Here are some references. Now, the second one points out that there just hasn't been enough research on arsenobetaine, the main organoarsenical in seafood to know if it's toxic. And it's hard to tease out what is from inorganic arsenic from organic in one of the main metabolites. Seems to be an area where more research is required.
I personally continue to eat fish, but only once every 4 days. I came to that habit after doing an elimination diet many years ago, and following recommendations of a nutritionist who said to give my gut a break between proteins (like meat, chicken, fish, nuts) to reduce the chance of provoking an immune response that might come from daily eating. That advice has served me well in improving my gut health to this day.REFERENCESDietary Sources of Methylated Arsenic Species in Urine of the United States Population, NHANES 2003–2010 (2014)
In a nationally representative sample of the US civilian, noninstitutionalized population, fish (adults), rice (children), and rice cakes/crackers (adolescents) had the largest associations with urinary DMA. For MMA, rice beverage/milk (adults) and rice cakes/crackers (children, adolescents) had the largest associations.
Since most arsenic species absorbed from the gastrointestinal tract is excreted in urine within 1–3 days
–, urinary arsenic is well-suited as an exposure biomarker to correlate with NHANES 24-hour dietary recall data. Although inorganic species have been a focus of concern because of their carcinogenicity , certain methylated arsenic species may be carcinogenic , . Indeed, there is greater awareness that methylation of inorganic arsenic species may also affect susceptibility to arsenic-induced disease and may vary among individuals depending on genetic polymorphism, dose, age, selenium intake, as well as folate and homocysteine status , , –.
The largest significant increase in urinary molar concentration of methylated arsenic species was for DMA (872.55 nmol/L per kg) attributable to rice cakes/crackers consumed by adolescents (Table 4). The next largest molar increase among methylated species was associated with fish consumption among adults: 181.16 nmol DMA/L per kg.
The third largest molar increase was for rice consumption among children at 115.38 nmol DMA/L per kg, followed by 105.58 nmol DMA/L per kg rice consumed by adults. At the fifth rank, MMA appears for the first time with 103.04 nmol MMA/L per kg rice cake/crackers consumed by adolescents (Table 5).
Increases in urinary methylated arsenic species for the 90th percentile diet comprised several food groups with positive and statistically significant regression slopes. The greatest molar increase among methylated species was associated with increased fruit consumption among children (2.41E-1 nmol DMA/L per kg bw), followed by fish eaten by adults (7.26E-2 nmol DMA/L per kg bw), meat, poultry eaten by adolescents (5.38E-2 nmol DMA/L per kg bw), fruits eaten by adults (4.71E-2 nmol DMA/L per kg bw), grain products eaten by children (4.26E-2 nmol MMA/L per kg bw), and legumes, nuts, seeds eaten by adolescents (1.95E-2 nmol DMA/L per kg bw). The next largest increase was associated with grain products consumed by adults (1.52E-2 nmol DMA/L per kg bw), followed by meat, poultry (1.32E-2 nmol DMA/L per kg bw), legumes, nuts, seeds (6.27E-3 nmol DMA/L per kg bw), sugars, sweets, beverages (6.10E-3 nmol MMA/L per kg bw), and fruits (4.29E-3 nmol MMA/L per kg bw).https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4176478/ Organoarsenicals in Seafood: Occurrence, Dietary Exposure, Toxicity, and Risk Assessment Considerations - A Review (2020)Diet, especially seafood, is the main source of arsenic exposure for humans.
The total arsenic content of a diet offers inadequate information for assessment of the toxicological consequences of arsenic intake, which has impeded progress in the establishment of regulatory limits for arsenic in food. Toxicity assessments are mainly based on inorganic arsenic, a well-characterized carcinogen, and arsenobetaine, the main organoarsenical in seafood. Scarcity of toxicity data for organoarsenicals, and the predominance of arsenobetaine as an organic arsenic species in seafood, has led to the assumption of their nontoxicity. Recent toxicokinetic studies show that some organoarsenicals are bioaccessible and cytotoxic with demonstrated toxicities like that of pernicious trivalent inorganic arsenic, underpinning the need for speciation analysis. The need to investigate and compare the bioavailability, metabolic transformation, and elimination from the body of organoarsenicals to the well-established physiological consequences of inorganic arsenic and arsenobetaine exposure is apparent.
This review provides an overview of the occurrence and assessment of human exposure to arsenic toxicity associated with the consumption of seafood.
Human exposure to AsLipids arises from ingestion of seafood for example fatty fish, algae, and crustaceans…In seafood, AsLipids comprise up to 70% of the total arsenic content…The greatest qualities are obtained in fatty fish like herring and mackerels…Due to their amphiphilic structure, intact AsLipids are seemingly able to substantially transfer across physiological carriers, such as intestinal carriers and the blood-brain barrier…
(They go on to call for more toxicity studies on the organoarsenicals and their metabolites.)https://pubmed.ncbi.nlm.nih.gov/31913614/
(Available in Sci-Hub, the DOI is 10.1021/acs.jafc.9b07532)Estimation of Inorganic Arsenic Exposure in Populations With Frequent Seafood Intake: Evidence From MESA and NHANES (2016)
Seafood, including fish, shellfish, and seaweed, are important sources of organic arsenicals (arsenobetaine, arsenosugars, and arsenolipids), which are believed to have low toxicity (26–29). Arsenobetaine is rapidly cleared from the blood stream and excreted unchanged via the kidneys, thereby contributing to total arsenic levels in urine (30–32). Seaweed, mollusks (e.g., scallops, mussels), and fatty fishes are rich in arsenosugars and/or arsenolipids that are metabolized into several arsenic species, including DMA, dimethylated thio arsenic species, and possibly MMA (30–33). Therefore, in populations with moderate-to-high fish intakes, the sum of inorganic and methylated arsenic species levels in urine cannot be used as a biomarker of iAs intake.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5065621/ Arsenic in the human food chain, biotransformation and toxicology--Review focusing on seafood arsenic (2015)
Fish and seafood are main contributors of arsenic (As) in the diet. The dominating arsenical is the organoarsenical arsenobetaine (AB), found particularly in finfish. Algae, blue mussels and other filter feeders contain less AB, but more arsenosugars and relatively more inorganic arsenic (iAs), whereas fatty fish contain more arsenolipids. Other compounds present in smaller amounts in seafood include trimethylarsine oxide (TMAO), trimethylarsoniopropionate (TMAP), dimethylarsenate (DMA), methylarsenate (MA) and sulfur-containing arsenicals. The toxic and carcinogenic arsenical iAs is biotransformed in humans and excreted in urine as the carcinogens dimethylarsinate (DMA) and methylarsonate (MA), producing reactive intermediates in the process. Less is known about the biotransformation of organoarsenicals, but new insight indicates that bioconversion of arsenosugars and arsenolipids in seafood results in urinary excretion of DMA, possibly also producing reactive trivalent arsenic intermediates. Recent findings also indicate that the pre-systematic metabolism by colon microbiota play an important role for human metabolism of arsenicals. Processing of seafood may also result in transformation of arsenicals.https://www.sciencedirect.com/science/a ... via%3Dihub Arsenic in the human food chain, biotransformation and toxicology--Review focusing on seafood arsenic (2015)
Fish and seafood are main contributors of arsenic (As) in the diet. The dominating arsenical is the organoarsenical arsenobetaine (AB), found particularly in finfish. Algae, blue mussels and other filter feeders contain less AB, but more arsenosugars and relatively more inorganic arsenic (iAs), whereas fatty fish contain more arsenolipids. Other compounds present in smaller amounts in seafood include trimethylarsine oxide (TMAO), trimethylarsoniopropionate (TMAP), dimethylarsenate (DMA), methylarsenate (MA) and sulfur-containing arsenicals. The toxic and carcinogenic arsenical iAs is biotransformed in humans and excreted in urine as the carcinogens dimethylarsinate (DMA) and methylarsonate (MA), producing reactive intermediates in the process. Less is known about the biotransformation of organoarsenicals, but new insight indicates that bioconversion of arsenosugars and arsenolipids in seafood results in urinary excretion of DMA, possibly also producing reactive trivalent arsenic intermediates. Recent findings also indicate that the pre-systematic metabolism by colon microbiota play an important role for human metabolism of arsenicals. Processing of seafood may also result in transformation of arsenicals.https://pubmed.ncbi.nlm.nih.gov/25666158/
(Available in Sci-Hub, doi 10.1016/j.jtemb.2015.01.010)Seafood Intake and Urine Concentrations of Total Arsenic, Dimethylarsinate and Arsenobetaine in the US Population (2012)
Participants reporting seafood in the past 24-h had higher urine concentrations of total arsenic (median 24.5 vs. 7.3 µg/L), DMA (6.0 vs. 3.5 µg/L), arsenobetaine (10.2 vs. 0.9 µg/L) and total arsenic minus arsenobetaine (11.0 vs. 5.5 µg/L). Participants reporting seafood ≥2/wk vs. never during the past year had 2.3 (95% confidence interval 1.9, 2.7), 1.4 (1.2, 1.6), 6.0 (4.6, 7.8) and 1.7 (1.4, 2.0) times higher (p-trend <0.001) concentrations of total arsenic, DMA, arsenobetaine and total arsenic minus arsenobetaine, respectively. In participants without detectable arsenobetaine and in analyses adjusted for arsenobetaine, seafood consumption in the past year was not associated with total arsenic or DMA concentrations in urine.
70.0% of the population reported seafood intake at least once a month during the past year (Table 1). Compared to participants reporting seafood intake <1/month, participants who reported seafood intake ≥ 1/month had higher median concentrations for all measured urine arsenic biomarkers: total arsenic (9.0 vs. 6.6 µg/L), DMA (4.0 vs. 3.1 µg/L), arsenobetaine (1.9 vs. 0.5 µg/L), and total arsenic minus arsenobetaine (6.0 vs. 5.2 µg/L). Urine concentrations of total arsenic, DMA, arsenobetaine and total arsenic minus arsenobetaine increased with increasing frequency of reported seafood consumption in the past year (Table 3). The percentage of participants with detectable arsenobetaine was 25.4% among those reporting no seafood during the past year and 59.4%, 75.0% and 84.8%, respectively, among those reporting seafood less than once a month, 1–4 times per month and at least twice a week in the past year.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3073506/ Humans seem to produce arsenobetaine and dimethylarsinate after a bolus dose of seafood (2012)
…the urinary DMA excretion was high in the blue mussel and salmon groups, counting for 25% and 11% of the excreted tAs respectively. In conclusion our data indicate a possible formation of AB as a result of biotransformation of other organic arsenicals. The considerable amount of DMA excreted is probably not only due to methylation of ingested iAs, but due to biotransformation of organoarsenicals making it an inappropriate biomarker of iAs exposure in populations with a high seafood intake.
The sum of excreted arsenite, arsenate, MA and DMA have commonly been used as a biomarker for recent iAs exposure (Mandal and Suzuki, 2002; Steinmaus et al., 2009). This assumption does not take into account that preceding seafood intake may influence the DMA excretion, particularly intake of seafood that contains arsenosugars and/or arsenolipids. Our results strongly support the notion that DMA excretion may poorly reflect iAs ingestion in subjects exposed to seafood arsenic.https://pubmed.ncbi.nlm.nih.gov/22137101/
(Available in Sci-Hub, doi 10.1016/j.envres.2011.11.007)