October 17, 2006
Eat Oily Fish For Longer Life Expectancy

Eating fish is good for your heart and will lengthen lifespans.

Boston, MA Many studies have shown the nutritional benefits of eating fish (finfish or shellfish). Fish is high in protein and omega-3 fatty acids. But concerns have been raised in recent years about chemicals found in fish from environmental pollution, including mercury, PCBs and dioxins. That has led to confusion among the public--do the risks of eating fish outweigh the benefits?

Researchers from the Harvard School of Public Health (HSPH) tackled that question by undertaking the single most comprehensive analysis to date of fish and health. In the first review to combine the evidence for major health effects of omega-3 fatty acids, major health risks of mercury, and major health risks of PCBs and dioxins in both adults and infants/young children, the results show that the benefits of eating a modest amount of fish per week--about 3 ounces of farmed salmon or 6 ounces of mackerel--reduced the risk of death from coronary heart disease (CHD) by 36%. Notably, by combining results of randomized clinical trials, the investigators also demonstrated that intake of fish or fish oil reduces total mortality--deaths from any causes--by 17%.

Included with the paper, which appears in the October 18, 2006, issue of The Journal of the American Medical Association (http://jama.ama-assn.org/), is the first comprehensive summary of levels of omega-3 fatty acids, mercury, PCBs and dioxins in various species of fish and other foods, including chicken, beef, pork, butter and eggs.

"Overall, for major health outcomes among adults, the benefits of eating fish greatly outweigh the risks," said Dariush Mozaffarian, lead author of the study and an instructor in epidemiology at HSPH and in medicine at Brigham and Women's Hospital. "Somehow this evidence has been lost on the public."

Don't worry. Be happy. Eat fish.

Since the study did not examine the effects of all potential benefits of fish the results may understate the benefit of fish consumption.

The researchers, Mozaffarian and Eric Rimm, associate professor of epidemiology and nutrition at HSPH, did a comprehensive search of publications through April 2006 to evaluate the evidence from studies that looked at the relationship between fish intake and major health benefits as well as at the health risks of mercury, dioxins and PCBs. For benefits, the researchers focused on cardiovascular health in adults and brain development in infants, areas in which the scientific evidence is strongest (other potential benefits of fish consumption--for example, for cognitive decline or depression--might make the overall benefits even greater). The researchers focused on evidence from large prospective studies and randomized clinical trials.

Eat oily fish.

The evidence across different studies showed that fish consumption lowers the risk of death from heart disease by 36%. The benefit was related to the level of intake of omega-3 fatty acids, and thus benefits are greater for oily fish (e.g. salmon, bluefish), which are higher in beneficial omega-3 fatty acids, than lean fish (haddock, cod).

Avoid high mercury fish types.

The evidence was suggestive that mercury may have subtle effects on brain development for a child exposed in the womb, or in early childhood. To obtain the benefits of omega-3 fatty acids for brain development and minimize the potential risk of mercury, the investigators' findings agreed with the recommendations of the Environmental Protection Agency and Food and Drug Administration that women of childbearing age, nursing mothers and young children should eat up to two servings per week of a variety of fish (for example, salmon, light tuna, shrimp, mackerel, and up to 6 oz. per week of albacore tuna) and avoid only four species of fish--golden bass (also known as tilefish), king mackerel, shark and swordfish--larger, predatory fish that have higher levels of mercury. The researchers emphasized that this advisory is only for women of childbearing age, nursing mothers and young children, not the general population. Importantly, the evidence suggests that, for those women, it is as important for their health and for the brain development of their infants that they eat a variety of other types of fish as it is to avoid the four fish species higher in mercury.

Do not worry about dioxins in fish unless you get fish from fresh water sources which are contaminated.

Some studies have shown that PCBs and dioxins may be carcinogenic. The authors found that the benefits of eating fish far outweighed the potential cancer risks from these chemicals. "The levels of PCBs and dioxins in fish species are low, similar to other commonly consumed foods such as beef, chicken, pork, eggs, and butter. Importantly, the possible health risks of these low levels of PCBs and dioxins in fish are only a small fraction of the much better established health benefits of the omega-3 fatty acids," said Mozaffarian. "For example, for farmed salmon, the cardiovascular benefits are greater than the cancer risks by a factor of at least 300:1. With the exception of some locally caught sport fish from contaminated inland waters, the levels of PCBs and dioxins in fish should not influence decisions about fish intake."

The study also points out that only 9% of the PCBs and dioxins in the U.S. food supply come from fish and other seafood; more than 90% comes from other foods such as meats, vegetables, and dairy products.

I continue to be partial to salmon. It has the most omega 3 fatty acids of many types of fish that I've compared. It also has very little mercury.

Depressed people also ought to eat fish. The omega 3 fatty acids might lessen your feelings of pain and depression.

Share |      Randall Parker, 2006 October 17 10:41 PM  Aging Diet Studies

Jerry Martinson said at October 18, 2006 1:31 AM:

I think benefits of n-3 fatty acids are so clear by now that I think more research and effort should be made on how best to increase the DHA/EPA serum levels the entire population of children, adults, and especially mothers/neo-nates. I think there needs to be a push for public-policy changes to get n-3 serum levels much higher throughout the whole population, not just for science-buffs like you and me who actually read this stuff and can afford to each fish.

I know of no federal, state, or local WIC/foodstamp program that allows (much less pushes) fatty fish, or n-3 supplements. It took over a decade for the FDA to finally approve n-3 additives as an _option_ in high-end baby formula. This means there is a huge potential to improve our society for only $80 per head per year in pills. $80/yr/head isn't much compared to having national IQ 3 points lower.

I also think the media's typcial coverage of the n-3 fatty acid issue has often overlooked several practical problems for people to get adequate n-3 fatty acid intake:

1. The n-3 fatty acid content not only varies by fish species, but also by the particular diet of the specific fish that you're eating. Specifically, farm-raised Salmon has lower n-3 fatty acid content than wild Salmon.
2. The oceans are already nearly fished to the limits already for most species, and, if _everyone_ ate enough "culniary fish" to meet adequate n-3 intake goals, the fisheries would utterly collapse.
3. Most people (but certianly not all) actually strongly dislike the taste of n-3 fatty acids, which dominate the flavor and aroma of any food that it's in in any significant quantity.
4. Told to eat fish, most will tend to select fish species that do not have high n-3 fatty acids or avoid them. I've had people tell me that their eating breaded fish sticks (which have essentially no n-3's) for their heart health! Even my wife's Obstectrian actually recommended fish sticks to "avoid methy-Hg" and still get the benefits of fish
5. Vegans and fishy-taste haters are often told in popular publications that they can eat flax seed because their body will convert LNA into DHA,EPA etc... While somewhat true, this is highly misleading as serum concentrations of DHA and EPA do not go up much when people eat lots of LNA.
6. The identified risk groups for methyl-mercury from fish are pre-nates/neo-nates and their mothers. This is the most critical time to get n-3 fatty acids. Yet mothers are cautioned about the fish but no other sources of n-3 fatty acids are competently recommended.
7. High-quality n-3 fatty acid fish costs a lot of money, out of the reach of many.

IMHO, the obvious answer to the above problems is to have the gov't officially recommend n-3 fatty acid supplemenation in the form of pills to the whole population. Less than 1 in a 1000 could be net-harmed by taking n-3 supplements due the fact that they thin the blood. I think there is a tremendous reluctance in the media and gov't to break down the dogma that "all supplements are a waste of money and are potentially dangerous".

Richard said at October 18, 2006 4:30 AM:


In all your posts about health you have never mentioned grassfed beef. Grassfed beef actually has more omega-3 fats than fish. Grainfed feedlot beef is a problem, but the grassfed stuff is something you should think about. I have selfish reasons here, as I raise my own and want to believe I am doing the right thing.

carl said at October 18, 2006 9:25 AM:

Richard, that's interesting, I had never heard that before. I did a quick google and all I could find are grass fed beef sellers making that claim. Do you know if this is more than a marketing ploy by them (I suspect it is for real, but just wondering how widely this is known)? Also, do you know if this is mostly ALA, DHA, or EPA? If it's mostly ALA then it's not such a great thing (you'd still want to eat fish).

Randall Parker said at October 18, 2006 5:01 PM:


The biggest problem is that all omega 3 sources are expensive. Fish is expensive and the oceans are getting overfished. Martek's DHA extracted from algae is an expensive way to get DHA. I am glad Martek got FDA approval to sell it for baby formula. But marketed under the Neuromins label it is not a cheap omega 3 fatty acid source.

I've written previously that the solution is genetic engineering of crops to make them synthesize omega 3 fatty acids. As I note there Monsanto and Dupont are both working on omega 3 fatty acid production in soy beans and BASF is chasing genetically engineered crops for omega 3s as well. That's how the problem is going to get solved.


I've read that grass fed beef has more omega 3s but still a higher ratio of omega 6s to omega 3s than many types of fish. You want to provide some links to research results that support your claims? I'd be happy to write about it if I had better data on it.

I very seriously doubt that grass fed beef measures up to even farmed salmon, let alone ocean salmon. Salmon is the best as far as I can tell.


You are correct, the conversion efficiency from ALA to EPA is 5% to 10% according to one source I found. See the link above in this comment and then go to the comments in that post and you'll see I cite a source there.

Tom said at October 18, 2006 10:15 PM:

Hi, I have some questions:

*Do you know of any website/sudy that list the potential contaminated sources of fish?. I mean a reference we could use to check the brand or origin of e.g. caned tuna and see if that area is reported as problematic.

*Which are the risks of eating raw fish (especially salmon)?. Do fatty acids get altered with heat?.

*Are enriched eggs as good as fish?. Any advantage to eat them raw?.

Regaring engineered soy, soy is a double sword, it is displacing other crops and grass fed animals in many places, not to mention destruction of forests to make place for soy.


Richard said at October 19, 2006 3:34 AM:


I have info, it is scattered around, as soon as I can get it, I shall post it here.

Nothing wrong with seafood, I love it. I just wish they would find out that fried clams had something necessary for the diet.

For that matter, Futurepundit needs to do some serious bacon research.

Richard said at October 19, 2006 7:11 AM:

Carl and Randall,

Here is some information. It is comparing grass to grain fed and all ratios presented are looking into that, however if you know the salmon ratio you should have an idea how they stack up:

Effect of Ration on Lipid Profiles in Beef (pdf)
A Literature Review of the Value-Added Nutrients found in Grass-fed Beef Products (doc)


Below is more a fairly exhaustive list of sources:
A Literature Review of the Value-Added Nutrients found in Grass-fed Beef Products (doc)

Richard said at October 20, 2006 4:06 PM:

Sorry, the second part should have read:

Health Attribute Literature
A Literature Review of the Value-Added Nutrients found in Grass-fed Beef Products (doc)


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