Donnan MS, Heath DD, Flatt SW, PakizB, Quintana EL, Rana BK, Natarajan L and Rock CL
Objective: The objective of this study was to assess factors associated with plasma α-, β-, γ-, and δ-tocopherol in obese women and to examine change in tocopherol levels after a 1-year weight loss intervention across three dietary approaches. Factors examined were dietary factors (alcohol consumption, diet composition, and supplement use) and non-dietary factors (body mass index, physical activity, plasma cholesterol levels, waist circumference, and age).
Methods: Overweight/obese, nondiabetic women were randomly assigned to one of three diets: lower carbohydrate (45% energy), higher fat (35% energy), lower fat (20% energy), higher carbohydrate (65% energy), or walnut-rich (18% energy), higher fat (35% energy), lower carbohydrate (45% energy). Data and blood samples were obtained at baseline, 6- and 12-month clinic visits (n=245, 213, and 194 respectively).
Results: At baseline, age was directly related to plasma α-tocopherol and inversely related to γ- and δ-tocopherol (P<0.05 for each); body mass index was inversely associated with plasma α-tocopherol and positively associated with β-, γ- and δ-tocopherol (P<0.05 for each). Physical activity was directly associated with α-tocopherol at baseline (P<0.05) and inversely associated with β-tocopherol at 12 months (P=0.03). Dietary supplement use was positively associated with α-tocopherol at baseline (P<0.05) and 12 months (P=0.007), and negatively associated with 12- month γ-tocopherol (P=0.02). Plasma cholesterol was positively associated with 12-month α- (P<0.001), β- (P=0.003), and γ-tocopherol (P=0.007). The walnut-rich diet group had higher plasma γ-tocopherol concentration than other diet groups at 12 months (P=0.002).
Conclusions: Plasma tocopherol levels generally declined in association with weight loss in obese women, although age, adiposity, physical activity, plasma cholesterol, and dietary supplement use influenced these levels. Responses were similar to lower carbohydrate and lower fat diets, and walnut prescription minimized the reduction in plasma γ-tocopherol.
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