Essential Fatty Acids

It is important that we consume fish on a regular basis. In an article entitled, "The Inversion Relation Between Fish Consumption and 20-Year Mortality from Coronary Artery Disease," which appeared in a New England Journal of Medicine, a team of Dutch researchers detailed the results of a 20-year study of middle-aged men in the Netherlands. Men free of known heart disease were selected. Dietary histories were obtained, paying special attention to fish consumption. Twenty percent of the men ate no fish. Among the rest, the intake varied, from a fraction of an ounce to 11 ounces per day. The researchers followed these men for 20 years. Seventy-eight died of coronary heart disease. The more fish consumed, the less risk of heart attack. This relationship held true from trace amounts up to the maximum intake. It is increasingly becoming known that the influence of the EPA found in fish on clotting tendency is one likely reason for these results.

EPA is a long-chain, highly unsaturated fatty acid that can be used in metabolism to make prostaglandins, as can several other fatty acids, including linolenic, alpha-linolenic acid, gamma-linolenic, and arachidonic acids. Prostaglandins are hormone-like substances excreting control over events throughout the body. They release the production of chemicals by blood platelets and cells lining the walls of the blood vessels. These chemicals control the tendency of platelets to form a clot, thus influencing the chances of a thrombus clot forming in the coronary arteries and causing a heart attack.

EPA is concentrated in the fat of salt-water fish and shellfish, especially the cold-water varieties. Concentrations of a closely related fatty acid, DHA, occur in some sources. DHA is also concentrated in the brain and retinal cells of the eyes of mammals. Some green plants have small amounts of alpha-linolenic acid. Most animals readily convert it to EPA. Humans are thought to accomplish this conversion under the right circumstances. The EPA is, then, utilized for synthesis of particularly beneficial prostaglandins.

Fish oils also dramatically lowered high blood fats in a study on fish consumption that was published in the New England Journal of Medicine. Patients were observed for four weeks. They were put on a diet rich in fish oils. An average of 64% of the patients had moderate elevations of triglycerides. Triglyceride levels fell an average of 79% for the patients with severe elevations. Cholesterol levels fell 27% for the moderate group and 45% for the severe group.

Another study, "Transactions of the Association of American Physicians," showed the sharpness of vision and brain development as they are related to blood levels of EPA and DHA. These fatty acids are essential for good vision. DHA is a normal constituent of the cells of the retina. The amount present is dependent upon the amount in the diet. Animal tests at Oregon Health Sciences University in Portland prove that deficiencies reduce the ability of retinal cells to be stimulated, thus they lacked clarity of vision.

Below is a chart that indicating fish that contain high amounts of omega-3 fats. In general, fattier fish are richer sources, but some, like farmed catfish, are relatively low in omega-3. Farmed fish are higher in fat than their wild cousins. More fat usually means an extra 30-80 calories a serving. However, it is important to note that, in our attempt to eliminate fat from our diet for the sake of heart disease, we must make sure we are getting the appropriate fats that our bodies need for optimal health. In the chart below, the figures are based on a six-ounce, cooked serving. Starting with eight ounces raw should result in six ounces cooked.

TYPE OF FISH
AMOUNT OF
OMEGA-3 FAT
(in grams)

Salmon, Atlantic, farmed
3.7

Salmon, Atlantic, wild
3.1

Sardines, in sardine oil, 3 ounces
2.8

Salmon, Coho, farmed
2.2

Trout, rainbow, farmed
2.0

Herring
1.8

Swordfish
1.4

Flounder
0.9

Halibut
0.8

Tuna, fresh
0.5

Tuna, light, canned
0.2

Again, fattier fish are richer in the omega-3 fatty acids, EPA and DHA that seem to prevent arrhythmias in animals. It is important that we include fish in our diet on a regular basis. Our recommendation is to include at least one serving weekly.

If you are vegetarian, plants such as flax have alpha-linolenic acid, a fatty acid that is similar to EPA and DHA. One preliminary study compared the two fats. In India, researchers gave fish oil, mustard seed oil (a good source of alpha-linolenic acid) or a placebo to 360 people suspected of having had a heart attack. After one year, both groups of oil takers had fewer arrhythmias, but only the fish oil takers had a lower death rate. This study was published in Cardiovascular Drugs Therapy 11:45, 1997.

When eating in restaurants, it is best to make sure any seafood is broiled. It was noted that, fried shrimp (seven ounces) contained 520 calories, 970 mg of sodium and 10 grams of artery-clogging fat, which is quite on the high end. So, it is important that you make sure you order your fish broiled or grilled. A bread coating on the fish significantly increases the sodium count.

If you have any questions, please contact Dr. Guyer in the office.