Showing posts with label function. Show all posts
Showing posts with label function. Show all posts

Functions of calcium - Health benefits of calcium

May 2014   › › › › › Functions of calcium and its health benefits
Calcium supports the structure and function of bones and teeth. Multiple health benefits of calcium include regulation of vasoconstriction and vasodilation, neuromotor transmission and several critical cell metabolic functions.
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It is the most abundant mineral in the human body. The bones and teeth contain 99% of the calcium present in the human body. The remaining 1% is found in the blood serum, soft tissues and interstitial fluids of the tissues. One of the health benefits of the mineral is the alkalizing effect.

Calcium presence in the blood serum is tightly regulated and the normal levels of its ionized form is 4.65 to 5.25 mg/dL (1.16 to 1.31 mmol/L). Irrespective of the quantity in diet, the levels are maintained by sourcing the mineral from the bones by demineralization. Mineral deficiency diseases like hypocalcemia occur when the concentration of free calcium ions in the blood serum falls below 4.0 mg/dL. Certain adverse health conditions may result in higher concentration of calcium ions in the blood serum and lead to diseases like hypercalcemia or milk-alkali syndrome.

Functions of calcium

Calcium has many functions in the human body. Apart from being the structural component of the bone tissue it has several physiological and biochemical functions. Some functions of calcium are listed below.
functions as a primary structural component of bones and teeth.
It functions as an universal intracellular messenger, activating or inhibiting several cellular processes.
Its another function is in signalling cellular secretions and hormone releases.
It is necessary for production and transmission of electrical signals within the nervous system.
It has major function in neuronal signal reception, neuronal signal transmission and the regulation of neuronal excitability.
It functions in bringing about cellular changes that underlie learning, cognisance, perception, creativity and memory.
Critical for the function of endothelial cell junctions (adherens and tight junctions) of the blood–brain barrier (BBB).
Calcium signaling pathways function as regulators of gene transcription and gene expression.
It functions as the necessary ion in the formation of the mitotic spindle for cell division and cell proliferation.
Required for coagulation factors to bind to phospholipid for coagulation cascade and blood clotting.
It has mediatory function in excitation and contraction of muscle fibres.
Regulating heartbeat is its major function.

Health benefits of calcium

Health benefits of calcium include protection from osteoporosis, hypocalcemia, amenorrhea, cardiovascular disease, hypertension, stress fractures, weight gain and certain cancers.

Benefits of calcium in bone health and function

Bone mass keeps increasing in childhood and adolescence.
    • The increase in bone size and mass reaches its peak by about 30 years of age. Greater bone mass delays serious bone loss in old age. If calcium intake is low or if there is poor absorption during childhood and teenage, sufficient bone mass is not attained. Such individuals are at high risk of developing osteoporosis. They become highly vulnerable to fractures of the hip, vertebrae, pelvis, ribs and other bones. Supplementation can benefits such persons and improve their health.

    Postmenopausal women health benefits

    With the onset of menopause, the estrogen production decreases causing many physiological changes in postmenopausal women. Decrease in estrogen production leads to increased bone resorption and decreased resulting in bone loss. Women affected by low estrogen levels are at the increased risk of hypocalcemia, osteoporosis and stress fractures. Taking calcium supplements and undergoing hormone replacement therapy (HRT) may benefit and improve their health by improving the bone function.

    Amenorrhea and health benefits of calcium

    Amenorrheic women and many female athletes tend to have decreased estrogen levels.
    • The condition primarily arises due low fat and high protein diet. The decrease in estrogen production, apart from causing amenorrhea can upset the calcium balance. There is increased excretion of the mineral in the urine and decreased rate of bone formation. Diet rich in calcium or intake of supplements may benefit such women and add to their bone health.

    Cancers

    Several observational and experimental studies have established the link between higher calcium intake and prevention of colon cancer. High levels of intake even reduced the risk of adenoma, a nonmalignant tumor, which sometimes become malignant. A.Galas et al in their study "Does dietary calcium interact with dietary fiber against colorectal cancer? A case-control study in Central Europe" published in Nutrition Journal, 2013 Oct 4;12:134, concluded that the study confirmed the effect of high doses of dietary calcium against the risk of colon cancer development.

    Cardiovascular health benefits

    The benefits of the mineral in cardiovascular health is still being debated. Chronic overdoses of the mineral had been found to cause cardiovascular disease. Some studies claim that moderate levels of supplementation can prevent cardiovascular disease.

    Hypertensive patients health

    It is well established that calcium supplementation, reduces the systolic blood pressure by 2–4 mmHg in hypertensive patients. However in normotensive individuals, supplementation does not appear to have any function and does not affect systolic or diastolic blood pressure.

    Calcium benefits for weight loss?

    The benefits of the mineral in weight loss is still being debated. A meta-analysis of randomized controlled trials had reported lack of significant effect on weight reduction. However the following studies show that supplementation with the mineral may help in weight loss.

    Genevieve C Major et al published their study "Supplementation with calcium + vitamin D enhances the beneficial effect of weight loss on plasma lipid and lipoprotein concentrations" in American Society for Clinical Nutrition (2007). They have concluded that regular intake of calcium and vitamin D during a weight-loss intervention in overweight women with low daily intake of the mineral, had beneficial effect on body weight loss.

    Zhu W et al of Department of Nutrition, Shanghai Institute of Health Sciences, have published their study "Calcium plus vitamin D3 supplementation facilitated fat loss in overweight and obese college students with very-low calcium consumption: a randomized controlled trial." in Nutrition Journal 2013, 12:8. They had reaffirmed the health benefits of the mineral by reporting that supplementation of the mineral plus vitamin D3 for 12 weeks facilitated body fat and visceral fat loss during energy restriction in overweight or obese very-low calcium consumers.
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    References:
    1.Dietary Supplement Fact Sheet. National Institutes of Health.
    http://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/
    2.Reinwald S, Weaver CM, Kester JJ. The health benefits of calcium citrate malate: a review of the supporting science. Adv Food Nutr Res. 2008;54:219-346. doi: 10.1016/S1043-4526(07)00006-X.
    3.Bootman MD, Rietdorf K, Hardy H, Dautova Y, Corps E, Pierro C, Stapleton E, Kang E, Proudfoot D. 2012. Calcium Signalling and Regulation of Cell Function. eLS.
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    Zinc immune system function - Disease resistance in human body

    Jan 2014  › › Zinc immune system function and disease resistance in human body
    Zinc, an essential trace mineral, exerts its ubiquitous effects on the function of the immune system in human body and modulates its disease resistance.
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    The basic cellular functions of Zinc in human body are in gene expression, deoxyribonucleic acid (DNA) replication, ribonucleic acid (RNA) transcription, cell membranes stability, and cell activation, division, proliferation and apoptosis.

    Zinc and disease resistance in human body

      Many research studies have documented that zinc has a pivotal role in the function in immune system of human body. It has been found to increase the infection resistance in human body. Its deficiency has been associated with recurrent episodes of diarrhea in children. Administration of zinc lozenges has been found to decrease the severity and duration of common cold. In many incidences of infections, lower plasma concentrations of this trace mineral have been recorded.

    However it is to be noted that there is a delicate zinc mediated regulation of the function of immune system in human body and any increased or decreased plasma levels of the trace mineral can disturb the function of the system. Reduction in taste acuity, growth retardation, retardation of reproductive growth, skin diseases, immune depression and slowed healing of wound are some of the clinical symptoms of marginally low plasma levels (<60 mcg/dL) of zinc on the human body systems. Very low plasma levels (<30 mcg/dL) are characterized by mental impairment, diseases, severe immune depression and alopecia.

    Excess zinc and immune depression

    On the negative side, excess supplementation of zinc is associated with disease resistance depression and a myriad of health issues and diseases. As the pathogens also require this mineral for their cellular functions, excess of this trace mineral may in fact increase the progression of diseases as found in some AID patients. However multifarious factors affect the availability of zinc for both the host human body as well as the pathogen and this aspect of immune system requires further research input.

    Zinc and innate immune system

    The nonspecific protective mechanism is affected by zinc deficiency with the effects like damages to epidermis, damages to pulmonary tract and gastrointestinal tract lining. As a consequence, diseases of skin, gastrointestinal and respiratory systems crop up. The functions of neutrophils or polymorphonuclear leukocytes (PMNs) are affected. The function of Natural killer cells and the complementary activities get compromised.

    Zinc and specific immunity

    Zinc deficiency causes reduction in the number of T and B lymphocytes present in the spleen tissue as well as in the peripheral blood. T and B lymphocytes function is depressed and their presence is reduced. In animal studies gestational deficiency of this trace mineral has been found to have epigenetic effects by which some immunodeficiency get passed on even to third generation offspring.
    Hematopoiesis in human body
    immune system development


    Thymus is the organ for T lymphocyte development and zinc deficiency leads to thymic involution and thymic atrophy, causing reduction of T lymphocytes. With the reduction of T lymphocytes, many protective mechanisms in human body like antigen recognition, cell proliferation, cytolysis, delayed hypersensitivity and cytotoxic activities are suppressed. Bone marrow is the center for the development of B lymphocytes. In case of deficiency the development of B lymphocytes is blocked and results in compromise of production of antibody molecules, especially immunoglobulin G in human body. The function of macrophage in phagocytosis of disease microbes is deregulated.

    The intra and extracellular reactions of zinc in human body clearly demonstrate its central role in defence from diseases and priming up immune system.
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    Selenium and thyroid hormone - Selenium for hypothyroidism

    Selenium is essential for proper functioning of our immune system and thyroid gland.

    Selenium is an essential trace mineral required for the human body in small amounts for boosting immunity against diseases as well as protecting it from oxidative free radicals.
    Its deficiency has direct effect on the thyroid gland which are regulators of body's metabolism, growth and function.
    The proper utilization of hormones, thyroxine (T4 or C15H11I4NO4) and triiodothyronine (T3 or C15H12I3NO4) and the conversion of T4 to active T3 is mediated and influenced by the quantities of selenium available in the body.

    Selenium and thyroid function

    For the proper hormone synthesis in the gland and its activation and metabolism, essential trace minerals iodine and selenium are required.
    In the human body selenium concentration is highest in the thyroid gland among all organs.
    Thyrocytes (gland epithelial cells, follicular cells and acinar cells) secrete the hormones thyroxine (T4) and triiodothyronine (T3).
    In their biochemical activities thyrocytes produce H2O2 continuously for oxidative hormone synthesis.
    Many selenium containing selenoenzymes are functionally expressed in thyrocytes as glutathione peroxidases, thioredoxin reductases, type I 5-deiodinase, type II 5-deiodinase and selenoprotein P.
    Selenoenzymes form an effective cell defence mechanism against hydrogen peroxide and other reactive oxygen species, protecting the gland and maintaining its normal function.

    Selenium for thyroid problems and autoimmune inflammation

    Autoimmune diseases are disorders of the gland wherein the body's own immune system attacks the gland cells.
    The incidence of the thyroid inflammation is higher in regions with selenium deficiency.
    It is found that deficiency of selenium, even at mild levels, can contribute to initiation of the gland disorders including autoimmune diseases.
    It is also found that continued use of supplements has a positive effect on the these autoimmune diseases, alleviating many of the symptoms.
    In a study by Roland Gärtner, Barbara C. H. Gasnier, Johannes W. Dietrich, Bjarne Krebs and Matthias W. A. Angstwurm of University of Munich, Germany, it was found that Selenoenzymes have diverse effects on the immune system and also within the this gland.
    GPx antioxidant activity is markedly diminished during severe selenium deficiency.
    This reduced antioxidant activity may initiate and contribute to oxidative damage of cells of this gland and fibrosis.
    In such conditions thyroid peroxidase antibodies (TPOAb) may be formed leading to autoimmune thyroiditis.
    Leonidas H. Duntas, University of Athens, Greece, in a recent paper 'Selenium and the Thyroid: A Close-Knit Connection' which is published by Journal of Clinical Endocrinology & Metabolism concluded that ' Maintenance of "selenostasis" via optimal intake not only aids preservation of general health but also contributes substantially to the prevention of the gland disease'.
    It is believed that viral and genetic components and gender could be co-factors triggering diseases like Grave’s Disease and Hashimoto's Thyroiditis in the absence of selenium antioxidant protection.

    Effect of selenium on the thyroid hormones T4 and T3

    Our understanding of the function of the mineral in metabolism has undergone major advancement with early 2000 discoveries.
    Selenoenzymes control or modulate many functional aspects of the metabolism of T4 and T3 hormones. Selenium-enzymes bring about the process of iodination of thyroglobulin in the gland.
    In humans type I iodothyronine deiodinase is the enzyme responsible for most of the peripheral conversion of thyroxine or 3,5,3',5'-tetraiodothyronine (T4) to the active form 3,3',5-triiodothyronine (T3).
    Type I iodothyronine deiodinase has been found to be a selenoenzyme.
    Type II deiodinase is responsible for T4 conversion to T3 in the brain.
    Type III deiodinase is the inner ring deiodinase responsible for deactivating T4 and T3.
    It was recently found that both type I and type II are also selenocysteine enzymes containing selenium.
    In a study conducted by Wayne Chris Hawkes and Nancy L. Keim of University of California, it was found that the serum level of T3 increased with low Selenium diet at 14 mcg/day leading to weight loss and sub clinical hyperthyroid responses.
    However it also found that high Selenium diet of 297 mcg/day led to weight gain and sub clinical hypothyroid responses with decrease in serum T3.
    Thus it is clearly evident that this mineral has direct effect on the hormone leading to hyperthyroid response or hypothyroid response depending on the deficiency or excess of its presence.
    It is imperative to maintain optimum selenium status through foods and if necessary by supplementation for general health of the body and thyroid gland in particular.
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    Selenium as antioxidant - Functions of selenium

    Home > Functions of selenium - Selenium as antioxidant.
    Selenium antioxidant function is brought about by the Glutathione peroxidase selenoproteins.
    In the biochemical processes in the body certain oxidative free radicals are produced. Though these are required in smaller quantities for the biological process, excess of them can be self-hurting, damaging our cells and membranes and also triggering oxidation of LDL and plaque deposit on the arterial walls.
    Antioxidant (catalyzed by selenium compounds) neutralizes these free radicals turning them into harmless products.
    We get some of the antioxidant forms from our food, whereas many of them are endogenously synthesized by our body.
    Many of their function are catalyzed by enzymes and among them selenoproteins (obviously containing selenium) like glutathione peroxidases (GPX) and thioredoxin reductases are very important.

    Selenium as antioxidant

    This mineral in its rare elemental form is not absorbed as such by our body and does not have any biological function except being toxic in excess exposure and inhalation.
    However the water soluble selenite and selenate salts of selenium, the amino acid selenomethionine and food forms are absorbed by the body.
    In protein building, selenomethionine can be used by the body instead of the amino acid methionine, resulting in some of the selenium incorporated in tissues and unavailable in plasma.
    Though selenium compound as such is not antioxidant, it has the vital action in catalyzing the reduction activity as an enzyme.
    The cellular and sub cellular membrane integrity depends totally on glutathione peroxidases.
    Further the protective catalyst function of glutathione peroxidase itself depends on the presence of selenium.

    Selenoproteins as selenium enzymes

    This mineral is a constituent of the selenoproteins enzymes glutathione peroxidases (GPXs) and thioredoxin reductases (TrxRs).
    GPXs main function is in catalysing the oxidation of glutathione (GSH), the most important endogenous antioxidant produce by the body cells.
    Glutathione (GSH) in the presence of selenium enzymes, participates directly to neutralize the harmful free radicals and other reactive oxygen compounds.
    It also keeps the exogenous polyphenols, vitamin C and vitamin E in their active reduced forms.
    Thioredoxin reductases (TrxRs) catalyse the reduction of the redox protein thioredoxin (Trx); the reaction is NADPH-dependent.

    Types of selenium antioxidant enzymes and their functions

    There are several isozymes of the selenium containing selenoprotein enzymes glutathione peroxidases.
    They vary in their substrate specificity and their cellular location.
    In humans, so far eight isoforms of glutathione peroxidases have been identified.
    The most abundant form Glutathione peroxidase 1 (GPX1) is found in the cytoplasm of nearly all cells with hydrogen peroxide (H2O2) as preferred substrate.
    Glutathione peroxidase 2 (GPX2) is an intestinal and extracellular enzyme.
    Glutathione peroxidase 3 (GPX3) is extracellular enzyme and abounds plasma.
    Glutathione peroxidase 4 (GPX4) is present in every cell and its preferred substrates are lipid hydroperoxides.
    The antioxidant catalyst process is as follows.
    2GSH +H2O2 → GS-SG + 2H2O
    (GSH represents reduced monomeric glutathione, and GS–SG represents glutathione disulfide.)
    The function and process is at the selenium-cysteine site, wherein it is in a Se(-) form as resting state.
    This is oxidised by peroxide to SeOH which then reacts with GSH to form GS-Se and water.
    Then Gs-Se reacts with another GSH molecule to form Se(-) again, releasing GS-SG as the by-product.
    Glutathione reductase then reduces the oxidized glutathione to form the GSH again.
    GS–SG + NADPH + H+ → 2 GSH + NADP+
    Thioredoxin reductases (TrxRs) are a family of selenium-containing pyridine nucleotide-disulphide oxidoreductases.
    The main function of TrxRs is catalysis of the NADPH-dependent reduction of the redox protein thioredoxin (Trx), as well as of other exogenous and endogenous compounds.
    Presently two confirmed forms have been identified.
    Again The availability of Selenium is a key factor for TrxR activity.
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    Function of vitamin C in human physiology

    Home > Functions of vitamin C

    Function of vitamin C in our body includes many vital metabolic activities like protein synthesis, energy production, antioxidative actions and neurotransmission.
    Vitamin C being a very essential nutrient has important functions almost in all systems of the body. Some of the functions are briefly listed.
    Function of vitamin C in the enzymatic reactions for collagen production
    Vitamin C acts as an electron donor in many different enzymatic reactions taking place in various organs of our body.
    It is a co-factor in lysyl hydroxylase and prolyl hydroxylase, the enzymes essential for collagen hydroxylation.
    This hydroxylation of collagen is essential for its role in the developing and maintaining cartilage, blood vessels and scar tissue.
    The function of vitamin C in energy production
    The role of ascorbic acid in the enzymatic reactions for the production of carnitine is crucial.
    Carnitine is biosynthesized from amino acid methionine and amino acid lysine.
    Carnitine is required for transporting fatty acids from cytosol or intracellular fluid into mitochondria, (powerhouse of the cell) for the generation ATP and metabolic energy by the breakdown of lipids.
    The role of vitamin C in neuro-transmission
    The role of ascorbic acid in the enzymatic reaction of dopamine beta hydroxylase is in the biosynthesis of stress hormone norepinephrine (also a neurotransmitter) from dopamine.
    This hormone along with epinephrine (another hormone and neurotransmitter) induces the brain for flight-fight response.
    In another enzymatic reaction the role of ascorbic acid is in regulation of tyrosine (an amino acid) metabolism.
    Tyrosine is a precursor of dopamine which in turn is a precursor for neurotransmitters.
    The function of vitamin C in hormone production
    In another enzymatic reaction with the association of ascorbic acid, amide groups are added to peptide hormones to increase their stability.
    Some of the peptide hormones like luteinizing hormone, follicle-stimulating hormone, prolactin, adrenocorticotropic hormone (ACTH), growth hormone and antidiuretic hormone are very important for reproductive health, excretory organs, hormone production and regulation.
    Vitamin C in immune reactions
    One of the important role of vitamin c is in the production of certain antibodies essential for neutralising proteins of pathogens and give faster recovery from diseases.
    Ascorbic acid helps in the production of interferon which gives resistance to the body for countering viral attacks.
    Ascorbic acid counters the allergic reactions by interfering in the release of histamines and reducing histamine levels in blood circulation.
    Nitrosamines are potential carcinogenic compounds. They are produced from nitrites found in food. These can cause cancer in the digestive system and their formation is blocked by vitamin C in the stomach.
    Function of vitamin C in nutrition
    Folic acid has to be converted into active form for proper utilisation and ascorbic acid aids in this metabolism of folic acid.
    Iron has to be in oxidized form for absorption and utilisation by the body and in the presence of vitamin C this is achieved.
    Vitamin E is regenerated from its reduced form by ascorbic acid.
    Ascorbic acid functions as a regulator of serum levels of copper, iron and lead keeping them below toxic levels by stimulating their excretion, decreasing their absorption or increasing their absorption as required.
    Function of vitamin C as antioxidant
    The antioxidant activity of ascorbic acid prevents the oxidation of LDL (low density lipoprotein), oxidative damage of DNA and proteins.

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