Calcium

Calcium is essential for building and maintaining bone. It combines with other minerals to form the hard crystals that give bone its strength. Almost all the body's calcium (about 99%) is found in the bones.

The remaining 1% is dissolved in blood and other fluids which is essential for maintaining healthy functioning of the heart, muscles, blood and nerves.

Our bodies cannot make calcium, so it must come from our diets. When you are not getting sufficient amounts of calcium in your diet, some of the calcium crystals in bone dissolve and give their calcium back to the bloodstream. Bones therefore act like a calcium bank, storing calcium and releasing it into the blood stream when needed. So if your calcium intake is too low and there are more withdrawals than deposits from your calcium bone bank, you risk losing bone strength.

Calcium absorption

Calcium intake is important and how well the calcium is absorbed is also important.

Calcium absorption may be reduced by excessive caffeine and alcohol, soft drinks containing phosphates and diets high in animal proteins. As well, calcium is continually lost from your body each day through your skin and nails, sweat, and urine.

Peak bone mass

By age 30, peak bone mass (maximum bone density) is reached and most of this is achieved by puberty when there is the greatest rate of bone growth.

The higher your peak bone mass, the more likely it is that you will maintain better bone health even during times of rapid bone loss such as menopause. This is why calcium is so important for children and teenagers.

Calcium intake

Your daily calcium needs depend on your age and sex.

In adults, dietary calcium is vital in order to maintain bone strength. Also, as we age calcium is absorbed less effectively from the intestine, so that intake needs to be increased. When the body can no longer replace calcium fast enough to keep the bones healthy, they become thinner and weaker, resulting in osteoporosis.

Less than half of all Australian adults get their daily recommended intake of calcium.

Who Needs to Eat What?

• Children 5 to 9 years should aim for 2 to 3 serves of calcium-rich foods each day to reach a total intake of 800 -1000 mg/day.
• Children and adolescents aged 9 to 18 years should aim for at least 3 serves of calcium-rich foods a day to reach a total intake of 1000 - 1300mg/day.
• Adults up to the age of 51 years should aim to consume at least 2 serves of calcium-rich foods a day to reach a total intake of 1000 mg/day.
• Postmenopausal women should aim for at least 3 serves of calcium-rich foods to reach a total daily intake of 1000 -1300 mg/day.
• For adults over 70 years, 1300 mg of calcium a day is recommended.

Sources of calcium

For most Australians, dairy foods are the main source of calcium. Dairy foods are the most convenient way to obtain adequate calcium because milk, yoghurt and most cheeses are particularly high in calcium. Small amounts of calcium are found in nuts, breads, cereals, fruits and vegetables. Three servings of dairy products each day will generally provide you with the recommended daily calcium intake around 1000 mg/day.

Calcium content of selected foods (click to enlarge)

Practical tips for getting more calcium in your diet

• Calcium is more easily absorbed from dairy products than most other food groups. Aim to get at least half your daily intake of calcium from dairy foods.
• Eat two to three serves of food each day that are high in calcium, eg a glass of milk, a container of yoghurt, a slice of hard cheese.
• Eat canned fish with bones, particularly canned salmon and sardines (the fish bones contain calcium).
• Add milk or skim milk powder to soups or casseroles.
• Use yoghurt in soups, desserts and salads.
• Some soy products such as tofu (bean curd) and a number of brands of soy milk are high in calcium or fortified with calcium. Check the labels as some unknown substances in soy products may impair calcium absorption.
• Eat more broccoli, beans, almonds, tinned salmon and sardines in your regular diet.
• If you cannot eat dairy foods, eat other types of food that contain calcium or that are fortified with calcium. Note: People with lactose intolerance are often able to eat yoghurt and cheese as the lactose levels in these foods have been broken down.
• Get advice from a dietician or nutritionist if you need help with increasing the calcium in your diet or for general advice on healthy eating.

Calcium Supplements

If you cannot get enough calcium in your diet, your doctor may suggest that you take a calcium supplement.

Supplements can be in the form of calcium phosphate, calcium carbonate and calcium citrate taken in pill, chewable or liquid form. Talk to your doctor about the type of supplement they recommend.

An extra 500-700mg of calcium per day is sufficient for most people. The easiest way to do this is with a single calcium tablet containing 600mg of calcium. Many companies now provide calcium tablets which also have vitamin D. Vitamin D helps the absorption of calcium from the gut. This is useful if you are vitamin D deficient.

When and How to Take Calcium Supplements

Generally it is not important whether calcium tablets are taken with or without food. Calcium carbonate requires gastric acidity for the best absorption, so it should be taken with meals. Calcium citrate is not dependent on gastric acidity so can be taken at any time.

Certain factors can interfere with calcium supplements being absorbed:

• foods such as phytates (cereals, brans etc) and oxalates (spinach, rhubarb etc)
• inadequate vitamin D
• long term corticosteroid use (eg prednisone and prednisolone)
• kidney disease.

Calcium supplements: latest debate - safety of calcium supplements - Click to download

Side Effects of Calcium Supplements

Calcium supplements are usually well tolerated and side effects are uncommon (but can include constipation, bloating and flatulence). There is no evidence of increased kidney stones from taking calcium supplements in the recommended amounts. 

Approved by Osteoporosis Australia Medical & Scientific Advisory Committee