Fish Safety: A Selenium/Mercury resource

Chris Kresser spent quite a bit of time in his Real Food Summit presentation discussing the "inactivation" of mercury by selenium.  The good news about this is that for many of the fish where mercury contamination is of concern -- particularly large coldwater ocean fish -- there is a high level of selenium.  Selenium binds mercury and in essence converts it to a non-toxic form.  Sorta like those amalgam fillings most folks over 35-40 (and younger but less common) have had*.  The good news is if a fish has high selenium, it's a low mercury toxicity risk.  The bad news is if the fish has a high mercury content, there's less of the beneficial "free" selenium you need.   

I went looking for mackerel since it was brought up in comments and found this "pamphlet".  Thought I'd share:  Selenium and Mercury - Fishing for Answers                                                

I feel much better eating my fatty fishies, farmed or otherwise.  Meanwhile Joel Salatin made me feel pretty bad about my real food based diet.  Maybe I'll share some thoughts on his intro video (free download with registration ... unfortunately missed his presentation yesterday).

*  I was a relatively lucky one and only had 3 of these fillings.  They were in back molars and a few years back I got to considering replacing these 25+ year old fillings.   So me being me, I looked into this thoroughly before "fixing what wasn't broke".   Much of the Mercola-style alarmism (man does that man manage to take hyperbole to new levels!) about amalgams is based on the same crapola alarmism he feeds you regarding a chlorine atom in a molecule.  The mercury in those fillings is for all intent and purposes inert.  It might as well be gold.  Drilling these out is more potentially harmful to you than having them there, because what mercury you could be potentially exposed to is magnified several-fold by creating and dispersing "dust".   Your dentist should take appropriate precautions to prevent such exposure, and then all is okey dokey.   My dentist convinced me that my lower molar fillings were "leaking" (not mercury, but that there was evidence of leakage at the edges and were no longer protecting the underlying tooth) and I had those replaced with tooth-colored composites.   There was some cosmetic consideration.  In retrospect I probably would have let them be until real signs of failure, because I "feel" the composites that replaced them, and many of the chemicals in those fillings can potentially be as or more toxic than miniscule amounts of mercury.  My last amalgam will probably go with me to the grave, it's small and in a back upper molar, closer to my brain which Mercola tells me I should worry over.   In any case, if anyone ever has questions about the safety of dental implants or dental materials, this IS my graduate work (materials science, metallurgy specifically, and corrosion!) wheelhouse, and while not the subject of this blog, I'm happy to answer questions you may have.  Cosmetic dentistry "for your health" of course, is rife with BS, and $$$$$$$$$$$ are well, that's why I put so many $ there.   You could redo your whole face for the cost of replacing one tooth!!  Look long and hard before you leap -- especially if leaping is an option (e.g. veneers for teeth straightening)  


MM said…
"many of the chemicals in those fillings can potentially be as or more toxic than miniscule amounts of mercury"

Are you saying that composites are more toxic than amalgam fillings?
CarbSane said…
Yes, in a different way. The monomers that form the polymers are toxic. So, for example, improperly cured composites could leach those. I think this is more of an immediate threat to the live tooth than to your body, but there's all sorts of stuff out there about the dangers of these fillings and you can find Mercola-style (if he hasn't weighed in on those too) rants. If some of these people had their way we'd all be running around with wooden dentures ;-) Of course if we never ate carbs we'd have no cavities or periodontal disease, right?
Lesley Scott said…
I've been thinking about Joel Salatin's notion of our "supermarket addiction" and switching our purchasing dollars to CSAs & online Farmer's Markets. It definitely takes more planning to shop that way, which is probably why people resist it. Still, he makes a good point.
Unknown said…
I resist it because I don't see how it could possibly make a difference in my quality of life.
P2ZR said…
OK, you gave the green light for questions, so here goes. I'm taking it you're saying that cosmetic restorations aren't worth the risk of potentially-toxic composites. What about comfort-related restorations? I have adjacent molars that developed a sizable gap between them due to teeth shifting, and they're really quite painful when food particles get stuck (e.g., meat that's even slightly stringy)--i.e., floss immediately or suffer tremendously (and it's still painful/bloody for a few minutes after flossing). Got a composite 'filling' that became ineffective in short order (unclear whether due to erosion or more moving teeth); have scheduled another one with different (presumably more durable) material. Not worth it?

I don't want to think that my teeth are out to sabotage me (I take care of them! Floss diligently and all--maybe THAT'S exacerbating the gap?!). Is there a chance teeth (bones) that have shifted will shift back to their normal, non-painful-gap position? Thanks :)

P.S. I *did* experience a noticeable acne breakout shortly after the time of the original 'filling' becoming ineffective, and it wasn't quite in phase with my monthly cycle. Possible detox effect from the leaching material?
CarbSane said…
I have other thoughts I'll save for a post, but I presume his mail order beef is frozen ... I think it pretty much has to be, right? There's a clear difference in taste, particularly of the better cuts between fresh and frozen. Heck, even when I make pot roasts I'll stew the beef and freeze the cooked -- no discernible difference -- rather than freeze the beef, thaw then stew when I can sometimes tell the difference, or I get curdle crud from the juices that come out that way, etc. Even Wendy's is running a new series about how their burgers are fresh, never frozen. While I see the economic point he's making vs. fast food, for $10 he says you can get 2 lbs of his, presumably frozen, ground beef. For $10 I can get 2 lbs of fresh porterhouse or 4 lbs of ground beef at Trader Joes. I get the priorities thing in terms of quality of food vs. a bigger TV and a larger data package for the smartphone, but if we're going to make that argument then what $10 can buy between the food options matters to me.

I just found it depressing that he would consider me supermarket addicted and eating such a poor diet. Might as well just eat Little Debbies I suppose.
CarbSane said…
I'd go ortho and move the teeth. There are economical means to do this with "clear braces" and retainers in most cases, and even the dreaded railroad tracks are better than nothing.

I do not want to instill fear in composites. I think the anti-hype is probably as over-the-top as that against amalgams. Composites to fill molars have come a long way and can withstand consistent compressive strength -- e.g. repetitive vertical pounding perpendicular to the interface between filling and tooth. If I understand you, you're building up the side(s) of molars to fill a gap? That's a shear stress on the interface. Think of hammering a brick wall. You hammer and hammer on a flat one in the center and it stays put. You hammer the same amount at the vertical one at the end? Composites, like all fillings and crowns and veneers and all that, overwhelmingly fail at the interface with the tooth. It is the "weakest link". Same goes for implantable prosthetics. An artificial hip, knee, whatever almost never breaks ....
bentleyj74 said…
He has a vested interest in that opinion :)
CarbSane said…
I presume you're referring to Salatin?
MM said…
Hmm, maybe I don't really want to know. I think I'd rather have a composite filling than a pulled tooth. If it's toxic, I haven't been able to tell. :) It's funny because around here it's very hard to find a dentist who will do an amalgam filling at all; I assume because of the mercury. Now I find out the composite stuff is toxic too. Bizarre.
CarbSane said…
PS In relating my story re: changing out fillings, I perhaps missed the mark. My point wasn't that restorations are toxic or not without benefit but huge risk, rather my point was that trading amalgams for composites from a health POV is likely a wash. I'm happy with my composites. Since I smile broadly and have a small lower arch you could see the lower amalgams that looked like one big filling (front of one tooth, back of the other) -- it was replace both or none.

If anyone has dental insurance and they will pay part of fillings replaced for "cause", guess what ... most dentists can find cause. However that won't stop others from convincing those without insurance that it is critical to replace those fillings before something worse happens. And most don't want to do stuff one tooth at a time ... so it's all quite a scam. Which is not to say folks shouldn't get those amalgams changed if they want to, for pure vanity if they want ... just don't let alarmism rule your decision. I had those fillings replaced 3 or 4 years ago. I should have had him image my upper molar even though I had no intention of replacing that one, just to see if there was anything to the leaky diagnosis. I like my dentist, he's done nice work and worked out reasonable fees for the excellent services he offers. But I also kinda think had I suggested doing the third tooth, he'd have found decay. And here it is 3-4 years later and no issues.

Dental insurance is a total scam ... if you don't get it free or very - and I mean very - low cost from your employer, go cash. They prefer it that way anyway and will discount things, etc.
P2ZR said…
'you're building up the side(s) of molars to fill a gap?'

Yeah, so rather than erosion of the material, I was thinking that it failed because the side surfaces of the molars (enamel of whatever thickness/quality) was too smooth for good adhesion. Not sure what sort of material was used, but in any case, I doubt its primary use is to be bonded to the tooth in that manner (vs. for filling cavities). I guess my *main* concern isn't even miniscule leaching of the material, but rather having most or all of the thing fall off (and unwittingly swallowing it), as I suspect happened with the old one (dentist has been vague on what exactly happened).

I'm loath to go ortho because I did already have braces as a kid (and teeth are supposedly more stubborn in adulthood, ouch), and because this is a new-ish problem. Weirdly acting up in the past year or so :(

You didn't scare me; I'd already seen true alarmism...thanks for elaborating!
Unknown said…
If you are relying on Selenium canceling out the mercury in seafood you are relying on one study without a human clinical trial. This panacea served up by the seafood industry is misleading and even dangerous. In 2004, a study found that the number of infants that are potentially exposed to dangerous levels of mercury in the womb was 630,000 children in the U.S. annually. This was double the previous estimates and was determined from mercury levels in umbilical cords, which contain mercury levels 1.7 times higher than those of the mother's blood level. Based upon this data, far more babies are being exposed to the reference dose than previously thought.
Check your mercury loading by eating tuna fish sandwiches or other fish on the website.
Bixy said…
I got a chance to see Joel speak here in Melbourne Oz last year. He does 2 main types of talks, one political, and one that just covers farming. Personally I'd skip the political rant unless that's your thing. I don't disagree with what he says in those talks, but they are a bit disjointed and rambling compared to his books / talks on farming, which in my opinion are fantastic.

Evelyn, his beef might be frozen, but I imagine there would be other farmers closer to you that you can order fresh from? I could be speaking out of my butt, as the farmers markets here are pretty good for choice, but you may not have that option.
Will Hui said…
Actually, there is at least one human clinical trial testing this idea. It used selenium supplementation to lower hair mercury levels.

But yes, we probably need more data on the extent of selenium's protective effect in humans.
CarbSane said…
Welcome Bixy! I suppose I could, and perhaps I have messed up priorities, but, TTBOMK the closest local source would be around a half hour away and not anywhere I go anyway and tack $10 for the gas. That's hard to justify for two porterhouses which is about all we could buy and consume fresh. If I buy bulk I'm freezing. Don't get me wrong, I have a chest freezer and do freeze steaks, but I prefer freezing cooked foods, and that don't work for a steak! We do have a farm nearby for seasonal produce, but around here it's super pricey. I do miss my former home for that reason -- a town that even though it's built up quite a bit probably still has more cows and chickens than people -- lots of local stands and cheaper than the supermarket. Which just goes to show that the laws of supply and demand rule and I think Salatin ignores these.

So in the end, I'm with Unknown in that I don't see how sourcing my food in this manner would improve my quality of life. Because meanwhile Stew Leonard's is on my hubs' way home from work, not far from our home anyway, along the route to any number of places we go. They do carry some local produce in season and work with family farms, but it's a supermarket alright ... a unique one ... but a supermarket nonetheless, and I'm not quite sure Salatin would approve. But if the sales are still going, there's whole filet mignon for $5.99/lb and lobster for $4.99/lb. Hmmm ... or Joel's ground beef ... which one should I choose :D
rodeo said…
With frozen meat you could try a Swedish recipe called Tjälknöl. It's delicious, even better than fresh meat. You put a frozen roast of meat in the oven at a low heat for about 14 hours and then in a marinade for 6 more hours. Incredibly tender :)
CarbSane said…
Welcome Shark, That calculator says my mercury dose is quite low so that makes me happy! I do believe the recs are good to err on the side of caution for pregnant and breastfeeding women. Either Se binds Hg in the fish or it doesn't.

Will, I'll look at that when I get a chance. One question I wanted to ask Chris is if there's any evidence that supplementing can help. Mercury accumulated by fish over time and combined with selenium makes sense to be inert if that association/bonding is indeed all that. But if I eat selenium with mercury laced fish, will that Se scavenge that Hg in my body? Slightly different thing.
Bixy said…
Hey Evelyn, long time reader, first time poster (actually second, but who's counting).

That's interesting to note the differences. Here, ordering direct from farmers is pretty comparable price wise to getting it from a supermarket. Either we have expensive supermarkets (more likely) or cheap produce from small farmers (less likely).

A lot of the farmers at my local market are actually getting quite internet and marketing savvy, where you can order ahead in bulk and it works out quite cheap. As long as you don't mind freezing, which I guess comes back to your point. I agree with not wanting to freeze steaks, but I don't tend to buy steaks when placing bigger orders, I usually just pick them up on the weekend every now and then when I feel like a steak. Most cuts that I order in bulk, like stewing beef, mince etc, do fine in the freezer in my opinion.

Everyone's different, I have got to a point where I actually don't have many expenses, so I don't mind paying a bit extra and spending a bit of time on a weekend morning to go to a farmers market and get better quality food. I realise not everyone has that option or time, but for most it just depends on your own priorities.

Your comment on not being sure how it would improve the quality of your own life...agree with that, it may not make any difference short term. I look at if from a longer term perspective though. "Conventional" farming is unsustainable. It relies on fertilisers from fossil fuels and depletes the soil quality. We keep going the way we are and eventually something's gotta give. So I figure the more of us who can support farming practises that regenerate, not degenerate the land, the better.

I guess it depends on whether or not you agree with that, and if you do, whether it’s important enough to you to consider when buying your food (please note I’m not being judgmental here, everyone is different and has different priorities in life).
Puddleg said…
1) if you're eating mercury you're not getting the benefit from the selenium in the fish
2) I've gone my whole life without eating swordfish, and I don't feel deprived
3) I consumed all of my many amalgam fillings when the teeth decayed around them anyway. Don't count on any filling staying out of your gut. My one composite filling is the only filled tooth still in my mouth; it's as sound as the day it was filled. It's the soundest tooth there.
CarbSane said…
1) That's the point of the linked pdf and my post. If the ratio is favorable there is still free Se, albeit less, for benefit.
2) ??
3) I am not saying amalgam = good, composite = bad. I am saying that you have to weigh the risks/benefits of both carefully and it's far from cut and dried. If I swallowed a restoration, yes, I would have more concerns over an amalgam. But composites -- especially older ones -- do not have longevity on their side.

I am amazed how many people are convinced to spend 20-30K on veneers not realizing that these have a lifetime of as few as 10 years and come with no guarantee of even that. And then what? If they shave down your teeth and they fall off and you have no money? You're in a world of hurt. Literally.

I don't want people looking at me trying to pick the tooth out of a lineup, but the only composite I had before those replacements was a teeny tiny one on the wall of a tooth. TINY. Filling lead to root canal (again, this was a surface filling) led to bone infection led to lost tooth and extensive bone grafting then implant and crown. All in all, that single tooth cost me 10K and that was with some pretty good insurance coverage kicking in. No, I don't blame composites, just saying you can't really tell anything about anything from n=1 ;) My remaining amalgam is over 30 years old and is larger than that small composite one was but there it sits, at the base of my brain, causing no problems.