As shown in Table 4, sufficient support from RCTs to satisfy the criterion for experimental evidence is observed only for marine or total ω-3 fatty acid intake and a Mediterranean dietary pattern. Little or weak evidence from RCTs is found for consumption of fruits, vegetables, fish, fiber, polyunsaturated fatty acids, and total fat and supplemental intake of beta carotene, vitamin E, ascorbic acid, and folate. Other factors have not been evaluated singly in clinical trials (Table 4). The evidence from RCTs agrees with the Bradford Hill results from cohort studies for intake of ascorbic acid and vitamin E supplements, polyunsaturated fatty acids, and total fats and a Mediterranean dietary pattern, but disagree for fish consumption, which shows moderate evidence of a causal link with CHD in cohort studies but virtually no effect in RCTs.Covered elsewhere:
Eating a Mediterranean diet rich in vegetables and nuts does help protect the heart, a new review concludes.Related:
"We took this on because there is a lot of confusion out in the public about what we should eat and what we should avoid eating in terms of preventing a heart attack," study co-author Dr. Sonia Anand of McMaster University in Hamilton, Ont., told CBC News on Tuesday.
"So the good thing is, we can say try and eat more like someone who would live in Greece or Italy, the Mediterranean diet, and try and avoid a Western-type of diet, which is your eggs and bacon breakfast or your hot dogs for lunch."
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A Systematic Review of the Evidence Supporting a Causal Link Between Dietary Factors and Coronary Heart Disease
Background Although a wealth of literature links dietary factors and coronary heart disease (CHD), the strength of the evidence supporting valid associations has not been evaluated systematically in a single investigation.
Methods We conducted a systematic search of MEDLINE for prospective cohort studies or randomized trials investigating dietary exposures in relation to CHD. We used the Bradford Hill guidelines to derive a causation score based on 4 criteria (strength, consistency, temporality, and coherence) for each dietary exposure in cohort studies and examined for consistency with the findings of randomized trials.
Results Strong evidence supports valid associations (4 criteria satisfied) of protective factors, including intake of vegetables, nuts, and "Mediterranean" and high-quality dietary patterns with CHD, and associations of harmful factors, including intake of trans–fatty acids and foods with a high glycemic index or load. Among studies of higher methodologic quality, there was also strong evidence for monounsaturated fatty acids and "prudent" and "western" dietary patterns. Moderate evidence (3 criteria) of associations exists for intake of fish, marine -3 fatty acids, folate, whole grains, dietary vitamins E and C, beta carotene, alcohol, fruit, and fiber. Insufficient evidence (2 criteria) of association is present for intake of supplementary vitamin E and ascorbic acid (vitamin C); saturated and polyunsaturated fatty acids; total fat; -linolenic acid; meat; eggs; and milk. Among the dietary exposures with strong evidence of causation from cohort studies, only a Mediterranean dietary pattern is related to CHD in randomized trials.Conclusions The evidence supports a valid association of a limited number of dietary factors and dietary patterns with CHD. Future evaluation of dietary patterns, including their nutrient and food components, in cohort studies and randomized trials is recommended.