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FEATURE ARTICLE
Food for Thought
fish and fatty acids
Fish oil is not "snake oil"...
At some point in the past many of us have heard a familiar phrase like "Eat that fish it's good for your brain" or "Open wide this (fish oil) is good for you and it doesn't taste that bad". Years later we have come to find out that these phrases, with the exception of the taste of a spoonful of fish oil, are true and more palatable. Today the market for fish and other seafood products has expanded and is in greater demand by the consumer. But the question still persists, "Why are marine fish and other seafood good for you?" To answer this the link can be found in the marine food chain and in a process known as bioaccumulation.
The marine food chain is unique...
Humans can synthesize fat from carbohydrates (as most of us know all too well!). However, three essential fatty acids cannot be synthesized this way and must be incorporated into our diet. A few of these fatty acids come mainly from the marine food chain.
In the background you can see phytoplankton, crustaceans, and fish larvae. These essential organisms are the base of the marine food chain that manufacture and carry the beneficial components that give fish and other seafood a healthy reputation. The marine food chain is the only one on earth that have algae, or producers, that naturally manufacture the compounds known as omega-3 fatty acids. Therefore, only animals that are part of this food chain from the sea contain omega-3 fatty acids as part of their physiological profile. This does not mean that freshwater fish are not good for you, but they do not contain the same beneficial fatty acids.
These substances are made initially by phytoplankton, the tiny aquatic plants that produce oxygen for the atmosphere and serve as food for small crustaceans and fish. Bioaccumulation occurs when fish devouring other fish accumulate the omega-3 fatty acids and become more concentrated in their tissues. Consequently, fish oils are the richest source of omega-3 fatty acids. The major omega-3 fatty acids in fish are:
- EPA (eicosapentaenoic acid), and
- DHA (docosahexaenoic acid)
Linolenic acid is an omega-3 fatty acid found in small amounts in plants but its fatty acid chain is not as long nor as unsaturated as omega-3 fatty acids from fish oil.
What is an omega-3 fatty acid?...
Fatty acids are one of the building blocks of fat molecules. They are composed of carbon, hydrogen, and oxygen. These elements are arranged into long hydrocarbon chains with a carboxyl group (COOH) at one end and a hydroxyl group (OH) at the other end. One system for naming unsaturated fatty acids is to indicate the position of the first double bond counting from the opposite end from the carboxyl group. That terminal carbon atom is called the omega carbon atom. Thus a monounsaturated fatty acid with its single double bond after carbon #3 (counting from and including the omega carbon) is called an omega-3 fatty acid.
Some studies have suggested that omega-3 fatty acids help protect against cardiovascular disease. Fish oils are a rich source of omega-3 fatty acids.
OK, why are omega-3s good for us?...
When we consume seafood rich in omega-3 fatty acids, the omega-3s become part of our platelet membranes. Once there, they inhibit the growth of blood clotting material in platelets thus having the effect of slowing the formation of blood clots which would prevent the flow of blood to the heart or brain. This has the effect of greatly reducing the risk of having a heart attack or stroke.
Research has shown that the consumption of fish with high levels of omega-3s causes a dramatic reduction in the levels of triglyceride in the blood, even in people with extraordinarily high triglyceride levels. Consumption of fish oil actually restored blood triglycerides to their normal range in people with very high triglyceride levels.
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Walnuts to the rescue...
Certain fish contain fatty acids that have been shown to help lower the risk of coronary artery disease. Because walnuts contain the same kind of fatty acids, researchers at UC Davis are seeking participants for a study that will investigate whether a diet that includes walnuts can lower blood fats that cause hardening of the arteries.
The study will compare a diet that conforms with guidelines set by the American Heart Association (AHA) with one in which walnuts replace certain fats. Participants must have high levels of serum cholesterol and triglycerides to take part in the six-month study.
Walnuts are high in omega-3 and omega-6 fatty acids. Omega-3 fatty acids are found in certain fish and have been shown to lower triglyceride levels, but not levels of low density lipoprotein (LDL), the so-called "bad cholesterol" that contributes to the buildup of fatty deposits inside arteries. However, omega-6 fatty acids have been shown to lower LDL levels.
High levels of LDL and triglycerides are known to increase a person's risk of coronary artery disease, the leading cause of death in the United States. The AHA recommends that a person consume no more than 30 percent of his or her daily calories from fat.
Participants will eat four different diets during the study: their regular diet; their regular diet with walnuts replacing certain fats, such as margarine; a diet conforming to AHA guidelines; and a diet conforming to AHA guidelines with walnuts replacing certain fats. Individuals will have their blood drawn every three weeks to measure their cholesterol and triglyceride levels.
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Some of the benefits of eating fish rich in omega-3 fatty acids are:
- owering cholesterol levels
- lowering triglycerides levels more powerfully than other polyunsaturated fatty acids
- inhibiting the clotting of blood
- helping slow the process of atherosclerosis
- helping to prevent certain cancers
- helping to counteract immune disorders and may improve symptoms of arthritis and psoriasis
Good sources of omega-3 fatty acids are in fish with higher fat content.
- High-fat fish (more than 5%) include salmon, mackeral, herring, anchovies, sardines, albacore tuna and trout.
- Medium-fat fish (2.5-5%) include blue fin tuna, bluefish, halibut, mullet, red snapper and swordfish.
- Low-fat fish (less than 2.5%) include cod croaker, flounder, haddock, monkfish, sea bass, pike and whiting.
Shellfish are low in fat but contain relatively more omega-3 fatty acids than other low-fat fish. Cholesterol levels in shellfish such as oysters, crabs, lobster and clams have been shown to be comparable in cholesterol levels to lean beef and poultry.
In addition, recent studies suggest that omega-3 fatty acids in crab, shrimp and lobster may neutralize any tendency to raise blood cholesterol even in people with high cholesterol levels.
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