There has been quite a bit of buzz recently over a study out of Harvard1 looking at the relationships between eating patterns and coronary heart disease (CHD) risk. Researchers analyzed data from the Health Professionals Follow-up Study, one of the largest prospective cohort studies (51,529 male health professionals) initiated back in 1986 when these men were between 40 and 75 years of age. Participants have been evaluated at regular intervals since then, resulting in a plethora of data on disease incidence, dietary habits, and mortality. From these data, researchers analyzed associations between eating habits, specifically if and when meals were consumed, and development of CHD.
There were several interesting findings from this analysis. For example, men who ate late at night had a 55% higher risk of CHD than men who did not eat late at night. Further, there was no difference in CHD risk in men who ate 1 to 2 times a day versus men who ate ≥6 times a day. But the media focused on only one finding, that skipping breakfast was associated with a 27% greater risk of CHD. And the resultant headlines used more riveting language such as, “skipping breakfast causes heart attacks”.
But a closer look at the data suggests that it may not be a very simple relationship. In fact, it’s never quite so simple when it comes to these prospective cohort studies. For example, men who did not report eating breakfast were more likely to exhibit unfavorable diet and lifestyle habits, such as smoking, being less physically active, and drinking more alcohol. Although these factors were included and adjusted for in the statistical models, there may be other potentially important lifestyle factors which were not assessed or assessed inadequately that may influence the relationship between breakfast eating and CHD risk.
Men who did not report eating breakfast were also more likely, albeit slightly, to have high cholesterol, high blood pressure, and a higher body mass index. Once these conditions were accounted for in the statistical models, there was no longer an association between skipping breakfast and incident CHD. How strong is the relationship between breakfast eating and risk of heart disease when you can completely attenuate the effect by adjusting for known mediators of CHD?
That’s not to say that this isn’t an important piece of the puzzle for understanding the impact of eating behaviors on disease risk. In fact, this new observational evidence dovetails nicely with findings from randomized, controlled trials showing favorable effects of breakfast eating on CHD risk factors2,3. Plus, eating breakfast, particularly one rich in nutrient-dense food choices, has been shown to impart other benefits, as reviewed in this recent blog. However like all observational evidence, results are merely associations and should be interpreted in this context before jumping to conclusions about breakfast skipping causing heart attacks.
1. Cahill LE, Chiuve SE, Mekary RA, Jensen MK, Flint AJ, Hu FB, Rimm EB. Prospective Study of Breakfast Eating and Incident Coronary Heart Disease in a Cohort of Male US Health Professionals. Circulation. 2013;128:337-43.
2. Farshchi HR, Taylor MA, Macdonald IA. Deleterious effects of omitting breakfast on insulin sensitivity and fasting lipid profiles in healthy lean women. Am J Clin Nutr. 2005;81:388-96.
3. Astbury NM, Taylor MA, Macdonald IA. Breakfast consumption affects appetite, energy intake, and the metabolic and endocrine responses to foods consumed later in the day in male habitual breakfast eaters. J Nutr. 2011;141:1381-9.