per day amount. If the label suggested a range of servings per day (for example, 1-2 servings per day), the maximum serving size was used to calculate per day amounts.

Laboratory results reported in mg/g were compared to Food and Drug Administration (FDA) required label information about the weight of GT and to any voluntary label claims for constituent content.

In summary, the GT DS in the multi-ingredient products analyzed in this study have a variety of label formats and a wide range of labeled amounts for GT and GT constituents. The weight of GT and other catechin-containing sources on the label may not permit accurate predictions for the content of specific phytochemical constituents. The GT weight may include the weight of dried leaf powder and/or botanical extract powders, which may or may not be highly concentrated or microencapsulated for improved shelf life or bioavailability. Voluntary label information (EGCG per serving and per day or caffeine per serving) is associated with a higher level of the actual phytochemical content, on average, compared to products without such information.

It is important to track the intake of phytochemicals, especially those that have intakes from foods and supplements to evaluate their association with health. An evaluation of flavonoid intake in NHANES 2007-08 using the USDA Flavonoid Values for Survey Foods and Beverages 2007–2008 (Bhagwat and Haytowitz, 2015), estimates the mean US daily intake of flavonoids to be 251 mg (81% are catechins; 203 mg) (Sebastion, et. al, 2015). If that number is compared to the analytical results for total catechins in this study, 13 products (listed in the Appendix, Table 3) would provide more catechins per day than the average daily estimate of 203 mg from foods and beverages. Since many DS in this study also contained other flavonoids, we would expect a higher number of flavonoid rich DS to exceed this average daily estimate.

Conclusions and Implications

DS containing green tea and sold in the U.S. have a wide range of catechin and caffeine content. On average, products that voluntarily provided information about their EGCG or caffeine content, were found to have more than twice the measured levels than those that were not labeled for these constituents.

The label information for GT amounts did not predict either total catechins or EGCG measured content. Thus, label claims with only the required FDA information do not have a strong relationship with the actual content of the phytochemical constituents analyzed in this study. Voluntary label claims for EGCG amount (per serving, per day) were positively associated with measured TC and EGCG amounts. These findings indicate that complete and more accurate label information on extract concentration would benefit consumers who make decisions on botanical DS use and researchers who track phytochemical bioactive intakes and their association with health outcomes.

Compliance with United States Pharmacopeia (USP) Performance Standards

In both of our green tea studies, we tested dosage form performance using USP protocols. We identified a high rate of failure for both disintegration (measures if the tablet/capsule breaks apart properly) and dissolution (measures the ability of the constituent to dissolve and be available for absorption by the body) in this in vitro testing. Compliance with the USP or other compendia’s performance standards for DS is currently voluntary, but the widespread inadequate DS performance for GT DS raises concerns that DS users may not achieve health benefits expected from GT DS and jeopardizes confidence in efficacy and safety studies for GT DS produced and sold in the US and used in clinical trials (See more details: Gusev et al., 2020).

Appendix

Each ingredient was categorized as a vitamin, mineral, botanical, blend (proprietary) or other. Examples of “other” included N-acetyl-L-tyrosine, 5-hydroxytryptophan, collagen, hyaluronic acid (HA), phosphatidylserine, inositol, amino acid blend, L-carnitine, omega-3 fatty acids, betaine, bromelain, phospholipids, alpha-lipoic acid. The ingredients are listed in the order they appear on Supplement Facts panels.