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About ConsumerLab.com


How Products Were Selected:

Products were selected to represent those commonly available nationally in the U.S. and popular among readers of ConsumerLab.com. ConsumerLab.com purchased products on the open market through retail stores, on-line retailers, and direct sales companies. Products were not accepted directly from manufacturers.

Testing Methods:

L-Glutathione products were tested in one or more independent laboratories for the following:
  1. Identification and quantification of L-glutathione and S-acetyl glutathione by High Performance Liquid Chromatography (HPLC) or other appropriate methods as determined by CL.
  2. Quantitative analyses for lead, arsenic, cadmium and mercury in all products by Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS).
  3. Disintegration of tablets (excluding chewable, sublingual, and time-release formulations) utilizing United States Pharmacopeia (USP) <2040> recommendations entitled "Disintegration and Dissolution of Nutritional Supplements."
  4. Disintegration time of enteric coated, time-release, and sustained release tablet, caplet and softgel formulations utilizing USP <2040> methodology for delayed-release (enteric-coated) tablets."
Testing was performed by one or more independent laboratories. Any product that did not initially pass (as defined below) was sent to another independent laboratory to repeat testing for criterion on which it did not pass.

ConsumerLab.com may modify or use other appropriate test methods if necessary to test special product formulations.

The identities of the products were not disclosed to the laboratories performing the testing.

Passing Score:*

To be "Approved" for quality, a product had to meet the following requirements:
  1. Contain at least 100% of its labeled amount of L-glutathione, S-acetyl glutathione or combination and no more than 130% of this amount.
  2. Heavy Metals: All Products. Products must not exceed the following limits:
    Lead:
    • Products marketed for use by children under 12 years of age may not exceed the State of California's Prop 65 limits for lead in dietary supplements of 0.5 mcg per recommended daily serving with an additional allowance of 0.8 mcg if the product contains more than 1,000 mg/day of calcium.
    • Products with a single serving weight of less than 5 grams that are not marketed for use by children under 12 years of age, may not exceed the State of California's Prop 65 limits for lead in dietary supplements of 0.5 mcg per recommended daily serving (above which a warning regarding reproductive harm, birth defects, or cancer risks is required in California) with an additional allowance of 0.4 mcg if containing 250-999 mg/day of any combination of elemental calcium, magnesium and potassium or 0.8 mcg if containing more than 1,000 mg/day of any combination of these minerals. An additional allowance of 0.5 mcg is provided if containing 250-999 mg/day of whole herb (not extract) or 1.0 mcg if containing 1000 mg/day or more of whole herb (not extract). However, total lead allowance must not exceed 2 mcg per daily serving.
    • Products with single serving weights of 5 grams or more that are not marketed for children under 12 years of age may not exceed 2.5 mcg per serving nor 4.0 mcg per daily serving.
    Arsenic:
    • Contain less than 10 micrograms of total arsenic per daily serving (based on Canada‚Äôs limit per daily serving of a natural health product, and U.S. EPA and state of New Jersey limit in 1 liter of water). Products found to exceed this amount were tested for inorganic arsenic and must not contain more than 2.1 micrograms of inorganic arsenic per daily serving (Canada's additional limit in natural health products).
    Cadmium:
    • If marketed for use by children under 12 years of age, may not exceed 3.0 micrograms of cadmium per recommended daily serving (based on Canada's limit for a child weighing 75lbs). If not marketed for use by children under 12 years of age, may not exceed 4.1 micrograms of cadmium per recommended daily serving (above which California's Prop 65 law requires a "reproductive harm" warning due to developmental toxicity and male reproductive harm.
    Mercury:
    • May not exceed 2 micrograms of inorganic mercury per daily serving (based on EPA limit for mercury in 1 liter of water).
  3. If applicable to the product, meet recommended USP <2040> parameters of disintegration for dietary supplement tablets (excluding sublingual, chewable and time-release products).
  4. Enteric coated, time-release, and sustained release tablet, caplet and softgel formulations must meet recommended USP <2040> parameters for delayed-release (enteric-coated) tablets, caplets and softgels by visual inspection.
  5. Meet FDA labeling requirements.
A "Pass" was based on meeting the above criteria in either the first or second rounds of testing.

* Passing scores allow for specific margins of technical error associated with each analysis. ConsumerLab.com reserves the right to disqualify a product at any time from passing its testing if it considers such product to display unacceptable variation in quality, present a safety risk or to provide misleading or inaccurate information in its labeling.

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