Researchers at the Harvard School of Public Health, led by Dr. Hongyu Wu, investigated the relationship between consumption of whole grains and risk of death from any cause, from cardiovascular disease, and from cancer. They used data from two large prospective studies the Nurses Health Study and the Health Professional Follow-up Study both of which are run by Harvard. In all, they examined data from over 74,000 women and nearly 44,000 men. At the start of both studies participants were free of both cancer and cardiovascular disease (CVD). Participants in both studies completed questionnaires about their diets every 2 or 4 years for the course of their studies (from the mid-1980s until 2010).
The investigators found that there was a significant trend toward a reduced risk of total overall risk of death and death from CVD as reported whole grain consumption rose, but that the same wasn t true for death from cancer. In particular, consumption of bran (the outer portion of a whole grain) seemed to be the most important part of the grain with respect to a decreased risk of death.
ACSH s Dr. Ruth Kava commented, While we at ACSH would encourage the consumption of whole grains, we must also point out that in this type of study finding a significant association does not mean that there is a causal relationship. That is, while there is an association between whole grain consumption and longer life, that doesn t mean that it was the whole grains that caused the decreased mortality. Also, these results depend on intermittent reporting of dietary intake, which is known to not be totally accurate. So while whole grains can provide many important nutrients as well as fiber, they do not, based on these data, decrease the risk of death from CVD or overall mortality.
ACSH s Dr. Gil Ross added this: My concern with making such a leap is summarized in the study s abstract: We documented 26 920 deaths during 2 727 006 person-years of follow-up. After multivariate adjustment for potential confounders, including age, smoking, body mass index, physical activity, and modified Alternate Healthy Eating Index score, higher whole grain intake was associated with lower total and CVD mortality but not cancer mortality... Listen, it s impossible to control for all those covariates in such a huge study, dependent on the participants own notations and recall. Moreover, even if this observed effect is true, it s just as likely that those consuming more whole grains had other healthier behaviors not so easily measured. So while we here at ACSH are fine with Americans adding an ounce of whole grains to their diets, I wouldn t do so with an expectation of healthy aging to age 100.