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In Part 1 of Teenager Nutrition, we examine the changes happening to teenagers and the need for iron and calcium.

In Part 2 of Teenager Nutrition we examine the need for zinc, protein and how to incorporate healthy eating habits.

If your cherub is fast approaching the teen years, now may be a good time to think about some of the nutritional challenges that you may be faced with. Remember, forward planning never goes astray and hopefully you can do it together. However, If you have already hit the adolescent years, then reviewing may help make sense of why they can have a bottomless pit for a stomach, but yet it can be hard to get them to eat sensibly.

In part 1 we look at some of the changes occurring in teenagers and additional nutritional need for iron & calcium.

Get ready for big changes

During adolescence many body changes are occurring: increases in height, weight, muscle mass, a drop of fat mass, concreting of many brain functions and the heralding of sexual maturity.

Girls, on average, tend to begin their growth spurt a little earlier than boys, at around 10-11 years of age and boys at around 11-12 years of age. While the growth spurts last about the same length of time (2-2½ years), boys grow far more in this time span.

The average weight gain for girls is 16kg and about 16cm in height, for boys it is about 20kg and 20cm. Naturally there is huge variation from one adolescent to another. Interestingly, a girl's menstrual cycle appears to time itself with peak height and body fat reaching around 17%.

Lazy or sleepy?

While all of this is going on, the brain of a teen is also changing. You may find your once early riser now barely draws the curtains before lunchtime on the weekends and school holidays; they also can begin to indulge in risk-taking behaviour as well as question your every decision. All very normal. As neural changes and pathways begin to establish and settle, such behaviours may take a little time to diminish, making 'reasoning' with an adolescent more, well shall we say, challenging!

Science tells us that as a child moves into adolescence their sleep patterns will change; it's not so much age related but body-change related. Girls appear to spend more time asleep and get up later than boys, though this may be explained in part by their earlier adolescent onset. Teens can report finding it hard to go to sleep, though this seems to be related to later waking times. Reports also suggest checking if they are leaving the light on at night as this may affect their sleep-wake cycles. It's good to be able to make sense of behaviour when you know it isn't necessarily of their own doing.

Teen nutrition

There are a number of increased nutritional needs for adolescents, largely due to their growth and increased body mass. Ideally your teen will get to maturity with a great foundation for life-long health.

A recent study of children (CNPAS, 2007) has highlighted some interesting trends and, while much of the information was via self-reports, it still provides a snapshot of how our teens are faring.

"...confectionary and ...drinks such as juice, energy drinks
and flavoured milk represent 12% of energy intake..."

Ironing out the gaps

Iron is required in greater amounts in this age group, particularly if your daughter has begun her periods. Boys are not exempt from an increased iron need; they require more iron when they hit their growth spurt, as their body grows, so too does their blood volume.

It is estimated that just under 10 per cent of girls are iron deficient. Menstrual blood loss of course accounts for the greatly increased need. However, other losses of iron include nosebleeds or other blood outlets, plus intense physical activity and some drugs. Interestingly, adolescent NZ Maori appear more at risk of depleted iron stores. Studies suggest that it is this that influences their early onset of peak growth and menarche.

The RDI for iron for girls aged 14-18 is 15mg per day and for boys 11 mg per day. Y es, meat, liver and other animal products are rich sources of iron, containing what is called heme-iron, which is more bioavailable to the body. Figure 1 lists other sources of iron. Offering foods containing iron with vitamin C foods will improve the uptake of the iron. Vegetarian teens will need to pay very close attention to their iron intake as it can be more challenging to gain iron from plant foods. Avoid drinking tea as the tannin binds iron; consume vitamin C-containing foods and beverages with meals to increase iron uptake; sprout beans and seeds and ensure beans are cooked well; eat calcium-rich foods at separate meals and ensure there are at least two forms of protein in a meal.

Calcium

At puberty a child's bone mass has undergone a massive seven-fold increase, with a three-fold increase in adolescence alone. Calcium RDIs peak at adolescence (14 years) to 1.3g a day, equalling that of older people. A teen's fast rate of growth means they are laying down more bone, so it's easy to see why their requirement increases. It is thought that we reach peak bone mass by maturity; it's this store of bone that may well influence how your bones age. Sadly, only about 11 per cent of 12-13 year olds reach their estimated adequate requirements or EAR, a more conservative estimate of 1080mg for calcium. This may in part be due to age-related perceptions of dairy products. Dairy consumption appears very low in girls 12-16 years and, whether by chance or not, 82-89 per cent don't meet the EAR for calcium.

The following are examples of calcium-rich foods that might be consumed over a day:

• Half a cup of baked beans has 40mg of calcium.
• 50g of tinned salmon (in water, drained and bones crushed) has 155mg.
• 30g of cheddar cheese gives 255mg.
• 200g of plain yoghurt has 342mg.
• 100ml of a calcium-enriched soy beverage can have up to 300mg of calcium.

It might help to know that low-fat dairy products are lower in fat but are rich in calcium, so if you have a fat-conscious teen this might be a good call.

In Part 2 of Teenager Nutrition, we look at the need for zinc, protein and how to incorporate healthy eating habits.

Created by Leanne Cooper © 2010, www.sneakys.com.au. This fact sheet may be reproduced in whole or in part for education and non-profit purposes with acknowledgment of the source. It may not be reproduced for commercial use or sale. The information provided is not meant to replace medical advice.

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