| Summary: | The long-term effects of total dietary protein and individual food sources of dietary protein on cardiometabolic risk are not clearly understood. The effects of the amount consumed and the timing of dietary protein intake as well as the contribution of overall dietary patterns on various cardiometabolic outcomes are largely unknown, particularly in children. The objective of this dissertation is to estimate the effects of patterns of dietary protein intake and egg consumption on cardiometabolic risk in adolescents and adults.
Prospective data from two studies were used: the National Growth and Health Study (NGHS) with 2105 pre-adolescent girls followed for 10 years and the Framingham Offspring Study (FOS) with 2054 middle-aged adults followed for 12 years. Diet was assessed in both cohorts via 3-day diet records. NGHS outcomes included %body fat, %truncal fat, waist circumference, body mass index, skeletal muscle mass (SMM), fasting glucose (FG), insulin resistance, blood pressure (BP), and lipids. FOS outcomes included FG and BP. Multivariable models including analysis of covariance, logistic regression, and Cox proportional hazards models were used.
Girls consuming ≥75 g/day of total protein (vs. less) had less body fat (p<0.0001) and more SMM (p<0.0001) by late adolescence. Girls consuming more morning protein had the highest total protein intakes, perhaps contributing to the observed beneficial effects of morning protein on body composition. Consumption of ≥3.5 eggs/week in 9-17 year-old girls was associated with lower %body fat (p=0.019) and higher %SMM (p=0.026) by later adolescence. There was no evidence that higher egg intake was detrimental to any cardiometabolic outcomes. Girls who consumed more eggs (ages 9-17 years) in combination with more fiber, fruits/vegetables, or physical activity led to statistically significant 43-58% reduced risks of becoming overweight by late adolescence. Adults who consumed ≥5 eggs/week had lower FG (p=0.0004) and systolic BP (p=0.0284) over time. Higher egg intakes were associated with a 27% lower risk of IFG or T2D (95% CI:0.51-1.04) and 30% lower risk of HBP (95% CI:0.52-0.96).
In summary, total protein intake, including regular egg consumption, has no adverse effects on cardiometabolic risk in adolescence or adults and may benefit body composition over time.
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