Cherry 2019 - Edible seaweeds risks and benefits

Cherry and colleagues reviewed edible seaweeds as food, functional-food ingredients, and nutraceutical inputs, balancing proposed nutritional benefits against safety concerns. The source is secondary evidence and does not generate new contaminant measurements. Its heavy-metal section is mainly useful for seaweed arsenic/speciation context and for identifying food and supplement monitoring needs.

Key numbers

The review states that global seaweed aquaculture accounts for approximately 27.3 million tonnes (96%) of global seaweed production per annum. It also states that Japan is a region where approximately one-fifth of meals contain seaweed.

In the heavy-metals section, the authors state that levels of arsenic, mercury, lead, and cadmium in 426 Korean dried seaweed products ranged from 0.2% to 6.7% of provisional tolerable weekly intakes when 8.5 g of seaweed was consumed per day. They also state that at an intake of 3.3 to 12.5 g/d, Laminaria digitata contains 24 to 90 µg of cadmium, corresponding to 40% to 150% of the tolerable daily intake. Laminaria japonica is reported to contain 0.45 to 0.80 mg/kg, exceeding the seaweed-product limits cited for France (0.5 mg/kg of dry weight) and Australia/New Zealand (0.2 mg/kg of dry weight), but not China (1.0 mg/kg).

The arsenic section reports that arsenic speciation and concentration in brown, red, and green seaweeds showed total arsenic from 4.1 to 111.0 µg/g, with most arsenic present as arsenosugars and inorganic arsenic content < 1.0 µg/g. The exception was Laminaria digitata, with inorganic arsenic 2.8 to 20.0 µg/g in USA samples and 2.2 to 87.0 µg/g in Ireland samples. Total arsenic in Laminaria digitata is reported as 36.0 to 131.0 µg/g of dry weight.

The review reports that Laminaria japonica from China contained inorganic arsenics at 0.16 to 0.58 mg/kg, below the limits cited for China (1.0 mg/kg of dry weight), France (3.0 mg/kg of dry weight), and Australia/New Zealand (1.0 mg/kg of dry weight).

For 23 seaweed food products, inorganic arsenic was reported as negligible except for hijiki 19.83 µg/g, agar 0.06 µg/g, and nori 0.03 µg/g. Total arsenic values for those products were reported in descending order: hijiki 83.7 µg/g, kombu 51.2 µg/g, kelp seasoning 43.5 µg/g, arame 41.6 µg/g, wakame 34.7 µg/g, dried red seaweed 35.2 µg/g, nori 19.4 µg/g, dulse 12.1 µg/g, agar 0.23 µg/g, and kelp noodles 0.08 µg/g.

For 112 edible seaweed products sold in Spain, inorganic arsenic was stated to be within safe limits except for hijiki, where inorganic arsenic ranged from 41.6 to 117.0 µg/g. The review states that arame, wakame, kombu, and nori were suggested as safe to eat because they contain inorganic arsenic at less than 0.3 µg/g.

The review reports several exposure or processing values, not product-occurrence concentrations: baking and boiling of Porphyra spp and Hizikia fusiforme increased inorganic arsenic species, while soaking, cooking, boiling, and washing/soaking of other seaweeds reduced total arsenic by up to 58.8%, 91.5%, 50%, and 60%, respectively. A Porphyra spp study reported total urinary arsenic peaking at an average 92.5 ng/mL after 20 to 30 hours. A Laminaria spp volunteer study used 20 to 25 g with total arsenic 43.2 µg/g; the peak ratios of arsenic to creatinine were 228, 158, 141, 72, and 70 ng/mL, and levels normalized after 80 hours.

Methods (brief)

This is a narrative review of edible seaweed nutrition, human intervention evidence, bioactive components, and adverse effects. Heavy-metal content is discussed from cited studies and supporting-information tables rather than from new measurements. The extracted PDF text flattened some µg/g units to mg/g; rendered pages 321-322 were checked directly before recording arsenic and cadmium units.

Implications

This source supports broad seaweed-food and seaweed-supplement context for arsenic speciation, cadmium exposure, and monitoring gaps. It should not be treated as a primary occurrence dataset because its numeric contaminant values are drawn from cited studies and supporting information. The review reinforces that total arsenic and inorganic arsenic must remain separate in seaweed routing.

Verification notes

• PDF text extracted with pdftotext -layout; title page, heavy-metals section, arsenic section, and conclusion were readable, but the text layer mis-rendered some micro symbols.
• DOI 10.1093/nutrit/nuy066, raw handle MFK_nuy066, and cite-key checks found no existing source page before creation.
• Heavy-metal and arsenic values were checked against extracted text and rendered PDF pages /tmp/nuy066-page-15.png and /tmp/nuy066-page-16.png to verify that key arsenic values are µg/g, not mg/g.
• Units and bases are preserved as the source shows them: µg, µg/g, mg/kg, ng/mL, and percent changes. No conversion was performed.
• Speciation: total arsenic and inorganic arsenic are recorded separately; total arsenic values are not promoted to inorganic arsenic.
• Brand firewall: no sampled product brands are attached to contamination values.
• Frontmatter slugs were checked against docs/gpt-collaboration/taxonomy-snapshot.md; no new product or ingredient slug was invented.

Page history

The five most recent substantive edits to this page. 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.