Omega 3

Description

Omega-3s play important roles in the body as components of the phospholipids that form the structures of cell membranes. DHA, in particular, is especially high in the retina, brain, and sperm. In addition to their structural role in cell membranes, omega-3s (along with omega-6s) provide energy for the body and are used to form eicosanoids. Eicosanoids are signaling molecules that have similar chemical structures to the fatty acids from which they are derived; they have wide-ranging functions in the body’s cardiovascular, pulmonary, immune, and endocrine systems.

Currently, most clinicians do not assess omega-3 status, but it can be done by measuring individual omega-3s in plasma or serum phospholipids and expressing them as the percentage of total phospholipid fatty acids by weight. Experts have not established normal ranges, but mean values for serum or plasma phospholipid EPA plus DHA among U.S. adults not taking omega-3 supplements are about 3%–4%. Plasma and serum fatty acid values, however, can vary substantially based on an individual’s most recent meal, so they do not reflect long-term dietary consumption. The “omega-3 index” proposed by Harris and von Schacky reflects the content of EPA plus DHA in erythrocyte membranes expressed as a percentage of total erythrocyte fatty acids. This index can be used as a surrogate for assessing tissue levels of EPA plus DHA. EPA and DHA typically comprise about 3%–5% of erythrocyte fatty acids in Western populations with low fish intakes. In Japan, where fish consumption is high, erythrocyte EPA and DHA levels are about twice those of Western populations.

The omega-3 content of fish varies widely. Cold-water fatty fish, such as salmon, mackerel, tuna, herring, and sardines, contain high amounts of LC omega-3s, whereas fish with a lower fat content—such as bass, tilapia and cod—as well as shellfish contain lower levels. The omega-3 content of fish also depends on the composition of the food that the fish consumes. Farmed fish usually have higher levels of EPA and DHA than wild-caught fish, but it depends on the food they are fed. An analysis of the fatty acid composition of farm-raised Atlantic salmon from Scotland showed that the EPA and DHA content significantly decreased between 2006 and 2015 due to the replacement of traditional marine ingredients in fish feed with other ingredients.

According to data from the 2011–2012 National Health and Nutrition Examination Survey (NHANES), The potential health benefits of consuming omega-3s are the focus of a great deal of scientific research. The majority of research has focused on EPA and DHA from foods and/or dietary supplements. Results from the Japan EPA Lipid Intervention Study in 2007 supported the growing body of evidence that LC omega-3s reduce the risk of heart disease, especially in people with a history of coronary artery disease. In this study, 18,645 people with hypercholesterolemia (total cholesterol of at least 251 mg/dL) with or without coronary artery disease received either 1.8 g/day EPA plus a statin or a statin only. After a mean of 4.6 years, the EPA group had 19% fewer major coronary events than the control group.

The EPA group also experienced a significant reduction in rates of unstable angina and nonfatal coronary events but not in rates of sudden cardiac death or coronary death in comparison with the control group.