by Craig Weatherby
Conventional wisdom—as reflected in advice from the American Heart Association (AHA)—is that diets low in fat and cholesterol are the best kind for preventing heart attacks.
However, it is important to define “fat” in this context. The statistics show that cardiac risks drop when people reduce their intake of saturated fats, from meats and dairy foods.
And the cardiovascular benefits of reducing saturated fat intake apply particularly to diets with three pro-inflammatory characteristics typical of the American diet:
- Low in dietary antioxidants from fruits, cooking herbs, and vegetables.
- Low in omega-3 fatty acids from fish and leafy green vegetables.
- High in omega-6 fatty acids from common vegetables oils and the packaged and prepared foods made with them.
In contrast, there is little risk that people so advised would reduce their intake of omega-6 fatty acids too much, because these fats are generally overabundant in the American diet.
Unfortunately, many of the omega-6 fatty acids in the American diet come in the heart-unhealthful “trans” form produced when omega-6-rich vegetable oils -- corn, safflower, soybeans, cottonseed, canola, and sunflower -- are hydrogenated to extend food products’ shelf life and/or modify their texture. The same process destroys the very small amounts of omega-3s in these oils.
Lowering saturated fat intake is seen as beneficial in the context of the typical American diet, because this step also lowers people’s blood levels of LDL cholesterol, which is easily oxidized by free radicals: the unstable oxygen-based molecules created by chronic inflammation in the blood.
Oxidation of LDL cholesterol promotes build up of unstable arterial plaque, which eventually bursts and releases clots into the blood stream, causing heart attacks and sudden cardiac death.
Since low-fat diets are hard to follow, and advice to reduce “fat” intake can be counterproductive, the results of a new study comparing the heart benefits of low-fat diets to those of higher-fat Mediterranean-style diets come as welcome news.
Omega-3-rich Mediterranean diet rivals low-fat alternative
Findings presented at the American College of Cardiology (ACC) 56th Annual Scientific Session indicate that, as the press release said, “…a Mediterranean-style diet rich in fish, monounsaturated fats, and other sources of omega-3 fatty acids” is just as beneficial as the low-fat, low-cholesterol “Step II” diet recommended by the American Heart Association (AHA).
The results apply to people who have had a heart attack, but likely also apply to people who’ve never suffered one.
(The term "Mediterranean diet" refers to the eating habits found in rural Greece and Italy by University of Minnesota Professor Ancel Keys during his famous Seven Countries health-and-diet survey, conducted from the late 1950's through the 1970's.)
It features grains, pasta, beans, vegetables, fruits, olive oil, bread, wine, and fish, rather than the loads of meat, refined starches, and omega-6-rich vegetable oils that dominate the American diet.
Katherine R. Tuttle, M.D. of Sacred Heart Medical Center in Spokane, Washington led the study—called “The Heart Institute of Spokane Diet Intervention and Evaluation Trial” (THIS-Diet)—the findings of which she presented at the 2007 ACC conference in New Orleans.
Dr. Tuttle and her colleagues recruited 101 patients who had had a heart attack within the previous six weeks.
Participants were assigned randomly to follow the American Heart Association’s low-fat Step II diet or a higher-fat Mediterranean-style diet:
- Participants assigned to the AHA diet were allowed to derive up to 30 percent of their daily calories from fat.
- Participants assigned to the Mediterranean diet were allowed to derive up to 40 percent of their daily calories from fat.
The 10 percent higher fat intake in the Mediterranean diet consisted of the heart-healthful omega-3 fats found primarily in fish and vegetables, and the heart-neutral monounsaturated fats found primarily in olives, olive oil, peanuts, and avocados.
Participants assigned to the Mediterranean diet had a higher intake of omega-3 fatty acids: more than 0.75 percent of calories, compared with 0.3-0.45 percent of calories with the AHA diet.
To the extent that people in the Mediterranean diet group used extra virgin olive oil, they also would have benefited from its extremely potent tyrosol-type antioxidants, which are proven to enhance artery health. Lesser grades of olive oil either lack these antioxidants entirely (“pure” grade) or contain much less of them (“virgin” grade).
Each patient attended six or more group nutrition classes over 24 months, and met twice with a dietitian for individual counseling within the first month, and again at three, six, 12, 18, and 24 months.
Results prove Mediterranean diets match low-fat diets
After an average of nearly four years, both groups enjoyed a two-thirds reduction in their risk of cardiovascular complications, compared to a control group of 101 heart attack survivors who did not change their diets or receive dietary counseling.
There was no difference between the two diet groups in the combined rates of death, repeat heart attack, unstable chest pain, stroke or hospitalization for heart failure.
According to Dr. Tuttle, “There has been a lot of interest in the Mediterranean diet because epidemiological studies have shown that it is associated with lower rates of cardiovascular disease. We did not find even a suggestion of a difference between the two groups. The good news for patients is that either diet is a good choice.”
What Dr. Tuttle did not say is that the Mediterranean diet is more enjoyable and palatable than the low-fat alternative, which should increase the chance that people will stick to it.
We suspect that if the study had lasted longer, the Mediterranean group would have stuck to their diet longer and would have shown better overall health, since the Mediterranean-style diet is richer in vegetables and fish, and therefore higher in antioxidants and omega-3s, both of which possess anti-cancer properties.
- Tuttle KR et al. American Heart Association or Mediterranean Diet Improves Cardiovascular Outcomes After Myocardial Infarction Trial. Presentation Number 404-7, American College of Cardiology 56th Annual Scientific Session, Sunday, March 25, New Orleans, LA.