This is going to be a long article and I know not everyone will have time to read it. So I’m going to summarize the key points right up front because I think this information is so important:
Overview
- Selenium protects against mercury toxicity, and 16 of the 25 highest dietary sources of selenium are ocean fish
- If a fish contains higher levels of selenium than mercury, it is safe to eat
- Most species of commonly eaten fish in the U.S. have more selenium than mercury
- Fish are not significant sources of PCBs and dioxins when compared to meat, dairy or vegetables
- The benefits of eating fish regularly far outweigh the potential risks, which are neglible
- Pregnant mothers and young children should eat 2-3 servings of oily ocean fish each week
These days a lot of people are scared to eat fish. They’ve been told that fish are full of contaminants like mercury, PCBs and dioxins that cause neurological problems and may increase the risk of cancer. Pregnant women have been especially warned due to the supposed risk of these toxins to the developing fetus.
In the last few articles I’ve established the importance of the long-chain omega-3 fatty acids EPA and DHA in human health. I’ve argued that the conversion of plant-based omega-3 fats like ALA into the longer chain EPA and DHA is extremely poor in most people.
The conclusion is obvious: fish should be a part of our diet. But is it safe to eat fish?
You might be surprised to learn that the answer is a resounding yes. In this article I’ll demonstrate that concerns about toxins in fish have been overblown, and that there is almost no risk associated with eating fish when a few simple precautions are taken.
The selenium story
Although people are increasingly concerned about the effects of mercury levels in fish, recent evidence suggests that the trace amounts of mercury in the fish Americans eat aren’t high enough to pose a health risk.
But measuring only mercury significantly exaggerates this risk, because it ignores the important role of selenium.
Selenium is plentiful in many ocean fish species, but the public is unaware of its protective role against mercury. Selenium has high binding affinity for mercury. This means that when the two elements are found together, they connect, forming a new substance.
This new substance makes it hard for the body to absorb the mercury separately. Simply put, when selenium binds to mercury, mercury is not longer free to bind to anything else – like brain tissue.
Studies have shown that relevant amounts of selenium (Se) can prevent oxidative brain damage and other adverse effects associated with mercury toxicity. (PDF)
University of North Dakota researcher Nicholas Ralston has published several papers on the protective effects of selenium. He describes the relationship between selenium and mercury as follows:
Think of dietary selenium as if it were your income and dietary mercury as if it were a bill that you need to pay. Just as we all need a certain amount of money to cover living expenses such as food and rent, we all need a certain amount of selenium.
And guess what foods are highest in selenium? You’re right! 16 of the 25 best sources of dietary selenium are ocean fish.
He goes on:
Only one major study has shown negative effects from exposure to mercury from seafood, and that seafood was pilot whale meat. Pilot whale meat is unusual in that it contains more mercury than selenium. When you eat pilot whale meat it’s like getting a bill for $400 and a check for less than $100. If that happens too much, you go bankrupt. On the other hand, if you eat ocean fish, it’s like getting a check in the mail for $500 and getting a bill for $25. The more that happens, the happier you are.
What Ralston is telling us is that as long as the fish we’re eating has more selenium than mercury, there’s nothing to worry about.
Fortunately, studies by several independent organizations have consistently shown that most of the fish we eat contain significantly more selenium than mercury. Fish that contain more mercury than selenium include pilot whale, tarpon, marlin, swordfish and some shark.
The following chart illustrates the relative levels of selenium and mercury in commonly eaten ocean fish:
The selenium health benefit value (SeHBV)
Researchers have proposed a new measure of seafood safety called the Selenium Health Benefit Value (SeHBV) that takes the protective role of selenium into account.
Fish with a positive (above zero) SeHBV ratio would be safe to eat, whereas fish with a negative ratio would be unsafe. Using these criteria, most varieties of ocean fish have positive SeHBV ratios and are thus safe to eat.
A study conducted by the Energy & Environmental Research Center (EERC) and the Environmental Protection Agency (EPA) also found that an estimated 97% of the freshwater fish from lakes and rivers in the western U.S. are safe to eat. It is the only study I’m aware of that has measured both mercury and selenium levels in the tissues of freshwater fish. 1
So how much fish is safe to eat?
The joint recommendation for fish consumption of the EPA and FDA as of 2004 is as follows:
- Eat up to 12 ounces (2 average meals) a week of a variety of commonly eaten fish and shellfish found consistently low in mercury, including shrimp, canned light tuna, salmon, pollock, and catfish
- Limit albacore tuna to 6 oz. per week
- Do not eat shark, swordfish, king mackerel, or tilefish because they contain high levels of mercury
Notice that these recommendations are already quite liberal compared to the fish-phobes who suggest we avoid fish entirely.
But even these recommendations are too strict, because they don’t take the protective effects of selenium into account. As long as the fish is higher in selenium than it is in mercury, there’s no reason to limit consumption to 12 ounces per week.
What about dioxins and PCBs?
PCBs are synthetic organochlorine compounds previously used in industrial and commercial processes. Dioxins are organochlorine by-products of waste incineration, paper bleaching, pesticide production, and production of certain plastics. Yummy!
While it makes perfect sense to try to avoid these toxins to the greatest extent possible, abstaining from fish isn’t a particularly good strategy.
The highest dietary sources of PCBs and dioxins are not fish, but beef, chicken and pork (34%), dairy products (30%) and vegetables (22%). Fish constitute only 9% of our dietary intake of these chemicals.
The primary concern with PCBs and dioxins is cancer. Animal studies and some evidence in humans suggest that both are carcinogenic.
However, an analysis has shown that, per 100,000 individuals, consumption of farmed vs. wild salmon would result in 24 vs. 8 excess cancer deaths, respectively, while consumption of either farmed or wild salmon would result in 7,125 fewer coronary heart disease (CHD) deaths.
Another analysis of the same data suggested that, for all ages evaluated (25-35 to 85 years), CHD benefits outweighed cancer risks by 100- to 370-fold for farmed salmon and by 300- to more than 1000-fold for wild salmon.
It’s important to note that the benefits of fish consumption are based on prospective studies and randomized trials in humans, whereas estimated cancer risks include a 10-fold safety factor and are based on experimental data in animals and limited studies in humans at extremely high doses.
Cancer estimates also assumed lifetime salmon consumption of 1,000 mg/d of EPA & DHA (four 6-oz servings of wild salmon every week for 70 years). Of course virtually nobody in the U.S. currently eats this much salmon.
On the other hand, CHD mortality reduction may be achieved with lower intake (i.e. 250 mg/d – one 6-oz. wild salmon serving per week). At this intake, CHD benefits would be the same (7,125 fewer deaths) while lifetime cancer risk would decrease by 75% (6 and 2 estimated deaths per 100,000 for farmed and wild salmon respectively). The CHD benefits would outweigh cancer risks by more than 3500-fold in the case of wild salmon.
Once again, with few exceptions (the species of fish with more mercury than selenium), it’s not only safe but incredibly beneficial to eat fish regularly.
How beneficial? Let’s find out.
Fish consumption, cardiovascular disease and total mortality
In 2006 Mozaffarian & Rimm published a paper in JAMA called “Fish Intake, Contaminants and Human Health: Evaluating the Risks and Benefits“. They analyzed several studies that examined the impact of fish consumption on both coronary and total mortality. They found that modest fish consumption (e.g. 1-2 servings/wk) – especially of oily fish higher in EPA and DHA – reduced the risk of coronary death by 36% and total mortality by 17%, and may favorably affect other clinical outcomes.
The authors summarized their findings this way:
For major health outcomes among adults, based on the strength of the evidence and the potential magnitudes of effect, the benefits of fish exceed the potential risks.
And:
For women of childbearing age, benefits of modest fish intake, excepting a few selected species, also outweigh risks.
They also pointed out that the Japanese eat 900 mg/d of EPA & DHA on average, and have death rates from coronary heart disease 87% lower than those in Western populations (like the U.S.).
If you’re interested in learning more about this study, I recommend listening to the JAMA Audio in the Room interview with its lead author, Mozaffarian.
Fish consumption, pregnant mothers, and children
DHA is essential for proper development of the brain. It is preferentially incorporated into the rapidly developing brain during gestation and the first two years of infancy, concentrating in the gray matter and retinal membranes.
In a meta-analysis of 14 trials, DHA supplementation improved visual acuity in a dose dependent manner. In another trial of 341 pregnant women, treatment with cod liver oil from week 18 until 3 months postpartum raised mental processing scores at age 4 years.
This is consistent with observational studies showing positive associations between maternal DHA levels or fish intake during pregnancy and behavioral attention scores, visual recognition, memory, and language comprehension in infancy.
An FDA report issued in 2008 noted that the nutrients in fish – especially n-3 LCFAs, selenium, and vitamin D – could boost a child’s IQ by an estimated ten points. 2
The FDA report summarizes evidence suggesting that the greatest benefits to children would result if pregnant women of childbearing age, nursing mothers and young children ate more than the 12 ounces of fish per week currently recommended by the EPA.
According to the National Fisheries Institute, Americans currently consume only five ounces a week of fish high in n-3 LCFA, which is less than half the recommended amount. The NFI also estimates that up to 14 percent of women of childbearing age eat no fish at all, despite the fact that n-3 LCFA are essential to proper fetal brain and eye development.
Based on the new understanding of selenium’s protective role, and the importance of DHA for fetal and early childhood development, pregnant mothers should be advised to eat oily ocean fish regularly.
Fish consumption and autoimmune and inflammatory disease
The first evidence of the significant role of dietary intake of n-3 LCFA in reducing inflammation came from epidemiological observations of the low incidence of autoimmune and inflammatory disorders in a population of Greenland Eskimos compared with gender- and age-matched groups living in Denmark. The Eskimos in this study had dramatically lower rates of psoriasis, asthma and type 1 diabetes, as well as a complete absence of multiple sclerosis.
Animal and human studies suggest that n-3 LCFA suppresses cell mediated immune responses. Increasing the amount of n-3 LCFA while decreasing omega-6 fatty acids leads to improvements and a decrease of steroid use in patients with rheumatoid arthritis and asthma.
This is because omega-3s have been shown to suppress the capacity of monocytes to synthesize interleukin-1 (IL-1) and tumor necrosis factor (TNF). IL-1 and TNF are the principal mediators of mediation in several different inflammatory and autoimmune conditions.
Summary
This is simply a re-cap of the overview presented at the beginning of the article. But it’s worth repeating.
- Selenium protects against mercury toxicity, and 16 of the 25 highest dietary sources of selenium are ocean fish
- If a fish contains higher levels of selenium than mercury, it is safe to eat
- Most species of commonly eaten fish in the U.S. have more selenium than mercury
- Fish are not significant sources of PCBs and dioxins when compared to meat, dairy or vegetables
- The benefits of eating fish regularly far outweigh the potential risks, which are neglible
- Pregnant mothers and young children should eat 2-3 servings of oily ocean fish each week
- Energy & Environmental Research Center, University of North Dakota (EERC). EERC Research Finds Mercury Levels in Freshwater and Ocean Fish Not as Harmful as Previously Thought. June 22, 2009. Accessed at http://www.undeerc.org/news/newsitem.aspx?id=343 ↩
- Energy & Environmental Research Center, University of North Dakota (EERC). EERC Research Finds Mercury Levels in Freshwater and Ocean Fish Not as Harmful as Previously Thought. June 22, 2009. Accessed at http://www.undeerc.org/news/newsitem.aspx?id=343 ↩
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{ 85 comments… read them below or add one }
Thanks for this article and for summarizing the crucial parts. Very helpful
Wow, great article. When I was researching what my ancestors ate, the Welsh. Not only were they introduced to grains much later than everyone else, oats about 1,000 years ago, they also ate lots of salmon. It could be readily caught in the rivers and was considered poor peoples food, and some were known to eat salmon up to 4 times a week. A far cry from the modern diet, very radically different indeed.
I always learn so much here, and it helps alot of pieces of the puzzle come together. Thanks!
Great piece, there has been lots of information I didn’t fully comprehend in this series. But I have a follow up question: Do you have suggestions for people who are allergic to seafood? As a child I could eat seafood no problem, and miss it.
However, I got mercury poisoning in chem lab in college, had chelation therapy, and ever since anything that comes from the ocean or lake makes me at best violently ill and at worst sends me to the hospital after a day or two of being unable to keep even water down. Fish oil that’s been detoxed? Nope. Farmed fish that’s supposed to be mercury free? Nope. A bit of seaweed or fish stock used in food prep? Nope. Frog legs (we used to catch them and cook them once or twice a week on summer vacation)? MSM/Chondrointin/Glucosamine supplements? Octopus or squid? No, no, no…
I know I’m not getting proper ratios of Omega 3′s, but I have no idea how to fix this. Also, I really miss blackened salmon, tuna salad, sushi, crabcakes, you name it. Any suggestions? (I should add I have auto-immune adrenal/thyroid disease, in treatment including added selenium, so that’s not the answer).
There’s an Omega-3 product that’s made from clary sage put out by a company called Marvalous http://marvaglobal.com/omega3-clary-sage.html. I haven’t tried it yet, but I know two people who have told me from personal experience that it works well, one of them being the holistic dentist that I just started using.
I’ve never heard of anything like that, so I don’t really have any ideas.
The best thing you could probably do is strictly limit omega-6 intake and take relatively high doses of flax oil and evening primrose oil. The lower your omega-6 intake, the higher your conversion rates of ALA to EPA & DHA will be.
I was going to suggest vegetarian DHA, but it’s made from marine algae so I doubt you’d be able to tolerate it.
Once again, very informative. This whole selenium, mercury thing is very good to know. Have you heard anything about selenium/mercury levels in other kinds of seafood like shrimp, crab, octopus, etc… ? Also DHA and EPA levels? I’m living in Taiwan right now which has a huge seafood component to its diet so its cool to hear reassuring info about fish consumption. There’s also loads of other kinds of seafood so just curious if you knew anything about their safety. I can’t imagine it being that harmful though when so many people eat it and have been doing so for quite awhile. I guess the issue is with recently introduced harmful substances entering the food web but it still seems the benefits would outweigh any costs.
Matthew,
I know that shrimp and crab both contain selenium, but I don’t know the relative levels of mercury and haven’t seen studies comparing mercury and selenium. However, Ralston didn’t include them on his “don’t eat” list, so I’m assuming they are safe. If you want to be sure, just increase your intake of other selenium rich fish and foods.
There is an environmental consideration with shrimp harvesting, but that varies from area to area. I don’t know the situation in Taiwan.
Hi Matthew and Chris,
I’m also living in Asia, Mainland China, at the moment and I’m a bit worried of buying seafood from the local markets because of the effects of farming around here ie. chemicals, anti biotic use, pollution, etc.
If you gather any useful information on seafood safety in Taiwan/China I would love to hear it.
Thanks
Thank for such an informative article on the positives of eating Fish. Also it’s nice to read that, “ The highest dietary sources of PCBs and dioxins are not fish, but beef, chicken and pork (34%), dairy products (30%) and vegetables (22%). Fish constitute only 9% of our dietary intake of these chemicals.” Fish is favorite of mine and with the media attacking salmon, and even more farmed salmon, it was nice to read some more positive articles about my favorite food!
Both Health Canada and The FDA have given farmed salmon the Green light. The demand for wild salmon is higher than the supply. With over fishing in our waters we need to take the pressure off wild salmon and turn more to farmed salmon.
Thank you for this useful information
Kind Regards,
Molly W.
An interesting article that addresses a real problem with some people. All the talk of eating fish being dangerous was putting me off, so thanks. It might be beyond the scope of this blog, as its a health blog, but would you consider talking about the sustainability of eating fish? That’s something that really worries me.
I mentioned in this article that sustainability is a real concern, and that choosing fish that are certified as safe by the Marine Stewardship Council is probably the best bet. I also recommended a book in the article if you want to learn more.
You did sorry, you’re right. The book looks like a good place to start. Thanks very much.
Chris,
The idea that “Selenium protects against mercury toxicity, and 16 of the 25 highest dietary sources of selenium are ocean fish” sounds too good to be true! After hearing many people recount stories of having their mercury levels tested, and coming away horrified with the results, I’ve drastically cut back on my fish intake… which sounds like it might have been a mistake. One point of clarification: would one’s mercury level appear to be the same, regardless of whether or not the mercury had been detoxified by selenium? Or does selenium physically change the nature of mercury, thereby lowering the amount shown in a test result? I only ask because it was my impression that heavy metals, like mercury, take an extremely long time to dissipate once ingested.
When mercury binds to selenium a new compound is formed, so I believe it wouldn’t show up on the tests. However, mercury testing is a controversial area. Some practitioners have pointed out that all of us have some level of mercury in our systems. The question is how much harm it’s causing, and whether it’s responsible for whatever symptoms you’re experiencing.
Do you know of any information on the cooking of fish and its effects on the EPA/DHA content?
I see. Do you know of anyone who has endeavored to at least do some personal testing, in regards to fish consumption and mercury levels? I really want to believe the selenium argument, but (in the spirit of this blog!), I am a bit skeptical. The chart you highlighted from the Western Pacific Regional Fishery Management Council didn’t do much to quell my suspicions. The last line of the paper (which was, incidentally, partially funded by the US Tuna Foundation and the Fisheries Scholarship Fund) is certainly true: ”Consideration of mercury-selenium relationships in diet and tissues of exposed individuals will clarify risk:benefit relationships associated with fish consumption.” Maybe that will be the Ralston’s next project (by the way, it’s remarkable that there seem to be no fewer than *three* Ralstons studying this topic…? Two of the four authors of the paper, plus the other one you quoted in your post!).
Chris,
I posted a short blog praising this article and your site on one of my blogs (http://dropoutnation.blogspot.com/2010/06/good-news-for-good-health.html) a couple of weeks ago.
Today I discovered a comment by someone from Got Mercury leading me to a site with a mercury content calculator that seems to disagree with your findings.
http://seaturtles.org/article.php?list=type&type=75
I’m not altogether sure how to address this. I find your site highly informative and your research would seem to be impeccable while the studies they site are a bit less convincing.
Any feedback from you would be appreciated since it is my intention to promote your site whenever possible.
Thanks, Richard
There is no way to Peace. Peace is the Way.
Richard,
There’s nothing there that I haven’t already addressed, as far as I can tell. As I’ve shown in my articles, you have to consider the protective value of selenium. If the amount of selenium in a fish is higher than its mercury content, then there’s no safety issue. Fortunately, that’s true for most commonly eaten species of fish.
Chris, I’ve got a question that’s eating at me. I love sushi, and it would be great for me to believe it’s safer than I’d thought. Your writing explanation about selenium being protective against mercury seems reasonable to a non-chemist like me, but I recently watched The Cove and it suggested that the high mercury in dolphin meat was having a horrendous impact on the people who ate the dolphins. If the dolphins are eating (presumably) mostly fish that have more selenium than mercury, then why do they have such a high mercury content (to the point of making people sick)? Is this a bogus claim in the movie or is it evidence that selenium doesn’t do as much good as you’re suspecting?
Perhaps because they concentrate the mercury. Pilot whale is another type of seafood consumed in some parts of the world that is higher in mercury than selenium – and I imagine it also eats mostly fish that are higher in selenium. I’ve not seen dolphin on that list, but that may be because dolphin is not commonly eaten in most parts of the world.
Thanks for the response. My recollection from the movie is that the mercury levels were sky high. I should have looked into it a bit further before posting here… wiki has an entry on the film and it seems that the mercury levels were overstated. Though I’d still never eat dolphin.
Keep up the good work.
Hi your site is greatly informative. I have listened to the podcast of Stephen Guyenet as well. But, I have to tell you I have been reading over Dr. Joel Fuhrmans’ site about to “eat fish or not”, it was enough to scare the daylights out of folks. Here it is…
http://www.drfuhrman.com/faq/question.aspx?sid=16&qindex=6
I always thought the good in fish outweighed the bad, especially after your articles. But now am wondering?? Hmm??? Or maybe Dr. F is not as informed….
•Fish are not significant sources of PCBs and dioxins when compared to meat, dairy or vegetables
•The benefits of eating fish regularly far outweigh the potential risks, which are neglible
I like your blog and have learned a lot. But I’m having trouble with the two bullet points above. I”ve googled a March 2010 report stating that some fish oil brands, like TwinLab and Nature Made, have very high levels of PCBs, which apparently have no standards as to what consititute ‘safe’ levels! There was also a report two years ago from Michigan, I think, showing that high doses of fish oil caused late stage colon cancer in mice. The tumors took a mere 4 weeks to present themselves! Apparently, the anti inflammation properties of fish oil are so good that they also curtail the defenses against various intestinal bacteria, necessary to kill off cancer cells.
I appreciate your fairness and tireless research, but I just don’t see where you have addressed these worrisome issues. Please advise and thank you in advance.
My quotes said fish, not fish oil.
There isn’t any information on freshwater fish in this article, does this exist for selenium levels? I eat lots of freshwater fish, being from the upper midwest as well as an avid fisherman, and have always doubted the mercury scare tactics. Any information on this would be terrific!
Joe: good news for you.
“Results from the first study, conducted jointly by the EERC, the U.S. Environmental Protection Agency (EPA) Western Ecology Division, and the University of Missouri’s Nuclear Reactor Center, show that an estimated 97% of the freshwater fish from lakes and rivers in the western United States are safe to eat. Conducted in 12 states in the western United States, it is the only study of this magnitude that has measured both mercury and selenium in fish tissue.”
See full article here: http://newsletter.vitalchoice.com/e_article001496263.cfm?x=bfPRTnr,b7b1jv7h,w
Hi Chris,
I have a question after reading this. When the selenium binds with the mercury does this cause the selenium to be unavailable for use by our bodies? Does the protective action of this process cause the selenium to be excreted with the mercury?
Thanks for your work.
Hannah
what about the broadway actor who had really bad mercury poisoning from eating lots of sushi? i think his name is jeremy piven……..
I thought PCBs were mainly a problem in farmed fish, which you did not cover, because of what they are fed. Same with cattle and chicken. They are fed industrial food waste (ground up carcasses, feathers and worse) and other bizarre but cheap ingredients. Isn’t it important, for your recommendations to be valid, to warn consumers to make sure they know the fish they eat is wild caught?
Thanks, Chris. Very informative. I reposted this on my FB page and a reader asked, “What about the concerns of radiation from Japan on the world’s oceans?” I personally don’t think this is an issue, for non-Japanese fish, but what do you think?
Thanks for the article. It’s important to note that fish is included in the diets of the world’s healthiest countries.
This is very interesting- a few years ago I was tested for mercury and had high levels of mercury- I did chelation to get rid of it – the thing is I didn’t know if the cause was my mercury fillings (which I subsequently had removed) or the fact that during a summer college course for 8 weeks I had a tuna fish sandwich from the college cafeteria literally almost everyday those 8 weeks- which one do you think it could have been? My mercury levels were quite high. It seemed like you were saying to still be cautious with tuna- is that because it’s ratio of selenium to mercury is not as good as some other fish like salmon?
Thanks!
I’d worry more about the BPA from canned tuna, and other canned fish for that manner, than the mercury levels
Hello Chris
This is a great and informative article. I’m glad to hear this because whenever I eat fish it has a dramatic effect on my overall health, including a very noticeable, at any weight, leaned out face. I tend to put weight on chin and cheeks, and fish brings this down within 2-3 days of eating it. Any ideas on why this is?
Also, with the recent happenings in Japan, should we be taking any precautions regarding what type of fish to buy or not?
Your article makes me feel much better about eating fish. My concern which I don’t think has been addressed here (I scanned the comments so I might have missed it) is what’s done to the fish after it’s caught. I keep reading about chemicals grocery store fish departments put on the fish to make it look better on display. I always ask grocery managers about this, but who is going to admit, “yeah, we poison our fish so it looks pretty!” Sometimes I buy fish and I feel really sick after eating it so I’m always leery about what I don’t know and the marketing scams businesses use to make an extra buck. It’s easier to just not eat it rather than worry.
When it comes to grocery stores bleaching and using borax to clean and polish junk fish, the Thailand fish farms seem to be the worst offenders. (Source: BottomFedeer by Grescoe )
Is Borax even an issue though? http://en.wikipedia.org/wiki/Borax Its a good source of Boron which is a trace mineral we need. The other things they used to bleach, clean, and polish the junk fish might be bad, but I’m thinking a little Borax residue isn’t an issue. Your thoughts?
What is king mackerel?
Is ordinary mackerel ok? What about herring & sardines/pilchards?
What about the fish in general available to those of us in the UK? (North Atlantic and North Sea I suppose).
For ALAs, I notice you recommend flax seed oil. In an interview with Dr Mercola, Dr Rudi Moerck was as skeptical about flax seed oil as you are about fish oil (he is also cautious about fish oil). The reason being that it is oxidised even by the time it gets into the bottles/capsules.
For ALAs, his preference would be chia seeds, which he says are smaller and digestible without being ground (whereas flax seed are indigestible, and once ground, need to be consumed within a few hours, so buying ready ground seeds is not an answer).
For DHA/EPA he strongly recommends krill oil, but then, you could say he is biased in that respect.
I have read that you are as lukewarm towards krill oil as you are towards fish oils, so I assume you will not agree with him on that. However, I would be interested to hear your take on his comments about flax seeds, flax seed oil, and chia seeds.
Flax seed oil, from the information that I’ve seen, does not convert well into our body. As far as sardines go, they have very high selenium, iodine, and omega 3 levels and very low mercury levels. The smaller the fish, in general, the lower the mercury level. According to Seafood Watch, look for Mackeral from the Atlantic and areas other than the Gulf of Mexico, where overfishing is occuring.
When it comes to Dr.Mercola, btw, he seems like a fear mongerer more than a reliable source.
Since you seem to be a critic of Dr. Mercola I’m curious as to your thoughts on one particular product that I’m thinking of buying.
I’ve heard of Full Spectrum lights being good from other sources so I think they make sense, but I’m wondering if his specific bulbs are a good pick? Its 119 dollars for 12 bulbs which is about 9 something a bulb. Do you know of any good sources for a close to natural light full spectrum bulb that’s cheaper?
Thank you for this analysis, glad to see some sanity backed with data to counter the fearmongering.
Now, if I could only source BPA-free canned tuna in Europe…
This is a very informative article, thank you! I would like to ask one question concerning PCBs in other foods (esepcially meat). I only buy organic meat which is not possible for fish (organic fish often is farmed fish, I think “oragnic wild-caught” is just nor possible). Does organic meat contain significant levels of PCBs as well, esepcially when compared to wild caught fish? I have found the information that PCBs gather in the fatty tissue, are there significant amounts in lean seafood?
Thank you!
Chris,
I’m from Minnesota and there is plenty of freshwater fish to be caught and consumed. I’ve been searching the internet for more info on the selenium levels of the fish in the Twin Cities metro area (mainly northern pike, largemouth bass, crappies, sunfish and walleye), but the info available is vague at best. Dr. Rolston’s research seems to indicate that most minnesota fish should be high in selenium, but I would imagine it would be different in the Metro than in the rest of Minnesota, due to more industry, greater population density, less open land and little to no farming. What are some markers I can look for, such as selenium levels in soil, other animals, etc that would indicate whether the fish from metro lakes have high selenium levels. Thanks for any response.
Ben
I’m struggling to find a site detailing the selenium v mercury content in fish. Do you have any suggestions or links to this information?
Its post like this that make people very ill…mercury at ANY level is horribly toxic to the body. I’ve never had filling in my mouth but became very mercury toxic just from eating tuna. I would highly recommend anyone who reads this to do your own research on the subject. No matter how protective selenium is mercury does not leave the body…it stays in your body (and more specifically your brain) for a very very long time, in which it causes a host of different problems. Pretty much any mainstream “disease” in my opinion is caused from some level of heavy metal poisoning (usually mercury poisoning).
Always do your own research folks.
Hi Chris,
great article. I am recently a converted pescetarian (with ample amount of raw eggs, fruits, veggies, and unpasteurised cheese thrown in for good measure). I eat a lot (as in every day) of Chilean farmed mussels, shrimp, and Alaskan pollock, and one of the criteria for me choosing these foods was, apart from them being among the cheap seafood in the UK (my budget is very tight), the low environmental impact, low level of mercury, PCB’s and dioxins.
However, i was reading Denise Minger’s comments about The China Study, and when she reviewed the parts concerning seafood intake and disease, she said that regular seafood consumers need to be wary of CADMIUM intake. Looking into it, cadmium seems to cause even worse problems than mercury. But surprisingly, everyone seems to focus on mercury when they are concerned about metals from fish.
Thanks to Darrin, one of the commenter’s on the PHD blog, I managed to find some limited info on cadmium intake in the type of seafood i eat mostly – i.e crustaceans and molluscs http://www.foodstandards.gov.au/consumerinformation/nuttab2010/nuttab2010onlinesearchabledatabase/onlineversion.cfm?&action=nutrientFoods&category=Minerals&nutrientID=CD .
Many studies examining cadmium concerns on seafood conclude withthe comment along the lines of “because high cadmium seafood is not a major part of the diet, you should be ok” or “as long as you dont eat it (e.g. mussels) every day, you should be ok”. The problem is, it is a major part of my diet and i DO eat it every day!
Am i right to be concerned over cadmium levels if i eat a daily diet containing molluscs and shrimp daily?
Hi! I enjoyed this posting and also shared it with my fans on facebook! I have been following the paleo diet (low carb, no grains) since Februar 2010 and lost ~50 pounds (no chronic-cardio, just weekly strenth and daily walks)! Back to my weight 12 (!!!) years ago! I want to promote the paleo diet and HIT (training) as best as I can. Thank you!
BRING ON THE SALMON AND HAMACHI!!!! I am going to town on them tonight! Thanks for making me feel as though I can without worrying! LOL
However Selenium has no protection against radiation. With an estimated 462 trillion bequerels of radiation dumped into the ocean from Fukishima. Will there be any large non-radioactive fish in the Pacific? These internal emitters, migrate to organs such as the thyroid, liver, bone, and brain, often causing cancer.
http://www.washingtonsblog.com/2011/06/coming-to-a-store-near-you-radioactive-fish.html
http://criminalisewar.org/?p=437
Iodine protects from Radiation to some extent…whether its enough to protect from that much…I’m not sure. It might be good to avoid fish from that immediate area or to have plenty of non radiated fish from other areas.
You might do some searches on it as there might be more on Iodine and its protective capacity in regards to radiation. I read something about it on Jack Kruse’s website but don’t remember which blog post.
Great article. I would like people to keep overfishing in mind, and please look up the fish you buy through Seafood Watch before purchasing. I think as proponents of paleo, we should also be proponents of environmental safety through our actions. Saying that, I’m about to go eat some oyster and sardines.
I really appreciate this article… I just started eating fish again recently after a few years of abstinence, and its been doing MuchGoodness for me. The facts presented here certainly open my mind to how much options there are available… I was being rather restrictive about it, which in a way is a good thing. Now I can expand my palette in confidence!
I understand that fish, cold water, fatty, ocean fish is good for us. But what about all those hunter-gatherer people–which we all were before agriculture–that didn’t live near the ocean, didn’t eat much if any fish, yet were quite healthy. The Masai comes to mind, as well as the North American Plains Indians, and the Koi San of South Africa.
Did the North American Plains Indians not eat freshwater fish? They do have many of the benefits of ocean fish though not to as much extent. Also I’ve heard insects provide some of the same benefits as fish…could that be something they eat?
Chris, is shellfish included in this information? When you recommend 2-3 servings of oily ocean fish per week for pregnant mothers and children, am I assuming you’re not including low mercury shellfish like shrimp, bay scallops and oysters in this? Thanks in advance!
Chris – Do you think that pregnant/trying-to-conceive/breastfeeing women need to worry about mercury or do you think that the rest of this article also applies to these women? You recommend oily fish, but what about the others? Thanks in advance and I love reading your work.
As he mentioned, you don’t need to worry about mercury if the selenium prevents the absorption. You might want to invest in his “healthy baby code” btw.
Thanks so much for clarifying and I will look into it!
Chris, Interesting, informative article but you don’t mention anything about purines. Sardines have very high purine levels up to 1,000 mg per 3.5 ounce serving. You mention “there’s no reason to limit (fish) consumption to 12 ounces per week”, but what about the problems with purines mentioned here in studies like this:
Choi, H. K., K. Atkinson, E. W. Karlson, W. Willett, and G. Curhan. “Purine-Rich Foods, Dairy and Protein Intake, and the Risk of Gout in Men.” N Engl J Med. 2004 350(11): 1093-103.
Choi, H. K., S. Liu, and G. Curhan. “Intake of Purine-Rich Foods, Protein, and Dairy Products and Relationship to Serum Levels of Uric Acid: the Third National Health and Nutrition Examination Survey.” Arthritis Rheum. (2005). 52(1): 283-9.
Thanks,
Jay
what if your allergic to fish? I recently had a lab done with an said I was deficient in EFA. I take Noridic Naturals EFA’s, and I’m still deficient. Is this because I need to eat fish too? The issue is I’m allergic to shell fish.
If you’re only allergic to shellfish, you could eat salmon, mackerel, herring and sardines to get your EPA/DHA. Another option if you’re allergic to all fish is taking marine algae (which is where the fish get their DHA).
Chris sorry if this has been covered before but I’m new to your site and haven’t had a chance to fully dive into all your great material.
My dad doesn’t eat fish anymore. Basically he believes you will get sick if you eat anything from the Gulf because of the oil spill and anything from the Pacific because of the Nuclear Plant problems in Japan and all the “radiation soaked garbage” from the earthquake making its way to the west coast waters. Also radiation in the air coming over.
To me I have trouble subscribing to this. I think if it were actually a problem we’d know not to eat fish….but alas, I don’t eat fish either. In my mind things are probably fine, but I like to get my information from sources I trust so I can better make a decision.
Do you have any opinion on this? Are there websites/people you can point me to that would be able to give me something to tell my dad and restore his faith in fish (something he ate often his whole life)?
Or is what he hears right? Should we be sticking to the Atlantic Ocean and fresh water fish?
Thanks,
Brian
Great article! However why does know one seem concerned about the contamination that’s STILL going into the ocean from Fukushima and its effects on seafood????
It’s not like the fish just stay near Japan. Obviously they swim throughout the pacific. I’d really love your thought on that Chris.
I don’t think Chris wants to talk about the radiation issue – I mentioned it on February 28th and the comments have been ignored. Unfortunately this story has not been sufficiently covered in the media. But there are articles around:
This one looks at the extent of the ocean pollution…
http://www.examiner.com/article/over-462-trillion-becquerels-fukushima-strontium-pacific-ocean-seafood-risk?CID=examiner_alerts_article
Tuna off the menu in California over radiation fears…
http://www.guardian.co.uk/environment/2012/may/30/california-tuna-radiation-sushi-industry
The main problem is that people aren’t going to start dropping dead from eating the fish. The cancer could take 5-10 years to develop. Even then it would be difficult to prove that the fish consumption was the cause.
Yes I’ve read those articles too. We actually just got back from Hiroshima snd many places aren’t serving tuna suddenly. We never ate seafood while there bc I’m so unsure about its safety. It’s very surprising to me that th every health conscious bloggers and health experts never talk about Fukushima in regards to seafood safety. I hope Chris does pay attention to this!!!
Thanks for the great article! I’ll be sharing this is one of my articles of the week over on Kevin’s Trek…love your work in general, keep it up!
Check out this article from SuppVersity before consuming any more fish:
http://tinyurl.com/8jswlzb
Additionally, the tests showing radioactive isotopes in fish — and the sparse (or lack) of safety testing — makes fish consumption a very risky proposition.
Those studies are problematic; I will be addressing them and discussing this topic again soon.
Hi Chris,
I’ve followed with interest your articles concerning eating fish and the issue of Mercury toxicity.
Have you read this study in the Journal of Biomedicine and Biotechnology Volume 2012 (2012), Article ID 681016?
A French research team sought to determine whether mercury from fish is less harmful than other dietary mercury, and whether beneficial nutriments from fish might counterbalance the deleterious effects of fish-associated mercury.
Mice were fed one of three diets:
Fish-based methylmercury diet: A diet that included fishmeal produced from fish containing five micrograms of methylmercury contamination per gram.
Added methylmercury diet: A special diet higher in DHA and EPA, with added methylmercury chloride (considered more toxic than fish-associated methylmercury) also totaling five mcg/g.
Control diet without mercury
Apart from mercury and selenium content, the three diets were comparable. Only the fish group suffered significant behavioral abnormalities at the end of 58 days.
The authors concluded:
“The two mercury-containing diets are differing by the fact that mercury was brought by the addition of either pure methylmercury chloride or by mercurial species associated to fish. Therefore, any differential effects observed between MeHg-containing and fish-containing diets should be attributed to different chemical species of mercury present in one diet and absent from the other and vice-versa along with the possible intervening role of fish PUFA and selenium.
If the beneficial role of fish nutrients such as PUFA and selenium was to counteract MeHg effects, the pattern of effects displayed after exposure to the fish-containing diet should appear less severe than that observed with the MeHg-containing diet. But in the present study, the mice fed the fish-containing diet displayed worse behavioral performances than those fed the control and the MeHg-containing diets, although the brain structures of both mercury-contaminated groups of mice contained comparable levels of mercury and even less in the striatum of those fed the fish diet.
Therefore, the different chemical species of mercury within fish flesh are likely to explain the deficit in cognitive performance in the Y maze and the decreased locomotory activity in the open-field maze.”
I’m not a big fan of extrapolating from mice to humans but I’d like to hear what you think of these results.
Peace,
Gregory
Gregory: Dr. Ralston and I addressed this study in our interview. http://chriskresser.com/the-truth-about-toxic-mercury-in-fish
The Article is very informative.
In Homoeopathy, Selenium is one of the great medicine, which is used for Prostetorrhoea, Constipation, Loss of weight, — . About 2000 symptoms covers Selenium. This article is very good to about Selenium and its sources as well as different views of readers.
Many Thanks esp. to Chris Kresser and all commentators.
I stopped eating fish as soon as the Fukushima disaster occurred, and I was eating it every day prior and experiencing dramatic health benefits. Why avoid the topic? I’ve noticed other practitioners with popular websites ignoring it also. I think we all see the elephant standing in the room. Why not address it?
How much fish is ok to eat a day and week?
Which fish are ok and is tongal or yellow jack tuna ok, which are said to be low mercury tuna (can these be eaten once a day??
It is the radiation from Fukushima in the tuna that would be of greater concern than the mercury.
http://news.stanford.edu/news/2013/march/bluefin-tuna-secrets-030413.html
Radiation is unsafe and causes cancer at any levels
http://www.nytimes.com/2011/05/01/opinion/01caldicott.html?_r=0
But how much of the low mercury fish is ok, like sardines, salmon, sole, cod, shrimp, etc?
Can these fish be eaten once twice a day?
There is a neurosurgeon who’s “leptin reset diet” promotes eating fish at least twice a day (jack kruse)…. Is eating this much fish healthy or harmful potentially?
Hi there nice article and very helpful, I’ve been reading to many articles who not saying the same thing and it’s getting confusing. I don’t know to much about fish since I’ve never eaten to much of it before, but been a vegetarian for almost a year I’ve decided to change to a pescetarian because i had to take some vitamins supplement and Omega 3 supp also. I went to a fishmarket because i like to buy fresh and since I didn’t know to much about fish the only thing I eat is salmon, shrimps, crab, lobster and talipia or sole. Since she didn’t carry any talipia or sole she recommended the ORANGE ROUGHY and I’ve notice in the research that I made when i got home that it was a species who were very HIGH in MERCURY, so now I’m not sure if I should eat it or not. I guess she didn’t know the species about it’s high mercury content, that she only knew that it was a species from New Zealand and Australia. I will really appreciate if you can help me about the Orange Roughy fish that I just bought if it’s okay to eat or it’s risky. I will never buy this kind again but i don’t want to trow it away. Thanks.
Hi Chris,
Could you comment on the difference between wild and wild-caught fish. I would like to know if you have any information on the differences in nutrients and toxins.
Hi Chris,
Great post!
Two questions:
1 Looking at it from the respective levels of nutrients and toxins is there a meaningful difference between wild and wild-caught fish?
2 What are your thoughts on BPA-free canned fish or glass-jarred fish as opposed to fresh fish?
I live in Taiwan and we have a great selection of local seafood, but I am suspcious of the amount of pollution in the surrounding waters and the fish here are generally sub-tropical and so not very fatty. I was thinking about purchasing some Wild Planet sardines and some various Crown Prince seafood products to compliment the local seafood I eat.
Whew! What a relief to learn about the selenium connection. For what it is worth: I have been eating tuna sandwiches practically every day for over 50 years. I never grow tired of the taste and texture of a tuna sandwhich. I have also been consuming mostly wild salmon and tilapia for dinner a couple of times a week. That’s alot of fish consumption! I am a healthy 61 year old man. My mental faculties are completely normal. If one believed the scare tactics regarding fish/mercury consumption I would have been committed to a mental facility long ago with the amount of fish I have consumed over the decades.
Craig, it really depends on ur methylation status. Looks like u are able to detox metals properly, whereas other people might not be as lucky. It also depends on genetics/snps. But, i agree that this tends to be overblown. How do these levels in fish compare to other foods? How does the arsenic in rice compare to other foods? And, most importantly, how absorbable are these toxins?
It also depends on what the rest of ur diet is like too
Dear CHRIS KRESSER
Sorry, but I read the original article about PCBs and Dioxins in the american diet that you quoted in your article (INTAKE OF DIOXINS AND RELATED COMPOUNDS FROM FOOD IN THE U.S. POPULATION), and there’s something that needs urgent correction. You quoted that “The highest dietary sources of PCBs and dioxins are not fish, but beef, chicken and pork (34%), dairy products (30%) and vegetables (22%). Fish constitute only 9% of our dietary intake of these chemicals.” The information is not wrong, but is incomplete and could be misunderstood by the readers.
The question is “why fish contributes only with 9% of ingestion of PCBs in the american diet?”. And the autors of the study gave the answer: “The share of TEQ contributed by fish is smaller than previous estimates, because fish is consumed in smaller quantities in the United States than in many other countries.” / Obs: TEQ = dioxin toxic equivalent
So, IS NOT BECAUSE THE FISH IS A SAFE SOURCE!!!! By the way, the same study puts freshwater fish as the HIGHEST source of PCBs (1.7 TEQ ppt), and even the seafish is higher than chicken, and as bad as beef and pork (0.39 TEQ ppt) !!!!!!
“Freshwater fish were found to have the highest wet weight dioxin toxicity, with 1.7 ppt TEQ, followed by butter with 1.1 ppt. Ocean fish, meat, poultry, sandwich meats, eggs, cheese, and milk desserts, as well as human milk, were found to have wet weight dioxin TEQ contamination in the range of 0.33 to 0.51 ppt.”
And as the study shows, the safer food group are the vegetables, with only 0.01 TEQ ppt (ND=0) and 0.09 TEQ ppt (ND=1/2):
“The food category with highest World Health Organization (WHO) dioxin toxic equivalent (TEQ) concentration was farm-grown freshwater fish fillet with 1.7 pg/g, or parts per trillion (ppt), wet, or whole, weight. The category with the lowest TEQ level was a simulated vegan diet, with 0.09 ppt.”
By the way, when the same study shows that vegetables contribute with 22% of the PCBs/Dioxin intake is just because this group (fruits, grains, leaves, tubers, roots, etc) is the major part of our meal. Thus, in a vegan diet vegetables will contribute with 100% of the PCBs/Dioxin intake because vegans only eat vegetables. So is clear to see that this number percentage alone means nothing.
Well, you don’t need to trust me, just read the original article by yourself: http://www.ejnet.org/dioxin/dioxininfood.pdf)
Bottom line: fish is healthy when you think about omega 3, but YES, It is a very important source of PCBs and Dioxins.
Best regards,
Daniel
Daniel, so are u saying that a vegan diet is healthiest and the least toxic way to eat?
Well, not me. Who are saying that vegetables have less PCBs and dioxins than the other food groups are the autors of the same article that was quoted by Cris. But this make sense, since the vegetables are at the bottom of the food chain.
But in my opinion, being a vegan is not enough to garantee a healthy diet. You could be a vegan and just eat french fries all day long and drink soft drinks. Well, definitly that is not healthy.
So we need to choose well what to eat (e.g., organic food, Brassica vegetables, nuts, all kinds of berries), and use the heathiest ways to mix and prepare the food. And we should not forget about daily exercises and, if you are a vegan, the B12 vitamin supplement.
By the way, I’m not a vegan because once in a while I eat cheese (organic if available) and fish (the less contaminated varieties), but is rare. In the other hand, I never eat red meat or junk food and never drink soda.
Best regards!
Daniel
Thanks daniel… u seem to know a lot about nutrition. if I may be nosey, what is your diet like on a typical day (meal by meal)?
Hi Chris,
Thanks for the information in this article. Very helpful! Just curious about one thing…I am considering making fish stock from the heads and bones of fish, as I read that this would be a great source of iodine and other minerals. Hoping to boost a sluggish thyroid. I am able to get heads and bones from a local (New England) fish monger for making the broth, but I wonder about whether this would be a healthy choice, given the presence of some toxins in the fish. More specifically, I wonder if a daily cup of homemade fish stock is excessive exposure, if the toxins are concentrated in any way by slowly simmering the fish heads and bones making broth more toxic than the meat of the fish itself, and whether toxins accumulate more in the thyroid, brains, etc. of the fish as they do in the fat of the fish. Any thoughts you might have on the overall safety of fish stock would be much appreciated!