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Green tea (GT) is a botanical that is commonly consumed and frequently studied for its health benefits and thus was chosen as the first botanical dietary supplement (DS) study for the DSID. The data from this study complements the data on the phytochemical intake of green tea from foods and beverages.
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 Office of Dietary Supplement 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.
The first GT study was limited to products containing GT in a relatively simple matrix (products with green tea as the only ingredient or with green tea as the primary ingredient with no other botanicals), to minimize interferences for analytical results and to compare to label claims for GT components.
Products with a wide range of dosage forms were purchased: hard-shell capsules, softgels, tablets, caplets (smooth-coated tablets), liquids and powders. Two lots of each 4 product (n=32) were purchased from the three major sales channels: mass market retail (e.g., Walmart, CVS, Target), natural and specialty retail (e.g., GNC or Whole Foods), and direct sales (products sold exclusively via the web or by multi-level marketers like Amway or Herbalife). Two 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.
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 laboratory precision and accuracy. 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 final laboratory data reported by the three laboratories for two lots of each product were statistically evaluated. Least squares means and standard deviations (SDs) were computed for each product using a mixed model procedure. Results for EGCG (the most prevalent catechin), total catechins (TC) and Caffeine (Caf) are reported as “amount per serving”, “amount per day” and “percent difference from label”, if applicable.
Data are reported for this study as per serving (Table 1) and per day (Table 2). The most useful comparison of content among GT DS products is accomplished by using per day amounts rather than per serving because, for many products, the label recommends more than one serving per day. Of the thirty-two products included in this study twenty had a suggested use of more than on serving per day. Suggested use was one serving per day for twelve products, two servings per day for fourteen products and three servings per day for six products. Analytically measured amounts for catechins and caffeine in green tea are reported as mg/serving and as mg/day in order to facilitate accurate comparisons between GT DS products. The suggested use for some products was a range of servings per day (for example, 1-2 servings per day). In this case the maximum servings per day was used to calculate per day amounts.
The product based mean values for analytically measured concentrations of EGCG, total catechins, and caffeine showed wide ranges (0.5-562, 1.4-1070, and 0.1-130 mg/serving, respectively; Table 1). Median per serving values for product based EGCG, total catechin, and caffeine content were 113, 205, and 11 mg/serving, respectively. The product based analytical mean per day ranges for EGCG, total catechins, and caffeine were (2.0-630, 4.2-1070, and 0.25-130 mg/day, respectively; Table 2). Median per day values for EGCG, total catechin, and caffeine content were 141, 280, and 22 mg/day, respectively.
The labeled levels for the amount of GT in the 32 products (information required by FDA) ranged from 150-2000 mg/serving and 300-6000 mg/day. At the most commonly labeled level for GT material (500 mg/serving; n=9), the analytical mean values for total catechin ranged from 1.4 to 410.6 mg/serving, and from 0.5 to 314.8 mg/serving for EGCG.
For the 23 products that voluntarily provided label claims for total catechins, EGCG or caffeine, we compared the mean percent difference from labels with label claim. For the 18 products with EGCG label claims, percent differences from label ranged from 35% below label to 186% above label, with 10 products within ± 20% of label claim. For the 10 products with total catechin label information, the percent differences from label ranged from 36% below label to 45% above label and for the 9 products with a label claim for caffeine, the ranges were 84% below to 70% above label (Table 3).
Seven products contained green tea from two different sources. Five of these had a claim for EGCG, TC or Caf for only one of the sources (usually the green tea extract). Not surprisingly, the analytical results for these products are all above label claims (Table 3). The two liquid GT DS (GTP07; GTP11) had the lowest levels of total catechins of all the products (results: 1.4 and 10.8 mg/serving). The analytical content of eight products labeled as decaffeinated (or below 4 mg) averaged 2.9 mg/day (range 0.4-12).
In summary, the GT DS in the simple matrices analyzed in this study have a variety of label formats and a wide range of labeled amounts for GT. The information about the total weight of GT may not permit accurate predictions for the content of specific phytochemical constituents, because green tea extracts may or may not be highly concentrated and they are often microencapsulated (adds additional weight) for improved shelf life. Voluntary label information (e.g., listing amounts of EGCG or caffeine) is associated with a higher level of the actual phytochemical content, on average, compared to products without such information. The caffeine content in these products was usually low for a DS (< 50 mg/day; n=28/32 products).
It is important to track the intake of phytochemicals, especially those that have intakes from foods and supplements to evaluate their health effects. In a recent evaluation of flavonoid intake in NHANES 2007-08 using the USDA Flavonoid Values for Survey Foods and Beverages 2007-2008 (Bhagwat and Haytowitz, 2015), the mean U.S. daily intake of flavonoids was estimated to be 251 mg (with 81% from catechins) (Sebastion, et. al, 2015). If you compare that number to the analytical results for total catechins in the GT DS studied, 19 products would provide more flavonoids per day than the average daily estimate of 251 mg from foods and beverages.
A second GT pilot study (GT-2) is in progress to evaluate the content of catechins and caffeine in complex matrices that include several botanical ingredients along with minerals, vitamins and/or other compounds. These botanical products were marketed for the purposes of weight loss, increasing energy, sports performance or increasing intake of antioxidants or bioflavonoids. Approximately half of the 36 products listed a label claim for green tea on the label. The other half listed green tea as part of a blend (these products are not required to list the amounts of ingredients within a blend—only the weight of the total blend).
The efficacy of a DS is determined not only by the amount of one or more active ingredients but also by the design and performance of the formulations into which they are incorporated. Currently, we are studying whether commercially sold single- and multi-ingredient green tea dietary supplements meet the United State Pharmacopeia general chapter specifications for disintegration and dissolution for immediate release formulations.
