Omega-3 Fatty Acids: An Overlooked Essential Nutrient

Ruth Carey, RD, LD

The American Heart Association's updated dietary guidelines have brought long overdue attention to the role of Omega-3 fatty acids in heart health. The AHA now recommends two servings of fatty fish per week to protect against heart disease because most Americans fall far short of meeting the recommended intake of 650 mg of Omega-3 fatty acids per day.1 Fish such as salmon, tuna, herring and mackerel are rich in the Omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Because these nutrients are so essential to health and many people either don't like or don't eat enough fish, supple-ments may be appropriate.

More than 30 years of research has documented the importance of Omega-3 fatty acids throughout the lifespan, from pregnancy to infancy and into adulthood. In addi-tion to cardiovascular bene-fits, Omega-3 fatty acids play a role in visual acuity and brain health in infants, reduced depression and rheuma-toid arthritis in adults, and reduced dementia in seniors. Because the human body cannot make Omega-3 fatty acids, we must obtain them from dietary sources.

Background

Interest in Omega-3 fatty acids was sparked 30 years ago as a result of studies of the Inuit Eskimos in Greenland. These Eskimos had a low prevalence of coronary heart disease despite a very high-fat diet.² The fat in their diet came from sea mammals, such as whales, which have high proportions of Omega-3 fatty acids. Researchers then looked at other populations with high fish consumption, such as the Japanese, and found dramatically lower mortality from heart diseases compared with populations who do not eat much fish.

The strongest evidence about the protec-tive effects of Omega-3 fatty acids is in the area of heart disease. Omega-3 fatty acids, particularly EPA, lower triglyceride and very-low-density lipoprotein levels, reduce platelet aggregation, are anti-thrombotic, have an anti-arrhythmic effect (ventricular tachycardia and fibrillation), and stimulate endothelial-derived nitric oxide.^3-7 One study documented a 29% decrease in mortality among men with cardiovascular disease who obtained Omega-3 fatty acids from fish or fish oil, probably by reducing cardiac arrests.⁸

In the Physicians' Health Study, consumption of at least one fish meal per week was associated with a 52% lower risk of sudden death compared with minimal fish consumption.⁹ In a landmark study in Italy involving 11,342 post-myocardial infarction patients, subjects who took Omega-3 fatty acid supplements had a significant 15% relative risk reduction in the combined rate of death plus non-fatal myocardial infarction and non-fatal stroke compared with subjects who did not receive supplements. Death from all causes was reduced by 21%.¹⁰

Other Beneficial Effects

DHA is beneficial for pregnant and lactating mothers and for infants. This Omega-3 fatty acid is important for the development of visual acuity and the brain.¹¹ Mother's milk is naturally high in Omega-3 fatty acids, but formula in the United States is not fortified with DHA. Therefore, formula-fed infants may not get adequate DHA for optimal retinal eye and brain development. Low levels of DHA in the brain have been documented in children with attention deficit disorder.

The average woman consumes only 0.08 g of Omega-3 per day and the recommended amount is 0.6 g to 0.7 g daily for all women.

Omega-3 fatty acids also have anti-inflammatory effects. A controlled, 12 month study of subjects with rheumatoid arthritis found that patients given 3g daily of Omega-3 fatty acids experienced reduced symptoms and need for medications.¹² Pain scores in the study group improved, and researchers documented an increase in grip strength over the placebo group.

Lastly, Omega-3 fatty acids have been linked to depression in adults and dementia in people older than 55. A 1999 study found that low levels of DHA in the brain were common in depressed subjects.¹² Another study of 5,000 subjects age 55 and older examined different components of dietary fat intake, including total fat, saturated fat, cholesterol and polyunsaturated fatty acids.¹³ The researchers collected dietary profiles and followed participants for 2.1 years. The follow-up profiles showed that 1.1% of the participants developed Alzheimer's-associated dementia. Total and high saturated fat intakes were most strongly associated with increased risk for dementia. Fish consumption was associated with a reduced risk for dementia, especially Alzheimer's disease. A reference autopsy study concluded that DHA was decreased in the brains of patients affected by Alzheimer's.

American Diets Deficient

Despite strong evidence that Omega-3 fatty acids are important to human nutrition, consumption surveys show that 65% of Americans are not getting the recommended amount of 650 mg per day.^l0 Three 3-oz servings of fatty fish per week would provide the recommended level of Omega-3 fatty acids. Survey results show that barriers to eating fish are taste (33%), preference of family members (31%), portability (28%), accessibility (22%), difficulty with preparation (20%) and allergies (14%).

All health care providers should ask at-risk patients about fish consumption and make recommendations to follow the new AHA Dietary Guidelines at minimum. Most health experts recommend obtaining nutrients from food sources first. For those who will not eat the recommended amount of fish, fish oil supplements seem appropriate.

Some concern has arisen about the safety of fish oil supplements. Concerns include excessive bleeding, thrombocytopenia, increased stroke incidence and increased gas-trointestinal side effects. But according to a review of the literature, there is no evidence of significant toxicity or increased bleeding associated with dosing up to 16 g of fish oil per day. Vitamin E is included in most supplements to prevent oxidation of fatty acids.¹⁴

When recommending supplements, choose products from a reputable company. Advise patients to read labels to make sure that whatever product they buy lists DHA, EPA and total milligram levels per recom-mended dose. Recommend only fish oil sup-plements that contain vitamin E.

References

1. Krauss RM and the AHA Dietary Guidelines Committee. AHA Dietary Guidelines Committee revision 2000: a state-ment for health care professionals from the nutrition committee of the American Heart Association. Circulation 2000;102:2284. Available at http://circ.ahajournals.org/cgi/content/full/102/18/2284.

2. Bang HO, Dyerberg J. The composition of food consumed by Greenlandic Eskimos. Acta Med Scand. 1973;200:69-73.

3. Phillipson BE, Rothrock DW, Connor WE, Harris SW, Illingworth DR. Reduction of plasma lipids, lipoproteins and apoproteins by dietary fish oil in patients with hyper-triglyceridemia. N EngJ Med. 1985;312:1210-1216.

4. Goodnight SH, Harris WS, Connor WE . The effects of dietary Omega-3 fatty acids upon platelet composition and function in man: a prospective, controlled study. Blood 1981;58:880-885.

5. Goodnight SH, Harris WS, Connor WE, Illingworth DR. Polyunsaturated fatty acids, hyperlipidemia and thrombosis. Arteriosclerosis. 1982;2:87-113

6. Kang JX, Leaf A. Antiarrhythmic effects of polyunsaturated fatty acids. Circulation 1996;94:1774-1780.

7. Shimokawa H, Vanhoutte PM. Dietary Omega-3 fatty acids and endothelium-dependent relaxation's in porcine coronary arteries. Am J Physiol. 1989;256:H968-H973.

8. Burr ML, et al, Effects of changes in fat, fish and fiber intakes on death and myocardial reinfarction: diet and reinfarction trial (DART). Lancet 1989;2:756-761.

9. Albert CM, et al. Fish consumption and risk of sud-den cardiac death. JAMA. 1998;279;2:87-113

10. Birch E, et al. Dietary essential fatty acid supply and visual acuity development. Invest Ophthalmol Vis. Sci. 1992;33;3242-3253.

11. Guesens P, et al. Long term effect of Omega-3 fatty acid supplementation in active rheumatoid arthritis. Arthritis Rhuem. 1994;37:824-829.

12. Maes M, et al. Lowered n-3 polyunsaturated fatty acids in serum phospholipids and cholesterol esters of depressed patients. Psychiatry Research. 1999;85:275-29l.

13. Lalmijn S, et al. Dietary fat intake and risk of incident dementia in the Rotterdam Study. Annals of Neurology. 1997;42:776-782.

14. Connor WE. Fish oil in hypertriglyceridemia: safety and recommendations, Lipids. 1999;34s27l.


Used here with permission from Advance for Nurse Practitioners; February, 2002