Safe Use of Herbal Kelp Supplements
Environ Health Perspect. doi:10.1289/ehp.10393 available via http://dx.doi.org [Online 26 November 2007]
Referencing: Case Report: Potential Arsenic Toxicosis Secondary to Herbal Kelp Supplement
In their report of a 54-year-old woman with a 2-year history of worsening alopecia, memory loss, and fatigue, Amster et al. (2007) attributed later-emerging symptoms to arsenic in a kelp-containing (Laminaria digitata) supplement. However, the authors failed to report that the product was used at two to four times the suggested amount, of potential significance because of the naturally occurring presence of iodine in kelp. Speciation of arsenic into organic and inorganic forms was not addressed, nor was the amount of arsenic consumed calculated from observed concentration levels. Also, there were errors in marketplace and regulatory descriptions.
The supplement was identified as Icelandic Kelp. The patient "initially took two tablets," which was later increased to "at least four pills per day" (Amster et al. 2007). The authors overlooked the product's label, which states that one tablet contains 225 µg iodine (150% of daily value) and recommends "one (1) tablet per day" (Nature's Life, Larkspur, CA). This labeling conforms to the federal regulation that limits daily ingestion of kelp to an amount that provides no more than 225 µg iodine [Food and Drug Administration (FDA) 2006]. The product label also includes the following statement:
CAUTION: Do not exceed recommended dosage without first consulting your healthcare practitioner, as excess iodine may adversely affect thyroid function.
In neglecting to mention the product's labeling and their patient's decision to ignore it, Amster et al. (2007) excluded important information. Under federal law, supplement marketers must disclose material facts associated with use of their products. When a consumer ignores a label caution though, he or she takes on responsibility for that decision.
Intake of iodine at least four times this product's recommended dose must be considered a potential factor in evaluating the observed symptoms. Four tablets contain 900 µg iodine, 600% of its daily value. Amster et al. (2007) noted that the patient had a "more severe presentation than would be expected" from the measured arsenic level. In fact, of the several symptoms recorded after the patient initiated use (and overdose) of the product, only four symptoms—weakness, nausea, vomiting, and possibly erythema—are identified in the presented "clinical manifestations of chronic arsenic exposure." However, these same symptoms, as well as headache and diarrhea—also observed in this patient—are also associated with iodine toxicity (Pease 1996), albeit usually at higher doses. It would have therefore been no more or less speculative to declare that the patient had a "more severe presentation than would be expected" from the consumed iodine.
In their analysis Amster et al. (2007) did not differentiate between organic and inorganic arsenic. Arsenic is commonly found in seaweeds used as food (Rose et al. 2007). With the exception of hijiki, most arsenic found in food seaweeds is the organic form, recognized as less toxic than the inorganic form (Rose et al. 2007). The European Pharmacopoeia (European Pharmacopoeia Commission 2007) allows up to 90 ppm arsenic in kelp used in medicinal products, whereas food regulators have advised that consumption of hijiki—but not kelp or other seaweeds—be avoided due to arsenic concentrations in this species (Food Standards Agency 2004).
Although Amster et al. (2007) noted that the arsenic concentration found in most of the analyzed supplements exceeded FDA tolerances for residues in meats and eggs, they did not compare consumed arsenic from these separate sources. Daily consumption of 5 oz chicken—about one-half a chicken breast [the amount of food from the meat or beans group needed daily by women > 51 years of age, according to the U.S. Department of Agriculture's (USDA) current food pyramid (USDA 2007)]—at the allowed arsenic concentration of 0.5 ppm would contain 71 µg arsenic. To take in the same amount of arsenic from the tested samples of Icelandic Kelp, the patient would have needed to consume between 2 g (at 34.8 ppm arsenic) and 45 g (at 1.59 ppm) of these tablets daily. Although she may have used an amount at the lower end of this range, her symptoms would be just as likely to be observed in persons eating more than half a chicken breast each day.
Financial data that Amster et al. (2007) attributed to Anonymous (2002) was misstated; sales of supplements in 2001 reached only about one-tenth of the reported $178 billion. Additionally, the authors were apparently uninformed about differences between "homeopathic medications," regulated as drugs since 1938, and dietary supplements, which have been placed in a specific regulatory class only since 1994. The authors' reports of adulterated products in Singapore (Tay and Seah 1975), England (Mitchell-Heggs et al. 1990), and Brazil (Mattos et al. 2006) are irrelevant to the U.S. marketplace and its regulations, as is the citation from a 1990 reference about labeling of "botanical medicines" in light of the 1994 law (Mitchell-Heggs et al. 1990), which requires supplement labels to disclose more information than conventional food products.
In conclusion, we have no disagreement with the authors' implication that marketers have a responsibility to control the level of potentially harmful contaminants in herbal products. Inaccurate reporting and speculative science, however, have no place in safety evaluations of case reports associated with supplements.
The authors are employees of a trade association that represents the herbal products industry; 100% of their wages are provided by companies in this trade. Some such companies sell products that contain kelp. The manufacturer of Icelandic Kelp is not a member of this trade association.
Michael McGuffin
Steven Dentali
American Herbal Products Association
Silver Spring, Maryland
E-mail: mmcguffin@ahpa.org
E-mail: sdentali@ahpa.org
References
Amster E, Tiwary A, Schenker MB. 2007. Case report: potential arsenic toxicosis secondary to herbal kelp supplement. Environ Health Perspect 115:606–608.
Anderson DM. 2002. Iodine poisoning. In: Mosby's Medical, Nursing, & Allied Health Dictionary. 6th ed. St. Louis:Mosby, Inc.
[Anonymous]. 2002. Annual industry overview VII. Nutr Business Journal May/June:1–11.
European Pharmacopoeia Commission. 2006. Kelp. In: European Pharmacopoeia. 5th ed. Strasbourg, France: Council of Europe, 1869–1870.
FDA (Food and Drug Administration). 2006. Kelp. 21CFR172.365. Available: http://a257.g.akamaitech.net/7/257/2422/10apr20061500/edocket.access.gpo.gov/cfr_2006/aprqtr/pdf/21cfr172.365.pdf [accessed 7 November 2007].
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Arsenic in Herbal Kelp Supplements: Schenker et al. Respond
Environ Health Perspect. doi:10.1289/ehp.10393R available via http://dx.doi.org [Online 26 November 2007]
We are heartened by the feedback we have received from concerned patients, health-care professionals, herbal supplement retailers, and government health officials regarding our recent case study (Amster et al. 2007), but we certainly understand the concern from the representatives of the herbal trade industry. We would like to take this opportunity to respond to some of their comments.
In their letter, McGuffin and Dentali suggest that iodine was the cause of our patient's symptoms, a conclusion with which we disagree. Daily intake of up to 500 µg iodine does not clinically affect the thyroid. Although it has been suggested that 1–2 mg/day is safe, there is also evidence that much higher intakes are tolerated without problems. In their comprehensive review of this subject, Backer and Hollowell (2000) concluded that "the strongest data suggest that low levels of iodine (1–5 mg/day) are safe for most people for years." The 10th edition of the Recommended Dietary Allowances (National Research Council 1989) suggested a maximum allowable dietary intake of iodine of 2 mg/day for adults, and Breecher and Dworken (1986) noted that chronic toxicity develops only when intake is > 2 mg/day. Increased iodine intake (≤ 10 mg/day) may cause hypothyroidism or hyperthyroidism, but this condition is quite rare and is usually associated with underlying risk factors such as thyroiditis, subacute thyroiditis, or previously treated Graves disease. Intake of very high concentrations (18 mg to > 1 g/day) has been associated with iodine goiter (Wolff 1969).
Although we wonder how many cases of hypothyroidism are caused by irresponsible supplement use, in our case iodine toxicity is not the most likely etiology. Our patient (Amster et al. 2007) had normal thyroid function tests on two different occasions when hypothyroidism was being considered. Furthermore, she fully recovered (especially memory loss and fatigue) within 3 weeks after discontinuation of the kelp supplement. This short span of time for recovery would most likely not occur if she had iodine-induced hypothyroidism. In summary, the clinical presentation of this case was not consistent with iodine toxicity, particularly at the dose ingested. It is our clinical opinion, given the supporting clinical history and laboratory evidence, that her symptoms were more likely from the arsenic found in her kelp supplement and not from iodine. We believe this case raises legitimate concerns about arsenic toxicosis from commercially available kelp supplements and that further testing is indicated.
McGuffin and Dentali suggest that the patient is to blame for taking more than the recommended dose. We agree that the patient has ultimate responsibility to stay within the manufacturer's guidelines, but we wonder if our patient may have been more careful in her self-prescribing if the presence of potentially toxic levels of heavy metals were included in the product labeling. This does, however, highlight a general concern of herbal medications as they are currently marketed and used: There is little oversight from prescribing health practitioners, and self-dosing commonly leads to overdosing and possible adverse herb–drug interactions (Bush et al. 2007).
McGuffin and Dentali are correct that our reporting of the dietary supplement market share was indeed misstated. We reported $178 billion from the Nutrition Business Journal (Anonymous 2002), but $17.8 billion is the correct figure.
Our study (Amster et al. 2007) was not intended to be a comprehensive survey of arsenic content in commercial kelp supplements, but rather to call attention to the large variability of arsenic concentrations. In his letter, Lewis suggests, without documentation, that "the arsenic most commonly found in seaweed and seafood products is relatively nontoxic," that is, organic arsenic. In a recent study on arsenic content in ethanolic kelp and bladderwrack extracts, Krishna et al. (Krishna MVB, Brewer TM, Marcus RK, unpublished data) found that the majority (90–95%) of the arsenic present was inorganic arsenic, and only minor amounts of arsenic (5–10% of the total arsenic) were dimethyl arsenic acid. This finding suggests that the majority of arsenic in kelp supplements is the more toxic inorganic arsenic.
McGuffin and Dentali, representatives from the American Herbal Products Association, point out the difference between homeopathic and herbal therapies. We agree that there are differences, but for the purpose of our study there are obvious similarities: Both are used for medicinal purposes on a nonprescription basis and have been found to have toxic levels of heavy metals. McGuffin and Dentali are correct to point out that homeopathic medicines are regulated in a similar fashion to allopathic medicinals, as opposed to dietary supplements, which under the Dietary Supplement Health and Education Act of 1994 (DSHEA 1994) lack regulatory standards for premarket approval, good manufacturing standards, and labeling of indication (Borneman and Field 2006).
In conclusion, it was in no way our intention to attack the complementary alternative medicine community. Fortunately we all agree that the supplement industry has a responsibility to control the level of potentially harmful contaminants in their products. However, if the majority of certain herbal supplements have detectable levels of toxic metals—as is the case in our and other studies on kelp—then perhaps we should not leave the responsibility to the industry itself, but instead encourage our government to regulate these medicinals the same as all other medications, and not as dietary supplements.
The authors declare they have no competing financial interests.
Marc Schenker
Eric Amster
UC Davis School of Medicine
University of California
Davis, California
Asheesh Tiwary
UC Davis School of Veterinary Medicine
University of California
Davis, California
References
Amster E, Tiwary A, Schenker MB. 2007. Case report: potential arsenic toxicosis secondary to herbal kelp supplement. Environ Health Perspect 115:606–608.
[Anonymous]. 2002. Annual industry overview VII. Nutr Business Journal May/June:1–11.
Backer H, Hollowell J. 2000. Use of iodine for water disinfection: iodine toxicity and maximum recommended dose. Environ Health Perspect 108:679–684.
Borneman JP, Field RI. 2006. Regulation of homeopathic drug products. Am J Health Syst Pharm 63: 86–91.
Breecher MM, Dworken AM. 1986. The Merck Manual. Med Herit 2:229–231.
Bush TM, Rayburn KS, Holloway SW, Sanchez-Yamamoto DS, Allen BL, Lam T, et al. 2007. Adverse interactions between herbal and dietary substances and prescription medications: a clinical survey. Altern Ther Health Med 13:30–35.
DSHEA. 1994. Dietary Supplement Health and Education Act of 1994. Public Law 103-417. Available: http://www.fda.gov/opacom/laws/dshea.html [accessed 7 November 2007].
National Research Council. 1989. Recommended Dietary Allowances. 10th ed. Washington, DC: National Academy Press.
Wolff J. 1969. Iodide goiter and the pharmacologic effects of excess iodide. Am J Med 47: 101–124.