March 2011 Issue
Ocean of Benefits — New Research Reveals Potential Powers of Omega-3s Beyond Heart Health
By Megan Tempest, RD, LDN
Vol. 13 No. 3 P. 26
Scientists are uncovering expanded uses for these fishy fats—from preventing liver disease to delaying cognitive decline.
Nutrition experts and health-savvy consumers alike are well versed in the reported health benefits of ramping up omega-3 fatty acid intake. While we’re aware these essential nutrients may do wonders for our health, perhaps a refresher is in order.
Earning their name from their unique chemical structure, omega-3s are polyunsaturated fatty acids obtained from a variety of foods, such as cold-water oily fish, flaxseed, walnuts, and canola oil. The nutritionally pertinent omega-3 fatty acids are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Because omega-3s cannot be synthesized by the body and therefore must be obtained from dietary sources, they fall into the category of essential fatty acids.
Jody Halouska, RD, bariatric coordinator at Presbyterian/St. Luke’s Medical Center in Denver, summarizes the health-promoting attributes of omega-3 fatty acids: “From decreasing risk of heart disease and stroke, lowering blood pressure, reducing inflammation, and alleviating autoimmune diseases, the potential health benefits are far reaching, particularly for individuals who are already at increased risk for many of these diseases and conditions.”
Yet not all omega-3 fatty acids are alike; they vary significantly in structure and form and thus the body metabolizes them differently. ALA is the shortest omega-3 fatty acid and is derived from plant sources such as walnuts, soybean oil, canola oil, flaxseed, and some leafy vegetables. The longer omega-3 fatty acids are EPA and DHA, both of which are derived from marine algae and from fish that have eaten these algae.
Although ALA is believed to be beneficial for cardiovascular health, it is to a lesser degree than EPA and DHA. “Marine-derived omega-3 fatty acids [EPA and DHA] are readily available to the body, whereas plant sources require conversion to EPA or DHA to be assimilated by the body,” Halouska explains.
While the conversion rate is not well defined, the human body is slow to convert ALA to EPA and perhaps even slower to convert ALA to DHA. As reported in the Canadian Medical Association Journal, although the human body can convert approximately 5% of ALA to EPA, the level of EPA in the blood does not rise when we eat ALA.1
The American Heart Association (AHA) steadfastly promotes the importance of omega-3 fatty acid intake to decrease the risk of cardiac arrhythmias, decrease serum triglyceride levels, delay the progression of atherosclerosis, modestly reduce blood pressure, and overall benefit the heart. The AHA recommends that healthy individuals eat a variety of oily fish (eg, tuna, salmon, sardines) at least twice per week while including plant foods rich in ALA. Noted in the AHA’s scientific statement “Fish Consumption, Fish Oil, Omega-3 Fatty Acids, and Cardiovascular Disease,” published in 2002 in the Journal of the American Heart Association, “Omega-3 fatty acids have been shown in epidemiological and clinical trials to reduce the incidence of CVD [cardiovascular disease]. … Evidence from prospective secondary prevention studies suggests that EPA+DHA supplementation ranging from 0.5 to 1.8g/d (either as fatty fish or supplements) significantly reduced subsequent cardiac and all-cause mortality.”
The bariatric patient population that Halouska counsels may not be getting adequate omega-3 fatty acids. “Due to relatively limited food sources of omega-3 fatty acids, the general population often has a hard time consuming enough. The significantly restricted food portion sizes and food intolerances that affect the postoperative bariatric surgery patient only accentuate their difficulty in getting adequate omega-3s from food.” Due to limited scientific evidence supporting supplementation in this specific patient population, omega-3s are not incorporated into the standard vitamin and mineral recommendations for postoperative bariatric surgery patients, based on those established by the American Society for Metabolic and Bariatric Surgery.
Nonetheless, Halouska adds, “I support patients who make the choice to supplement omega-3s with approval from their physician. In the future, as further evidence unfolds, we’ll continue to adjust our practices to provide the most scientific-based recommendations.”
In addition to the aforementioned health benefits, an evolving body of research is steadily revealing new potential benefits of omega-3 fatty acids—from reversing liver disease in neonates to enhancing cognitive function in older adults.
Researchers at Iowa State University are currently immersed in an in-depth analysis of omega-3 fatty acid intake in pregnant women. The Blossom Project, led by Christina Gayer Campbell, PhD, RD, an associate professor of nutrition, is a mission to better understand how diet and exercise during pregnancy can produce healthier moms and babies.
Acknowledging that a healthy pregnancy leads to the prevention of chronic disease for the fetus while positively impacting the mother’s health, Campbell is particularly interested in examining the role of omega-3 fatty acid intake in pregnancy. “We know that DHA plays a pivotal role in fetal neurodevelopment. When I initially began my research in this area, I hypothesized that the intake of DHA in pregnant women living in noncoastal communities would be low due to less accessibility to fish. I also wondered how much of an influence safety issues were to fish consumption during pregnancy,” she says.
Several years ago, she began the Blossom Project, an observational study to determine the current intake of omega-3 fatty acids and physical activity habits in pregnant women living in noncoastal communities. Since then, the project has become an umbrella for a series of observational and interventional studies. Campbell speculates on the reasons for low DHA consumption among pregnant women: “We have found that the reasons behind low fish intake are numerous. To better understand the perceived barriers to fish consumption during pregnancy, we will conduct a survey this spring. I have found that most people have one very strong reason that easily comes to mind, and these vary from dislike, cost, don’t know how to prepare, didn’t grow up eating fish, and safety concerns.”
Scientists have speculated that inadequate maternal intake of omega-3 fatty acids may be a precursor to increased risk of childhood allergy. The mechanism of action is not well understood, but it’s speculated that a high ratio of omega-6 to omega-3 fatty acids, which is typical in the Western diet, may be the culprit in the relationship to allergic disease.2 Additionally, EPA and DHA play a role in modulating immune cell function and the body’s inflammatory response.3 Prenatal fish oil intake has been shown to increase the DHA concentration of the mother’s breast milk as well as significantly increase levels of immunoglobulin (Ig) A, a critical immune antibody. Lower incidence of food allergy has been observed in the first year of life among infants whose mothers consumed a fish oil supplement during their pregnancy and for three to four months of lactation.4 A positive correlation has also been observed between high levels of DHA in breast milk and decreased allergic disease in children at 18 months.3
Reduced episodes and duration of upper respiratory infection and diarrhea have been noted among 9- to 12-year-old healthy children consuming fish oil-supplemented milk.4
A randomized, placebo-controlled trial by Swedish researchers, published in 2009, assessed 145 pregnant women who were either personally affected by allergies or had a husband or previous child with allergies. The women were supplemented with EPA and DHA or a placebo from the 25th week of pregnancy through approximately three to four months of breast-feeding. Researchers found that the prevalence of food allergy, as well as the incidence of IgE-associated eczema, was lower in the omega-3 group compared with the placebo group, suggesting that omega-3 fatty acid supplementation may decrease the risk of both conditions during the first year of life in infants with a family history of allergy.5
In a 2009 study published in the Archives of Disease in Childhood, “Early Introduction of Fish Decreases the Risk of Eczema in Infants,” Alm and colleagues found that while familial history of eczema is the strongest risk factor for the condition, introducing fish to a child’s diet before 9 months of age has a protective effect against it.
In the study “The Impact of Early Nutrition on Incidence of Allergic Manifestations and Common Respiratory Illnesses in Children,” published in the June 2010 issue of the Journal of Pediatrics, Birch and colleagues investigated the incidence of allergic and respiratory diseases through the age of 3 in children fed formulas supplemented with DHA and arachidonic acid, an essential polyunsaturated omega-6 fatty acid, consistent with human milk levels. Their results showed that infants fed supplemented formula, initiated within the first week of life and continued for one year, had a lower incidence and delayed onset of upper respiratory infection, common allergic diseases, wheezing, and asthma and fewer physician visits related to these illnesses throughout the first three years of life.
Use of Fish Oil-Based Lipid to Treat and Prevent PNALD
Omega-3 fatty acids from fish have been shown to improve serum lipid levels and potentially treat or prevent dyslipidemia associated with long-term parenteral nutrition, making this a focus of intense research. The capability of fish oil to prevent parenteral nutrition-associated liver disease (PNALD) was previously noted in Today’s Dietitian by Theresa A. Fessler, MS, RD, CNSD. In the article “Omegaven: New Hope From the Sea for PNALD,” Fessler outlined the proposed benefit of using a fish oil-based lipid emulsion (Omegaven) vs. a soybean-based emulsion (Intralipid): “It is theorized that soybean oil emulsions might contribute to liver injury due to the large content of omega-6 fatty acids, which are proinflammatory, and phytosterols, which may impair bile flow. In contrast, omega-3 lipids are thought to protect the liver by inhibition of lipogenesis, improved lipid clearance in the bloodstream, and reduced inflammatory mediators.”
At that time, a team of researchers at Children’s Hospital of Boston were seeing positive outcomes with the use of Omegaven to reverse PNALD. That same team, Gura and colleagues, later published the study “Safety and Efficacy of a Fish Oil-Based Fat Emulsion in the Treatment of Parenteral Nutrition-Associated Liver Disease” in 2008 in Pediatrics. Subjects receiving a fish oil-based lipid experienced reversal of cholestasis 4.8 times faster than those receiving soybean-based lipids. Two deaths and no liver transplantations were observed in the fish oil group compared with seven deaths and two transplantations in the soybean group. The findings strongly support the use of fish oil-based lipid emulsions (Omegaven) to treat PNALD.
Children’s Hospital of Boston has further research under way, gathering evidence to support the efficacy of an omega-3–based intravenous fat emulsion in preventing PNALD in children with intestinal failure due to the suspected ability of these fatty acids to improve triglyceride clearance and provide anti-inflammatory benefits.6
Le and colleagues reported concurrent findings in the September 2010 issue of the Journal of Parenteral and Enteral Nutrition. They analyzed 10 children exclusively administered a fish oil-based lipid emulsion over an average of 10 weeks and concluded that parenteral fish oil may be the preferred lipid source for PN-dependent children with dyslipidemia given significant improvements in all major lipid panels and improvement in hyperbilirubinemia.7
In 2010 in Nutrition in Clinical Practice, Rollins and colleagues reported that the temporary elimination of a soybean-based lipid emulsion and supplementation with enteral fish oil improved cholestasis in PN-dependent infants. After analyzing 23 infants with short-bowel syndrome (SBS) who developed cholestasis due to prolonged PN, they removed the soybean lipid emulsion in a portion of these patients and replaced it with an enteral fish oil emulsion and subsequently observed resolution of cholestasis within 1.8 to 5.4 months.8
Diamond and colleagues from the Hospital for Sick Children in Toronto published their report “Changing the Paradigm: Omegaven for the Treatment of Liver Failure in Pediatric Short Bowel Syndrome” in 2009 in the Journal of Pediatric Gastroenterology and Nutrition. After examining a retrospective cohort of 12 children with SBS and advanced PNALD who were treated with Omegaven, they concluded that the provision of omega-3–based parenteral lipids has “the potential to fundamentally alter the paradigm of neonatal SBS from one of early death or transplantation from liver failure to a more chronic disease.”
Enhanced Cognitive Function
The relationship between omega-3 fatty acids and cognitive function in older adults is another burgeoning research focus. Large epidemiological studies have suggested that DHA consumption may prevent or delay cognitive decline, and animal studies have shown that oral DHA may reduce Alzheimer-like brain alterations.
The importance of ensuring adequate omega-3 intake in older individuals is emphasized by Katie Hartoin, RD, LDN, director of food and nutrition services at HCR Manor Care, a skilled nursing facility in Wilmette, Ill.: “We serve fish to our residents a minimum of twice per week, generally serving salmon [an omega-3–rich fish] once per week.”
Hartoin recommends the consumption of fish and fish oil to her residents for a variety of reasons, including reducing the risk of CVD and cognitive benefits. She believes adequate omega-3 may help people with mood disorders (eg, depression), which are common in older people.
In a 2010 issue of Dementia and Geriatric Cognitive Disorders, Israeli researchers from the Tel-Aviv Sourasky Medical Center published results of a study examining the cognitive effects of phosphatidylserine containing omega-3 (PS-DHA) on nondemented older adults with memory complaints. Phosphatidylserine is a phospholipid cell component found most abundantly in bovine brain matter and organ meats such as liver and kidney and has garnered attention for its potential to reduce cognitive dysfunction in older adults. After assessing about 130 subjects given either PS-DHA or a placebo, the researchers found that verbal immediate recall was improved and that those with higher baseline cognitive status responded more favorably to PS-DHA.9
As published in 2010 in Alzheimer’s and Dementia, DHA may enhance cognitive function in older adults. Yurko-Mauroa and colleagues tested the theory that decreases in plasma DHA are associated with cognitive decline in healthy older adults as well as in patients with Alzheimer’s disease. They conducted a randomized, double-blind, placebo-controlled study at 19 clinical sites through the United States, including a total of 485 healthy subjects at least 55 years old. They concluded that supplementing 900 mg/day of DHA over a 24-week period improved learning and memory function and that DHA “is a beneficial supplement that supports cognitive health with aging.”10
Hartoin rationalizes her proactive approach to providing adequate omega-3 to older adults. “DHA and fish oil have been shown to stimulate memory and the ability to learn and may prevent degenerative conditions in the elderly, such as Alzheimer’s, which has been linked to a deficiency in DHA.” Yet, she concedes, “I realize there is a lot of conflicting data on the Alzheimer’s subject.”
An example of such conflicting data was presented in November 2010 in The Journal of the American Medical Association by researchers from the department of neurology at Oregon Health and Sciences University. They found that DHA supplementation did not slow cognitive or functional decline in individuals with mild to moderate Alzheimer’s disease. Over an 18-month period, subjects with mild to moderate Alzheimer’s disease were randomly given a 2 g/day dose of DHA or a placebo. Supplementation was found to have no significant effect on cognitive function nor was rate of brain atrophy affected.11
Where Do We Go From Here?
Undoubtedly, further research examining the health effects of omega-3 fatty acids will bring new findings to light, substantiate the existing ones, and precipitate improved evidence-based practice guidelines.
Campbell says, “We don’t yet know what it means to be deficient in DHA. It may be quite some time before we can answer this question, as DHA ‘deficiency’ may be influenced by the rest of your diet.”
The fact that scientists are taking a hard look at a nutrition-based intervention to alleviate conditions such as liver disease, childhood allergy, and Alzheimer’s disease is an affirmation of the importance of considering alternative and complementary therapies to treat illness and disease. Hartoin remains confident that, in the absence of any obvious contraindications, the potential health benefits of increased intake of omega-3 fatty acids far outweigh the risks. She concludes, “I believe it can only help.”
— Megan Tempest, RD, LDN, works at Presbyterian/St. Luke’s Medical Center in Denver and is a freelance writer.
1. Jenkins, DJA, Josse AR. Fish oil and omega-3 fatty acids. CMAJ. 2008;178(2):150.
2. Alm B, Åberg N, Erdes L, et al. Early introduction of fish decreases the risk of eczema in infants. Arch Dis Child. 2009;94(1):11-15.
3. Duchén K, Casas R, Fageras-Böttcher M, Yu G, Björkstén B. Human milk polyunsaturated long-chain fatty acids and secretory immunoglobulin-A antibodies and early childhood allergy. Pediatr Allergy Immunol. 2000;11(1):29-39.
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5. Furahjelm C, Warstedt C, Larsson J, et al. Fish oil supplementation in pregnancy and lactation may decrease the risk of infant allergy. Acta Paediatr. 2009;98(9):1461-1467.
6. Puder M. Cholestasis prevention: Efficacy of IV fish oil. In: ClinicalTrials.gov (Internet). Boston (Mass.): 2007 (cited January 31, 2011). Available at: http://clinicaltrials.gov/ct2/show/NCT00512629?intr=%22Omegaven%22&rank=12. NLM identifier: NCT00512629.
7. Le HD, de Meijer VE, Zurakowski D, et al. Parenteral fish oil as monotherapy improves lipid profiles in children with parenteral nutrition-associated liver disease. J Parenter Enteral Nutr. 2010;34(5):477-484.
8. Rollins MD, Scaife ER, Jackson WD, et al. Elimination of soybean lipid emulsion in parenteral nutrition and supplementation with enteral fish oil improve cholestasis in infants with short bowel syndrome. Nutr Clin Pract. 2010;25(2):199-204.
9. Vakhapova V, Cohen T, Richter Y, Herzog Y, Korczyn AD. Phosphatidylserine containing omega-3 fatty acids may improve memory abilities in non-demented elderly with memory complaints: A double-blind placebo-controlled trial. Dement Geriatr Cogn Disord. 2010;29(5):467-474.
10. Yurko-Mauroa K, McCarthy D, Romb D, et al. Beneficial effects of docosahexaenoic acid on cognition in age-related cognitive decline. Alzheimers Dement. 2010;6(6):456-464.
11. Quinn JF, Raman R, Thomas RG, et al. Docosahexaenoic acid supplementation and cognitive decline in Alzheimer disease: A randomized trial. JAMA. 2010;304(17):1903-1911.