Tag Archives: Fish

“Doc, Will I Get Mercury Poisoning From the Fish You Recommend?”

paleo diet, low-carb, Steve Parker MD

 A beautiful brown trout

The Environmental Working Group published an 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. Seafood is key component of the Ketogenic Mediterranean Diet, the foundation of the Low-Carb Mediterranean Diet.

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

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Omega-3 Fatty Acid Supplements Fail to Prevent Dementia

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

Supplementation with omega-3 fatty acids 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.

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.

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WHY Is the Mediterranean Diet So Healthy?

I’ve found that nearly everbody’s eyes glaze over if I try to explain how, physiologically, the Mediterranean diet promotes health and longevity.  Below are some of the boring details, for posterity’s sake, mostly from my 2007 book, The Advanced Mediterranean Diet: Lose Weight, Feel Better, Live Longer.

Many of the nutrient-disease associations I mention below are just that: associations, linkages, not hard proof of a benefit.  Available studies are often contradictory.  For instance, there may be 10 observational studies linking whole grain consumption with reduced deaths from heart disease, while three other studies find no association, or even suggest  higher death rates. (I’m making these numbers up.)  If you want hard proof, you’ll have to wait.  A long time.  Such is nutrition science.  Take it all with a grain of salt. 

Also note that the studies supporting my claims below are nearly all done in non-diabetic populations.

Coronary Heart Disease

Coronary heart disease, also known as coronary artery disease, is the No.1 cause of death in the world. It’s responsible for 40% of deaths in the United States and other industrialized Western countries. The Mediterranean diet is particularly suited to mitigating the ravages of coronary heart disease. Mediterranean diet cardiac benefits may be related to its high content of monounsaturated fat (in olive oil), folate, and antioxidants.

The predominant source of fat in the traditional Mediterranean diet is olive oil, which is rich in monounsaturated fatty acids. High intake of olive oil reduces blood levels of triglycerides, total cholesterol, and LDL (“bad”) cholesterol. HDL or “good” cho-lesterol is unaffected. Olive oil tends to lower blood pressure in hypertensive people. Monounsaturated fatty acids reduce cardiovascular risk substantially, particularly when they replace simple sugars and easily digestible starches. Monounsaturated fatty acids and olive oil may also reduce breast cancer risk. The cardioprotective (good for the heart) and cancer-reducing effects of olive oil may be partially explained by the oil’s polyphenolic compounds.
    
Nuts are another good source of monounsaturated fatty acids and polyunsaturated fatty acids, including some omega-3 polyunsaturated fatty acids. Nuts have been proven to be cardioprotective. They lower LDL and total cholesterol levels, while providing substantial fiber and numerous micronutrients, such as vitamin E, potassium, magnesium, and folic acid. Compared with those who never or rarely eat nuts, people who eat nuts five or more times per week have 30 to 50% less risk of a fatal heart attack. Lesser amounts of nuts are also cardioprotective, perhaps by reducing lethal heart rhythm dis-turbances. 
    
Another key component of the Mediterranean diet is fish. Fish are excellent sources of protein and are low in cholesterol. Fatty, cold-water fish are particularly good for us because of their omega-3 polyunsaturated fatty acids: eicosapentaenoic acid (EPA) and docosahexanaenoic acid (DHA). The other important omega-3 polyunsaturated fatty acid is alpha-linolenic acid (ALA), available in certain plants. Our bodies can convert ALA into EPA and DHA, but not very efficiently. Fish oil supplements, which are rich in EPA, lead to lower total cholesterol and triglyce-ride levels. Fish oil supplements have several properties that fight atherosclerosis (hardening of the arteries). In people who have already had a heart attack, the omega-3 polyunsaturated fatty acids have proven to dramatically reduce cardiac deaths, especially sudden death, and nonfatal heart attacks. So omega-3 polyunsaturated fatty acids are “cardioprotective.”

The first sign of underlying coronary heart disease in many people is simply sudden death from a heart attack (myocardial infarction) or heart rhythm disturbance. These unfortunate souls had hearts that were ticking time bombs. I have little doubt that a significant number of such deaths can be prevented by adequate intake of cold-water fatty fish. As a substitute for fish, fish oil supplements might be just at beneficial. The American Heart Association also recommends fish twice weekly for the general population, or fish oil supplements if whole fish isn’t feasible. Compared with fish oil capsules, whole fish are loaded with vitamins, minerals, and protein. The richest fish sources of omega-3 polyunsaturated fatty acids are albacore (white) tuna, salmon, sar-dines, trout, sea bass, sword-fish, herring, mackerel, anchovy, halibut, and pompano.
    
Cardioprotective omega-3 polyunsaturated fatty acids (mainly ALA) are also provided by plants, such as nuts and seeds, legumes, and vegetables. Rich sources of ALA include walnuts, butternuts, soy-beans, flaxseed, almonds, leeks, purslane, pinto beans, and wheat germ. Purslane is also one of the few plant sources of EPA. Several oils are also very high in ALA: flaxseed, canola, and soybean. Look for them in salad dressings, or try cooking with them.

Macular Degeneration

Omega-3 fatty acid and fish consumption may also be “eye-protective.” Eating fish one to three times per week apparently helps prevent age-related macular degeneration (AMD), the leading cause of blindness in people over 50 in the United States. While AMD has a significant hereditary component, onset and progression of AMD are affected by diet and lifestyle choices. For instance, smoking cigarettes definitely increases your risk of developing AMD. Other foods associated with lower risk of AMD are dark green leafy vegetables, orange and yellow vegetables and fruits: spinach, kale, collard greens, yellow corn, broccoli, sweet potatoes, squash, orange bell peppers, oranges, mangoes, apricots, peaches, honeydew melon, and papaya. Two unifying phytochemicals in this food list are lutein and zeaxanthin, which are also found in red grapes, kiwi fruit, lima beans, green beans, and green bell peppers. Increasing your intake of these foods as part of the Advanced Mediterranean Diet may well help preserve your vision as you age.      
    
Alzheimer’s Dementia
    
Another exciting potential benefit of fish consumption is prevention or delay of Alzheimer’s dementia. Several recent epidemiologic studies have suggested that intake of fish once or twice per week significantly reduces the risk of Alzheimer’s. Types of fish eaten were not specified. No one knows if fish oil capsules are equivalent. For now, I’m sticking with fatty cold-water fish, which I call my “brain food.”
    
Vitamin E supplements may slow the progression of established Alzheimer’s disease; clinical studies show either modest slowing of progression or no benefit. As a way to prevent Alzheimer’s, however, vitamin E supplements have been disappointing. On the other hand, high dietary vitamin E is associated with reduced risk of developing Alzheimer’s. Good sources of vitamin E include vegetable oils (especially sunflower and soybean), sunflower seeds, nuts, shrimp, fruits, and certain vegetables: sweet potatoes, asparagus, beans, broccoli, Brussels sprouts, carrots, okra, green peas, sweet peppers, spinach, and tomatoes. All of these are on your new diet. 

Wine

For centuries, the healthier populations in the Mediterranean region have enjoyed wine in light to moderate amounts, usually with meals. Epidemiologic studies there and in other parts of the world have associated reasonable alcohol consumption with prolonged lifespan, reduced coronary artery disease, diminished Alzheimer’s and other dementias, and possibly fewer strokes. Alcohol tends to increase HDL cholesterol, have an antiplatelet effect, and may reduce C-reactive protein, a marker of arterial inflammation. These effects would tend to reduce cardiovascular disease. Wine taken with meals provides antioxidant phytochemicals (polyphenols, procyanidins) which may protect against atherosclerosis and some cancers. 

What’s a “reasonable” amount of alcohol? An old medical school joke is that a “heavy drinker” is anyone who drinks more than the doctor does. Light to moderate alcohol consumption is generally consi-dered to be one or fewer drinks per day for a woman, two or fewer drinks per day for a man. One drink is 5 ounces of wine, 12 ounces of beer, or 1.5 ounces of 80 proof distilled spirits (e.g., vodka, whiskey, gin). The optimal health-promoting type of alcohol is unclear. I tend to favor wine, a time-honored component of the Mediterranean diet. Red wine in particular is a rich source of resveratrol, which is thought to be a major contributor to the cardioprotective benefits associated with light to moderate alcohol consumption. Grape juice may be just as good—it’s too soon to tell.
    
I have no intention of overselling the benefits of alcohol. If you are considering habitual alcohol as a food, be aware that the health benefits are still somewhat debatable. Consumption of three or more alcoholic drinks per day is clearly associated with a higher risk of breast cancer in women. Even one or two drinks daily may slightly increase the risk. Folic acid supplementation might mitigate the risk. If you are a woman and breast cancer runs in your family, strongly consider abstinence. Be cautious if there are alcoholics in your family; you may have inherited the predisposition. If you take any medications or have chronic medical conditions, check with your personal physician first. For those drinking above light to mod-erate levels, alcohol is clearly perilous. Higher dosages can cause hypertension, liver disease, heart failure, certain cancers, and other medical problems. And psychosocial problems. And legal problems. And death. Heavy drinkers have higher rates of violent and accidental death. Alcoholism is often fatal. You should not drink alcohol if you:
            ■  have a history of alcohol abuse
                or alcoholism
            ■  have liver or pancreas disease
            ■  are pregnant or trying to become
                pregnant
            ■  may have the need to operate
                dangerous equipment or machinery,
                such as an automobile, while under
                the influence of alcohol
            ■  have a demonstrated inability to
                limit yourself to acceptable
                intake levels
            ■  have personal prohibitions due
                to religious, ethical, or other
                reasons. 
    
Cancer

Do you ever worry about cancer? You should. It’s the second leading cause of death. Over 500,000 people die from cancer each year in the United States. One third of people in the United States will develop cancer. Twenty percent of us will die from cancer. About half the deaths are from cancer of the lung, breast, and colon/rectum. Are you worried yet?

According to the American Cancer Society, one third of all cancer deaths can be attributed to diet and inadequate physical activity. So we have some control over our risk of developing cancer. High consumption of fruits and vegetables seems to protect against cancer of the lung, stomach, colon, rectum, oral cavity, and esophagus, although other studies dispute the protective linkage. Data on other cancers is limited or inconsistent. If you typically eat little or no fruits and vegetables, you can start today to cut your cancer risk by up to one half. Five servings of fresh fruits and vegetables a day seems to be the protective dose against cancer. Make it a life-long habit. The benefits accrue over time. Fruits and vegetables contain numerous phytochemicals thought to improve or maintain health, such as carotenoids (e.g., lycopene), lignans, phytosterols, sulfides, isothyocyanates, phenolic compounds (includ-ing flavonoids, resveratrol, phytoestrogens, anthocyanins, and tannins), protease inhibitors, capsaicin, vitamins, and minerals. 
   
In addition to cancer prevention properties, fruits and vegetables provide fiber, which is the part of plants resistant to digestion by our enzymes. The other source of fiber is grain products, especially whole grains. Liberal intake of fiber helps prevent constipation, diverticular disease, hemorrhoids, irritable bowel syndrome, and perhaps colon polyps. Soluble fiber helps control blood sugar levels in diabetics. It also reduces LDL cholesterol levels, thereby reducing risks of coronary heart disease. Whether or not related to fiber, high fruit and vegetable intake may reduce the risks of coronary heart disease and stroke. Legume consumption in particular has been associated with a 10 to 20% lower risk of coronary heart disease, with the effective dose being around four servings per week. 

Fiber and Whole Grains

Processed, refined grain products have much less fiber than do whole grains. For instance, white all-purpose enriched flour has only about one fourth the fiber of whole wheat flour. The milling process removes the bran, germ, and husk (chaff), leaving only the endosperm as the refined product, flour. Endosperm is mostly starch and 10–15% protein. Many nutrients are lost during processing. The germ is particularly rich in vitamins (especially B vitamins), polyunsaturated fatty acids, antioxidants, trace minerals, and phytochemicals. Phytochemicals protect us against certain chronic diseases. Bran is high in fiber and nutrients: B vitamins, iron, magnesium, copper, and zinc, to name a few. Enriched grain products are refined grains that have had some, but certainly not all, nutrients added back, typically iron, thiamin, niacin, riboflavin, and folate. Why not just eat the whole grain? Whole grain products retain nearly all the nutrients found in the original grain. Hence, they are more nutritious than refined and enriched grain products.
    
Liberal intake of high-fiber whole grain foods, as contrasted with refined grains, is linked to lower risk of death and lower incidence of coronary heart disease and type 2 diabetes mellitus. For existing diabetics, whole grain consumption can help im-prove blood sugar levels. Three servings of whole grains per day cut the risk of coronary heart disease by about 25 percent compared with those who rarely eat whole grains. Regular consumption of whole grains may also substantially reduce the risk of sev-eral forms of cancer.

Average adult fiber intake in the United States is 12 to 15 grams daily. Expert nutrition panels and the American Heart Association recommend 25 to 30 grams daily from whole grains, fruits, and vegetables.

The health benefits of the Mediterranean diet likely spring from synergy among multiple Mediteranean diet components, rather than from a single food group or one or a few food items. 

Steve Parker, M.D.

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What About Fish?

"Waiter, I didn't order sushi!"

Darya Pino over at Summer Tomato recently 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.

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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 sources 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 the Ketogenic Mediterranean Diet has a prominent role for 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

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For Heart’s Sake, Should You Avoid Red Meat in a Low-Carb Diet?

Low carbohydrate diets tend to contain disproportionate amounts of fat from animal sources.  Red meat has long been vilified as a major source of saturated fat that some experts believe cause hardening-of-the-arteries (atherosclerosis) via elevations in LDL cholesterol.  Others disagree.  Poultry, fish ,and shellfish generally have lower amounts of saturated fat than red meat.  Would a low-carb diet with a predominance of poultry, fish, and shellfish lead to a more advantageous cholesterol profile?

A 2007 report from U.S. researchers found no lipid advantage to the poultry/fish/shellfish model.    In fact, despite high cholesterol and fat intakes, neither diet caused a significant change in total, HDL, or LDL cholesterol levels.  Triglycerides fell in both groups, but to a statistically significant degree only on the poultry/fish/shellfish group.

Fun Fact:  Did you know that four of every 10 women in the U.S. are trying to lose weight?  The figure for men is one in three.  

Methodology

Researchers in Minnesota and Iowa enrolled 18 subjects (6 males, 12 females) between the ages of 30 and 50 who wanted to lose weight.  Average body mass index was 31.7, which is mildly obese.  The were encouraged to eat an Atkins-style ketogenic diet with a maximum of 20 g carbs/day, providing 1,487 total daily calories, with 7% of calories from carbohydrate, 43% from protein, and 50% from fat.  This included two or three cups of salad greens and low-carb vegetables.  Three ounces of cheese daily was allowed.  Subjects were randomly assigned to eat either red meat or poultry/fish/shellfish.  Dietary intervention lasted 28 days.

[This is very similar to Atkins Induction Phase, although Atkins does not limit total calories.  The researchers did not say why they wanted to limit total calories.] 

Data were not used from six subjects for good reasons (see article).  So final data analysis included only 12 subjects.

Results

Both groups lost the same amount of weight: about 5.5 kg (12 pounds) over 28 days.

Average carbohydrate intake was about the same for both groups: 55 g/day.

Average total daily caloric intake was about the same for both groups: 1,380.

The poultry/fish/shellfish group ate 630 mg cholesterol daily, twice as much as the other group.  [Eggs and shrimp were popular.]

The difference in intake of saturated fat approached, but did not reach, statistical significance (32 g/day in the red meat group vs 25 g).

Neither diet caused a significant change in total, HDL, or LDL cholesterol levels.  Triglycerides fell in both groups, but to a statistically significant degree only on the poultry/fish/shellfish group.

Urine ketones at or above 5 mg/dl were detected on 75% of all dipstick tests.

My Comments

I’m skeptical about the accuracy of the calorie counts.  Most people eating Atkins-style take in about 1,800 cals/day.  The preponderance of females, however, may explain the unusually low average caloric intake.  They didn’t follow their carb restriction very closely, did they?  These were free-living subjects not locked in a metabolic ward.

The researchers note that the allowance of cheese in both groups may have sabotaged their efforts for a clear delineation of higher versus lower saturated fat groups. 

HDL cholesterol usually rises significantly on low-carb diets.  Lack of that here may just be a statistical aberration.

This is such a small study that it’s impossible to draw firm conclusions.  Nevertheless, if someone is losing weight on a low-carb diet, it may not matter much from a lipid viewpoint whether they eat a predominance of meat or a predominance of poultry, fish, and shellfish.  The study at hand cannot address the long-term consequences of such a choice.

Steve Parker, M.D.

Reference:  Cassady, Bridget, et al.  Effects of low carbohydrate diets high in red meats or poultry, fish and shellfish on plasma lipids and weight lossNutrition & Metabolism, 4:23   doi: 10.1186/1743-7075-4-23   Published October 31, 2007

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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 recent research report

European researchers noted that cod consumption in a prior study increased 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-weeksNutrition, Metabolism and Cardiovascular Diseases, 19 (2009): 690-696.

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