cardiovascular diseases | MY SPECIAL DOCTOR

Celebrated for about two decades as an extraordinary means of preventing cardiovascular disease (to the point of being prescribed as a true prophylactic therapy after a heart attack) and as a potential defense against several types of cancer, in recent months the role of the omega-3 is seeing substantial retrenchment on both fronts.

After the results of the study ASCEND (A Study of Cardiovascular Events in Diabetes.) published during 2018, had questioned the real utility of these essential fatty acids as protection against acute cardiovascular events in people with diabetes, the findings of the double-blind randomized controlled trial VITAL (Vitamin D Omega-3 Trial), recently published in the New England Journal of Medicine, deal a further blow to their use for preventive purposes in the general population, which lacks specific risk factors.

Contrary to past inferences from observational studies, which seemed to indicate a lower incidence of cardiovascular disease and cancer among people who consumed larger amounts of fatty fish from the North Seas (salmon, mackerel, tuna, herring, sardines, etc.) known to be rich in omega-3, fish oil or targeted supplements, the results of the VITAL study showed no difference in incidence for either group of diseases between those taking omega-3 (at a dosage of 1 mg/day) and vitamin D3 (at a dosage of 2,000 IU/day) and those taking preparations similar in appearance but completely inert biologically (placebo).

Even deepening the analysis and focusing on individual aspects, supplementation with omega-3 and vitamin D3 resulted in effects entirely superimposed on placebo, with comparable rates of overall cardiovascular events, stroke, death from cardiovascular causes, death from oncological causes, and death from all causes. The only favorable data concerned myocardial infarction rates, which were slightly lower among those taking omega-3, and side effects, which were similar for omega-3 and placebo (indicative of the harmlessness and good tolerability of supplementation, but not sufficient to justify its use).

But how is it possible that what seemed useful until yesterday is no longer useful today? As mentioned, until now, the benefits associated with omega-3 supplementation for primary prevention had been highlighted mainly in observational studies, that is, comparing the incidence of cardiovascular disease and cancer in populations that were or were not taking these essential fatty acids for various reasons, but without prior patient selection criteria or standardization of administration for timing, mode and dosage.

Studies of this kind can provide insights into the potential effects of a substance or drug in the body, which must, however, be confirmed in the context of double-blind randomized controlled trials, in which two groups of patients with overlapping characteristics and exposed to comparable conditions are randomly assigned to take either the active treatment or the inactive placebo and monitored for a predefined period of time. Only such studies, such as the VITAL study, can provide reliable information about the effects of a drug or other preventive or therapeutic intervention.

The outcomes of the VITAL study deserve special attention because they were obtained on a very large population (nearly 26 thousand people) and of different ethnicities (although all of them are residents of the United States), being, therefore, decidedly robust.

On the other hand, the new data are not inconsistent with those obtained in the late 1990s as part of the GISSI – Prevention study, conducted by the Italian Group for the Study of Survival in Myocardial Infarction. This “landmark” trial had, in fact, clearly demonstrated the preventive benefits of omega-3 supplementation in patients who had already had a first heart attack and were, therefore, at increased risk of experiencing a second one (secondary prevention).

Source

Manson JE et al. Marine n-3 Fatty Acids and Prevention of Cardiovascular Disease and Cancer. N Engl J Med 2019;380:23-32
Keaney JF, Rosen CJ. VITAL Signs for Dietary Supplementation to Prevent Cancer and Heart Disease. N Engl J Med 2019;380:91-92
Italian Group for the Study of Survival in Myocardial Infarction. Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. Lancet 1999;354(9177):447-55.

Walnuts, hazelnuts, almonds, and pistachios contain high amounts of omega-3 and omega-6 series polyunsaturated fatty acids, which countless studies have shown to be valuable allies of cardiovascular health and nervous system function, to the point of recommending targeted supplementation in situations of deficiency (insufficient dietary intake) or increased need (for example, in pregnancy or after an acute cardiovascular event). Although recent reviews of the scientific literature have, in part, cast doubt on the ability of some of these essential fatty acids to help prevent heart attack and other cardiovascular diseases, a large body of evidence suggests that these compounds are beneficial to human health at various levels. Among the most recent evidence supporting the benefits of their regular dietary intake are those provided by research presented at the European Society of Cardiology Congress (ESC 2019), held in Paris from Aug. 31 to Sept. 4. Specifically, the study monitored the incidence of cardiovascular disease (myocardial infarction, unstable angina, and sudden cardiac death), stroke, cardiovascular mortality, and all-cause mortality in a cohort of more than 5,400 healthy people over the age of 35 followed for a period of 13 years, in relation to the extent and frequency of nut consumption. The evaluation found that people who habitually consumed larger amounts of walnuts, hazelnuts, pistachios, and almonds were less likely to experience cardiovascular events and to die from cardiovascular or other causes. After repeating the analysis taking into account potentially confounding factors such as age, sex, smoking, educational attainment, level of physical activity, place of residence (rural or urban setting), family history and individual risk of cardiovascular disease, etc., the favorable effect of nut consumption zeroed out in terms of reduced risk of cardiovascular disease and all-cause mortality, but remained significant for cardiovascular mortality. More specifically, the study indicated that, compared with those who consumed little or no nuts, those who consumed at least two servings per week (equal to about 3-5 nuts each) had a 17% lower risk of mortality from cardiovascular causes: a value that corresponds to protection comparable to that offered by many drug treatments specifically designed for this purpose, but completely free of side effects. Since nuts contain not only omega-3 and omega-6 essential fatty acids, but also vitamins, antioxidant compounds, phytosterols, minerals and other micronutrients that are potentially beneficial to the body, on the basis of this study it is not possible to assign a precise protective role to any single element or to provide guidance for specific supplementation. What does seem clear, however, is that munching on a few walnuts, almonds or pistachios as snacks throughout the day or adding them to salads or other dishes can benefit your health as well as your palate. The only caveat is not to overdo the quantities, since nuts are quite caloric (about 550-650 kcal per 100 g), and to prefer “fresh” or freshly dried/toasted ones, but not salted or sweetened, to avoid seeing blood pressure and blood sugar rise, wiping out the potential cardiometabolic benefit.

Sources:

– Mohammadifard N et al. Nut consumption, the risk of cardiovascular disease and all-cause mortality: Isfahan Cohort Study. ESC 2019; Abstract 46

– Piepoli MF, Hoes AW, Agewall S, et al. 2016 European Guidelines on cardiovascular disease prevention in clinical practice. Eur Heart J 2016;37:2315-2381.

Photo by Daria Rudyk on Unsplash

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