Dietary Grains and Heart/Stroke Mortality

Dietary intake of whole grains and fiber shows consistent beneficial effects on a variety of health and mortality measures.

In a post in 2011, I reviewed study results from the NIH-AARP cohort. That study reported reduced cardiovascular disease but not cancer in men and women with the highest fiber intake.

A recent Harvard University study examined mortality risk in a group of U.S. health professionals grouped by level of whole grain intake.

Participants in this study were over 118,000 men and women from the Health Professionals Follow-Up Study and the Nurses' Health Study.

Participants completed dietary questionnaires every two to four years over the course of the study. Each participant had an estimated daily grain consumption level calculated from dry weight whole grain intake of rice, bread, pasta and breakfast cereals.

Participants were grouped into quintiles (5 groups each containing 20% of the sample) from lowest to highest whole grain intake. Mean levels of whole grain daily intake in three of the five quintiles for women/women were reported:

• Lowest (g/day): 4.2/5.9
• Low: 9.7/14.4
• Middle: 14.7/22.1
• High: 21.1/31.3
• Highest: 33.0/47.8

The study team follow participants for death using next of kin, postal information and the National Death Index.

Death certificate and medical record information was used to assign deaths into cardiovascular deaths (including myocardial infarction and stroke), cancer or other categories.

During the follow-up period of 26 years, 15,106 deaths were identified with 2989 assigned to the cardiovascular disease death group, 5964 assigned to cancer and 6,153 assigned to other causes.

Analysis of the rates of heart/stroke death rates by whole grain intake showed a consistent finding in men and women.

Those in the highest whole grain intake group had about a 15% reduction in rates of heart/stroke deaths during the follow-up period (see chart left).

Additionally, total mortality was about 8% over the follow-up period in the highest whole grain intake group.

This estimate controlled for potential confounding variables such as age, BMI, smoking status, physical activity and aspirin use.

Getting to the high or higher quintile group status takes between two and three daily servings of whole wheat, whole oats, whole cornmeal, whole rye, brown rice, popcorn or bran additive.

One concern with whole grains is the carbohydrate levels. Individuals on a low carbohydrate diet may find a big portion of their daily carbohydrate limit is taken up with two or three portions of whole grain. Using bran additives, like All-Bran Buds may reduce the carbohydrate load associated with whole grains.

The authors note their findings are consistent with several other studies linking whole grain intake to lower heart/stroke death risk. Additionally they note their findings support federal guidelines urging daily whole grain intake.

This is an important study due to the large sample size, ability to examine effects in both men and women and the quality of dietary and mortality data.

Photo of blue jay is from the author's files.

Chart was an original chart made by author using data from the manuscript.

Follow the author on Twitter WRY999.

Wu H, Flint AJ, Qi Q, van Dam RM, Sampson LA, Rimm EB, Holmes MD, Willett WC, Hu FB, & Sun Q (2015). Association Between Dietary Whole Grain Intake and Risk of Mortality: Two Large Prospective Studies in US Men and Women. JAMA internal medicine PMID: 25559238