Osteoporosis and diet

What is osteoporosis?

Osteoporosis means 'porous bones'. The texture inside our bones is like honeycomb, and over the years the holes in the honeycomb become larger as they lose bone mineral. This is called osteoporosis, and it weakens bones and makes them more vulnerable to breaking.

Often osteoporosis is called 'the silent disease' as it can remain undetected until someone has a broken bone as a result of a fall or accident. Broken wrists, hips and spinal bones are the most common fractures as a result of osteoporosis.

What causes osteoporosis?

We often think of bones as being 'static', but we're constantly making new bone and breaking down old bone. There are two kinds of cells that help in this process. During childhood and up to our 20s, the 'building' cells dominate over the 'destruction' cells. After the age of about 30, the 'building' cells slow down and by the age of around 40 the 'destruction' cells dominate. This means we lose bone mineral faster than we replace it, and the end result is osteoporosis.

It's important to build up as much bone mineral as we can while we're growing because our 'building' cells are at their peak.

Who's at risk of osteoporosis?

Your genes play a role in bone health, so a family history of osteoporosis means a greater risk. Other risk factors include:

• Early menopause or hysterectomy
• Taking corticosteroids (steroids) for conditions such as asthma, arthritis or inflammatory bowel disease
• Illness and inability to move very much
• Conditions that affect absorption of foods, such as coeliac disease
• Excessive drinking
• Smoking
• Being very underweight

How to minimise the risk of osteoporosis

There are many ways to help our bodies build strong and healthy bones, especially during childhood and adolescence. After about the age of 30, it's difficult to increase bone mass, but protecting your bones can begin at any age.

Here are a number of ways to build and maintain healthy bones:

• Get active - regular weight-bearing activity can help maintain bone strength and reduce the rate of loss of bone mineral. Activities such as brisk walking, climbing stairs or jogging are good examples of weight-bearing exercise. Short bouts of high-impact activity, such as jumping up and down, are helpful for building bones when you're young.
• Boost calcium intake - calcium is important for healthy bones, and a mature adult skeleton contains about 1,200g. Many foods contain calcium, but the richest and most easily absorbed source is found in dairy products. Aim for about three servings of these a day to meet your calcium needs, such as a glass of milk, a small matchbox-sized piece of cheese and a 150g pot of yogurt. Fish eaten with bones, pulses, cereals, nuts, seeds, dried fruit and green vegetables also contain calcium.

• Soak up vitamin D - vitamin D helps our bodies to absorb calcium from the digestive system. Most of the vitamin D we need comes from exposing our skin to sunlight. It's also found in oily fish and fortified margarines. Some groups - such as older people, those who aren't able to go outside or those who cover up completely when outside - might need a daily supplement (10 micrograms) of vitamin D. Speak to your GP if you think you might need this.
• Choose plenty of fruit and vegetables - fruit and vegetables (particularly green leafy vegetables) contain vitamin K, which is thought to have a role in building healthy bones. Fruit and vegetables also make the body less acidic, which helps to keep calcium in bones.
• Watch your intake of certain foods - animal protein foods, salt, fizzy drinks, alcohol and caffeine can all work to leech minerals out of bones
• Keep a healthy body weight - a very low body weight can affect bone health and increase the risk of osteoporosis. Heavier people tend to have a higher bone mass, but being too overweight has other effects on health.
• Smoking - smoking prevents the bone-building cells from working as efficiently as they should.

The MRC Human Nutrition Research last medically reviewed this article in June 2008.
First published in March 2001.