Weight loss associated with low-energy diets with different glycaemic loads does not improve arterial stiffness: a randomised clinical trial.

We evaluated the effects of two low-energy diets with different glycaemic loads on arterial stiffness in adults with excess weight. This was a 45-day parallel-group, randomised clinical trial including seventy-five participants (20-59 years; BMI 32 kg/m2). They were assigned to two similar low-energy diets (reduction of ∼750 kcal.d-1) with macronutrient composition (55 % carbohydrates, 20 % proteins and 25 % lipids) but different glycaemic loads: high-glycaemic load (HGL 171 g.d-1; n 36) or low-glycaemic load (LGL 67 g.d-1; n 39). We evaluated: arterial stiffness (pulse wave velocity, PWV); augmentation index (AIx@75); reflection coefficient; fasting blood glucose; fasting lipid profile; blood pressure and body composition. We found no improvements in PWV (P = 0·690) and AIx@75 (P = 0·083) in both diet groups, but there was a decrease in the reflection coefficient in the LGL group (P = 0·003) compared with baseline. The LGL diet group showed reductions in body weight (Δ -4·9 kg; P = 0·001), BMI (Δ -1·6 kg/m2; P = 0·001), waist circumference (Δ -3·1 cm; P = 0·001), body fat (Δ -1·8 %; P = 0·034), as well as TAG (Δ -14·7 mg/dl; P = 0·016) and VLDL (Δ -2·8 mg/dl; P = 0·020). The HGL diet group showed a reduction in total cholesterol (Δ -14·6 mg/dl; P = 0·001), LDL (Δ -9·3 mg/dl; P = 0·029) but a reduction in HDL (Δ -3·7 mg/dl; P = 0·002). In conclusion, a 45-day intervention with low-energy HGL or LGL diets in adults with excess weight was not effective to improve arterial stiffness. However, the LGL diet intervention was associated with a reduction of reflection coefficient and improvements in body composition, TAG and VLDL levels.

Effects of grape juice consumption on muscle fatigue and oxidative stress in judo athletes: a randomized clinical trial.

Physiological levels of reactive oxygen species (ROS) are important for intracellular and extracellular redox regulation in signaling and defense processes. Strenuous exercise can also contribute to this imbalance, and the muscle fatigue, evidenced by impaired strength or power generation, can be caused by various reasons, including oxidative stress. Antioxidants can prevent the formation of ROS by intercepting free radicals. Twenty judo athletes were included in this randomized, double-blind clinical trial into grape juice and placebo groups, and they consumed grape juice or placebo daily for 14 days in a crossover model. The outcomes were analyzed before and after combat simulations. The upper limb strength was higher in the grape juice group than in the placebo (p [group] = 0.003). The lipid damage levels were 10% higher in the placebo group (p [interaction] = 0.048). During the pre-exercise, the placebo group showed 19% more DNA damage than the grape juice group. The superoxide dismutase activity was 80% lower in the grape juice group (p [interaction] < 0.001). The consumption of grape juice can improve parameters of oxidative stress by reducing the lipid and DNA damage.

Comparison of the effects of two antioxidant diets on oxidative stress markers in triathletes.

Intense exercise generates an imbalance in the redox system. However, chronic exercise can yield antioxidant adaptations. A few studies with humans have investigated the effects of antioxidant diets on athletes. Therefore we compared the effects of two dietary interventions on oxidative stress in competitive triathletes. Thirteen male triathletes were selected and divided into 2 groups: one that had a regular antioxidant diet (RE-diet) and the other that had a high antioxidant diet (AO-diet). The diet period was 14 days and blood samples were collected before and after this period. The AO-diet provided twice the dietary reference intake (DRI) of α-tocopherol (30 mg), five times the DRI of ascorbic acid (450 mg), and twice the DRI of vitamin A (1800 g), while the RE-diet provided the DRI of α-tocopherol (15 mg), twice the DRI of ascorbic acid (180 mg) and the DRI of vitamin A (900 µg). The oxidative stress parameters evaluated were: thiobarbituric acid reactive substances (TBARS), total reactive antioxidant potential (TRAP), total sulfhydryl, carbonyl, superoxide dismutase (SOD) activity, hydrogen peroxide consumption and glutathione peroxidase (GPx) activity. We observed, after the diet period, an increase in sulfhydryl, TRAP, TBARS and SOD activity, and a decrease in carbonyl levels. However, no changes were found in hydrogen peroxide consumption or GPx activity. We concluded that antioxidant-enriched diets can improve the redox status of triathletes.