Fish and your health: Dismantling the myths

Apr 03, 2012

Freelance writer and blogger Tamar Haspel discussed the contradictory expert advice on fish. For example, should the protein, which is rich in omega-3 fatty acids, be included in your diet? Or should you avoid fish due to PCB or mercury contamination? Read Haspel's story about fish and health myths. Haspel was online at Noon EDT on Tuesday, April 3 to answer questions about her story.

Do farmed fish present mercury risks, including salmon that is released into the sea for a period of time?

Both wild and farmed salmon, and all farmed fish, are low in mercury -- they don't live long enough to accumulate it.  So have at it!

Is taking omega-3 pills (or Salmon oil pills) an adequate or good substitute for fish-avoiding mercury and PCB contamination?

Most pills that have been tested have almost no contamination, but there's some question about whether you get all the same benefits.  I'm not an expert on this, but I know studies have shown fish-eating to out-perform supplement-taking in some studies, and there may be other things about fish, besides omega-3s, that are helpful

Hello Tamar - I've been on a bagel and lox kick. I was at Whole Foods picking out salmon and was amazed that 100% of products were farm raised and had color additives to match color of "normal" salmon. I was curious, why bother putting fake color additive and also implying stocks of wild fish as there was no wild option available.

Everyone wants nice salmon-colored salmon!  And don't necessarily dismiss farmed salmon. Some is raised very responsibly.

Your article was rife with inaccuracies, half-truths and few citations. I had to laugh at your implication of the "anecdotal" evidence that mercury is a neurotoxin. I don't think there is any question about that. Furthermore I don't think the danger is with acute poisoning from a single meal but the fact that mercury, as you mention in your article, bioaccumulates so you must consider your consumption over many years. You also fail to acknowledge another significant reason to avoid fish: the fact that so many fish stocks are on the verge of population collapse worldwide. It would also have been worth noting that it is completely possible to receive the most important Omega 3 fatty acids, DHA and EPA, through supplements that are either microbial-based or have been purified.

No one (least of all me) has any doubt that mercury is a neurotoxin.  The anecdotal evidence is for mercury poisoning in adults from environmental mercury at the levels we see in the US.  And no one doubts that the danger is from long-term accumulation.  And no one doubts that fish are overfished.  I do, however, doubt that it's possible to get all the fish benefits from supplements.  The evidence doesn't bear you out on that.

Should I eat farm raised salmon or wild salmon? I love fish and my family ate fish at least twice a week when we were younger. This DMV area has a wonderful selection of wild fish from the Bay and the Atlantic Ocean. I never considered canned tuna a true fish because of the variety of fish that I eat.

Eat what's available, and what you can afford.  There are a lot of issues on farmed vs. wild, and each type can have problems.  Do some research and try to shop somewhere that takes care where it sources fish from.

I have avoided fish due to the mercury scare - fresh or canned. Can I eat it without worrying about mercury and if so how often and how much?

As long as you're not pregnant or planning to become so, you shouldn't worry.  Follow the guidelines in the article.

I try to buy wild rather than farmed fish. Now, I've noticed labeling on frozen fish that says "Wild Caught". What does that mean?

Unless there's something tricky I don't know about, "Wild Caught" means wild fish.  If anybody knows different, please holler!

I love the diagram showing increasing levels of mercury and Omega-3 in different fish (I wish I liked herring and mackerel more). Salmon is in the safer range at the top right part of the diagram, but the article mentions the high levels of PCB in salmon. Is there a similar diagram showing levels of PCB in fish? I don't know much about PCB, but after seeing the documentary "The Cove" I tend to stay away from fish to avoid the mercury.

There is a similar diagram for dioxin and dioxin-like PCBs (in the same report that has the mercury graphic, from the FAO/WHO), but it doesn't isolate PCBs.  But they tend to vary greatly depending on area (as does mercury, actually, so not every example of every kind of fish will have the same levels).  

So if I catch and eat a catfish from the Potomac river can I assume it has the same level of contaminants as, say a farm raised catfish from Louisiana? Assuming the same age/weight.

No, you can't.  For fish you catch, check with your local fish and game department.  Local catfish is likely to be radically different from farmed catfish.

Are there certain ways to cook the fish, so as not to waste its nutritious value? And does the high temperature affect the nutrients in fish?

The nutrients (the ones at issue, at any rate) are in the fat, so if you cook it so the fat renders out, you'll lose some.  But I wouldn't worry too much about it.  Cook it the way you like to eat it.  It's food, not medicine, after all.  

I note that my fish oil capsules say "Purified to Eliminate Mercury". I don't think that was on the last bottle I bought. Clearly either such processing is new or the makers figured it was good advertising to comment on it. They are made from "herring, mackerel, sardine, sprate, and salmon". Do you suppose mercury contamination in the oil was ever a real concern, and do you suppose that their statement of purity should allay concern? Do you have any information about PCBs or dioxin in processed fish oil? What general comments do you have about such supplements?

I tackled this a little bit above.  My understanding is that mercury is not a concern, but other contaminants may or may not be tested for.  Since fish oil is generally made from small fish, I wouldn't worry about it.  But I wouldn't take it, either.  I prefer to get my fish benefits in actual fish, both because then I get a nice meal with my nutrients and because isolated nutrients in a pill almost never turn out to have the benefits of those same nutrients in situ.  

I realize the article covered only the direct health benefits and risks to humans from eating certain kinds of fish. However, isn't environmental impact one of the issues that environmental groups are concerned about when they make those recommendations? I've read that you should avoid most farmed fish - especially salmon because of the detrimental environmental impact. For example, tilapia has been farmed in sectioned-off portions of lakes in central America, but those fish break through and invade the rest of the lake. Since they're bred to mature quickly, this causes additional problems.

You're right that it's really, really complicated.  And I do believe environmental agendas guide, at least to some extent, the recommendations of the NGOs.  The short answer is that there's no simple answer for "what fish should I eat?"  Some farmed fish is a bad choice, but some isn't.  Ditto wild fish.  We all just do our best.

I feel silly asking this, but what kind of tuna is in plain old canned tuna (Starkist, etc)? It comes in two options, usually - chunk light and albacore.

Don't feel silly.  I don't know the answer.  I do know that the chunk light has less mercury, but I can't tell you what species it is.  Shows what I know, eh?

What difference does it make if you consume half salmon and half tuna instead of all salmon or all tuna if they have similar levels of contamination? Or are you saying the same thing as the study, that says not to eat swordfish and some others more than twice a year?

The recommendation to not eat the same fish over and over is, I think, a hedge against uncertainty.  Not every fish you eat will have exactly the same level of contaminants, but if you eat from the same source, over and over, and that particular source happens to be high, well ... you get the picture.  I wouldn't eat swordfish daily.

I found that chart to be rather confusing and had to examine it in great depth. I noticed that shrimp wasn't listed anywhere in the chart and I don't recall reading anything about it in the article, which I admittedly didn't read thoroughly. Isn't shrimp the most popular seafood in the US? Where does shrimp fit in all this?

Shrimp is low in contaminants and low in omega-3s, and a fine choice for dinner.

Can I get at least some of the benefits of fish by taking pills -- and what's the correct dose? I take Vitamin E and was thinking of adding Omega-3 or other fish oil pills but I'm totally confused about the latest research and what to believe. If pills are either a waste of money or bad for you, I don't want to take them! Also -- What ever happened to "cod liver oil"? It used to be a punishment and laxative but I haven't heard about it in years. Thanks!

I've covered pills a bit already (and it's not my area of expertise so I don't want to overstep).  As far as cod liver oil, it's very nutrient-rich, but I think it's that punishment aspect that made it fall out of favor.  They still take it in Iceland, I think!

I love smoked salmon, Nova, gravlax and lox, which are all forms of salmon. But I don't know if the benefits of fresh fish convey when it's been preserved or "cooked" with salt, sugar or smoke. What do you think?

You still get the fats, but you also get the salt, sugar and smoke.  How bad is that for you?  Hard to say.  I don't suppose I should admit this, but I eat smoked bluefish all year long (we catch a lot and smoke our own).  

I love sardines--are they still a good fish choice to eat? I eat the boneless skinless variety and sometimes just the boneless (both canned). Are there better sources of canned sardines than others e.g., Portuguese vs Norwegian?

Sardines are an A-1, primo, excellent choice.  High in omega-3s, low in contaminants.  On many people's "Super-Food" list.  Get the kind you like!

Thank you for your very well researched article. I teach an environmental toxicology class and I am surprised at how poorly most people, especially in the regulatory community, understand the risks and benefits of fish consumption. One point you might have included was that the study that showed the biggest risk to children and pregnant women consuming methyl mercury was done in the Faeroes Islands, where people consume pilot whales, which have all the risks and none of the benefits. Other studies with people consuming a diet more similar to Americans have shown benefits for learning and higher level thinking, but impairment of fine motor function. If anything, I think your recommendations were a little on the conservative side, since even for pregnant women the benefits of moderate fish consumption likely outweigh the risks (although they should stick to the safer fish species). Also, because these pollutants accumulate in fats and can be released later on, the recommendations should be the same for women of child-bearing age, regardless of whether they are currently pregnant.

THanks for adding to the discussion.  There's just so much to say.  You're right about the Faroe Islands study, and it's that and a similar study in the Seychelles (where they eat fish, and which found lower levels of neurologic impairment associated with mercury) that people point to when they discuss this.  And your point about women of child-bearing age is well-taken; many pregnancies are unplanned.

Dear Ms Haspel, I am a proponent of eating the smaller ocean fishes, some of which I can catch myself here on the central California coast. These are sardines, mackerel and anchovies. The rather strong flavor of these fish preclude large "slab" quantities typically associated with fish as we are used to it being served. Personally, I really like these strong flavored fish, but I have been reading that these kinds of fish have been over exploited as sources of food for the fish farming industry. What is your opinion on these subjects?

So many issues, so little time!  Yes, the small fish are being fished to make feed for farmed fish, and that's problem.  It's a particular problem for menhaden, a bottom-of-the-food-chain fish critical to many fisheries here on the east coast.  My opinion is that it's great to eat those little fish (I can't wait for the mackerel to arrive here so we can go out for them), and we need to be very careful about how we use those fisheries.  Bon Appetit!

No matter what the research shows, the medical establishment always just advocates eating a balanced diet. Thus when a study consisting of giving people Omega-3 supplements found strongly positive results, the establishment's recommendation was just eat more fish, instead of advocating taking the same supplements in the study.

A "balanced diet' is a bit of a cop-out, since some foods are most certainly better than others.  But supplements do not show all the benefits of fish-eating, so I think the advice to continue to eat fish is reasonably well-founded.

I have friends with allergies to farm raised fish and seafood. We assumed it was due to the feed or antibiotics used to farm the fish. Have you heard of this problem?

I haven't, and I'd be skeptical.  While it's possible that there's a protein in farmed fish that doesn't exist in wild fish, and it's possible that that protein is an allergen, I'd do the old double-blind, placebo-controlled ingestion test before I decided I was allergic to farmed fish.

Forgive me if this has been answered, but I worry about oysters. Supposedly, they "clean" the bay. So if I eat them, am I eating the contaminants they remove from the water?

So glad you asked!  As it happens, my husband and I have a small oyster farm, and I can actually claim some expertise on this one!  When they say oysters clean the bay, they mean that they filter out organic material like algae and dead fish scraps and all kinds of things that make the water cloudy and ripe for more algae blooms, which deprive fish and other marine life of oxygen.  As for toxins -- yes, they ingest them, but they're not long-lived enough to accumulate them in their flesh.  Also, some they excrete as pseudofeces, and neutralize them in the process by wrapping them in a kind of oyster mucus.  Appetizing, eh?  In any case, farmed oysters are an outstanding choice, and it's not just because I'm an oyster farmer.

Are there reasons that eating fresh, locally caught seafood is healthier than eating frozen seafood? Or is this just something that helps the local economy and fishermen?

It's B.  Frozen seafood is often better-quality than "fresh" because it's flash-frozen on the boat and doesn't deteriorate.  I'm a fan.

Several Asian grocery stores in Fairfax have extensive selections of whole fresh fish. I wonder how long they keep the fish on display and how can you tell whether or not the fish is fresh?

I can't, and I suspect it's hard for anyone to.  I'm not sure what happens to a fish kept in a tank for a long time, but it's probably not too good.  Just guessing here.

Recent years have seen consumers more selective and suppliers more careful about mercury and PCB contamination. But what about radioactive tuna (or other fish) from near Fokushima, Japan?

I have no idea.  I'm assuming authorities are testing the fish.  Let's hope so, at any rate.

Great discussion, I would like to reccomend the following website for helpful information about many of the issues raised during this Q and A session.

I second that.  I think it's a great site.

I absolutely hate all fish and seafood and have never had more than a few "no thank you" bites. Am I causing any health problems or deficiencies by completely avoiding it?

In your case, I might turn to pills.  I don't think people should eat food they don't like, and you'd get at least some of the benefits with supplements.

Is it equally healthy to eat, say canned salmon, canned tuna, even anchovies, as their fresh counterparts? We're sometimes told frozen veggies retain more nutrients than fresh, so maybe the same is true with fish?

Canned are as good as fresh, and frozen are as good as (sometimes better than) fresh.   In my opinion, "fresh" is overrated.  Fish deteriorate quickly, and it makes a lot of sense to freeze or can when it makes sense.

I think you are confusing the effectiveness of a general multivitamin with fish oil supplements. They are effective at providing necessary omega-3s. It is other nutrients that are questionable.

It's certainly true of multivitamins, but it's also true of fish oil supplements.  If you go to Pubmed and look at the individual studies that compare supplements to fish, you'll find that sometimes the benefits pan out and sometimes they don't.  You're certainly right that fish oil does better than most other nutritional supplements, though. 

We actually did the blind test and at least for shrimp, the farm raised caused the problem and wild caught did not.

Very interesting.  And beyond my pay grade!  That sounds like a job for an allergist.

I live on the Alabama Gulf Coast and while we don't fish ourselves, we're frequently offered freshly caught fish (and can buy fresh caught crab, shrimp, etc). Do we need to worry about any of these? Red snapper seems to be the most prominent, and I've read mixed things about their mercury content.

I'd check with your Alabama fish and wildlife authorities.  ALmost all states routinely test fish from local waters, and post evaluations online.  

I envy you the Alabama Gulf Coast!  I recently spent time on Dauphin Island, and was ready to buy real estate.

Should I still eat fish on Friday?

I'm Jewish and uniquely unqualified to answer that one.

Albacore is a species of tuna, with white flesh. It is the typical species that is sold canned in the US, and called "white tuna"? "Light tuna" is every other kind of tuna, not albacore, but mostly skipjack. "Chunk" just means "chunk", large pieces as opposed to little bits. White tuna has more fat, generally, though it is "good" fat. It is considered more desirable than some others, and may be priced higher. Albacore are generally caught as larger fish, which is why they might have more mercury (they are older), though the mercury content also depends on other factors. Sushi bar tuna is various species, by the way, usually more fatty because it tastes better. Often you have a choice of types, yellowfin, etc.

Thank you thank you!  I knew only the albacore part (and that's on the label).

I'm skeptical of their assertions about the dangers of eating fish, not because of the science, but because of their mission. Eating less fish would tend to lend itself to curbing overfishing. Maybe I'm cynical, but it seems for them it's another tool in their box to use a health scare to further their environmental goals. FWIW, I have no problem with them advocating for less overfishing, it's a concern.

The EDF spokesperson pointed out that it's hard to completely separate human health and overfishing because, if the fish disappear, it will have profound implications for human health.  But you're right that they have an environmental agenda, and told me that they could never recommend eating a fish that was seriously overfished, no matter how good it was for you.  They are straightforward about their agenda and the nature of their advice.

Here in Maryland-DC-Virginia, we have lots of crabs -- and skate, scallops, jellyfish. Are any of these seafood that you recommend eating? Do they work as a healthy substitute for fish like salmon and tuna?

I think you should eat the fish you like.  I'm a big skate fan, myself, and I almost never make it because it's one of the few foods my husband doesn't care for.  Check with the MD/VA authorities on contaminant levels, but keep the benefits in mind.  And power to you if you can make jellyfish taste good!  

From the viewpoint of the fish, it is zero benefit and all risk. Your opinion?

Sucks being prey, doesn't it?

I haven't found a way to thaw most species of frozen fish so that...a) it doesn't lose at least ten to twenty percent of it's water; and b) it turns mealy (rather than flaky) on cooking. Cod seems to be the only exception, although I'm told that mahi-mahi also thaws well. Any suggestions on making frozen fish more palatable.

Frozen vs local-fresh fish. Not a health/taste issue maybe, but don't forget all the energy use to bring non-local food to your table. That is a serious concern, although not the topic today. Everyone should give it some weight in their eating choices.

Definitely an issue, but not one with an obvious answer.  A fish shipped a long distance from an efficient fishing operation may have a smaller footprint than a local fish from an inefficient operation.  Very hard to know.  But absolutely an issue.

I have been getting Omega-3 supplements in gel tabs I purchased from the vitamin store. The label says "purified to eliminate mercury." What about other contaminants? Is the use of supplements a suitable or preferred alternative to eating fish?

I think we've covered that one, at least to the limits of my knowledge on the subject.   The short answer is that supplements aren't preferred, but still have some benefits. 

Thanks to everyone for coming to talk fish today!

In This Chat
Tamar Haspel
Tamar Haspel, a freelance writer based in Cape Cod, has been writing about food and health for the better part of two decades. She's the author of four books, including Dreaded Broccoli (Scribner, 1999), and currently writes about harvesting food first-hand at (Photo by Maggie Cole)
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