Calcium

Calcium is thought to be the most abundant mineral in the body, making up about 1 – 2 % of body weight and about 39 % of total body minerals. Approximately 99 % of calcium exists in bones and teeth, while the remaining 1 % is located in the blood, extracellular fluids and within cells, where it regulates many important metabolic functions. Good dietary sources of calcium include milk and dairy products, tinned fish inclusive of bones, dark green leafy vegetables, and pulses.

Functions

Calcium has a range of crucial functions within the body, some of which are highlighted below;

assists with normal growth and development
helps to regulate fluid balance by controlling the flow of water in and out of cells
enables nerve cells to send messages back and forth from one to another
is a component of bones and teeth
facilitates muscle contraction
enables normal blood clotting
may assist with regulating cholesterol levels
acts as a buffer for excess acidity
assists in providing cell structure
is part of iron metabolism
assists with the absorption of vitamin B12

Reference Intake (RI)

AGE

CHILDREN

MALES

FEMALES

MALES

FEMALES

PREGNANCY

YEARS

1-3

4-6

7-10

11-14

15-17

11-14

15-17

18-64

65+

18-64

65+

Calcium (mg / d)

350

450

550

1000

800

700

(no increment)

MONTHS	0-3	4-6	7-9	10-12	LACTATION
Calcium (mg / d)	525	525	525	525	(+550)

Food Sources

PRODUCTS	Watercress	Mozzarella Cheese	Milk & Yogurt	Chinese Cabbage (Pak Choi, Bok Choy)
(mg / 100 g)	120	961	125	105
PRODUCTS	Fortified Soy Products (tofu)	Fish Canned (sardines, in oil, with bones)	Broccoli	Almonds
(mg / 100 g)	350	383	47	264

Below we have highlighted foods that will provide approximately one third of the adult reference intake (RI) for calcium:

Milk (200 mls)
Cheese - a small chunk (30g)
Yoghurt - one small carton (150g)
Cottage Cheese - one large carton (200g)
Canned Sardines - 1 serving (60g)
White bread - 5 large slices
Green Leafy Vegetables - 5 servings (500g)
Baked Beans - 3 servings (500g)
Mixed Nuts – a large portion (300g)
Sesame Seeds - 3 tablespoons (35g)

Deficiency / Toxicity

Signs of calcium deficiency may include:

Muscle cramps
Muscle tremors
Insomnia
Nervousness
Joint pain
Tooth decay
High blood pressure
Poor bone healing following fracture
Brittle nails
Rickets

Calcium taken in excess may be toxic to the body. It is known to interfere with the absorption of zinc, magnesium, iron, phosphorous and other nutrients. Indeed, it has recently been suggested that growing trends of fortifying foods with calcium, and not magnesium, may be causing an imbalance in the optimal calcium to magnesium ratio. When the calcium / magnesium balance id disrupted, excess calcium may be the deposited in the soft tissues resulting in calcium deposits in the heart, kidneys and arteries.

Factors influencing the uptake of calcium

The following factors may hinder the uptake of calcium;

Tea
Coffee
Alcohol
Chocolate
Red wine
Excess protein intake
Hyper- / hypo-vitamin D
Corticosteroids
Lack of exercise
Kidney damage
Post Menopausal status

It is also important to note that individual absorption of calcium can vary depending on race, gender and age.

It is thought that optimal vitamin D, magnesium and boron status may help in the absorption of calcium.

Calcium

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