by Ariella Cohen
Ariella Cohen was Canfei Nesharim’s summer intern in 2006.
Question: Is eating fish good for my health?
Answer:
Fish are an extremely nutritious form of sustenance. They are high in protein, low in fat and many species contain omega-3-fatty acids which offer special health benefits. However, it is appropriate to be cautious about eating fish because of modern environmental contamination. Let’s look at what’s so good about fish and how you can benefit from them while still protecting yourself from chemical pollution.
What makes fish so good for you?
The major reason for eating fish is the protein that it provides. Fish also provide a very special nutrient that is important to our health: omega-3-fatty acid, a type of polyunsaturated fat known as “essential fatty acids.” These nutrients are vital to human health, and must be consumed in food, because the body can not manufacture them. [1] Omega-3-fatty acids have been shown to prevent cardiovascular disease by regulating blood clotting and vessel constriction. They may also ease the symptoms of rheumatoid arthritis, depression, irregular heartbeat, and irritable bowel syndrome.
There are three kinds of omega-3-fatty acids: alpha-linolenic acid (ALA), docasahexaenoic acid (DHA), and eicosapentaenoic acid (EPA). EPA and DHA have longer fatty acid chains than ALA. This structural difference influences the way each fatty acid behaves, and thus the health benefits that each omega-3-fatty acid provides. Both EPA and DHA, typically found in seafood, help prevent irregular heartbeat, and lower cholesterol levels, blood pressure and triglyceride levels. ALA, typically found in flax seed oil, leafy green vegetables, and walnuts, prevents cardiovascular disease and reduces cholesterol.
Although ALA is important for good health, EPA and DHA can be more efficiently used by the body. If an insufficient amount of DHA and EPA from fish are consumed the human body can convert some of its ALA into DHA and EPA. However, this conversion is not a very efficient process and the consumption of fish as a direct source of EPA and DHA omega-3-fatty acids is highly recommended.
All About Omegas
Omega-3-fatty acids are found in fish, but they are not manufactured by the fish. At the bottom of the food chain, phytoplankton, microscopic ocean plants and bacteria, manufacture ALA omega-3-fatty acids. Zooplankton, microscopic ocean animals, consume phytoplankton and convert their ALA into EPA and DHA. Larger fish then eat the phytoplankton and absorb the phytoplankton’s omega-3-fatty acids and build up their own levels of these nutrients.
Not all omega fatty acids are created equal. Another type of essential fatty acid, which most people have no problem consuming in sufficient (or even excessive) amounts, is omega-6-fatty acid. Omega-6-fatty acids are found in foods such as red meat, cereal, baked goods, margarine, poultry, eggs and most vegetable oils. While omega-3 and omega-6 are similar in that they are both poly unsaturated fatty acids, each omega fatty acid is both structurally and functionally distinct. It is the placement of each molecule’s double bonds, relative to its methyl group at the end of its carbon chain, which influences its biological function. [2] For example, it has been shown that the consumption of DHA omega-3-fatty acids can mitigate the harmful effects of methyl mercury poisoning while ingestion of omega-6-fatty acids does not have the same effect.[3] Additionally, omega-3-fatty acids help reduce inflammation while omega-6-fatty acids boost inflammation.
It is, therefore, exceptionally important for the body to maintain the correct ratio of omega-6 and omega-3 fatty acids.The ideal ratio is five omega-6-fatty acids for every one omega-3-fatty acid.[4] In the past fifty years Americans have begun to consume a large percentage of their daily calories from highly processed foods. These foods usually have a much greater omega-6 to omega-3 ratio than other foods. This has caused the typical American’s omega-6 to omega-3 ratio to range anywhere from ten to thirty times greater than the desired ratio. It has been postulated that this imbalance of omega-3 and omega-6 fatty acids may account for the fact that heart disease has become the current leading cause of death in the United States. [2] In order to correct this imbalance, the American Heart Association advises Americans to consume fish high in omega-3 such as mackerel, lake trout, herring, sardines, albacore tuna, and salmon at least twice a week.
Fish Cautions – For Your Health and For the Environment
While the protein and omega-3-fatty acids found in fish are extremely healthy, some precautions are necessary, because fish can become contaminated by a variety of pollutants. Some of the potential pollutants include naturally occurring metals, such as mercury or lead; pesticides, such as dieldrin and DDT; or chemicals such as PCBs, used as insulators in electrical devices.
Fish can absorb these contaminants either from smaller fish which have absorbed toxins from the ocean or directly from the water through their gills. The ocean can become polluted by rainfall, which can wash pesticides such as DDT dieldrin and PCBs into the ocean. Once in the ocean, these pesticides are likely to settle on the bottom of the ocean and affect fish such as wild striped bass, bluefish, American eel and sea trout that typically settle there.
Larger predatory fish generally have higher levels of toxins, because they are at the top of the food chain. Older fish also have higher levels of pollutants, because as fish age, contaminants build up within their bodies. Bottom feeding fish are also more likely to become tainted by pollutants because they ingest food from the bottom of the ocean where various toxins tend to accumulate.
When people over-consume affected fish, toxins can accumulate in the human body and cause serious health problems such as cancer and birth defects. Mercury is especially harmful for developing children, pregnant women and fetuses. Fetuses can absorb mercury through their mothers’ placentas, and this can adversely affect their development and ability to learn later in life.
Likewise, PCBs, sometimes found in farmed salmon, are carcinogenic and have been proven to cause cancer in animals. PCBs can also affect a young child’s ability to learn. This is particularly true for those who were exposed to these contaminants as fetuses, because these toxins can cause lifelong damage. Exposure to PCBs can also harm the nervous, reproductive and immune systems [5]
Finally, over-fishing has caused tremendous pressure on our global fisheries, and some species of fish are threatened by these practices. Some fish are also being accidentally caught (and killed) by efforts to catch other fish (in a phenomenon called “by-catch”), causing a lot of waste and disruption to the ocean ecosystems. To protect these fish for future generations, it is best to avoid or reduce your consumption of them.
To Your Health
The good news is that there are ways to reduce your risks of fish contamination while still enjoying the health benefits of fish.
First, cut back on fish with high levels of contamination, such as canned white tuna, bluefish, striped bass, spotted sea trout, and blue marlin. Try not to eat the same kind of fish (even those not known to be particularly dangerous) more than twice in one week. Additionally, it is sensible to avoid eating “bottom-feeding” fish that eat the animals that live at the bottom of the ocean, such as catfish and lobster (not a problem if you keep kosher!) because toxins such as lead, methyl mercury, PCBs and dioxins often accumulate there.
Finally, because PCBs tend to accumulate in the fat of fish, remove all visible fat and skin before cooking. Frying fish traps the pollutants that gather in the fat so try to avoid fried fish as much as possible. Alternative cooking methods such as grilling, broiling or poaching allows the fat to drip away leaving your fish leaner and PCBs free. However, grilling and broiling fish increases the amount of polynucleated aromatic hydrocarbons (PAH’s) which are mutagenic. Baking fish may, therefore, be the best option. [6]
It is important to note that fish consumption advisories may differ from lake to lake. One species in a particular lake may be affected, while the same species in a different lake may be safe to consume. It is therefore advisable to check with you state Department of Natural Resources regarding which species and lakes are affected by toxins.
Following these guidelines, and taking the necessary precautions to avoid harmful or threatened species of fish, will allow one to enjoy the health benefits of fish while steering clear of the health risks. For a list of the best choices from an environmental and health perspective.
Notes:
[1] http://www.umm.edu/altmed/ConsSupplements/Omega3FattyAcidscs.html
[2] http://en.wikipedia.org/wiki/omega-3
[3] Clarkson TW, Strain JJ. 2003, Nutritional factors may modify the toxic action of methyl mercury in fish-eating populations. J Nutr.(5 Suppl 1):1539S-43S
[4] http://www.umm.edu/altmed/ConsSupplements/Omega3FattyAcidscs.html
[5] http://www.med.umich.edu/umim/clinical/pyramid/fish.htm
[6] McDonald JD, Zielinska B, Fujita EM, Sagebiel JC, Chow JC, Watson, JG.2003,Emissions from charboiling and grilling of chicken and beef. J Air Waste Manag Assoc. 53(2):185-94
Originally posted in “On Eagles’ Wings” March 10th 2006