Family doctor


Bones And Joints

BONE HEALTH - an overview for patients


A good intake of calcium is important for maintaining healthy bones. This article provides an in depth look at how to prevent osteoporosis and profiles the calcium content of a variety of foods.

Your bone health and the years ahead

The stooped back ... the falls that result in fractures ... little incidents that become more and more serious to your health and independence as the years go by.

Is this what we have to look forward to - a life marred by pain and deformity? Not necessarily - if you take the time now to take a little care of your bones. It's an investment that will pay off in a more active, independent lifestyle for longer - helping to ensure you get the most of the years ahead.

The importance of good bone health

Bones perform vital functions in your body. They provide the framework for your body to move and protect your vital organs. Understanding now what keeps your bone structure healthy will help keep you mobile and agile in later years.

Bone is a living tissue that is continually remodelled and rebuilt throughout your life. New bone is made and old bone is lost. When we are first born, bones are quite soft. They harden (or calcify) when calcium, protein and phosphorus are deposited in them.

Your body cannot make its own calcium, so it is essential to supply your calcium needs from your diet. (99 percent of the calcium in your body is in your bones, and 1 percent is in your blood and body fluids). Eating a balanced diet that includes calcium-rich foods can supply the calcium required to maintain these levels.

Under the microscope you can see bone has a honeycomb structure with lots of tiny holes. In some circumstances your body may start to take the calcium it needs from your bones. This leaves the honeycomb structure inside your bones thinner and weaker.

As we grow we need to provide enough calcium for building new bone as well as rebuilding and remodelling bone structure. By about age 30 bones have reached their strongest and most dense point. At this time bones contain high levels of calcium and have reached a stage called peak bone mass.

How does ageing cause bone loss?

As a natural part of ageing the bones lose calcium, making them less dense and therefore weaker. This decrease in bone mass affects both men and women. In women it becomes more pronounced during the middle years at menopause when the levels of the female hormone oestrogen fall.

Oestrogen helps to keep calcium in bones, so when levels drop women lose calcium from their bones more rapidly.

The rapid loss slows down after a few years, but if bone mass falls below a certain percentage of its maximum, you may cross the 'fracture threshold'. Below this point even minor falls can result in fractures. This is the condition called osteoporosis.

It is estimated that more than one in three women in this country over the age of 60 will suffer a broken bone due to osteoporosis.

What happens when bones become thin?

When bone loss occurs the hard outer shell of the bone thins out and the holes in the honeycomb structure become larger, causing a decrease in bone mass.

While bones remain the same size on the outside, they become thinner and weaker on the inside - particularly at the hip, wrist and spine.

The weakening of the bones makes them more prone to breaking. If this becomes severe it can result in older people getting shorter (due to the bones in the spine squashing), and suffering a variety of bone fractures - especially of the hip and wrist.

In extreme cases, bones have been known to fracture as a result of very minor movements such as sneezing.

As well as the pain and inconvenience of broken bones other health problems can often set in while people are immobolised, such as pneumonia.

Fractures occurring from low bone density have been diagnosed in people both young and old. For the elderly, this can be a real threat to their health, their independence and their enjoyment of life.

What can I do to help keep my bones strong?

Keeping plenty of calcium in the diet and following other steps for healthy living can help lessen the effect of calcium loss from bones.

These steps are covered further in the article, but basically it's a matter of maintaining an active and healthy lifestyle, taking care with what you eat and drink, and making sure you're giving your body the calcium and other nutrients it needs.

Do I need to make changes to my lifestyle?

A moderate and balanced way of living is important for maintaining good all round health and enjoying life to the full.

If you smoke, seriously consider giving up. As well as other benefits you will increase your ability to absorb important nutrients such as calcium.

Weight is an important factor too. Keeping active is a great way of controlling weight and is also good for bones because it encourages the uptake of calcium.

Being fine boned or underweight puts you at extra risk, especially when oestrogen levels fall at menopause.

But being overweight can decrease mobility, and has other health implications too.

The importance of exercise

Exercise is important right though life, even if you're not following an active "fitness" plan.

You should try and exercise for a total of 30 minutes a day or at least three times a week. It needn't be strenuous; if you are on the move at work or in the garden or have a pet to exercise, this will benefit your bones.

Exercises such as walking, golf, tennis, bowls or aqua-jogging create a pushing and pulling effect on the bones as they support your weight. These "weight bearing" exercises encourage the uptake of calcium and are best for bone health.

Swimming isn't a weight bearing exercise but it's beneficial in keeping you moving and agile.

It is important to do a range of activities for bone health, as well as for cardiovascular fitness, flexibility and general well-being.

What should I be eating?

Eat a variety of foods from the four food groups - fruits and vegetables; breads and cereals; meat and alternatives; milk and dairy products.

Dairy products come in a wide range of milks, cheeses, cultured and cream products. Low fat varieties often contain more calcium than the standard variety - for example, many non-fat milks contain more calcium than standard milk.

Eating too much fibre can reduce the availability of calcium from food when eaten at the same time. "Too much" fibre is more than 1/2 cup of unprocessed whole bran, but it doesn't include processed cereals containing bran.

More than four alcoholic drinks a day can also reduce calcium uptake.

Having adequate amounts of vitamin D helps your body to use calcium more efficiently.

  • Try to eat no more than 3 servings per day of protein foods such as meat, chicken or fish (imagine a serving as about the amount of food you could fit in the palm of your hand).
  • Have no more than six cups in total of either coffee, tea or cola drinks. Having milk with your coffee or tea helps to offset the negative effects of caffeine.
  • Try to limit the amount of salt you use in cooking and at the table. Many processed, takeaway and "fast" foods (including instant soups, sauce mixes and gravy mixes) are high in salt. Try and eat them no more than twice a week.

Am I getting enough calcium?

Your body can't make calcium: it relies on you to supply it. And when your bones start losing calcium as a natural part of ageing, it becomes even more important to ensure you're getting enough in your diet.

Most dairy products are an excellent source of calcium, including cheese, yoghurt, ice-cream and milk. This is where most New Zealanders get most of their calcium from.

If you're not eating three servings of dairy products every day (or alternative sources of calcium) then you may not be getting enough calcium.

Don't forget about milk. Most adults don't drink nearly as much milk as they did when they were younger. But milk isn't just for children - it's a valuable source of calcium for all age groups. Milk also contains other nutrients that are important for bone health including phosphorous, zinc and magnesium.

Fifty six percent of our calcium comes from diary products, 12 percent from bread and baked foods, 10 percent from fruit and vegetables, 7 percent from meat and alternatives, 5 percent from cereals and grains and 10 percent from other sources.

What if I don't eat diary products?

If you choose to avoid diary products you can still obtain calcium from other sources with a little thought and planning.

However, vegetable sources of calcium are not as concentrated as dairy products. The calcium may not be as well absorbed due to the presence of fibre, so you will need to eat more for the same benefit.

Other sources of calcium:
  • Fish such as sardines and tinned salmon eaten with the bones (these are also a good source of vitamin D)
  • Tofu
  • Soya milk fortified with calcium
  • Dried beans, nuts and seeds, such as almonds, sesame seeds or red kidney beans
  • Green vegetables such as broccoli, kale and cabbage

How much calcium do I need?

Your calcium requirements vary depending on your stage of life. From menopause you need more to compensate for your body's greater loss of calcium and reduced ability to absorb it.

Adults need approximately 800 mg of calcium per day and women over the age of 54 need 1000 mg per day. (These recommendations are the Australian Recommended Dietary Intakes (1990) for calcium that have been officially recognised and adopted for New Zealand).


Calcium content (approx.)

1 glass homogenised milk (200 ml)

200 mg

1 glass high-calcium milk (200 ml)

400 mg

1 glass non-fat milk (200 ml)

300 mg

1 pottle of yoghurt (150 g)

200 mg

3 slices cheddar cheese (40 g)

300 mg

1 cup ice cream (140 g)

200 mg

1/2 can sardines (50 g)

300 mg

1 cup of salmon (240 g)

200 mg

I medium bowl of muesli (80 g)

200 mg

2 (2.5 cm) cubes of tofu (80 g)

200 mg

1 cup cooked broccoli

100 mg

1/2 cup of almonds

200 mg

1 cup of baked beans (270 g)

100 mg

1/2 cup dried figs (105 g)

300 mg

1 cup of mussels (160 g)

300 mg

I eat well - do I need to take supplements?

Vitamin D is important for effective calcium absorption, so it is important to ensure you are getting enough of this vitamin as you grow older.

Normally you get enough from the action of sunlight on your skin, even when it's overcast. But as you get older, your skin is not as effective in creating vitamin D. So it is important that you ensure you include foods rich in vitamin D in your diet such as sardines, tuna, eggs and liver.

If you're housebound and don't get outside regularly you may also need a vitamin D supplement. You should talk it over with your doctor before you decide, because high amounts of vitamin D can be harmful.

Calcium supplements may also be a solution if you don't like or can't eat calcium rich foods. Supplements are a useful way of getting additional calcium, but provide little else nutritionally - in comparison to milk for example, which also provides minerals important to bone health such as phosphorus, zinc and magnesium. Ask your doctor which type of calcium supplement is best for you.

How can I check my bone health?

Bone strength is often assessed by measuring bone mineral density. This can be measured in a number of ways, using either x-rays or ultra sound.

The best way uses a bone densitometer (DEXA) which measures the amount of x-rays that the bones absorb. It is quick, simple, safe and doesn't hurt.

Bone density is a good predictor of your lifetime fracture risk. It helps to decide if you need treatment.

If you are concerned about osteoporosis, you should discuss these options with your doctor. The results of your assessment will be sent to your doctor who will explain them to you and, if necessary, recommend treatment.

What if I have osteoporosis already?

Although osteoporosis cannot be cured, loss of bone mass can be slowed or even reversed. This is important, as osteoporosis has been diagnosed in people as young as 20.

If you do have osteoporosis it is really important to keep eating a good supply of calcium-rich foods daily, such as those listed above.

Good eating habits may not be enough to affect the initial rapid drop in bone mass at menopause, but they may slow or even stop the continuing decline later on.

Hormone replacement therapy (HRT) can postpone the initial rapid decline.

You may be advised to also take a calcium supplement. Ask your doctor which type of supplement is best for you. There are other treatments for osteoporosis in women not suited to HRT or calcium supplements. If you want to know more, talk to your doctor. If is never too later to treat osteoporosis.

*Reproduced with kind permission from the Dairy Advisory Bureau, the Arthritis Foundation of New Zealand and Osteoporosis New Zealand.

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