Bone and Joint Health

Bone is living tissue which continues to be renewed throughout life, with older cells being replaced by new ones. Bone is made up of a protein matrix, upon which hydroxyapatite (a crystalline structure made up of calcium and phosphorus) is deposited. Magnesium, zinc and fluoride are also deposited in the protein matrix, although calcium is the most abundant mineral in bone; and it has been estimated that the average adult skeleton contains 1kg of calcium.  Bone plays a structural role in the body and also serves as a reserve of calcium that is used to maintain calcium levels in the blood within narrow limits (calcium is essential for many basic metabolic processes, such as signal transmission, muscle contraction, normal blood clotting). Healthy bone is strong and does not break easily. During childhood, adolescence and early adulthood, large amounts of calcium and other substances are added to the bone, strengthening the skeleton as it grows.
 
Bone is continuously being remodelled, that is old bone tissue is replaced by new. Bone formation and bone resorption (replacement of old bone tissue) take place throughout life, although at different rates at different times and at different sites within the skeleton. In childhood the process enables the bones to grow; in adulthood the purpose is maintenance. Bone formation and bone resorption are influenced by a variety of factors including diet and physical activity. Bone formation is greater than bone resorption during growth and up until we reach our mid-twenties, when peak bone mass is reached, the net effect being an increase in bone mass. Peak bone mass is influenced by genetic factors such as build and ethnic group. It can be increased by ensuring that the diet contains adequate amounts of calcium and vitamin D during childhood, adolescence and early adulthood, and by regular activity especially weight-bearing exercise such as brisk walking, running, dancing and climbing stairs.

As we progress through adulthood, bone resorption occurs at a faster rate than bone formation. The consequence of this is a gradual fall in bone mass as we age. In women, bone loss is accelerated following the menopause, particularly during the first 5-10 years. This is because the hormone oestrogen (production of which ceases after the menopause) protects bone, and bone formation and loss is influenced by such hormones.

A healthy balanced diet will help you build healthy bones from an early age and maintain them throughout your life.

You need sufficient calcium to keep your bones healthy and vitamin D to help your body absorb calcium.

Poor bone health can cause conditions such as rickets and osteoporosis and increase the risk of breaking a bone from a fall later in life.

You should be able to get all the nutrients you need for healthy bones by eating a balanced diet.

A good diet is only one of the building blocks for healthy bones, which also includes exercise and avoiding certain risk factors for osteoporosis.

Calcium

Adults need 700mg of calcium a day. You should be able to get all the calcium you need by eating a varied and balanced diet.

Good sources of calcium include:

• milk, cheese and other dairy foods
• green leafy vegetables, such as broccoli, cabbage and okra, but not spinach
• soya beans
• tofu
• plant-based drinks (such as soya drink) with added calcium
• nuts
• bread and anything made with fortified flour
• fish where you eat the bones, such as sardines and pilchards

Although spinach contains a lot of calcium, it also contains oxalate, which reduces calcium absorption, and it is therefore not a good source of calcium.

Vitamin D

Adults need 10 micrograms (400 International Units or IU) of vitamin D a day.

It’s difficult to get all the vitamin D we need from our diet and we get most of our vitamin D from the action of the sun on our skin.

From late March/April to the end of September, you can make vitamin D from sunlight by having short daily periods of sun exposure without sunscreen. However, everyone should consider taking a daily vitamin D supplement during the autumn and winter when we cannot make vitamin D from sunlight.

Vegans

Non-vegans get most of their calcium from dairy foods (milk, cheese and yoghurt), but vegans will need to get it from other foods.

Good sources of calcium for vegans include:

• fortified soya, rice and oat drinks
• soya beans
• calcium-set tofu
• sesame seeds and tahini
• pulses
• brown and white bread (in the UK calcium is added to white and brown flour by law)
• dried fruit such as raisins, prunes, figs and dried apricots

The vegan diet contains little, if any, vitamin D without fortified foods or supplements but, for everyone, sunlight on the skin in spring and summer is the main source of vitamin D. Remember to cover up or protect your skin before it starts to turn red or burn (see how to make vitamin D from sunlight).

Other vegan sources of vitamin D are:

• fortified fat spreads, breakfast cereals and plant-based drinks such as soya drink (with vitamin D added)
• vitamin D supplements

During pregnancy and when breastfeeding, women who follow a vegan diet need to make sure they get enough vitamins and minerals for their child to develop healthily.