Omega-3 Fatty Acids: Health Benefits Galore

Written by Joyce A. Nettleton, DSc, RD, ScienceVoice Consulting, Denver, CO. © American Fishermen's Research Foundation, 2003

What are omega-3 fatty acids?

Fish such as tuna, salmon, rainbow trout, sardines, Atlantic mackerel, and herring are rich in fat and have particular, natural fatty acids - the main component of fat - not found in any other foods. These fatty acids are missing many hydrogen atoms so they are highly polyunsaturated, more so than other polyunsaturated fatty acids in food. Also, they are longer than most other fatty acids. These structural differences give fish oil fatty acids their unique health properties. They are called "omega-3" fatty acids because of the location of the first two missing hydrogens in their chemical structure. The two main omega-3 fatty acids in fish oils are called EPA* and DHA* for short. EPA and DHA occur naturally only in seafood, and are abundant only in fatty fish and marine animals.

* EPA: eicosapentaenoic acid; DHA: docosahexaenoic acid

Why are omega-3 fatty acids healthful?

Once they are consumed, omega-3 fatty acids are avidly absorbed by different tissues and incorporated mainly into cell membranes. There, they affect the metabolic activities carried out in the cells, sometimes restraining activity, other times facilitating certain functions. For example, these long-chain omega-3 fatty acids are incorporated into the retina of the eye where they affect visual function. In the brain, they affect neurodevelopment and function. In the heart, they influence electrical activity so that abnormal heart rhythms are discouraged. No other fatty acids have been shown to have such effects. Our understanding of omega-3 metabolism is advancing rapidly and revealing an enormous array of functions positively influenced by these fatty acids.

Are all omega-3 fatty acids the same?

No. Fish contain mainly EPA and DHA omega-3s. Some plants and seeds contain another omega-3 fatty acid, alpha-linolenic acid or ALA. This particular fatty acid is the omega-3 found in walnuts, flax seed and oil, canola oil and to a lesser extent, soybean oil. ALA is shorter, has fewer missing hydrogens, and behaves differently in the body from EPA and DHA. Most ALA is oxidized or "burned" before it can affect metabolic activity.

ALA is healthful and has been favorably linked to heart health. However, it does not have all the functions of EPA and DHA, particularly in maternal and infant nutrition. For neurodevelopment and other activities, ALA needs to be converted to EPA and DHA. The human body can perform this conversion, but it does so very inefficiently. In adults, the conversion to DHA may be less than 5 percent. Under the best circumstances, consuming large amounts of ALA yields only small amounts of EPA and DHA. Thus, the easiest and most effective way to obtain the health benefits of omega-3s is to get them already preformed - in Pacific troll-caught albacore and other fatty fish.

Omega-3 Fatty Acids and Cardiovascular Health

Fish oil omega-3 fatty acids have been shown to improve heart health in the following ways:

• Reduce the chance of sudden cardiac death. Almost half of all cardiac deaths in the U.S. - about a quarter of a million each year - are attributable to sudden cardiac death.

• Reduce the chance of having a first heart attack. People at high risk of having a heart attack may reduce their chance of a first myocardial infarction (heart attack) by consuming fish oil omega-3s regularly.

• Reduce the risk of stroke. Several studies have shown that people who consume fish regularly are less likely to have a stroke.

• Lower blood triglycerides (fats). Many people, especially those with type 2 or non-insulin dependent diabetes mellitus, have high triglycerides, which significantly increases the risk of heart disease. Regular consumption of fish oil omega-3s lowers blood triglyceride levels, especially in people whose triglycerides are above normal levels.

• May increase high-density lipoprotein levels, the so-called "good" cholesterol that reduces the risk of heart disease. This favorable change often occurs in people with high triglycerides or type 2 diabetes, where the risk of heart disease is increased three times or more.

• Reduce the likelihood of blood clots forming in arteries. Blood clots can be fatal. Fish oil omega-3 fatty acids make platelet clumping less likely and reduce the activity or production of several substances that promote clot formation. They may encourage the production of substances that promote the breakdown of clots, as well.

• Improve vascular function. The cells lining the blood vessels are called endothelial cells. They produce substances that maintain blood fluidity and vessel wall muscle tone. Fish oil omega-3 fatty acids inhibit excessive endothelial cell activity that could lead to a heart attack. Omega-3s encourage blood vessel wall relaxation, which improves blood flow and reduces pressure.

• Reduce inflammation. Fish oil omega-3 fatty acids discourage the development of inflammation in blood vessels that frequently accompanies heart disease. Inflammatory conditions stimulate the production of substances involved in clot formation and make artery disease worse. Inflammation increases the risk of heart failure.

• May stabilize atherosclerotic plaques. Recent findings suggest that fish oil omega-3s may increase the stability of atherosclerotic plaques making them less likely to rupture and cause a heart attack.

• Modestly reduce blood pressure. High blood pressure greatly increases the risk of heart disease and stroke. Consuming fish oil omega-3s is associated with small but beneficial reductions in blood pressure.

Maternal and Infant Health

Fish oil omega-3 fatty acids are essential for healthy fetal and infant development. During pregnancy, the developing baby obtains omega-3 fatty acids from the mother. After birth, the infant must obtain them from breast milk or formula supplemented with essential fatty acids. In early human development, fish oil omega-3 fatty acids are beneficial for:

Healthy infant visual function. The photoreceptor cells in the retina of the eye have large amounts of DHA, which is involved in visual function. Infants whose diets contain fish oil omega-3 fatty acids have improved visual scores on a number of measures of visual acuity when compared with infants not receiving them.

Improved infant neurodevelopment. Several tests of motor skills, learning behavior, language development, and mental function in infants and children have shown that infants consuming fish oil omega-3 fatty acids from breast milk or supplemented formula have higher developmental measures than those not receiving them. In several studies, infants consuming omega-3s exhibited a more mature type of neurodevelopment than those of the same age who did not have omega-3 fatty acids. It is not certain whether the findings in infancy carry over into childhood and adulthood.

Reduced risk of premature and underweight births. Consuming omega-3s - particularly DHA* - in pregnancy, especially in the last trimester, reduces the risk of premature and underweight babies. Studies have shown that babies of mothers who consumed DHA in the last trimester were heavier than those of mothers not fed DHA. Gestation time is also prolonged and this reduces the risk of prematurity.

Important in pregnancy. In the last three months of pregnancy, the fetus avidly takes up omega-3 fatty acids from the mother's circulation. These fatty acids are incorporated into brain, eye, and other tissues. Because the mother's diet and body stores are the only source of these essential nutrients, pregnant women are wise to consume fatty fish regularly.

Important in lactation. In the first six months of life, infants depend on breast milk or infant formula for all or most of their nutrition. Nursing women can ensure their infants receive essential fatty acids by eating fatty fish regularly, at least once a week. These dietary omega-3s are transferred to breast milk, so the infant will obtain them.

Low birthweight and premature infants. Underweight and "preemie" babies are at increased risk of receiving too little omega-3 fatty acids during gestation. When a baby is born early, it has less time to acquire these vital fatty acids from its mother. Thus, it is especially important for these infants to receive all essential fatty acids, including omega-3 fatty acids, to ensure healthy development. Human milk and fatty acid supplemented formula will supply the necessary omega-3s.

Improvements in Clinical Conditions*

* Note: always check with your doctor before taking any substances to alleviate any clinical conditions. These statements are provided only for information and are not intended to treat, cure, prevent, or mitigate any existing health conditions.

Omega-3 fatty acids in fish oils have beneficial effects on the symptoms of several health conditions that involve the immune and inflammatory system, intestinal tract, and brain. They appear to have important benefits in type 2 or non-insulin dependent diabetes.

Type 2 Diabetes Mellitus

Type 2 diabetes greatly increases the risk of cardiovascular disease and heart attack. However, diabetics who consume fatty fish regularly - once or more per week - are less likely to incur a first heart attack. Mortality from heart disease is also significantly lower among diabetics who do compared with those who do not eat fish.

Sugar and fat metabolism are impaired in type 2 diabetes. Blood triglyceride (fat) levels are increased while high-density lipoprotein (HDL) levels - the "good cholesterol" - are reduced. Regular consumption of fatty fish or omega-3 fatty acids significantly lowers triglycerides and often raises HDL levels, thereby diminishing the risk of heart disease.

Omega-3s improve blood circulation, reduce the tendency of blood to clot, improve vascular (blood vessel) function in several ways that reduce the risk of heart disease, and slightly lower blood pressure. These changes favor heart health.

Inflammatory Conditions

Omega-3s in fish dampen the production of inflammatory substances produced in rheumatoid arthritis, psoriasis, asthma, and some skin conditions. They also stimulate the production of substances the counteract inflammation. The result is often an improvement in the symptoms of these conditions, e.g., less soreness or itching, easier breathing, and less swelling. Omega-3s may need to be consumed over a long period before improvements appear.

Crohn's Disease, Ulcerative Colitis

These serious intestinal diseases have strong inflammatory responses that may become less severe with the regular consumption of omega-3s from fish. Omega-3s tend to reduce the severity of the symptoms, but do not cure these conditions.

Mental Function

Emerging evidence suggests that the regular consumption of omega-3s from fish may be beneficial in reducing the severity of several mental conditions such as Alzheimer's disease, depression, and bipolar disorder. In children, improvements with the consumption of omega-3s have been reported in attention deficit hyperactivity disorder and dyslexia. Caution is warranted because data are inconsistent and do not permit firm conclusions.