Omega-3 fatty acids are considered essential fatty acids because the human body cannot manufacture them. For this reason they must be obtained from your food source. Because of this, interest in the Mediterranean diet with its high content of omega-3 fatty acids from fish has skyrocketed in recent years; especially since it has been observed that people living in regions bordering the Mediterranean Sea appeared to live longer and suffer less from cardiovascular disease. In particular, a Mediterranean diet that includes fish has long been associated with a lower rate of heart disease in countries such as Spain, Greece, and Italy.
But whether or not this diet can benefit patients who have already suffered a heart attack has not been tested in depth before the GISSI study. Thus, the purpose of GISSI was to investigate the effects of omega-3 fatty acids and vitamin E on cardiovascular events after people have had a heart attack.
Who Forms the GISSI Study Group?
GISSI, an Italian group for the study of the survival of heart attacks (myocardial infarction) is an influential cardiology research group founded as a collaboration between two Italian organizations – the Mario Negri Institute and the Associazione Naxionale dei Medici Cardiologi Ospedalieri (ANMCO). The trials carried out by GISSI have obtained wide recognition in the international world of cardiology and are considered a methodological landmark. Four large-scale clinical trials over the past 20 years have involved more than 60,000 patients with acute myocardial infarction.
The GISSI Study
There are three major types of omega-3 fatty acids: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Once eaten, the body will convert ALA to EPA and DHA which are the two types of fatty acids used most by the body. There is a large body of research that demonstrates the ability of omega-3 fatty acids to reduce inflammation and help prevent the risk factors associated with chronic diseases such as heart disease, cancer, and arthritis. It is interesting to note that these essential fatty acids are highly concentrated in the brain and appear to be important for brain memory and performance. What the researchers didn’t know was whether these fatty acids would benefit those who have suffered a heart attack.
Between October 1993 to September 1995, 11,324 patients participated in the GISSI trial. To qualify as a participant for the study, the patients must have survived a recent heart attack (less than three months prior to being enrolled in the study). Patients were randomly assigned to four treatment groups:
The results were very significant for dietary supplementation with omega-3s from fish oil. Treatment with omega-3s resulted in a 45% reduction in the risk of having a sudden fatal heart attack, a 30% decrease from cardiovascular mortality and a 20% reduction in overall mortality. According to the researchers, vitamin E supplements were found to have no benefits on heart attacks.
Marchioli, senior author of the study, reported that the people who followed a Mediterranean style diet that included more vegetables, fruit, fish, but little butter, were less likely to die than people who reported eating higher amounts of butter, cheese, and vegetable oils other than olive oil. Similar benefits of a Mediterranean-style diet were seen in earlier, smaller randomized trials. In the Lyon Diet Heart Study, benefits were seen in patients who after a heart attack were assigned to a diet rich in alpha-linolenic acid, ALA, from plant sources along with plenty of legumes, cereals, fresh fruits, and vegetables. Compared with those assigned to a “prudent” diet similar to the American Heart Association step 1 diet, those on the Mediterranean style diet had a 70% reduction in deaths, repeat heart attacks, unstable angina, stroke, congestive heart failure, or embolic events.
Where do you find EPA and DHA?
Long-chain fatty acids, EPA and DHA, are most abundant in fish and shellfish, particularly fatty fish such as salmon, rainbow trout, tuna, mackerel, herring, and sardines. All seafood has some EPA and DHA. Fish oil capsules are a rich source of EPA and DHA, too.
How Much Omega-3s do you need to take?
100 grams (3.5 ounces) of salmon provide 5,000 mg of EPA and DHA, followed by tuna with about 2,300 mg and trout with 1,470 mg. Other fish with high content of fatty acids are sardines, mackerel, and anchovies. A daily ingest should contribute between 1.1 and 1.4 grams. A fatty fish portion will cover this need.
For people who already have a heart condition, eating seafood more often, or consuming marine fatty acids from supplements, is just as important. If you have already suffered a heart attack, you could supplement your fish intake with a good quality fish oil supplement that is certified mercury-free by a reputable third-party lab.
Are Plant and Fish Omega-3s Born Equal?
No. The omega-3s found in terrestrial plants, such as some nuts or the ones found in enriched foods, are ALA. Terrestrial plants have only ALA. This fatty acid has some, but not all, of the health benefits associated with fish oil omega-3s. It can also be converted in the body to EPA and very small amounts of DHA but humans perform this conversion very poorly, less than 5%, so relying only on ALA for all fatty acids risks creating a deficiency in EPA and especially in DHA.
And Don’t Forget That
Our body either cannot produce fatty acids or does not produce enough quantities to support good health. Therefore, they have to be ingested from our diet. Additionally, those who follow a traditional Mediterranean diet typically have greater high density lipoproteins (HDL) which are the good cholesterol. Several large clinical studies using fish oil supplements containing EPA and DHA have reported a significant reduction in low density lipoproteins (LDL – bad cholesterol) and a significant reduction in triglycerides.
If you’re interested in ways to include a variety of fishes into your diet for their omega-3 fatty acids benefits, then you might be interested in the recipes that I offer in my book “Your Heart Needs the Mediterranean Diet!”
Have a great day,
P.S. As a convenience, I’ve also included links to the following Blood Pressure & Cardiovascular Health articles:
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