Intake of food supplements based on algae or cyanobacteria may pose a health risk due to elevated concentrations of arsenic species

Overview

Cheyns and colleagues measured total arsenic and selected arsenic species in 33 algae- or cyanobacteria-based food supplements purchased in Belgium. The source is directly relevant to algae/seaweed supplement occurrence because it reports sample-level total As, inorganic As, DMA, arsenobetaine, recommended dose, and exposure estimates. All sample results are reported on a whole-weight, product-as-sold basis.

Key numbers

The abstract reports total As (Astot) concentrations in the range 0.053-57 mg/kg, with the highest concentrations in supplements containing brown algae. Inorganic As (Asi) concentrations were reported in the range <0.02-4.7 mg kg−1. The paper states that a large fraction of arsenic in algae/cyanobacteria supplements was present as arsenosugars and that negligible amounts of arsenobetaine were detected.

Table 1 reports concentrations in µg g−1. All rows below preserve the source’s sample IDs and units; no brand names are reported in the source.

The source’s exposure calculation used package-recommended daily dose and a 70 kg adult body weight. It reports daily supplement-derived Asi intake in the range 0.00004-0.02 µg kgbw−1 d−1, potentially toxic As fraction (Astot-AB) intake in the range 0.00012-0.20 µg kgbw−1 d−1, and DMA intake in the range 0.00008-0.011 µg kgbw−1 d−1.

Selected source risk-screen outputs, reported here as source context rather than HMTc thresholds:

• The highest calculated Asi exposure, including background exposure, was 2.6% of the source’s acute MRL screen.
• The highest calculated DMA exposure, including background dietary exposure, was 0.1% of the chronic MRL screen.
• For Asi, the source concluded no concern for the general population across all collected supplements, while 8 of 33 supplements were classified as of concern for the source’s sensitive-population screen.
• For the Astot-AB potentially toxic fraction, the abstract states 26 out of 33 supplements showed no concern and 7 had potential health risk. The body text states 24 out of 33 (= 79%) showed no concern and 7 had potential health risk; the percentage and complement align with 26/33, so the inconsistency is preserved rather than resolved here.

Methods (brief)

Thirty-three algae/cyanobacteria food supplements were purchased from local and online stores in Belgium during 2013-2016 and analyzed within six months after purchase. For each supplement, at least 10 tablets, capsules, or soft gels were homogenized; liquid supplements were homogenized by shaking, and dry formulations were ground before extraction or mineralisation. Soft-gel and capsule casings were separated from contents because of heterogeneity problems; for worst-case exposure calculations, the authors initially assumed casing concentrations equaled content concentrations.

Total As was determined by ICP-MS after acid digestion in PTFE vessels in a microwave oven. Arsenic species were extracted with 0.10 M HNO3 and 3% hydrogen peroxide, following a procedure similar to EN 16802:2016; this oxidizes As(III) to As(V), so Asi is measured as total inorganic arsenic without distinguishing oxidation state. Speciation was performed by HPLC-ICP-MS. The LOQ for Asi and DMA on the anion-exchange method was 0.020 mg kg−1, and the LOQ for AB on the cation-exchange method was 0.092 mg kg−1. CRMs included NMIJ 7405a hijiki seaweed, NMIJ 7532 brown rice flour, BCR 627 tuna fish, BCR 729 sea lettuce, and IRMM 804 rice flour.

Implications

This source provides a primary, sample-level occurrence dataset for algae and cyanobacteria supplements on an as-sold basis. It is especially important because it separates total arsenic from inorganic arsenic and DMA, and because the brown-algae/kelp subset shows higher total arsenic while individual samples vary substantially in inorganic arsenic. The page should not be used to infer brands or product rankings; the source anonymizes samples as FS1-FS33 and reports ingredient/species categories rather than brand-linked contaminant values.

Wiki pages this source may touch

• Ingredient class — algae/seaweed-based
• Dietary Supplements
• Seaweed
• Herbal botanicals
• Arsenic, Total
• Arsenic, Inorganic

Verification notes

• Identity checks before writing found no existing source page for DOI 10.1080/19440049.2021.1877834, raw handle MFK_cheyns2021, title text, or cite key cheyns2021-algae-cyanobacteria-supplements-arsenic.
• All sample-level concentration values in the Key numbers table were rechecked against /tmp/hmi-seaweed-032.txt, extracted with pdftotext -layout. The rows are copied from Table 1 in source order; na and < censoring markers are preserved.
• Units are preserved as the source reports them: Table 1 concentrations are µg g−1, abstract and text ranges use mg/kg or mg kg−1, and exposure values use µg kgbw−1 d−1. No unit conversion was performed.
• Speciation check: Astot is recorded as total arsenic; Asi is the source’s measured inorganic arsenic fraction after extraction/oxidation; DMA and AB are not collapsed into total or inorganic arsenic. The Astot-AB metric is the source’s potentially toxic fraction, not a measured inorganic-arsenic value.
• Brand firewall: the page retains only anonymized source sample IDs (FS1-FS33) and species/formulation categories; no brand names or retailer names are attached to values.
• Missing-slug note: the taxonomy snapshot has no exact ingredient slugs for Chlorella, Spirulina, cyanobacteria, Ascophyllum, Fucus, Macrocystis, or Lithothamnium. Frontmatter uses broad existing seaweed, herbal-botanicals, supplements-algae-seaweed-based, and dietary-supplements slugs; exact organism names remain in source text.

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.