Adolescents need between 45g and 60g of protein a day. You can work out exactly how much protein you need if you know how much you weigh.

Teens need to eat about 0.5g of protein for every 0.5kg they weigh. For example, if you weigh 50kg, then you'll need to eat 55g of protein a day.

You can look at food labels or check the table on this page to find out how much protein is in a serving.

Most teens easily meet their daily protein requirements by eating beef, eggs, fish and dairy products.

Tofu and other soy products, grains, beans and nuts are all good sources of protein.

Protein deficiency in young people is quite rare in modern cities.

However, it occurs in situations of extreme poverty, in hospitalised patients and the elderly. Protein deficiency leads to a severe lack of energy.

Our bodies need sufficient energy to stay healthy and break down protein and fat to ensure we have enough.

Protein deficiency can lead to stunted growth in children and muscle wasting. It also affects the heart, makes you more vulnerable to infections, stops cuts healing and causes swelling in the hands and feet.

Jason's diary

Breakfast: Fried egg and brown bread

Lunch: Chicken or beef with rice and Chinese vegetables

Dinner: Chicken or beef with rice and Chinese vegetables

Drinks: Milk, orange juice, apple juice, water

Exercise: Swimming everyday, five hours of badminton a week, hiking during the weekend

Protein content in food

Food Protein

55g cheddar cheese 14g

100g cooked chicken breast 31g

100g roast duck 24g

100g pork spare ribs pork 29g

100g stewed beef 20g

100g cooked cod 17g

2 large pork sausages 9g

1 whole boiled egg 6g

1 cup milk 8g

1 tablespoon peanut butter 4g

2 tablespoons baked beans 4g

1 cup cooked white rice 4g

1 cup cooked pasta 5g

100g tofu 9g

12 cooked prawns 17g

140g canned tuna 24g

220g low-fat yoghurt 12g

Adapted from McCance and Widdowson's The Composition of Foods, sixth edition. The Royal Society of Chemistry, Cambridge, 2000