Dietary magnesium and fiber intakes and inflammatory and metabolic indicators in middle-aged subjects from a population-based cohort.

BACKGROUND: Type 2 diabetes (DM), metabolic syndrome (MetS), and inflammation are linked to reduced magnesium and fiber intakes; these associations are attenuated by adjustment for each of these nutrients.
OBJECTIVE: We investigated the association among magnesium and fiber intakes, metabolic variables, and high-sensitivity C-reactive protein (hs-CRP) values.
DESIGN: Cross-sectional analyses were performed in a representative cohort of 1653 adults and in a subgroup with normal body mass index without dysmetabolisms (n = 205). A validated semiquantitative food-frequency questionnaire was used; magnesium intake was computed by multiplying its content in each food by the frequency of food consumption.
RESULTS: The prevalence of DM, MetS, and hs-CRP >/= 3 mg/L significantly decreased from the lowest to the highest tertile of magnesium and fiber intakes. Subjects within the lowest tertiles of magnesium and fiber intakes were 3-4 times as likely to have DM, MetS, and hs-CRP >/= 3 mg/L, after multiple adjustments. After the analysis was additionally controlled for fiber intake, associations with hs-CRP >/= 3 mg/L proved to be significant (odds ratio: 2.05; 95% CI: 1.30, 3.25), whereas reduced magnesium intake and DM and MetS were no longer significant. The lowest tertile of fiber intake remained associated with DM, hs-CRP >/= 3 mg/L, and MetS after adjustments for multiple confounders and magnesium intake. In the lean, healthy subject subgroup, hs-CRP values were inversely associated with magnesium and fiber intakes in a multivariate model (P < 0.001).
CONCLUSIONS: Reduced fiber intake was significantly associated with metabolic abnormalities; the magnesium effect might be confounded by fiber being in foods that also provided magnesium. Lower magnesium and fiber intakes were linked to hs-CRP >/= 3 mg/L in both the entire cohort and healthy persons.