How children’s bones grow
Children’s bones keep growing throughout childhood. They grow fastest of all very early in life and when children go through puberty.
The bones keep getting denser until they reach what’s known as ‘peak bone mass’. This usually happens between the ages of 18 and 25.
The denser your child’s bones are at the time of peak bone mass, the greater their reserves of bone to protect against the fragile bone disease osteoporosis later in life.
“The reserve of bone you establish during childhood and the teenage years is with you through early adulthood,” explains Dr Paul Arundel, a consultant in paediatric metabolic bone disease at Sheffield Children’s Hospital. “We all start to lose bone mass later in life. If you are starting from a low baseline you are more likely to develop osteoporosis sooner.”
The good news is that you can protect your child’s bone health with some simple lifestyle measures.
Your child’s bone-friendly diet
Building strong bones in childhood requires a range of vitamins and minerals. A healthy, balanced diet will provide this. That means a diet that includes:
• fruit and vegetables – at least five portions every day (but no more than one 150ml glass of fruit juice)
• carbohydrates – such as potatoes, pasta, rice and bread (preferably wholegrain)
• protein – such as meat, fish, eggs, beans, nuts and seeds
• dairy products – such as milk, cheese and yoghurts
There are a couple of nutrients that are particularly important for building strong healthy bones.
Calcium for healthy bones
Our bodies contain about 1kg of calcium. About 99% of this is found in our bones and teeth – it’s what makes them strong and hard. Most of this calcium is laid down during childhood and the teenage years.
Calcium is particularly vital during puberty when the bones grow quicker than at any other time. Puberty takes place over a number of years, typically sometime between 11 to 15 for girls and 12 to 16 for boys.
The recommended calcium intake for children and young people aged from 11 to 18 is 800-1,000mg compared with 700mg for adults. But research shows that, on average, children and young people in this age group don’t get enough.
“Teens need more calcium because they’re growing,” says Dr Arundel. “People don’t think about bone health in teenagers as much as they do with toddlers, but teenagers are growing a lot more.”
Foods that contain lots of calcium include dairy foods such as milk, cheese and yoghurt, but also tinned sardines (with the bones in), green, leafy vegetables (but not spinach), peas, dried figs, nuts, seeds and anything that’s fortified with calcium, including some soya milk.
Vitamin D for kids’ bone health
Vitamin D is important for bones because it helps our bodies to absorb calcium.
Our main source of vitamin D is sunlight. This is made by our skin when it’s exposed to the sun during the summer months. The problem is that, here in the rainy UK, more than one in five of us lack vitamin D, and this may affect the health of our bones.
There are only a few foods that contain useful amounts of vitamin D. These include oily fish, eggs and foods that have been fortified with vitamin D, such as spreads and cereals.
Vitamin D and under-fives
Children under five are one of the groups that are more likely to have low levels of vitamin D. Because of this it’s recommended that children aged from six months to five years take a daily vitamin D supplement.
If you breastfeed your baby it’s recommended that you give them vitamin D drops from soon after birth. Formula milk contains enough vitamin D to support babies’ bone health in the first six months.
For under-fives, it’s best to choose a vitamin D supplement that’s formulated especially for children. The supplement you choose should contain 7-8.5 mcg (about 300 units). Other supplements may not contain the right amount.
If you receive benefits, you may be eligible for free Healthy Start vitamins, which contain vitamin D. Your health visitor can tell you more, or visit the Healthy Start website.
Sunlight and children’s bone health
Sunlight is our main natural source of vitamin D. Short, regular periods of sun exposure without sunscreen from May to September is enough for most people to get the vitamin D they need. About 10 to 15 minutes is probably enough for lighter-skinned children. Children with darker skin will need to spend a little longer in the sun to produce the same amount of vitamin D.
It’s important never to let your child’s skin go red or start to burn. Babies under six months should never go in direct sunlight.
Bone-strengthening exercises for children
Daily physical activity is important for children’s health and development, including their bone health.
Try not to let your child be sedentary for long periods. You can do this by reducing the amount of time they spend sitting down, for example, watching TV or playing video games.
Children under five who aren’t yet walking should be encouraged to play actively on the floor. Children who can walk on their own should be physically active daily for at least 180 minutes (three hours) spread throughout the day. This should include some bone-strengthening activities, such as climbing and jumping.
Children aged five to 18 need at least 60 minutes (one hour) of physical activity every day, which should include moderate-intensity activity, such as cycling and playground games.
In order to strengthen muscles and bones, vigorous-intensity activities should be included at least three times a week. This could be swinging on playground equipment, sports such as gymnastics or tennis, or hopping and skipping.
Eating disorders and bone health
Eating disorders affect people of all ages, both male and female. But girls and women are more likely to be affected and anorexia most commonly develops in the teenage years.
The bones are still growing and strengthening at this time and eating disorders like anorexia can affect their development. Low body weight can lower oestrogen levels, which may reduce bone density. Poor nutrition and reduced muscle strength caused by eating disorders can also lower bone density.
If your teenage child has anorexia or another eating disorder, it’s important to seek medical advice about their bone health.