Calcium has many important functions in the body but most importantly in children and adolescents is the development of healthy bones, teeth.
Calcium requirements increase dramatically from about the age of 11 years in what is known as the pre-pubertal growth spurt.
A lack of calcium can lead to poor mineralization of bones and low bone mineral density (a measure of bone strength). This can lead to many problems including permanent bone deformities and diseases of the bone such as osteoporosis (where bones are weak and break easily) in later life.
We have a once in a lifetime opportunity to build strong bones. Approximately 30% of all mineral deposited in our bones throughout life, occurs during adolescence and 90% of our adult skeleton is formed by the age of 18 and even earlier in girls. Therefore it is essential that enough calcium is received to allow this to happen.
For 11 to 18 year olds, about 1 in 17 boys and 1 in 9 girls have an intake below the LRNI. These figures have fallen from the previous national survey. Future surveys will reveal if this is a real change, but the fact remains large numbers of teenagers, particularly girls, don't get enough calcium.
Dairy products are good providers of calcium and many other nutrients important to good bone health and of increased demand during childhood and adolescence e.g. phosphorus, magnesium and protein.
Consumption of a glass or 200ml milk, a matchbox sized (30g) piece of low-fat cheese and a pot (200g) yogurt will go a long way to helping this age group meet their daily calcium requirement.
Contribution of just 1 glass of milk a day to bone friendly nutrient requirements
Recommended amounts are provided by the Department of Health DRV’s (Dietary Reference Values).
Other foods containing dietary calcium include fish with edible bones, green leafy vegetables, nuts, bread etc.
However significantly greater quantities of these foods are required in order to provide the same amount of calcium as dairy foods. This is because the calcium in dairy foods is more easily absorbed than from other foods and is therefore a very valuable provider of calcium for children and teenagers.
Iron is important for growth, brain development and the immune system, however it is commonly deficient or sub optimal in both children and adolescents.
The latest National Diet and Nutrition Survey (2008/2009) found that many teenage girls had a low intake of iron; 46% of 11- 18 year-olds had intakes below the lower reference nutrient intake (LRNI), suggesting that they were extremely inadequate.
Teenage girls in particular are affected by poor iron status due to increased iron losses during menstruation that are not replaced through the diet.
If iron levels become too low it can lead to a condition called iron deficiency anaemia. Anaemia is known to compromise all work performance, both physical and mental, but recent studies have suggested that even low iron stores without anaemia can negatively affect brain function.
It was therefore worrying that The National Diet and Nutrition Survey (2000) found that 1% of boys and 9% of girls aged 15 to 18 years were actually classified as anaemic. Other studies of teenagers have found anaemia to be three times more common in vegetarians compared to meat eaters, and in girls who had recently tried to lose weight.
Consumption of sufficient iron in the diet is therefore very important for ensuring stores are sufficiently high to allow correct development in children and adolescents. Good dietary providers of iron include meats such as beef, lamb, pork, chicken, green leafy vegetables, fortified cereals and pulses.
Consuming foods containing vitamin C along with iron providing foods will help iron to be absorbed by the body e.g. a glass of citrus fruit juice with a meal or a piece of citrus fruit such as orange or grapefruit after a meal.
Other vitamins and minerals
Zinc is essential for adequate growth and sexual development.
Foods containing zinc include meats e.g. beef, lamb, pork etc.
Vitamin A is essential for good development of the eyes and for the immune system.
Foods containing vitamin A include dairy foods, dark green vegetables and orange/red fruits and vegetables.
The B vitamins including B6, B2 and thiamin and niacin are important for many functions including breakdown and use of carbohydrate and protein in the body. Vitamin B12 and folate are also important for the nervous system and for making new cells in the body.
Requirements for these nutrients are increased in children and adolescents but the latest National Diet and Nutrition Survey suggests that levels of these are mostly adequate except for vitamin B2 which is inadequate in girls aged 11-18 years old.
Foods containing B vitamins include meats, cereals and vegetables.