Effect of high-dose vitamin D supplementation in combination with weight loss diet on glucose homeostasis, insulin resistance, and matrix metalloproteinases in obese subjects with vitamin D deficiency: a double-blind, placebo-controlled, randomized clinical trial

As there is limited and inconsistent evidence in potential role of vitamin D on insulin resistance and matrix metalloproteinases, this study aimed to examine the effect of vitamin D supplementation on glucose homeostasis, insulin resistance, and matrix metalloproteinases in obese subjects with vitamin D deficiency. A total of 44 participants with serum 25-hydroxyvitamin D (25(OH)D) level ≤ 50 nmol/L and body mass index (BMI) 30-40 kg/m² were randomly allocated into receiving weight reduction diet with either 50 000 IU vitamin D₃ pearl (n = 22) or placebo (n = 22) once weekly for 12 weeks. Primary outcomes were changes in fasting serum glucose (FSG), homeostasis model assessment of insulin resistance (HOMA-IR), quantitative insulin sensitivity check index (QUICKI), and matrix metalloproteinases (MMPs). Secondary outcomes were changes in weight, BMI, 25(OH)D, calcium, phosphorous and parathyroid hormone (PTH). Sun exposure and dietary intakes were also assessed. Serum levels of 25(OH)D3 increased significantly with a simultaneous decrease in serum concentration of PTH in the vitamin D group. Weight, BMI, FSG, and MMP-9 decreased significantly in both groups, and there were significant differences in changes in weight, serum 25(OH)D3, PTH, and MMP-9 levels between the groups. Within- and between-groups analysis revealed no significant differences in serum calcium, phosphorous, serum insulin, HOMA-IR, QUICKI, and MMP-2 after intervention. Our results indicated that improvement in vitamin D status resulted in greater reductions in weight and MMP-9 during weight loss. These preliminary results are sufficient to warrant a bigger study group.

Effects of Vitamin E and Zinc Supplementation on Antioxidants in Beta thalassemia major Patients

OBJECTIVE

In beta thalassemic patients, tissue damage occurs due to oxidative stress and it happens because of the accumulation of iron in the body. This study was conducted to determine the effect of zinc and vitamin E supplementation on antioxidant status in beta-thalassemic major patients.

METHODS

This double blind randomized clinical trial was carried out on 120 beta thalassemic patients older than 18 years. Patients were randomly categorized in four groups. Zinc (50mg/day) and vitamin E (400mg/day) supplements were administered for former and latter group, respectively. In the third group both supplements were administered in similar doses. The fourth (control) group received no supplement. The effect of supplementations on serum zinc and vitamin E, superoxide dismutase (SOD), glutathione peroxidase (GPX), total antioxidant capacity (TAC) and body mass index (BMI) were measured at the beginning and the end of the study.

FINDINGS

Serum zinc levels in group 1 and 3 were significantly increased (P<0.007 and P<0.005, respectively). Serum vitamin E levels in group 2 and 3 were also increased significantly (P<0.001). Mean GPX activity in group1, 2 and 3 decreased significantly (P<0.015, P<0.032 and P<0.029, respectively). Mean SOD activity and TAC did not show significant change after supplementation. BMI had significant increase in all treated groups (P<0.001).

CONCLUSION

Our results suggest that beta thalassemic patients have enhanced oxidative stress and administration of selective antioxidants may preclude oxidative damage.

Effect of advice to increase carbohydrate and reduce fat intake on dietary profile and plasma lipid concentrations in healthy postmenopausal women

BACKGROUND

The current dietary guidelines advise an increase in carbohydrate intake. However, there is concern regarding the effect this may have on coronary heart disease (CHD) risk, in particular in postmenopausal women, in light of the knowledge that raised triacylglycerol (TAG) may pose a stronger risk for CHD in this group.

AIM

To evaluate the effect of advice to increase carbohydrate intake to 50% of energy intake as part of advice to follow current dietary guidelines on the dietary profile, including dietary glycaemic index (GI) and plasma lipids in healthy postmenopausal women.

METHODS

Twelve healthy postmenopausal women (56 +/- 6.5 years) took part in the study. Habitual diet was assessed by a 7-day weighed intake. On the basis of the results, subjects were advised to increase their carbohydrate intake to comply with the current dietary guidelines. Subjects were asked to follow this diet for 4 weeks, in a free-living situation. Fasting blood samples were obtained at baseline and after 1 and 4 weeks.

RESULTS

There was a significant decrease in body mass index (BMI; p < 0.05) after 4 weeks. There was a significant increase in fasting TAG concentrations after 1 week (p < 0.05), and the high-density lipoprotein (HDL) cholesterol concentration was significantly decreased (p < 0.05) after 1 and 4 weeks. The subjects significantly increased their percentage of energy from carbohydrates and starch (p < 0.05 and p < 0.01, respectively) after 1 week, and their percentage of energy from starch after 4 weeks (p < 0.05). Dietary GI was significantly increased (p < 0.05) after 1 and 4 weeks. Fruit and vegetable intake was significantly increased after 1 week (p < 0.01), as was fruit intake alone (p < 0.05), and there was a significant increase (p < 0.05) in the 'antioxidant power' as measured by the ferric reducing ability of plasma assay.

CONCLUSION

In postmenopausal women, following the UK dietary guidelines resulted in changes in the lipid profile that were more likely to favour an increased risk of CHD, as TAG concentrations were increased and HDL cholesterol concentrations were reduced. However, in addition, we found a significant reduction in BMI and a significant increase in the 'antioxidant power' of plasma, which should benefit health.