Influence of Calcium Salt Supplementation on Calcium Equilibrium in Skim Milk During pH Cycle

Screening, separation and identification of metal-chelating peptides for nutritional, cosmetics and pharmaceutical applications

Metal-chelating peptides, which form metal-peptide coordination complexes with various metal ions, can be used as biofunctional ingredients notably to enhance human health and prevent diseases. This review aims to discuss recent insights into food-derived metal-chelating peptides, the strategies set up for their discovery, their study, and identification. After understanding the overall properties of metal-chelating peptides, their production from food-derived protein sources and their potential applications will be discussed, particularly in nutritional, cosmetics and pharmaceutical fields. In addition, the review provides an overview of the last decades of progress in discovering food-derived metal-chelating peptides, addressing several screening, separation and identification methodologies. Furthermore, it emphasizes the methods used to assess peptide-metal interaction, allowing for better understanding of chemical and thermodynamic parameters associated with the formation of peptide-metal coordination complexes, as well as the specific amino acid residues that play important roles in the metal ion coordination.

Effects of Calcium-Vitamin D and Calcium-Alone on Pain Intensity and Menstrual Blood Loss in Women with Primary Dysmenorrhea: A Randomized Controlled Trial

Objective

There is limited evidence on effectiveness of calcium and vitamin D on dysmenorrhea. The authors aimed to determine the effect of combined calcium-vitamin D and calcium-alone on pain intensity and menstrual blood loss in women with primary dysmenorrhea.

Design

A randomized double-blind trial.

Setting

Dormitories of Tabriz University of Medical Sciences.

Subjects

85 students with moderate or severe primary dysmenorrhea.

Methods

Participants were randomized into three groups: receiving one tablet/day of 1000 mg calcium + 5000 IU vitamin D3, calcium-alone 1000 mg, or matched placebo, from 15th cycle day until menstrual pain disappearance in the following cycle, for three cycles. Pain intensity and menstrual blood loss were assessed one cycle before, three cycles under, and one cycle following intervention using 10-cm visual analog scale and pictorial blood loss assessment chart, respectively. The groups were compared using repeated measures ANOVA.

Results

Time after intervention and interaction of time with group had no significant effects on the outcomes. Compared to the placebo group, mean pain intensity was lower in the both calcium-vitamin D (adjusted difference -0.7, 95% confidence interval -1.6 to 0.3) and calcium-alone (-1.6, -2.6 to -0.6) groups, but the difference was statistically significant only in the calcium-alone group. Menstrual blood loss was not significantly different in the either calcium-vitamin D (-4.7, -21.9 to 12.4) or calcium-alone (-0.4, -17.4 to 16.4) groups compared to placebo.

Conclusions

Intake of the calcium-alone was effective in reducing menstrual pain intensity. The results could not indicate significant effects of calcium-vitamin D on the pain or any of the interventions on menstrual blood loss.

Clinical trial registration

This study was approved by the Ethics committee of Tabriz University of Medical Sciences (code 92145) and registered at the Iranian Registry of Clinical Trials with IRCT201402043706N21.

Study of calcium-soy protein interactions by isothermal titration calorimetry and pH cycle

The aim of this work was to understand Ca-induced soy protein (nonhydrolyzed, NH; or hydrolyzed, H) aggregation and to characterize the involved interactions using ITC and pH cycle. The endothermic signals obtained upon titration of soy proteins with Ca were fitted with a one set of sites model. NH soy proteins bound more Ca than H soy proteins ( approximately 52 and approximately 2 mg of Ca/g of proteins, respectively). The binding constant K indicated the easier Ca binding onto H soy proteins than for NH soy proteins. The exothermic part involved by electrostatic interactions was completely hidden by the strong endothermic signal from the water molecule release. Ca binding onto soy proteins should be described as a H(+)/Ca(2+) exchange. Whatever the soy proteins, the positive value of heat capacity changes indicated a reduction in the number of surface-exposed polar residues. Ca-induced soy protein aggregation was irreversible for pH cycle to 3.5.