Plasma carotenoids, tocopherols, and antioxidant capacity in a 12-week intervention study to reduce fat and/or energy intakes.

OBJECTIVE: We examined plasma levels of carotenoids, tocopherols, and total antioxidant activity in women before and after dietary intervention to reduce fat and/or energy intakes. Dietary fat and energy may affect intake and bioavailability of carotenoids and tocopherols, and these micronutrient levels in turn can contribute to the antioxidant capacity of plasma. METHODS: Women were randomized onto one of four diets for 12 wk: non-intervention, low fat (15% of energy from fat with maintenance of energy intake), low energy (25% energy reduction with maintenance of percentage of energy from fat), and combined low fat and low energy. Fasting plasma was available for analysis from a subset (n = 41) of women enrolled in the study. RESULTS: Levels of carotenoids and tocopherols did not change significantly over 12 wk on any diet arm, despite a modest but statistically significant increase in fruit and vegetable intake in the women following the low-fat diet (from 3.3 to 5.2 servings/d excluding potatoes). Levels of Trolox-equivalent antioxidant capacity (TEAC), total cholesterol, and two major plasma antioxidants (urate and bilirubin) also did not change significantly. Of the individual micronutrients measured, lycopene and lutein/zeaxanthin correlated most strongly with TEAC values, and the correlation with lycopene was statistically significant before intervention. CONCLUSION: The decreases in dietary fat and energy intakes in this study were quite large, but this did not appear to have detrimental effects on plasma micronutrient levels, nor did it appreciably affect plasma antioxidants. Because lycopene levels were significantly associated with plasma TEAC before intervention, interventions that increase levels of lycopene might be more likely to increase the antioxidant capacity of plasma.

Effect of varying caloric restriction levels on female rat growth and 5-hydroxymethyl-2'-deoxyuridine in DNA.

Caloric restriction has previously been shown to decrease levels of oxidative stress in rats. In this study, we examined the effects of 5 different caloric intake levels on one type of oxidative DNA damage in rat mammary gland, blood, and liver. Animals were fed modified AIN-93G diets to accommodate 10, 20, 30, or 40% calorie restriction (CR), relative to ad libitum (AL) consumption. The intakes of fat, protein, vitamins, and minerals thus remained constant, but total carbohydrate intake decreased. Body weights of the animals at 20 weeks reflected the degree of restriction, but in the first 10 weeks, weight gain in the 10% CR group was not reduced relative to animals fed ad libitum. Levels of 5-hydroxymethyl-2'-deoxyuridine increased with time in mammary gland and nucleated blood cells regardless of CR level, indicating an effect of animal age, despite the fact that the animals were only 7 months old after the 20-week dietary study. In liver, however, there was a trend towards decreased DNA damage levels with time. The effect of diet on levels of 5-hydroxymethyl-2'-deoxyuridine was not statistically significant, indicating no protective effect of restricted dietary carbohydrate. This dietary study differed from previous work in that the modified AIN-93G dietary formulation contains relatively higher levels of fat and vitamins K, E, and B(12), and it has certain added trace minerals. This data raises the question of whether the previously reported effects of calorie restriction on preventing oxidative stress in mammary gland are dependent on the type of dietary formulation used.