Calcium

Functions:

Structurally, Calcium is involved in the maintenance of intracellular structures such as organelles and chromatin.
Calcium bound to amines, such as catecholamines, plays a structural role in the secretory granules of endocrine cells and nerve terminals.
Calcium bound to phospholipide and proteins is necessary for maintaining integrity and permeability properties of biological memtranes, and when
bound to DNAs is required for determining some of the structural features of chromosomes.

Calcium role in digestion

Calcium is required for optimal activity of several extracellular digestive enzymes including proteases, phospholipases and nucleases.
Along the strengh of the gastrointestinal tract a calcium ion sensing receptor is expressed and it is though that the expression of this receptor plays a role in gastric acid secretion.
Bone health and osteoporosis
Bones need plenty of calcium and vitamin D throughout childhood and adolescence to reach their peak strength and calcium content by about age 30.
After that, bones slowly lose calcium, but people can help reduce these losses by getting recommended amounts of calcium throughout adulthood and by having a healthy, active lifestyle that includes weight-bearing physical activity (such as walking and running).
Osteoporosis is a disease of the bones in older adults (especially women) in which the bones become porous, fragile, and more prone to fracture. Adequate calcium and vitamin D intakes as well as regular exercise are essential to keep bones healthy throughout life.

Cardiovascular Disease

Whether calcium affects the risk of cardiovascular disease is not clear. Some studies show that getting enough calcium might protect people from heart disease and stroke.

High blood pressure

Some studies have found that getting recommended intakes of calcium can reduce the risk of developing high blood pressure (hypertension). One large study in particular found that eating a diet high in fat-free and low-fat dairy products, vegetables, and fruits lowered blood pressure.

Cancer

Studies have examined whether calcium supplements or diets high in calcium might lower the risks of developing cancer of the colon or rectum and decrease the risk of prostate cancer. The research to date provides no clear answers. Given that cancer develops over many years, longer term studies are needed.

Weight loss

Although several studies have shown that getting more calcium helps lower body weight or reduce weight gain over time, most studies have found that calcium—from foods or dietary supplements—has little if any effect on body weight and amount of body fat.

What food it is found in

Calcium in selected cereal products (FSA 2002) Calcium (mg/100 g)

Wheat flour, brown 130
Wheat flour white, plain 140
Wheat flour, white, self-raising 350
Wheat flour, wholemeal 38
Rice, brown, boiled 4
Pasta, fresh, cooked 37
Digestive biscuits, plain 92
Gingernut biscuits 130
Brown bread 186
White bread 177
Wholemeal bread 106
Pitta bread, white 138
Rye bread 80
Cornflakes 5
Weetabix 35
Frosties 453
Doughnuts, jam 72
Sponge cake 69
Sultana bran 50
Porridge, made with water 7

Calcium content in selected dairy foods (mg/100 g)

Skimmed milk (average) 160
Semi-skimmed milk (average) 156
Whole milk (average) 118
Channel Island milk (whole, pasteurised) 130
Condensed milk, sweetened 330
Dried skimmed milk 1280
Goat’s milk (pasteurised) 100
Human milk (mature) 30
Sheep’s milk (raw) 170
Butter 18
UHT dairy cream (canned spray) 54
Cream, single 89
Cream, double 49
Crème fraiche 58
Crème fraiche, half fat 95
Brie 256
Cheddar 739
Cheddar type, half fat 840
Cheese spread, plain 498
Cottage cheese, plain, reduced fat 13
Feta 360
Edam 795
Goats cheese, soft 133
Stilton 326
Parmesan 1025
Yoghurt, whole milk, plain 200
Yoghurt, low fat, plain 162
Drinking yoghurt 100
Ice cream, dairy, vanilla 100
Ice cream, non-dairy, vanilla 72

Calcium content in selected plant foods (mg/100g)

Baked beans, canned in tomato sauce 53
Chick peas, dried, boiled 46
Lentils, green/brown, dried, boiled 22
Peas, frozen, boiled 42
Broccoli, boiled 40
Cabbage, average, boiled 33
Carrots, old, raw 25
Curly kale, boiled 150
Spinach, boiled 160
Tomatoes, canned 12
Watercress, raw 170
Lettuce, average 28
Soya beans, dried 240
Soya beans, dried, boiled 83
Soya non-dairy alternative to milk, unfortified 13
Soya non-dairy alternative to yoghurt, fruit 14
Almonds 240
Hazelnuts 140
Walnuts 40
Sunflower seeds 110
Potatoes, new in skins, boiled 13
Potatoes, old, baked, flesh and skin 11
Potatoes, old, boiled 5
Apples, average 4
Apricots, ready to eat 73
Figs, dried 250
Olives, in brine 61
Pineapple 18
Banana 6
Oranges 47
Rhubarb, raw 93
Sultanas 54
Tofu, steamed* 510
*If nigari is used as a coagulant in tofu the calcium content is 150 mg/100 g.
Soya non-dairy alternative to milk, calcium fortified 89
Soya dessert (Provamel) 108
Cashew nuts 32
Peanuts (plain) 60
Sesame seeds 670
Pumpkin seeds 39
The Calcium contents is an extract of the 2005 British Nutrition Foundation Nutrition Bulletin

What symptoms and disorders deficiency causes

If calcium concentration in the plasma fall too law, hypocalcaemic may occur. This causes paraesthesia (itchy, tingly skin), laryngeal spasms, respiratory arrest, cardiac arrhythmia and can be fatal.
Insufficient intakes of calcium do not produce obvious symptoms in the short term because the body maintains calcium levels in the blood by taking it from bone. Over the long term, intakes of calcium below recommended levels have health consequences, such as causing low bone mass (osteopenia) and increasing the risks of osteoporosis and bone fractures.
Symptoms of serious calcium deficiency include numbness and tingling in the fingers, convulsions, and abnormal heart rhythms that can lead to death if not corrected. These symptoms occur almost always in people with serious health problems or who are undergoing certain medical treatments.

Problems related to excessive doses:

Some studies show that some people who consume high amounts of calcium, particularly from supplements, might have an increased risk of heart disease. More research is needed in this area.
Most kidney stones are rich in calcium oxalate. Some studies have found that higher intakes of calcium from dietary supplements are linked to a greater risk of kidney stones, especially among older adults.
But calcium from foods does not appear to cause kidney stones.
For most people, other factors (such as not drinking enough fluids) probably have a larger effect on the risk of kidney stones than calcium intake.
Getting too much calcium can cause constipation.
It might also interfere with the body's ability to absorb iron and zinc, but this effect is not well established.
Calcium dietary supplements can interact or interfere with certain medicines that you take, and some medicines can lower or raise calcium levels in the body.
Here are some examples:

Calcium can reduce the absorption of these drugs when taken together:

Bisphosphonates (to treat osteoporosis)
Antibiotics of the fluoroquinolone and tetracycline families
Levothyroxine (to treat low thyroid activity)
Phenytoin (an anticonvulsant)
Tiludronate disodium (to treat Paget's disease).
Diuretics differ in their effects. Thiazide-type diuretics (such as Diuril® and Lozol®) reduce calcium excretion by the kidneys which in turn can raise blood calcium levels too high. But loop diuretics (such as Lasix® and Bumex®) increase calcium excretion and thereby lower blood calcium levels.
Antacids containing aluminum or magnesium increase calcium loss in the urine.
Mineral oil and stimulant laxatives reduce calcium absorption.
Glucocorticoids (such as prednisone) can cause calcium depletion and eventually osteoporosis when people use them for months at a time.

Recommended doses for people in the UK

The Government’s National Diet and Nutrition Survey has identified calcium as generally lacking in the British diet, particularly among young children and women.

Daily calcium requirements:

Age RNI*
0-12 months (non breast-fed infants only) 525mg
1-3 years 350mg
4-6 years 450mg
7-10 years 550mg
11-18 years 1,000/800mg
19+ years 700mg
Pregnant women 700mg
Breast-feeding women 700+550mg

* RNI - Reference Nutrient Intake. Taken from the Government's Committee on the Medical Aspects of Food Policy (COMA), Report 41.

An average adult should aim to take in 700mg calcium each day.
However, the amount of calcium required by our bodies is dependent on our life stage. Babies, children and adolescents require large amounts for growth and development, while pregnant and breast-feeding mothers must have an adequate intake to ensure their own calcium levels are not compromised.
Post-menopausal women, who are particularly at risk from osteoporosis, may need to boost calcium intake to approximately 1,200mg per day.
A calcium supplement can help.
Other nutritional and lifestyle factors are important for bone health.
Vitamin D plays a crucial role in bone metabolism and calcium absorption.
Most of our vitamin D comes from normal daily exposure to sunlight.
Dietary sources include oily fish, eggs and fortified foods, such as margarine.