Bmj Usa: Editorial

What is the optimal diet for cardiovascular health?

BMJ 2003; 327 doi: https://doi.org/10.1136/bmjusa.01050002 (Published 19 November 2003) Cite this as: BMJ 2003;327:E31
  1. Thomas E. Kottke, Professor of Medicine (thomas.kottke{at}mayo.edu)
  1. Mayo Clinic and Foundation, Project Director, CardioVision 2020, Rochester, Minnesota 55905, USA

    Fruits, vegetables, grains, and fish should be advised for everyone over a lifetime

    This article originally appeared in BMJ USA

    After 25 years of follow-up in the Seven Countries Study, death rates from coronary heart disease (CHD) ranged from 268 per 1000 in East Finland to 25 per 1000 in Crete, Greece.1 This difference is one order of magnitude, and more than 90% of the variance across cohorts is attributable to differences in consumption of saturated fat. A systematic review of randomized controlled trials, published in this issue of BMJ USA, contributes to the evidence that the association between a low-fat diet and low death rates from CHD is causal.2 To take the next step and apply this information to practice, we need to answer four questions:

    • What diet should we recommend?

    • For how long should the diet be followed?

    • To whom do we recommend the diet?

    • How do we best promote adherence?

    What diet should we recommend?

    Among the Seven Countries Study cohorts, consumption of dairy products was high in Northern Europe; meat consumption was high in the US; large amounts of vegetables, legumes, fish, and wine were the fare in Southern Europe; and the Japanese cohorts consumed mostly cereals, soy products, and fish. Animal food-groups were directly correlated with CHD mortality; with the exception of potatoes, vegetable food-groups, fish, and alcohol were inversely correlated with CHD mortality. Three variables (butter, lard and margarine, and meat) explained 92% of the variance in deaths from CHD. Consumption of fish high in omega 3 fatty acids (for example, salmon, albacore tuna, and mackerel) was associated with low CHD mortality.3

    How long does the diet need to be followed?

    In randomized clinical trials of low-fat diets, there is a positive association between time in trial and trial effect: Among the trials lasting longer than two years, the interventions are associated with reductions in cardiovascular events as large as 24%.2 This explains why the rate ratios are near unity for the relatively short randomized trials and greater than 10 for the life-long nutrition patterns of the Seven Countries Study.

    To whom do we recommend the diet?

    The answers to this question and the next—“How do we promote adherence?”—are closely related. Even though coronary heart disease is the leading cause of death for both American men and women, it is difficult to predict who will die from coronary heart disease and when they will die. But large reductions in population event rates can be achieved without precisely classifying the risk of individuals.4 Finland is an excellent case study of the effect of population-wide dietary change.5

    Coronary heart disease mortality declined in Finland by 55% among men and 68% among women between 1972 and 1992.5 About three-quarters of this decline has been explained by changes in smoking, blood pressure, and serum cholesterol levels. The greatest portion of the decline has been attributed to the decrease in serum cholesterol. The total fat content of the Finnish diet changed from 38% of energy to 34%, saturated fat from 21% to 16%, and polyunsaturated fat from 3% to 5%; intake of cholesterol decreased by 16%. Fruit and vegetable consumption increased two- to three-fold during this time period. Based on the Keys equation, the changes in diet explain the entire decline in serum cholesterol levels (38 mg/dl) over the 20-year period.

    It goes almost without saying that food preferences are socially determined. Even so, population-wide consumption patterns can change rapidly

    How do we best promote adherence?

    It goes almost without saying that food preferences are socially determined. Even so, population-wide consumption patterns can change rapidly. Publicity about the link between cholesterol and heart disease, combined with news from several trials that tested whether the risk of heart disease could be reduced through cholesterol lowering,6 helped lower fat consumption significantly in both American men and women between 1960 and 1990.7

    In may seem paradoxical that it appears possible to create larger changes in cholesterol levels in entire populations than in selected individuals undergoing intense intervention. However, in the Multiple Risk Factor Intervention Trial (MRFIT), mean serum cholesterol in the intervention group declined only from 240.3 mg/dl at baseline to 228.2 mg/dl at 72 months (a 5% decrease) despite intensive counseling.8 In North Karelia, Finland, serum cholesterol declined by 19% over the 25-year period from 1972 to 1997.9 One problem with trying to change risk factor levels in a small group of selected individuals is that the remaining population acts as an attractive model of the behaviors to avoid.

    Putting it all together

    The evidence from trials, cohorts, and international comparisons indicates that the diet of choice for the prevention of CHD is based on fruits, vegetables, and whole grains, with a minimal amount of animal fats. Fish that is high in omega 3 fatty acids (for example, salmon, albacore tuna, and mackerel) provides additional benefits. While there is a negative correlation between alcohol consumption and coronary heart disease, caution in recommending alcohol consumption is warranted in the absence of trial data.10 This is the diet that we are recommending life long to all residents of Olmsted County, Minnesota.11

    http://www.bmj.com/cgi/content/full/322/7289/757

    Acknowledgments

    Papers BMJ USA p 233

    References

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