Of the 3799 Offspring cohort members who attended the 5th examination, baseline for the present analysis, 346 individuals who had diabetes were excluded. In addition, participants who were missing data on diet (n = 333) or age, BMI, or smoking status (n = 16) at the 5th study examination and participants who were missing dietary data at baseline or 2 consecutive follow-up examinations prior to diagnosis of T2D or the end of follow-up (n = 189) were excluded. The time-dependent analysis using cumulative mean flavonoid intake was based on 2915 participants with 308 events during a mean follow-up period of 11.9 y (range 2.5–16.8 y).
displays the median and 25th and 75th percentile values for intake of the different flavonoid classes (mg/d). Total flavonoid intakes increased modestly over time, driven largely by increased intakes of anthocyanins and polymeric flavonoids. There was a wide range of intakes for all flavonoid classes. This can be seen using the ratio of the 75th and 25th percentile values for the different flavonoid classes. This ratio ranged from 2.3-fold for flavonol intake at the 7th examination to 5.8-fold for flavanone intake at the 5th examination. These data indicate that the flavonoid intakes for the quarter of the population with the highest intakes exceeded the intake of those in the lowest quarter of the population by at least 2.3-fold for all flavonoid classes.
The mean age at baseline was 54 y old and participants were on average overweight (). Men constituted 46% of the sample, 19% of the sample were current smokers, and ~7% had existing CVD. There were strong associations between many of participants’ characteristics and lifestyle behaviors and total flavonoid intakes. Men were much less likely to consume higher amounts of total flavonoid than were women (P-trend < 0.001). There was a modest increase in intakes with age (P-trend = 0.05) and a decrease in intakes with increasing BMI (P-trend < 0.001). Participants who were smokers and who had CVD were less likely to have higher flavonoid intakes (P-trend < 0.001 and 0.005, respectively). Energy, fruit, vegetable, fiber, potassium, and magnesium intakes were positively associated with flavonoid intakes (P-trend < 0.001), whereas meat and processed meat intakes were inversely associated with flavonoid intakes (P-trend = 0.004 and < 0.001, respectively). Age- and sex-adjusted total flavonoid intake, based on only baseline values, was inversely associated with cumulative incidence of T2D (P-trend = 0.08).
Participant characteristics of members of the Framingham Heart Study Offspring cohort across quartile categories of total flavonoid intake at baseline (5th examination)1
In multivariable-adjusted analyses, we observed a significant inverse association between flavonol intakes and T2D incidence (). These time-dependent analyses, which accounted for long-term flavonoid intake during the follow-up period, demonstrated that a 2.5-fold higher intake of flavonols was association with a 26% lower incidence of T2D [HR = 0.74 (95% CI: 0.61, 0.90); P-trend = 0.003]. We also observed a marginally significant inverse association between flavan-3-ol intake and T2D risk after multivariable adjustment [HR = 0.89 (95% CI: 0.80, 1.00); P-trend = 0.06). No other associations between intakes of other flavonoid classes or total flavonoids and risk of T2D were observed after multivariable adjustment. Further adjustment for fruit and vegetable intakes resulted in a slightly stronger association between flavonols and T2D incidence [HR = 0.68 (95% CI: 0.54, 0.86); P-trend = 0.001] but did not materially alter any of the relationships between other flavonoids and T2D risk.
Relation between cumulative mean flavonoid intake and diabetes incidence in members of the Framingham Heart Study Offspring cohort: time-dependent analyses1
In secondary analyses, we adjusted the flavonol intakes for intakes of all the other flavonoid classes and total flavonoids. The relation between flavonol intake and T2D incidence was unchanged by this adjustment, but the associations with flavan-3-ols, polymeric flavonoids, and total flavonoids were all attenuated after they were adjusted for flavonol intake. We also adjusted for dietary fiber, potassium, magnesium, meat and processed meat intakes, which had no effect on the association between flavonol intake and T2D risk. Similarly, further adjustment for dietary fiber and potassium did not affect the observed association between flavan-3-ol intake and T2D, but adjustment for meat and processed meat [HR = 0.91 (95% CI: 0.81, 1.02); P-trend = 0.11] and magnesium [HR = 0.92 (95% CI: 0.82, 1.03); P-trend = 0.15] intakes did attenuate this association. Finally, additional adjustment for waist circumference and physical activity did not materially affect our findings.
We identified the foods that were the top contributors to each of the flavonoid classes (). Based on the observed associations between flavonols and flavan-3-ols, we examined the associations between the foods that were the major contributors of these flavonoid classes and T2D incidence. Tea and apples/pears, the only foods contributing ≥10% of the total flavonol intake, together contributed ~30% of the flavonol intake. Tea, apples/pears, and bananas, the 3 foods that contributed ≥10% of the total flavan-3-ol intake, combined accounted for just more than 50% of flavan-3-ol intake in this population. None of these foods was individually associated with T2D risk ().
Mean contributions of flavonoids from foods providing at least 10% of the total intake for each flavonoid class at one or more examination cycles for members of the Framingham Heart Study Offspring cohort
Relation between cumulative mean food intake and diabetes incidence in members of the Framingham Heart Study Offspring cohort: time-dependent analyses