Calcium
Sue McGarrigle ND DipION CNHC MBANT Bionutri Ltd
Introduction Minerals such as calcium, magnesium and phosphorus are inorganic elements that play essential roles in metabolism and structure. They must be obtained from the diet and are needed as co-enzymes (catalysts) in metabolic pathways e.g. energy production and detoxification. Calcium is the most abundant mineral in the body and is found in some foods, added to others, is available as a food supplement but also present in some medicines. A large amount of calcium is stored in bone; around 98% in adults is in the skeleton and the teeth where it is combined with phosphates to form a crystal lattice and where it supports their structure and function. The body will use this reservoir to maintain calcium levels in blood which is tightly regulated within a narrow range. The remainder of calcium is present within the extracellular and intracellular fluids. In body fluids calcium is mainly an extracellular cation (Ca2+) and is essential for cell physiology; it is transported through the bloodstream as dissolved ions or bound to proteins such as serum albumin (a marker for calcium levels) and complexed with phosphate and citrate. Ca2+ ions are one of the most widespread second messengers used in signal transduction and their movement functions as a signal for many cellular processes which include; playing an important part in blood clotting, acidity and alkalinity, vascular contraction and vasodilation, cell division and differentiation, neurotransmitter release, maintenance of muscle tone and excitability of nervous and muscle tissue.
The two main regulators of Ca2+ concentration in plasma are parathyroid hormone (PTH) and calcitriol (1, 25-dihydroxy vitamin D3), in the form of vitamin D that acts as a hormone. A low plasma Ca2+ level promotes release of more parathyroid hormone, which stimulates osteoclasts in bone tissue to release calcium (and phosphate) from mineral salts of bone matrix. Calcitriol also increases Ca2+ production from the gastrointestinal tract and enhances reabsorption of Ca2+ from glomerular filtrate through renal tubule cells and back into blood. Calcitonin secreted from the parafollicular cells of the thyroid gland also affects calcium levels by opposing parathyroid hormone. Circulating levels of these two hormones are adjusted automatically to maintain normal calcium levels in the blood. Many other hormones such as cortisol and insulin and those that affect growth can also affect calcium metabolism.
Deficiency of Calcium Deficiency of calcium (hypocalcaemia) may be due to increased calcium loss, reduced calcium intake, oestrogen deficiency 1, elevated levels of phosphate (commonly from fizzy drinks)2, gastro-intestinal surgery 3 and hypoparathyroidism. Symptoms include numbness and tingling of fingers, hyperactive reflexes, muscle cramps and twitching, nervousness, irritability, insomnia, spasm of the larynx, tooth decay, heart arrhythmia, cold sores, herpes and bone fractures.
Causes include:
Vitamin D deficiency
Chronic renal failure
Magnesium deficiency
Alcoholism which promotes excretion through the kidney
Biphosphonate therapy - drugs used to treat high blood calcium levels or osteoporosis.
Certain types of leukaemia or blood disorders 4,5,6
A complication of chemotherapy, tumour lysis syndrome, occurs when the body breaks down tumour cells rapidly, after chemotherapy. This may cause hypocalcaemia, high blood potassium levels, and other electrolyte abnormalities.7
Drugs such as diuretics, H2 blockers, magnesium salts, mineral oil, oestrogen replacement therapy, fluorides, glucose, insulin, excessive laxative use, anticonvulsive drugs such as phenobarbital and corticosteroids may also lead to hypocalcaemia.
Caffeine, excess fibre, phosphates, and certain antibiotics may make it difficult to absorb calcium.
Food intolerances/allergies may also contribute where eating a narrow range of foods combined with malabsorption due to gut inflammation can cause lower calcium levels. Poor protein intake also causes imbalanced calcium metabolism. Calcium antagonists can also contribute to calcium deficiency. The following are examples of foods and physical imbalances that can reduce absorption of calcium:
Fluoride
Low stomach acid
Low dietary protein
Excess phosphorus
Rhubarb
Spinach
Chard
Grains
Cereals
The following can be antagonistic to utilisation:
Lead
Cadmium
Excess sodium
Excess potassium
Excess calcium (Hypercalcaemia) may result from hyperparathyroidism, some cancers8, excessive intake of vitamin D and Paget’s disease9. Symptoms include constipation, lethargy, weakness, anorexia, nausea, vomiting, polyuria, itching, depression, confusion, paresthaesia, kidney stones, gall stones, bursitis and arthritis.(10) Examples of granulomatous diseases that cause elevated calcium levels include tuberculosis, candidiasis, histiocytosis, sarcoidosis and Crohn's disease. High calcium in the blood occurs because these diseases can cause elevated calcitriol levels. Examples of endocrine disorders that cause high levels of calcium in the blood include Cushing's disease and Addison's disease. (10) Lithium therapy can cause mild elevations that usually resolve once therapy has been discontinued. Thiazide diuretics can also cause increased blood calcium levels because they decrease the excretion of calcium by the kidneys.(10) People who are immobilised may develop high levels of calcium in the blood because of the breakdown of bone that occurs.
Immobilisation may be due to paraplegia, quadriplegia, orthopaedic casts or traction, or osteoporosis.(10) Calcium plays a central role in mitochondrial function. Stress can cause abnormal calcium levels leading to mitochondrial dysfunction.
