Study gives detailed view of arsenic in omega-3 supplements, but sounds no alarms

By Hank Schultz

- Last updated on GMT

©Getty Images - batuhan toker
©Getty Images - batuhan toker

Related tags Fish oil Fish oil supplements Omega-3 fatty acid Docosahexaenoic acid Eicosapentaenoic acid Omega-3 fatty acids EPA and DHA arsenic

An analytical study on marine sourced dietary supplements found different forms of arsenic present in most of them, but at sub-toxic levels. GOED said the results were not a concern to consumers with the caveat that the risk posed by one of the arsenic forms found is still mostly unknown.

The research was published recently in the journal Chemosphere​.  It was the work of a pair of faculty members from Dartmouth College.

The researchers, one from the college’s Earth Sciences division and another from the medical school, purchased 32 marine sourced supplements for their test.  The supplements consisted of fish oils, krill oils, algal oils, one calanus oil supplement, as well as seaweed supplements.

Arsenic content could pose risk to fetuses

The researchers’ primary goal was to assess arsenic concentrations in light of the frequent recommendation for pregnant mothers to take omega-3 supplements, in particular those high in DHA (docosahexaenoic acid) to aid in proper fetal brain development.  Developing fetuses are of course highly sensitive to many trace elements in the mother’s diet.

To get a handle on the scope of the risk, the researchers used statistics from a longitudinal health outcomes survey.

“Survey data from the New Hampshire Birth Cohort Study (NHBCS) found 13.5% of pregnant women (n = 1997) reported taking fish oil supplements; and of those, most did so daily (75.6%, 6 or more times per week). Only a small percentage (9%) of those who reported consuming fish oil used products associated with higher arsenic levels. Higher urinary arsenic concentrations were found among women who consumed fish oil compared with those who did not, and specifically higher arsenobetaine and dimethyl arsenic concentrations,”​ they wrote.

Most concentrations low, and all within published limits

The supplements were first measured for total arsenic levels, with levels ranging from Concentrations of total arsenic ranged from 3.5 to 13300 ng g− 1.  Most of the concentrations were low, with seventeen of the products tested having less than 10 ng g− 1 arsenic, and twenty-two having concentrations less than 1000 ng g− 1. 

Those with levels higher than 1000 ng g− 1  were subjected to further analysis.  This group included four krill and zooplankton oils, two fish oils and two fish liver oils, and two seaweed- based thyroid support supplements. 

The more complex analysis looked for levels of inorganic arsenic, arsenic hydrocarbons and arsenolipids in the 10 supplements.

The researchers found varying levels of these compounds, but all at below cytotoxic levels.  One seaweed supplement had the highest inorganic arsenic level at 8900 ng g− 1. Inorganic arsenic is the most troublesome of the forms tested for in this study.

Given the large number of marine-sourced supplements available, and the insufficient levels of omega-3 consumed by a majority of pregnant women in the U.S, this study adds to information useful to providing recommendations on supplement use, particularly for this vulnerable population. Most marine-sourced products are low in arsenic concentrations, however, seaweed-based products in this study and others have found elevated inorganic arsenic concentrations,”​ the researchers concluded.

GOED:  Arsenolipids risks still unknown

Gerard Bannenberg, PhD, director of compliance and scientific outreach for the industry group Global Organization of EPA and DHA Omega-3s (GOED), said the news was a welcome sign of quality in the industry, with few if any of the marine-sourced oil products showing any problematical signs.  One caveat, though, is that arsenolipid levels are rarely assessed, and their potential health risks remain uncharacterized.

The study by Taylor & Karagas shows the results of testing of 32 marine-sourced EPA/DHA-rich omega-3 supplements for their contents of arsenic. Besides the measurement of total and inorganic arsenic, a wide range of organic arsenic species were measured, including arsenic hydrocarbons and arsenic fatty acids – a large family of still poorly characterized arsenolipids that are not usually analyzed in the quality control of edible oils,”​ he said.

All tested retail products containing refined fish oil complied with regulations stipulating maximum limits for inorganic and total arsenic. Minimally-processed fish and fish liver oils and calanus oil were found to be a source of arsenic hydrocarbons at concentrations below those associated with cytotoxic effects. Krill oil was found to contain arseno fatty acids but was not a source of inorganic arsenic or arsenic hydrocarbons.  As expected, marine oil supplement consumption was associated with a small increase in urinary concentrations of total arsenic, including the metabolites arsenobetaine and dimethyl arsenate. Based on the results of this study, GOED currently does not view the findings of concern to human health until the specific actions of the individual arsenolipids are further understood,” ​he added.

DOI: 10.1016/j.chemosphere.2022.133930
Exposure to arsenolipids and inorganic arsenic from marine-sourced dietary supplements
Authors: Taylor VF, Karagas MR

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