Omega-3 Fatty Acids - FISH OIL for Heart Prevention - the Facts!

In the 1970's, studies in Greenland Eskimos showed 1/10 the incidence of heart disease compared to an ethnically similar population in Denmark. Both populations had a comparable and even high intake of total fat (42% of dietary calories) but the intake of omega-3 polyunsaturated fat (PUFA) or "fish oil", was 4-times as much in the Eskimos. A more recent study in the US Physicians Health Study showed that consuming at least 1 fish meal per week reduce the risk of sudden cardiac death by 52% compared with those consuming fish only monthly. One recent study also showed that omega-3 intake reduced the risk of stroke.

Omega-3 PUFA can be derived from a diet rich in α-linolenic acid (legumes, leafy vegetables, flax, flaxseed oil, canola oil) or directly via eichosapentaenoic acid (EPA) and DHA (docosahexenoic acid) from fish oil or direct supplements. EPA and DHA are the major omega-3 PUFA’s and are thought to be responsible for the heart protective effects. The table below summarizes the results of 4 large scientific studies.

Study	Dietary Modification	Effect on Mortality
Finnish Mental Hospital Study	Replacement of fat with polyunsaturated fat	53% decrease in men and 34% decrease in women
Lyon Diet Heart Study	Low saturated fat and high α-linolenic acid diet	65% decrease over 4 years
DART (diet alone and reinfarction trail]	Supplementation with fish oil (1-2 gm/day)	33% decrease
GISSI [Italy]	Supplementation with fish oil (1-2 gm/day)	20% decrease

Remember that these dramatic effects were found in patients already known to have heart disease ["secondary prevention"]. Data are still sparse on the value of PUFA for "primary prevention" - but most experts feel that a diet of fish at least once per week, or alternatively supplementation with "fish oil" capsules can be part of a heart protection program. The American Heart Association recommends omega-3 in some form as part of the prevention program in women. However all “fish oil” capsules are not the same. The amounts of the active ingredients EPA and especially DHA determine efficacy. It is suggested that that the total amount of combined EPA and DHA (taken, as with all supplements, in two-divided daily doses) should be on the order of 1,200 mg per day. This can be confusing to the consumer who finds a “1,000 mg” fish oil capsule to contain only 500 mg or less of combined EPA and DHA.

Your patients with an allergy to fresh-water fish should NOT take these supplements. Also, they have mild effects on increasing blood sugar levels, but the risk versus the benefit is very low. Omega-3 supplementation does not increase LDL values, although it may increase the HDL, a small amount and it may also help change the more dangerous “low-dense” LDL particles into the less dangerous “large-fluffy” particles. Higher doses (combined EPA and DHA of about 3,000 mg per day or more) can lower the blood triglyceride levels. In patients with high triglycerides, I recommend supplementation with higher doses of fish oil. Some evidence indicates that Omega-3 also may have some cancer preventing effects, may slow down the development of Alzheimer’s, and may even have some benefit in reducing depression. Finally, recent data also show that omega-3 from any source has anti-inflammatory (and thus anti-oxidative stress) effects.

John A. Rumberger, M.D., FACC