Omega-3 Fatty Acids from Fish Oil
Today’s Dietitian
By Gretchen Vannice, MS, RD
Vol. 7, No. 3, p. 32

Omega-3 fatty acids are essential. The human body requires them for proper growth and development, and because it cannot manufacture them, dietary sources are important. At the same time, epidemiologists continue to report a decrease in omega-3 essential fatty acid (EFA) intake in Americans. Indeed, some clinicians are concerned with an imbalance in fatty acids created by an overconsumption of omega-6 EFAs relative to omega-3 intake.1 Current research shows that the ratio of consumption of omega-6 acids to omega-3s averages 20:1 rather than a healthier ratio such as 4:1.2 This is most likely due to the ready availability of omega-6s in common vegetable oils, salad dressings, processed foods, etc. In addition, the two fatty acid families are metabolized by the same enzymes, making them competitive.3

In many cultures, fish is a central source of high-quality, lean protein and omega-3s. In the United States, fish consumption has been on the decline for many years, due in part to the advent of fast-food advertising with its emphasis on beef and chicken, as well as consumer concerns about the toxins found in many fish species today. Yet, fish and fish oil are considered the best sources of two particularly important omega-3 fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). DHA is one of the most predominant fats in brain and eye tissue and EPA is predominant in red blood cells.

What About Flax?
Oil from flaxseed (and walnuts) contains an important omega-3: alpha-linolenic acid (ALA). Of interest to dietitians, ALA is generally reported as the essential omega-3 fatty acid in nutrition and biochemistry textbooks. This is because technically, ALA is a precursor to both EPA and DHA. However, research over the past couple of decades indicates that humans do not readily convert ALA to the more functional EPA and DHA fatty acids as efficiently as previously thought. Flaxseeds are nutritionally dense, offering vitamins, fibers, important lignans, and ALA, and some flaxseed oil manufacturers even add lignans to oil, but neither are reliable sources of EPA and DHA.4

Not Just a Fish Tale
Omega-3s from fish have been the subject of considerable recent clinical study. For example, research indicates that increasing EPA and DHA levels in blood plasma increases support for a host of lipidemic factors, including healthy circulation, blood pressure, lipoprotein levels, C-reactive protein levels, and low-density lipoprotein protection from unfavorable oxidation.5 And a significant body of research clearly shows that both EPA and DHA have triglyceride-lowering effects.6

Omega-3s appear to have numerous effects on cardiovascular health. In one study of 11,000 myocardial infarction survivors, those who took 1 gram daily of omega-3 EFAs had a 20% decrease in total deaths, a 30% decrease in cardiovascular deaths, and a 45% decrease in sudden deaths.7 And in a randomized, double-blind, placebo-controlled clinical trial of 223 patients with angiographically proven coronary artery disease, the group consuming 1.5 grams per day of omega-3 fatty acid supplements showed less progression and more regression of the disease.8 The American Heart Association published recommendations for omega-3 fatty acids and cardiovascular disease in 2003.9

Brain Food
There appears to be a strong link between decreased omega-3 fatty acid consumption and an increased prevalence of depression in the United States.10 In three recent randomized, double-blind, placebo-controlled studies, the groups receiving omega-3 fatty acid supplementation from fish showed a statistically significant improvement in measurable symptoms of depression.11-13

Omega-3 deficiency may also play a special role in behavioral disorders, as these EFAs have been specifically implicated in maintaining central nervous system function and they affect neurotransmitters, peptides, releasing factors, and hormones in the brain.14 In 1995, researchers found that 53 children with attention deficit hyperactivity disorder (ADHD) had significantly lower concentrations of omega-3s in their plasma polar lipids and their red blood cell total lipids.15 In a 2003 pilot study, 50 children were randomized into groups receiving EFA supplementation or an olive oil placebo. Supplementation proved to substantially increase the plasma phospholipid and red blood cell levels of EPA and DHA and significantly decreased two ADHD behaviors (oppositional defiant behavior and attention deficit) and nonsignificantly improved all the others.16

Prevention and Intervention
Researchers are also looking at the role of fish oil in preventing age-related diseases, as well as the role of EPA and DHA in infant development, arthritis, cancer, diabetes, metabolic syndrome, and more. For example, research on Alzheimer’s and other forms of dementia is showing that older individuals with low levels of omega-3s in their blood appear to be more at risk for developing cognitive disorders, while those who regularly consume fish or fish oil supplements appear to be less likely to do so.17 Arthritis sufferers are finding relief from regular supplementation of adequate doses of fish oil, and many are able to reduce or eliminate the need for problematic nonsteroidal anti-inflammatory medications.18,19

Keep it Clean
Because of growing information about environmental toxins in fish, there is anxiety about eating fish at a time when the need for the essential fats that fish provides is great. Purity of fish oil supplements is of primary importance. In general, purity refers to levels of heavy metals, polychlorinated biphenyls (PCBs), and dioxins and other toxic elements. Toxic levels of lead and the neurotoxin mercury are a real concern with dietary fish and less of a concern in supplements. Concern about PCBs and dioxin levels in supplements, however, is valid. Natural filtering methods, microdistillation, and careful manufacturing processes help ensure purity. It’s important to know the source and the manufacturer.

Freshness is also critical. EPA and DHA are long-chain polyunsaturated fatty acids and highly susceptible to oxidation. Some fish oil products are made with oil from by-products of the fishing industry while others are made from fish harvested specifically for supplement production. There is concern that during the by-product process, the oil is not immediately protected from oxidation as it is in the direct process. Oxidation not only influences the taste (and aftertaste) of the fish oil but it also impacts efficacy. Freshness is measured by peroxide value, a measure of oxidation. Containing the fresh oil in an oxygen-free environment at all times, along with low-temperature manufacturing, maintains freshness.

Further, better fish oil supplements contain natural stabilizers and antioxidants to 1) preserve and improve the stability of the unsaturated oil in the capsule or bottle and 2) reduce oxidative stress, thereby improving biological utilization.

Standards
Currently, no quality standards for fish oil exist in the United States. The Council for Responsible Nutrition (CRN), a trade organization for supplement suppliers and manufacturers, has recently developed U.S. voluntary guidelines. Some fish oil supplement manufacturers adhere to European standards for fish oil, such as the Norwegian Medicinal Standard and the European Pharmacopoeia Standard. European standards are higher than the current voluntary and proposed U.S. standards. For example, while the CRN encourages dioxin levels to be measured in parts per million, Euro standards are set in parts per trillion.

Two organizations to be familiar with include the International Society for the Study of Fatty Acids and Lipids, an international body of scientists and health professionals, and International Fish Oil Standards, which offers third-party validation. Dietary supplement third-party certification programs within the U.S. currently follow the CRN’s voluntary guidelines.

Fish oil supplements come in capsules and liquids; some are lightly flavored. Children’s chewables are also on the market. Different ratios of EPA to DHA are available. Liquid products need refrigeration after opening. Because oil is readily absorbed, enteric coating of fish oil supplements is unnecessary (except in unique circumstances) and significantly increases cost. Practitioners know that the burping experience with fish oil supplements is a barrier to compliance. While a fish oil supplement does require functional digestion, persistent burping and bad taste tends to indicate an inferior product. It is not necessary to freeze fish oil capsules.

Fish and fish oil provide two important, functional fatty acids essential in human nutrition. From conception to older age, the need for EPA and DHA is compelling. Because of current dietary practices in the United States, many people are consuming insufficient amounts of omega-3s. Today, dietitians have an opportunity to educate and influence healthful consumption of omega-3 fatty acids through diet and supplements. Dose, duration, freshness, and purity matter.

— Gretchen Vannice, MS, RD, is a science-based nutrition writer and educator. She has worked in healthcare and the dietary supplement industry for 18 years and served on the board of Nutrition in Complementary Care, an American Dietetic Association dietary practice group since 1999.

References
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