Research from JAMA — Effect of a Low–Glycemic Index or a High–Cereal Fiber Diet on Type 2 Diabetes — A Randomized Trial

Feeding stimulates robust increases in muscle protein synthesis (MPS); however, ageing may alter the anabolic response to protein ingestion and the subsequent aminoacidaemia. With this as background, we aimed to determine in the present study the dose–response of MPS with the ingestion of isolated whey protein, with and without prior resistance exercise, in the elderly. For the purpose of this study, thirty-seven elderly men (age 71 (sd4) years) completed a bout of unilateral leg-based resistance exercise before ingesting 0, 10, 20 or 40 g of whey protein isolate (W0–W40, respectively). Infusion ofl-[1-¹³C]leucine andl-[ring-¹³C₆]phenylalanine with bilateralvastus lateralismuscle biopsies were used to ascertain whole-body leucine oxidation and 4 h post-protein consumption of MPS in the fed-state of non-exercised and exercised leg muscles. It was determined that whole-body leucine oxidation increased in a stepwise, dose-dependent manner. MPS increased above basal, fasting values by approximately 65 and 90 % for W20 and W40, respectively (P < 0·05), but not with lower doses of whey. While resistance exercise was generally effective at stimulating MPS, W20 and W40 ingestion post-exercise increased MPS above W0 and W10 exercised values (P < 0·05) and W40 was greater than W20 (P < 0·05). Based on the study, the following conclusions were drawn. At rest, the optimal whey protein dose for non-frail older adults to consume, to increase myofibrillar MPS above fasting rates, was 20 g. Resistance exercise increases MPS in the elderly at all protein doses, but to a greater extent with 40 g of whey ingestion. These data suggest that, in contrast to younger adults, in whom post-exercise rates of MPS are saturated with 20 g of protein, exercised muscles of older adults respond to higher protein doses.

Weight loss can have substantial health benefits for overweight or obese persons; however, the ratio of fat:lean tissue loss may be more important. W

Strategies that decrease postprandial glucose excursions, including digestive enzyme inhibition, and low glycemic index diets result in lower diabetes incidence and coronary heart disease (CHD) risk, possibly through lower postprandial oxidative damage to lipids and proteins. We therefore assessed the effect of decreasing postprandial glucose excursions on measures of oxidative damage. Fifteen healthy subjects ate 2 bread control meals and 3 test meals: almonds and bread; parboiled rice; and instant mashed potatoes, balanced in carbohydrate, fat, and protein, using butter and cheese. We obtained blood samples at baseline and for 4 h postprandially. Glycemic indices for the rice (38 ± 6) and almond meals (55 ± 7) were less than for the potato meal (94 ± 11) (P < 0.003), as were the postprandial areas under the insulin concentration time curve (P < 0.001). No postmeal treatment differences were seen in total antioxidant capacity. However, the serum protein thiol concentration increased following the almond meal (15 ± 14 mmol/L), indicating less oxidative protein damage, and decreased after the control bread, rice, and potato meals (−10 ± 8 mmol/L), when data from these 3 meals were pooled (P = 0.021). The change in protein thiols was also negatively related to the postprandial incremental peak glucose (r = −0.29, n = 60 observations, P = 0.026) and peak insulin responses (r = −0.26, n = 60 observations, P = 0.046). Therefore, lowering postprandial glucose excursions may decrease the risk of oxidative damage to proteins. Almonds are likely to lower this risk by decreasing the glycemic excursion and by providing antioxidants. These actions may relate to mechanisms by which nuts are associated with a decreased risk of CHD.

We aimed to determine whether women consuming fat-free milk versus isoenergetic carbohydrate after resistance exercise would see augmented gains in lean mass and reductions in fat mass similar to what we observed in young men. Young women were randomized to drink either fat-free milk (MILK: n = 10; age (mean +/- SD) = 23.2 +/- 2.8 yr; BMI = 26.2 +/- 4.2 kg x m(-2)) or isoenergetic carbohydrate (CON: n = 10; age = 22.4 +/- 2.4 yr; BMI = 25.2 +/- 3.8 kg x m(-2)) immediately after and 1 h after exercise (2 x 500 mL). Subjects exercised 5 d x wk(-1) for 12 wk. Body composition changes were measured by dual-energy x-ray absorptiometry, and subjects' strength and fasting blood were measured before and after training. CON gained weight after training (CON: +0.86 +/- 0.4 kg, P < 0.05; MILK: +0.50 +/- 0.4 kg, P = 0.29). Lean mass increased with training in both groups (P < 0.01), with a greater net gain in MILK versus CON (1.9 +/- 0.2 vs 1.1 +/- 0.2 kg, respectively, P < 0.01). Fat mass decreased with training in MILK only (-1.6 +/- 0.4 kg, P < 0.01; CON: -0.3 +/- 0.3 kg, P = 0.41). Isotonic strength increased more in MILK than CON (P < 0.05) for some exercises. Serum 25-hydroxyvitamin D increased in both groups but to a greater extent in MILK than CON (+6.5 +/- 1.1 vs +2.8 +/- 1.3 nM, respectively, P < 0.05), and parathyroid hormone decreased only in MILK (-1.2 +/- 0.2 pM, P < 0.01). Heavy, whole-body resistance exercise with the consumption of milk versus carbohydrate in the early postexercise period resulted in greater muscle mass accretion, strength gains, fat mass loss, and a possible reduction in bone turnover in women after 12 wk. Our results, similar to those in men, highlight that milk is an effective drink to support favorable body composition changes in women with resistance training.