These Canadian authors conducted a systematic review of prospective cohort studies or randomized trials investigating dietary exposures in relation to CHD. They used the Bradford Hill guidelines to derive a causation score based on 4 criteria (strength, consistency, temporality, and coherence) for each dietary exposure and examined for consistency of cohort studies with the findings of randomized trials.
They found: "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."
The authors concluded: "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."
Family physicians can confidently recommend vegetables, nuts, and Mediterranean diet to reduce risk of heart disease.
For the full abstract, click here.
Arch Intern Med 169(7):659-669, 13 April 2009 © 2009 to the American Medical Association
A Systematic Review of the Evidence Supporting a Causal Link Between Dietary Factors and Coronary Heart Disease. Andrew Mente, Lawrence de Koning, Harry S. Shannon, Sonia S. Anand. Correspondence to: Dr. Anand: anands@mcmaster.ca
Category: T. Endocrine/Metabolic/Nutritional, K. Circulatory. Keywords: diet, coronary heart disease, CHD, vegetables, nuts, Mediterranean diet, trans-fatty acids, glycemic index, fish, marine-3 fatty acids, folate, whole grains, dietary vitamins E and C, beta carotene, alcohol, fruit, fiber, systematic review of cohort studies and randomized trials, journal watch.
Synopsis edited by Dr Linda French, Toledo, Ohio. Posted on Global Family Doctor 21 April 2009
