Tag Archives: fish

Fish Oil Supplements Are a Waste for Many

Salmon is one the the cold-water fatty fish loaded with omega-3 fatty acids

Salmon is one the the cold-water fatty fish loaded with omega-3 fatty acids

Many of us are eating fish or taking fish oil supplements, hoping that they will prevent heart attacks and the associated premature death. As it turns out, they may do neither.

I’ve been sitting on this research report a few years, waiting until I had time to dig into it. That time never came. The full report is free online (thanks, British Medical Journal!). I scanned the full paper to learn that nearly all the studies in this meta-analysis used fish oil supplements, not the cold-water fatty fish the I recommend my patients eat twice a week.

Here’s the abstract:

Objective: To review systematically the evidence for an effect of long chain and shorter chain omega 3 fatty acids on total mortality, cardiovascular events, and cancer.

Data sources: Electronic databases searched to February 2002; authors contacted and bibliographies of randomised controlled trials (RCTs) checked to locate studies.

Review methods Review of RCTs of omega 3 intake for 3 6 months in adults (with or without risk factors for cardiovascular disease) with data on a relevant outcome. Cohort studies that estimated omega 3 intake and related this to clinical outcome during at least 6 months were also included. Application of inclusion criteria, data extraction, and quality assessments were performed independently in duplicate.

Results: Of 15 159 titles and abstracts assessed, 48 RCTs (36 913 participants) and 41 cohort studies were analysed. The trial results were inconsistent. The pooled estimate showed no strong evidence of reduced risk of total mortality (relative risk 0.87, 95% confidence interval 0.73 to 1.03) or combined cardiovascular events (0.95, 0.82 to 1.12) in participants taking additional omega 3 fats. The few studies at low risk of bias were more consistent, but they showed no effect of omega 3 on total mortality (0.98, 0.70 to 1.36) or cardiovascular events (1.09, 0.87 to 1.37). When data from the subgroup of studies of long chain omega 3 fats were analysed separately, total mortality (0.86, 0.70 to 1.04; 138 events) and cardiovascular events (0.93, 0.79 to 1.11) were not clearly reduced. Neither RCTs nor cohort studies suggested increased risk of cancer with a higher intake of omega 3 (trials: 1.07, 0.88 to 1.30; cohort studies: 1.02, 0.87 to 1.19), but clinically important harm could not be excluded.

Conclusion: Long chain and shorter chain omega 3 fats do not have a clear effect on total mortality, combined cardiovascular events, or cancer.

If you’re taking fish oil supplements on your doctor’s advice, don’t stop without consulting her. The study at hand doesn’t address whether eating cold-water fatty fish twice a week prevents heart attacks and premature death. 

Steve Parker, M.D.

Reference: Hooper, Lee et al. Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review. BMJ  2006;332:752-760 (1 April), doi:10.1136/bmj.38755.366331.2F (published 24 March 2006).

Minimize Mercury and Maximize Health With These Fish

paleo diet, low-carb, Steve Parker MD

This hunter-gatherer snagged himself a brown trout

The Environmental Working Group has a fresh article reviewing the risk of mercury poisoning from seafood consumption. I’m not familiar with EWG. I’m trying not to hold it against them that Dr. Mark Hyman is on the board of directors.

Anyway, the EWG has some advice for you if you worry about mercury toxicity from fish. I try to stay up to date on the issue since I’m convinced that consumption of cold-water fatty fish twice a week is good for your health, in general. If the mercury doesn’t kill you.

Here are some quotes from the EWG article:

…EWG has compiled a list of “moderate mercury” species that would pose a mercury risk for pregnant woman and children who eat fish regularly. This list is more comprehensive than the 2004 EPA/FDA advisory, which warned that women of childbearing age and young children, who are most susceptible to the damage done by mercury, should eat only six ounces a week of albacore tuna and should avoid four other high-mercury species – swordfish, tilefish, king mackerel and shark.

EWG rightly points out that much of the “seafood” consumed in the U.S. really doesn’t provide much of the healthful omega-3 fatty acids.

Among popular seafood species, salmon stands out as an excellent choice.  Four to eight ounces of salmon weekly, depending on the species, can provide 100 percent of the recommended amount of omega-3s. Some types of farmed salmon present significant environmental health concerns. EWG recommends that people choose wild salmon instead.

EWG’s analysis highlights several other affordable and sustainably produced species, including anchovies, sardines, farmed trout, and mussels.  Just four to eight ounces of these species weekly would meet recommended omega-3 requirements for pregnant women and people with heart disease.

***

Americans eat more than 400 million pounds of canned imported tuna because it is affordable and can be stored for a long time. Canned tuna is the second most popular seafood in the U.S., after shrimp.  An average American eats an average of 2.5 pounds of tuna every year (NOAA 2012).  Albacore tuna, also called “white” tuna, contains significant amounts of omega-3s, but tests indicate that it also contains significant amounts of mercury. “Light” tuna is usually skipjack tuna but can also contain yellowfin tuna. Skipjack and yellowfin have lower mercury levels than albacore, but fewer omega-3s.

As Jim Gaffigan asked, “Has anyone even bothered to ask why the tuna are eating mercury?”

In 30 years of practicing medicine, including 12 years right on the U.S. Gulf Coast, I’ve never seen a case of mercury toxicity. Maybe I’ve missed it. Maybe it’s quite rare.

Read the whole enchilada.

Steve Parker, M.D.

h/t Conner Middelmann-Whitney

Omega-3 Supplements Fail to Prevent Age-Related Cognitive Decline

I like fish, but cold whole dead fish leave me cold

Consumption of omega-4 fatty acids, mainly from fish, is thought to prevent dementia and certain types of heart disease such as heart attacks and dangerous rhythm disturbances. For those who don’t like fish or can’t afford it, would taking omega-3 fatty acid supplements be just as effective?

Unfortunately, supplementation does not help prevent age-related cognitive decline and dementia, according to an article at MedPage Today.

The respected Cochrane organization did a meta-analysis of three pertinent studies done in several countries (Holland, UK, and ?).

The investigators leave open the possibility that longer-term studies—over three years—may show some benefit.

I leave you with a quote from the MedPage Today article:

And while cognitive benefits were not demonstrated in this review, Sydenham and colleagues emphasized that consumption of two servings of fish each week, with one being an oily fish such as salmon or sardines, is widely recommended for overall health benefits.

Consumption of cold-water fatty fish also helps return our dietary omega-6/omega-3 fatty acid ratio toward our ancestral level.

Steve Parker, M.D.

Reference:
Sydenham E, et al “Omega 3 fatty acid for the prevention of cognitive decline and dementia” Cochrane Database of Systematic Reviews 2012; DOI: 10.1002/14651858.CD005379.pub3.

Does Eating Fish, Meat, and Poultry Ruin Your Mood?

Cow’s in a good mood. What a great place to live!

Your mood might improve if you restrict meat, poultry, and fish, according to a pilot study in Nutrition Journal. I don’t have time to read it anytime soon. Why don’t you, and comment below?

My gut tells me these researchers are wrong.  At least for me.  To each his own.

-Steve

Reference: Beezhold, Bonnie and Johnston, Carol. Restriction of meat, fish, and poultry in omnivores improves mood: a pilot randomized controlled trial. Nutrition Journal 2012, 11:9 doi:10.1186/1475-2891-11-9. Published: 14 February 2012