Evidence for the relationship of calcium to blood pressure

Fermentation Improves Calcium Bioavailability in Moringa oleifera leaves and Prevents Bone Loss in Calcium-deficient Rats

Nowadays, there is an increasing demand of healthier plant calcium supplements. Moringa oleifera leaves (MOL) are rich in calcium and thus are promising candidates for developing efficient calcium supplements. Here, using fermentation-based approaches, we developed a Moringa oleifera leaf ferment (MOLF), which contents higher levels of calcium. The therapeutic potential of the MOLF was also examined both in vitro and in vivo. Nine lactic acid bacteria and four yeasts were tested for better fermentation of MOL. Calcium-deficient rats were used for evaluating the therapeutic effects of MOLF. The results of liquid fermentation showed that the mixture of Lactobacillus reuteri, Lactobacillus acidophilus , and Candida utilis elevated the content of MOL calcium most strikingly, with the content of calcium increased nearly 2.4-fold (from 2.08% to 4.90%). The resulting MOLF was then subjected to cell experiments and animal experiments. The results showed that calcium absorption in Caco-2 cells in MOLF group was higher than that in CaCl2 group significantly. Interestingly, in calcium-deficient rats, MOLF treatment significantly increased the thickness of cortical bone, rat body weight, wet weight of the femur, and the femur bone density, whereas it decreased osteoclast numbers. These results indicate that microbial fermentation increased calcium bioavailability of MOL, promote the growth and development of calcium-deficient rats, bone calcium deposition, and bone growth; enhance bone strength; reduce bone resorption; and prevent calcium deficiency.

In vitrodigestion profile and calcium absorption studies of a sea cucumber ovum derived heptapeptide–calcium complex

A novel sea cucumber ovum derived heptapeptide (NDEELNK) could bind one calcium ionviaits carboxyl oxygen and amino nitrogen atoms, and the formed complex underwent disaggregation and self aggregation during simulated gastrointestinal digestion.

Preparation and bioavailability of calcium-chelating peptide complex from tilapia skin hydrolysates

BACKGROUND

With the continuous improvement in material life, the generation of fish by-products and the market demand for calcium supplements have been increasing in China. Therefore a calcium-chelating peptide complex (CPC) from tilapia skins was prepared and its effect on calcium (Ca)-deficient mice was investigated.

RESULTS

The molecular weight distribution of CPC mainly ranged from 2000 to 180 Da, and its contents of complete amino acids and free amino acids were 85.30 and 8.67% (w/w) respectively. Scanning electron microscopy images and Fourier transform infrared data revealed that Ca crystals were bound with gelatin hydrolysates via interaction between Ca ions and NH/CN groups. When Ca-deficient mice were fed CPC and CaCO₃ respectively for 4 weeks, no significant differences in serum biochemistry or bone mineral density were found. However, the length, weight, Ca content and hydroxyproline content of the femur, Ca absorption and body weight gain of mice fed CPC were significantly higher than those of mice fed CaCO₃ .

CONCLUSION

It is concluded that the prepared CPC could promote bone formation via better bioavailability of Ca and an increase in bone collagen. © 2017 Society of Chemical Industry.

A Specific Peptide with Calcium-Binding Capacity from Defatted Schizochytrium sp. Protein Hydrolysates and the Molecular Properties

Marine microorganisms have been proposed as a new kind of protein source. Efforts are needed in order to transform the protein-rich biological wastes left after lipid extraction into value-added bio-products. Thus, the utilization of protein recovered from defatted Schizochytrium sp. by-products presents an opportunity. A specific peptide Tyr-Leu (YL) with calcium-binding capacity was purified from defatted Schizochytrium sp. protein hydrolysates through gel filtration chromatography and RP-HPLC. The calcium-binding activity of YL reached 126.34 ± 3.40 μg/mg. The calcium-binding mechanism was investigated through ultraviolet, fluorescence and infrared spectroscopy. The results showed that calcium ions could form dative bonds with carboxyl oxygen atoms and amino nitrogen atoms as well as the nitrogen and oxygen atoms of amide bonds. YL-Ca exhibited excellent thermal stability and solubility, which was beneficial for its absorption and transport in the basic intestinal tract of the human body. Moreover, the cellular uptake of calcium in Caco-2 cells showed that YL-Ca could enhance calcium uptake efficiency and protect calcium ions against precipitation caused by dietary inhibitors such as tannic acid, oxalate, phytate and metal ions. The findings indicate that the by-product of Schizochytrium sp. is a promising source for making peptide-calcium bio-products as algae-based functional supplements for human beings.

Purification and characterisation of a glutamic acid-containing peptide with calcium-binding capacity from whey protein hydrolysate

The bioavailability of dietary ionised calcium is affected by intestinal basic environment. Calcium-binding peptides can form complexes with calcium to improve its absorption and bioavailability. The aim of this study was focused on isolation and characterisation of a calcium-binding peptide from whey protein hydrolysates. Whey protein was hydrolysed using Flavourzyme and Protamex with substrate to enzyme ratio of 25:1 (w/w) at 49 °C for 7 h. The calcium-binding peptide was isolated by DEAE anion-exchange chromatography, Sephadex G-25 gel filtration and reversed phase high-performance liquid chromatography (RP-HPLC). A purified peptide of molecular mass 204 Da with strong calcium binding ability was identified on chromatography/electrospray ionisation (LC/ESI) tandem mass spectrum to be Glu-Gly (EG) after analysis and alignment in database. The calcium binding capacity of EG reached 67·81 μg/mg, and the amount increased by 95% compared with whey protein hydrolysate complex. The UV and infrared spectrometer analysis demonstrated that the principal sites of calcium-binding corresponded to the carboxyl groups and carbonyl groups of glutamic acid. In addition, the amino group and peptide amino are also the related groups in the interaction between EG and calcium ion. Meanwhile, the sequestered calcium percentage experiment has proved that EG-Ca is significantly more stable than CaCl2 in human gastrointestinal tract in vitro. The findings suggest that the purified dipeptide has the potential to be used as ion-binding ingredient in dietary supplements.

Nutritional composition of Zizyphus lotus L. seeds

BACKGROUND

Zizyphus lotus seeds are an unutilized source of vegetable oil and protein and nothing has been reported on their physicochemical characteristics which would indicate the potential uses of these seeds.

RESULTS

The percentage composition of the Zizyphus lotus seeds is (on a dry-weight basis): ash 1.05%, oil 32.92%, protein 19.11%, total carbohydrate 40.87% and moisture 6.05%. Calcium, potassium and magnesium constitute the major minerals of Zizyphus lotus seeds. The seed proteins are rich in threonine, glutamic acid, leucine, arginine and aspartic acid (26.73%, 17.28%, 13.11%, 9.47% and 7.76%, respectively). The main fatty acids of the oil are oleic (61.93%), linoleic (18.31%) and palmitic (9.14%) acids. Glycerol trioleate (OOO; O: oleic acid) was the most abundant triacylglycerol, representing 26.48% of the total triacyglycerols. β-Tocopherol was the major tocopherol (130.47 mg 100 g(-1) ). This oil was rich in Δ7-campestrol and β-sitosterol (147.82 and 82.10 mg 100 g(-1) oil), respectively.

CONCLUSION

Zizyphus lotus seeds are rich in fat and protein which are of potential industrial significance. In addition, Zizyphus lotus L. seed oil contained many bioactive compounds. This fact is of great economic interest owing to several applications of Zizyphus lotus L. seeds in the food, cosmetics and medicinal industries.

The relationship between blood pressure and serum parathyroid hormone with special reference to urinary calcium excretion: the Tromsø study

The aim of the present cross-sectional epidemiological study from Tromsø, Northern Norway, was to evaluate the relation between blood pressure and serum PTH, and to examine whether this relation can be explained by a blood pressure-induced increase in urinary calcium. Ten thousand-four hundred and nineteen subjects were invited to participate and 8,128 attended. Those with serum calcium outside the reference range (2.20-2.60 mmol/l), with increased serum creatinine (upper limit 120 micromol/l for men and 100 micromol/l for women) and those using antihypertensive medication were excluded. Three thousand- six hundred and twenty subjects had complete data on outcome measures. Height, weight, blood pressure, serum calcium, PTH, and creatinine were measured and smoking status recorded. A morning urine sample was collected and urinary calcium, sodium and creatinine measured. The urinary calcium/urinary creatinine ratio (Uca/Ucr) and urinary sodium/urinary creatinine ratio (Una/Ucr) were calculated. There was a significant association between both systolic and diastolic blood pressure and serum PTH. The Uca/Ucr increased with increasing blood pressure. However, the Uca/Ucr did not affect the association between blood pressure and serum PTH in a multiple linear regression model. The relationship between blood pressure and serum PTH was also seen in subjects with similar Uca/Ucr, and a negative association between serum PTH and the Uca/Ucr was found. In conclusion, blood pressure and serum PTH are associated. This association cannot be explained by the urinary calcium excretion alone.

Beyond Calcium: The Protective Attributes of Dairy Products and Their Constituents

Functional foods are gaining in popularity as consumers are living longer and are seeking to reduce disease and optimize their health through diet. Dairy products and their components are one category of foods under investigation for their functional attributes. Recent research suggests the health benefits of consuming dairy foods may extend well beyond bone health to enhancing the immune system, reducing risks of some chronic diseases, and regulating body weight. This article examines the associated components of dairy foods and the evidence for these putative health benefits.

Calcium from dairy products, vitamin D intake, and blood pressure: the Tromso Study

BACKGROUND

The present epidemiologic study was conducted in Tromso, Northern Norway, in 1994-1995.

OBJECTIVE

The objective was to evaluate the relation between calcium intake from dairy products and the intake of vitamin D on systolic and diastolic blood pressure.

DESIGN

Subjects who were taking drugs for hypertension or heart disease, those taking calcium tablets, subjects reporting cardiovascular disease, and pregnant women were excluded, leaving 7543 men and 8053 women aged 25-69 y for analysis. Calcium and vitamin D intakes were calculated from a food-frequency questionnaire.

RESULTS

After correction for age, body mass index, alcohol and coffee consumption, physical activity, cigarette smoking, and vitamin D intake, there was a significant linear decrease in systolic and diastolic blood pressure with increasing dairy calcium intake in both sexes (P < 0.05). However, the difference in blood pressure between subjects with the highest and those with the lowest calcium intake was </=1-3 mm Hg. Similarly, with increasing blood pressure there was a significant (P < 0.001) linear decrease in age-adjusted calcium intake from dairy sources; the difference between the highest and the lowest blood pressure groups was 3-10%. Vitamin D intake had no significant effect on blood pressure.

CONCLUSIONS

There is a negative association between calcium intake from dairy products and blood pressure. However, although the effect of calcium on blood pressure appears to be small, calcium could have a significant effect on primary prevention of cardiovascular diseases.