A large study found that eating whole-grain foods such as cereal or dark bread was linked to a lower risk of heart failure.

by Judith Groch, Contributing Writer, MedPage Today
 

MINNEAPOLIS, Oct. 31 — Eggs and high-fat dairy products are on the menu for eventual heart failure and whole-grain cereals may help ward it off, found a large observational cohort study.

Action Points 
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Explain to patients who ask that eating whole-grain foods such as cereal or dark bread was linked to a lower risk of heart failure, whereas consuming eggs and high-fat dairy products, such as whole milk, cheese, and ice cream, was associated with an increased risk.

Explain that this study found an association but did not determine causality.

Using data from the Atherosclerosis Risk in Communities (ARIC) study, whole-grain foods such as cereals were associated with a 7% decrease in the risk of heart failure, Jennifer A. Nettleton, Ph.D., of the University of Minnesota (now at the University of Texas in Houston), and colleagues reported in the November issue of the Journal of the American Dietetic Association.

Whole-grain foods included oatmeal or grits, whole-grain cold cereal, and whole-grain or dark bread.

On the other hand, a greater intake of eggs in all forms — including omelets, egg salad, and quiche, but not egg substitutes — were associated with a 23% higher risk, and a greater consumption of high-fat dairy foods had an 8% higher risk. High-fat dairy foods included whole milk, cheese, and ice cream.

The investigators analyzed the relationship between incident heart failure (death or hospitalization) over 13 years and intake of seven food categories (whole grains, fruits and vegetables, fish, nuts, high-fat dairy products, eggs, and red meat).

The observational cohort included 14,153 African-American and white adults, ages 45 to 64, sampled from four U.S. communities.

Other food groups, such as fruits and vegetables, red meat or processed meat, fish, and nuts were not significantly associated with heart-failure risk after multivariable adjustment. Fish included seafood, dark-meat fish, tuna, other fish, while nuts also included peanut butter. Red meat included hamburger, meat in sandwiches and mixed dishes, hot dogs, sausage/salami, bacon, and liver.

Although studies have suggested that micronutrient supplementation can reduce symptoms and improve quality of life for heart failure patients, a more critical investigation is needed, including attention to foods rather than food components, the researchers said.

Although some reports indicate that changes in diet can reduce heart failure risk, there have been few large, prospective studies in diverse populations such as this, they said. Most studies have been conducted in white populations.

From baseline (1987-1989) to 1993-1995, dietary intake was measured by responses to a 66-item food-frequency questionnaire administered at baseline.

Thereafter, intake was based on averaged baseline and 1993-1995 responses. Hazard ratios (95% CI) for heart failure were calculated per one-daily serving difference in food group intake.

Frequency categories for the consumption of specific foods and beverages ranged from never or less than once a month, to six or more times a day. Standard portion sizes were used for estimates.

During a mean of 13 years, there were 1,140 heart failure hospitalizations.

After multivariable adjustment (energy intake, demographics, lifestyle factors, prevalent cardiovascular disease, diabetes, hypertension), heart failure risk was 7% lower with greater whole-grain intake (HR 0.93, 95% CI 0.87 to 0.99).

By contrast, the risk was 23% higher with greater intake of eggs (HR 1.23, 95% CI 1.08 to 1.41) and 8% higher with greater consumption of high-fat dairy foods (HR 1.08, 95% CI 1.01 to 1.16).

After adjustment for confounders, these associations remained significant, independent of intakes of the five other food categories, which were not significantly associated with heart failure.

These findings are consistent with other studies that have found whole-grain intake is associated with a lower risk of cardiovascular disease and hypertension, all factors related to heart failure risk, the investigators said. Also, they added, the Physicians’ Health Study found a positive association between egg consumption and heart failure risk, as corroborated in the current analysis.

It is possible, the researchers said, that although egg consumption (ranging from never to at least daily) was independent of the intake of other foods, egg consumption may simply be a marker for a larger dietary pattern that influences heart failure risk. Given the long history of debate regarding egg consumption, it is important that these observations be disentangled in studies to determine whether to recommend omitting eggs from the diet, the researchers said.

The positive association between high-fat dairy intake, namely saturated fat as the main component, and heart failure in this study has been fairly well established elsewhere as a cardiovascular disease risk.

The finding in this study that fish consumption did not lower the risk of incident heart failure might be explained by the fact that it is likely that a large proportion of the fish consumed was fried.

As for the value of fruits and vegetables in the diet, it is possible that life-long awareness of these diet-disease relationships among those at greater risk for heart failure may have interfered with finding true associations, the researchers said.

Study limitations included the need to rely on hospital discharge records and death certificates. Some questions assessing intake of grains included a combination of whole- and refined-grain foods (white rice, brown rice, and wild rice, for example).

The study used a strict definition of heart failure and thus did not take into account milder heart failure symptoms that did not result in hospitalization.

Furthermore, although confounding was carefully assessed, the possibility of residual confounding cannot be excluded. Dietary changes may have occurred secondary to heart failure symptoms, for example.

Lastly, the researchers said, these data indicate only an association. Randomized interventions are necessary to demonstrate causality and to understand potential mechanisms.

Overall, these data are consistent with traditional diet-cardiovascular disease hypotheses and support recent findings suggesting that greater whole-grain intake reduces heart failure risk while greater intake of eggs and high-fat dairy products increases heart failure risk, the researchers said.

Although the risk estimates were modest, most of the literature suggests that it would be prudent to recommend that those at high risk of heart failure increase their intake of whole grains and reduce their intake of high-fat diary products and eggs, along with following other healthful dietary practices consistent with those recommended by the American Heart Association, the investigators concluded.

This research was supported by the National Institutes of Health and the National Heart, Lung, and Blood Institute. The authors had no conflicts of interest to report.


Primary source: Journal of the American Dietetic Association

Source reference: Nettleton JA, et al “Incident Heart Failure Is Associated with Lower Whole-Grain Intake and Greater High-Fat Dairy and Egg Intake in the Atherosclerosis Risk in Communities (ARIC) Study” J Am Diet Assoc 2008; 108: 1881-1887.

Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston.

Published: October 31, 2008

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