Tag Archives: fish

Is Pollution Causing Type 2 Diabetes and Obesity?

It sounds like Jerome Ruzzin is convinced it does. I put some thought into it last August and was skeptical—still am, but I’m keeping an open mind. Mr. Ruzzin has a review article published in 2012 at BMC Public Health (“Public health concern behind the exposure to persistent organic pollutants and the risk of metabolic diseases”). Here’s his summary:

The global prevalence of metabolic diseases like obesity and type 2 diabetes, and its colossal economic and social costs represent a major public health issue for our societies. There is now solid evidence demonstrating the contribution of POPs [persistent organic pollutants], at environmental levels, to metabolic disorders. Thus, human exposure to POPs might have, for decades, been sufficient and enough to participate to the epidemics of obesity and type 2 diabetes. Based on recent studies, the fundaments of current risk assessment of POPs, like “concept of additive effects” or “dioxins and dl-PCBs induced similar biological effects through AhR”, appear unlikely to predict the risk of metabolic diseases. Furthermore, POP regulation in food products should be harmonized and re-evaluated to better protect consumers. Neglecting the novel and emerging knowledge about the link between POPs and metabolic diseases will have significant health impacts for the general population and the next generations.

Read the whole enchilada.

Salmon is a good source of omega-3 fatty acids, but are they dangerously polluted?

Salmon are a good source of omega-3 fatty acids, but are they dangerously polluted?

The cold-water fatty fish I so often recommend to my patients could be hurting them. They are major reservoirs of food-based POPs.

Steve Parker, M.D.

Which Fish Provide Maximum Health Benefit and Least Mercury?

Salmon is a good choice

Salmon is a good choice

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 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

Read This If You Worry About Mercury In Fish



An article at ScienceDaily suggests concern about mercury poisoning from fish consumption is overblown. Fish didn’t contribute much at all to blood mercury levels in pregnant UK women. Fatty cold-water fish are good source of omega-3 fatty acids that are linked to health of mom and her spawn. But they also contain mercury. A snippet:

Speaking about the findings, the report’s main author, Professor Jean Golding OBE, said:

‘We were pleasantly surprised to find that fish contributes such a small amount (only seven per cent) to blood mercury levels. We have previously found that eating fish during pregnancy has many health benefits for both mother and child. We hope many more women will now consider eating more fish during pregnancy. It is important to stress, however, that pregnant women need a mixed balanced diet. They should include fish with other dietary components that are beneficial including fruit and vegetables.’

Higher Blood Levels of Omega-3 Fatty Acids Protect Against Death

…so how do you raise your omega-3 level?  Eat cold-water fatty fish, as recommended in my Advanced Mediterranean and Ketogenic Mediterranean diets.  A quote from the New York Times Well blog:

The lead author, Dr. Dariush Mozaffarian, an associate professor of medicine at Harvard, said that the most beneficial levels could be achieved by consuming an average of 400 milligrams of omega-3s a day — the equivalent of weekly consumption of about 3.5 ounces of farmed salmon, 5 ounces of anchovies or herring, or 15 to 18 ounces of cod or catfish.

Read the rest.

Tuna Preserves Brain Blood Flow In People Over 65

Among people over 65, consumption of tuna/other fish is associated with preserved blood flow to the brain, according to a 2008 research report in the journal Neurology.

“Silent” brain infarcts – tiny strokes that are not obvious – are very common with advancing age. If a group of people 65 and older is MRI scanned and found to have no strokes, MRI scans performed five years later will show tiny strokes in 20% of them. Almost 90% of these new strokes are simply incidental findings without clinically evident stroke or transient ischemic attack.

As the authors point out:

Subclinical infarcts and white matter abnormalities are considered to be of vascular origin, presumably resulting from occlusion of small arteries in the brain and subsequent ischemia.

These subclinical strokes, along with brain white matter abnormalities, are not benign. They are associated eventually with impairment in thinking and behavior, and with higher risk of future obvious stroke.

Eating tuna or other broiled or baked fish tends to raise plasma omega-3 fatty acid levels and is associated with lower stroke risk and dementia and Alzheimer disease. Researchers wondered if fish consumption affected the risk of subclinical brain infarcts or other subclinical brain abnormalities.


Scientists studied 3,660 participants over 65 years old in the Cardiovascular Health Study, by MRI scanning, lab testing, physical exam, and food frequency questionnaire. Five years later, 2,313 were rescanned. Hospital and clinic records were reviewed. Participants were men and women in four U.S. communities. Fish intake was classified as to whether tuna, other broiled or baked fish, and fried fish or fish sandwiches (fish burgers). In a subset of participants, blood levels of omega-3 fatty acids were measured.

Conclusions of the Scientists

Among older adults, modest consumption of tuna/other fish, but not fried fish, was associated with lower prevalence of subclinical infarcts and white matter abnormalities on MRI examinations. Our results add to prior evidence that suggest that dietary intake of fish with higher eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA] content, and not fried fish intake, may have clinically important health benefits.

…the results of the present article support the growing evidence that the type of fish meal consumed is important for obtaining the health benefits of fish consumption.


The fish with higher omega-3 fatty acids, such as EPA and DHA, are the cold-water fatty fish such as albacore tuna, salmon, trout, sardines, anchovies, herring, halibut, sea bass, swordfish, and mackerel. These are sometimes referred to as dark meat fish or oily fish. These are the same types of fish most closely associated with lower rates of coronary artery disease and sudden cardiac death.

The types of fish used in fish sticks, fish burgers, and other fried fish meals are typically low in omega-3 fatty acids.

If you choose to eat fish for the health benefits, aim for two servings per week of cold-water fatty fish. The Friday night all-U-can-eat fried catfish buffet doesn’t cut it.

Steve Parker, M.D.

Reference: Virtanen, J.K., et al. Fish consumption and risk of subclinical brain abnormalities on MRI in older [U.S.] adults. Neurology, 71 (2008): 439-446.

Eat Cod to Lose More Weight

BUS30079Five servings of cod per week led to loss of an extra 3.7 pounds (1.7 kg) over eight weeks, according to a 2009 research report.

European researchers noted that cod consumption in a prior study enhanced weight loss. They wondered if that result could be reproduced, and whether the effect was “dose dependent.” In other words, would those eating more cod lose more weight than those eating less?

They studied 125 subjects between the ages of 20 and 40, with body mass index between 27.5 and 32.5. The abstract doesn’t mention sex of the participants. They were all placed on calorie-restricted diets with identical percentages of protein, fat, and carbohydrate, and were followed for eight weeks. Researchers divided the subjects into three groups:

  1. One group was given 150 g (a little over 5 ounces) of cod three times weekly
  2. Another group was given 150 g cod five times weekly
  3. The third group was given no seafood

Average weight loss overall was 11 pounds (5 kg). The more cod consumed, the greater the weight loss. Those eating five servings a week averaged 3.7 pounds (1.7 kg) more than the group not eating seafood.

It’s unclear whether other types of fish would produce similar results.

These results support the prominent role of fish in the Ketogenic Mediterranean Diet.

Steve Parker, M.D.

Reference: Ramel, A., et al. Consumption of cod and weight loss in young overweight and obese adults on an energy reduced diet for 8-weeks. Nutrition, Metabolism and Cardiovascular Diseases, 19 (2009): 690-696.

Fish With Omega-3 Fatty Acids Reduce Risk of Blindness

Age-related macular degeneration is the leading cause of blindness in Americans over 65. Impaired vision precedes blindness. A recent study linked consumption of omega-3 fatty acids with 30% lower risk of developing macular degeneration. Believe me, it’s a lot better to prevent it than try to treat it once present.

(I have a couple older relatives with macular degeneration, so I pay close attention to the scientific literature.)

What’s the best source of omega-3 fatty acids? Our friend, the fish. Especially cold-water fatty fish such as tuna, trout, sardines, herring, mackerel, halibut, and sea bass. A few plants are also decent sources, but our bodies don’t utilize those omega-3 fatty acids as well as they do from fish.

Note that both the Advanced Mediterranean Diet and Ketogenic Mediterranean Diet feature fish.

Steve Parker, M.D.

Reference: SanGiovanni, J.P., et al. Long-chain polyunsaturated fatty acid intake and 12-y incidence of neovascular age-related macular degeneration and central geographic atrophy: AREDS report 30, a prospective cohort study from the Age-Related Eye Disease Study. American Journal of Clinical Nutrition, 90 (2009): 1,601-1,607. First published October 7, 2009. doi:10.3945/ajcn.2009.27594

Something Fishy

Fish is a major feature of my Ketogenic Mediterranean Diet as well as a healthy component of the traditional Mediterranean diet.

Darya Pino over at Summer Tomato wrote about eating fish: health aspects, which are best to eat, shopping, and sustainability. I recommend it to you, even though I don’t agree with everything. For instance, I think in general the risk of mercury contamination is overblown. (I know that’s little consolation for those few who have suffered mercury poisoning from fish.)

Steve Parker, M.D.