Biology: February 2008 Archives


February 9, 2008

Lutsey, Steffen, and Stevens report study of dietary intake and "metabolic syndrom" (MetSyn), described as "a cluster of cardiovascular risk factor abnormalities associated with increased risk of type 2 diabetes mellitus, cardiovascular disease, and all-cause mortality." Here's what they found:
Background--The role of diet in the origin of metabolic syndrome (MetSyn) is not well understood; thus, we sought to evaluate the relationship between incident MetSyn and dietary intake using prospective data from 9514 participants (age, 45 to 64 years) enrolled in the Atherosclerosis Risk in Communities (ARIC) study.

Methods and Results--Dietary intake was assessed at baseline via a 66-item food frequency questionnaire. We used principal-components analysis to derive "Western" and "prudent" dietary patterns from 32 food groups and evaluated 10 food groups used in previous studies of the ARIC cohort. MetSyn was defined by American Heart Association guidelines. Proportional-hazards regression was used. Over 9 years of follow-up, 3782 incident cases of MetSyn were identified. After adjustment for demographic factors, smoking, physical activity, and energy intake, consumption of a Western dietary pattern (Ptrend=0.03) was adversely associated with incident MetSyn. After further adjustment for intake of meat, dairy, fruits and vegetables, refined grains, and whole grains, analysis of individual food groups revealed that meat (Ptrend<0.001), fried foods (Ptrend=0.02), and diet soda (Ptrend=< 0.001) also were adversely associated with incident MetSyn, whereas dairy consumption (Ptrend=0.006) was beneficial. No associations were observed between incident MetSyn and a prudent dietary pattern or intakes of whole grains, refined grains, fruits and vegetables, nuts, coffee, or sweetened beverages.

Conclusions--These prospective findings suggest that consumption of a Western dietary pattern, meat, and fried foods promotes the incidence of MetSyn, whereas dairy consumption provides some protection. The diet soda association was not hypothesized and deserves further study.

(Full article behind a paywall, but I have sources).

So, working through the actual analysis, it looks like what they did was cut the level of consumption of each pattern or individual food group into quintiles and then compare the relative risks in each quintile. So, for instance, the highest quintile of the Western diet has an 18% (1.03 - 1.37) higher risk of MetSyn than the lowest quintile. At some level, this is good news if you tend to eat an "unhealthy" diet. An 18% increased risk really isn't that much, and you might well be willing to absorb it in order to keep eating stuff you like all the time, especially because the second quartile has a 13% increased risk, so you'd need to make pretty dramatic changes in order to see much improvement.

One question I'm having trouble extracting here is the extent to which the effect of the "Western Diet" is dominated by consumption of meat and fried foods (the only factors tha are significant in this model.) It's certainly possible that you could get away with eating all the sugar you wanted as long as you stayed off the chicken fried steak. On the other hand, it doesn't look like eating your vegetables helps at all.

The other result that's gotten a lot of press here is the association between diet soda consumption and MetSyn (34% in the highest tertile). As the authors say, it's hard to know if this is a cause or an effect, and needs some more study.