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Nutrient - Focus on Calcium

By Jenny Bodenham BA (Hons) Dip ION MBANT

Recent press coverage has suggested there is an increased risk of heart disease in people who take Calcium. The report is not only at odds with Department of Health advice but The National Institute of Health and Clinical Excellence (Nice) also recommends Calcium supplements for women who need treatment for osteoporosis, unless they already get enough in their diet. Jenny Bodenham explores the potential health benefits of this mineral further.

Calcium is the most abundant mineral in the body. Approximately 99% of the body’s calcium is found in the bones and teeth supporting their structure and function. Circulating calcium in the blood is tightly regulated with the bone tissue acting as a calcium reservoir. Bone undergoes constant resorption (the breaking down of bone) and remodelling where calcium is deposited into the bone. When there is a deficiency, the process of bone resorption releases calcium into the bloodstream through the action of bone osteoclasts to maintain constant serum levels. Calcium is regulated by vitamin D, calcitonin and parathyroid hormone. The hormones insulin and oestrogen are also known to affect calcium retention.

Functions

Calcium is needed by the body for:

• bone health

• heart function

• nerve transmission

• muscle function

• vascular contraction and vasodilation

• cell membrane and capillary permeability

Calcium also plays a role in enzyme reactions, respiration, renal function, hormonal secretion and blood coagulation. Additionally it is used in neurotransmitter and hormone release and storage, uptake and binding of amino acids, vitamin B12 absorption, and gastrin secretion. Low dietary calcium has been linked with symptoms of pre-menstrual syndrome. Studies have shown that calcium supplementation has resulted in a reduction in water retention, depressed mood and pain associated with PMS. 

Deficiency signs

• In adults, calcium deficiency may lead to osteomalacia (softening of the bone)

• In children, calcium deficiency may lead to rickets (bone deformities and retardation of growth), though this is more commonly associated with vitamin D deficiency

• Low levels of calcium may lead to muscle spasms and leg cramps, particularly at night without any real exertion

• Long-term low calcium intake may contribute to the development of osteopenia, which can lead to osteoporosis

• Low tissue calcium may lead to anxiety and irritability

Food Sources

• Dairy products including milk, yoghurt and cheese

• Tofu (made with calcium salts)

• Broccoli and green leafy vegetables which are not high in oxalic acid including kale, turnip greens and dandelion leaves

• Nuts and seeds such as almonds, brazil nuts, hazelnuts, sesame and sunflower seeds

• Tinned fish with edible bones such as sardines, salmon

The rate of calcium absorption from kale is superior to that of milk. Spinach, however, is not a good source of absorbable calcium. Although it is calcium-rich it is also high in oxalic acid, which binds the calcium, reducing its absorption. Pulses, grains, nuts and seeds contain phytic acid, which impairs absorption of minerals such as zinc and iron and to a lesser extent, calcium and magnesium. The effects of the phytic acid may be minimised by sprouting seeds and soaking beans and lentils before cooking. 


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