An article just published in the New England Journal of Medicine claims that a Mediterranean diet is much more effective than a "low-fat diet" in preventing cardiovascular disease. A careful reading of the study reveals that this is simply not true.
- The comparison (control) group did not follow a low-fat diet. As the authors wrote, "We acknowledge that, even though participants in the control group received advice to reduce fat intake, changes in total fat were small." This is not surprising, since they gave the control group virtually no support at all in following this diet during the first half of the study.
In the "low-fat" group, total fat consumption decreased insignificantly, from 39 percent to 37 percent (Table S7, appendix). This doesn't even come close to the American Heart Association guidelines of a low-fat diet (<30 percent fat) or ours for reversing heart disease (<10 percent fat).
So, they weren't comparing a Mediterranean diet to a low-fat diet, because the control group was not following a low-fat diet. And I'm not talking about a very low-fat diet that we found (with other nutritional and lifestyle changes) could reverse heart disease, but even a moderately low-fat diet.
The authors should have concluded that the Mediterranean diet reduced cardiovascular risk when compared to whatever diet they were eating before, not when compared to a low-fat diet, since patients in the control group ("low-fat diet") were not consuming a low-fat diet.
The authors might as well have concluded, "The Mediterranean diet reduced cardiovascular risk when compared to a randomized control group of patients who were asked to walk and chew gum at the same time" since they didn't do that, either.
- Also, the researchers appear to have done everything they could to bias the outcome in favor of the Mediterranean diet by encouraging the "low-fat" diet to increase consumption of foods that are known to increase the risk of cardiovascular disease, including bread, potatoes, pasta, and rice, and not to limit their intake of sodas (which also increase cardiovascular disease risk). See Table 1.
- The "low-fat" diet group patients were discouraged from eating fatty fish that are rich in omega‑3 fatty acids that are highly protective from cardiovascular disease. (In my program, we have recommended for decades that patients take 4 grams/day of fish oil or flax oil to provide the omega‑3 fatty acids.) See Table 1.
In contrast, both Mediterranean diet groups were consuming fatty fish such as salmon, which have significant omega‑3 fatty acids. Also, they were consuming either more walnuts and/or more olive oil, which have omega‑3 fatty acids. Because of this, the researchers found that omega‑3 fatty acid levels (alpha-linolenic acid) were significantly higher in both Mediterranean diet groups (Figure S5).
- There was no significant reduction in heart attacks (myocardial infarction), death from cardiovascular causes, or death from any cause. They only found a significant reduction in death from stroke (Table 3).
The authors wrote, "Only the comparison of stroke risk reached statistical significance." They only found a reduction in cardiovascular causes when these were pooled with deaths from stroke, because the reduction in strokes was sufficiently high that it "carried along" the average of the other conditions (Table 3).
In summary, the most responsible conclusion should be, "We found a significant reduction in stroke in those consuming a Mediterranean diet high in omega‑3 fatty acids when compared to those who were not making significant changes in their diet."
Over the past 36 years, my colleagues and I have published a series of randomized controlled trials showing that this diet can reverse the progression of even severe coronary heart disease and cause 2.5 times fewer cardiac events. Also, it can stop or reverse the progression of early-stage prostate cancer, improve gene expression, and increase telomerase.
For this reason, Medicare is covering "Dr. Dean Ornish's Program for Reversing Heart Disease" in sites that we've trained.
An optimal diet that I recommend for preventing and reversing heart disease is:
- Rich in fruits, vegetables, whole grains, legumes, and soy products in their natural, unrefined forms.
- Low in total fat (<10 percent fat), saturated fats, and trans fats.
- High in omega‑3 fatty acids (fish oil, flax oil, salmon).
- Low in refined carbohydrates such as sugar, white flour (bread, pasta), white rice, and sugar-sweetened beverages.
- Low in processed and refined foods.
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