© Food – a fact of life 2010

Teenage diets, nutrition and health

© Food – a fact of life 2010

Teenagers (12-18 years)

• Nutritional requirements

• Dietary recommendations

• Macronutrients

• Micronutrients

• Energy balance

• Physical activity

• Diet and cognitive ability

• Diet and behaviour

• Eating disorders

• Summary - key issues

© Food – a fact of life 2010

Nutritional requirements

• Growth and development are rapid.

• Onset of puberty - characterised by a spurt in physical growth (height and weight).

• Considerable gain in muscle and bone mass.

• Changes in body composition, e.g. increased deposition of fat in girls.

• Energy and nutrient requirements at their highest.

© Food – a fact of life 2010

A healthy diet is important for teenagers

Eating a healthy, balanced diet can:

•promote wellbeing by improving mood, energy and

self-esteem to help reduce anxiety and stress;

•boost concentration and performance;

•reduce the risk of ill-health now and in the future, e.g.

obesity, heart disease, cancer, and type 2 diabetes;

•increase productivity/attainment and reduce days off

sick.

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© Food – a fact of life 2010

Dietary recommendations

Teenagers should consume a variety of foods from each

of the four main food groups:

Fruit and vegetables (33%)

Bread, rice, potatoes,

pasta and other starchy

foods (33%)

Milk and dairy foods (15%)

Meat, fish, eggs, beans

and other non-dairy

sources of protein (12%)

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Macronutrients

Macronutrient Recommended

intake

(% food energy)

Boys average

intake

(% food energy)

Girls average

intake

(% food energy)

Fat 35% 35.4% 35.9%

of which saturates 11% 14.2% 14.3%

Carbohydrate 50% 51.6% 51.1%

of which added

sugars (NMES)

11% 16.7% 16.4%

- average intakes

(Scottish NDNS and Survey of Sugar Intake data)

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What about dietary fibre?

• NDNS survey found average dietary fibre (NSP)

intakes to be low in teenagers:

- Boys (11-14 years) 11.6 g/day

(15-18 years) 13.3 g/day

- Girls (11–14 years) 10.2 g/day

(15-18 years) 10.6 g/day

• Reference values:

- 15 g/day (11-14 years)

- 18 g/day (15 years or above)

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Vitamin Boys

11-14 yrs

Girls

11-14 yrs

Boys

15-18 yrs

Girls

15-18 yrs

Vitamin A 8% 20% 13% 12%

Riboflavin (B2) 6% 22% 6% 21%

Folate 1% 3% 0% 4%

Micronutrients

- percentage of older children and teenagers with

intakes below the LRNI

Source: National Diet and Nutrition Survey 2003

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Mineral Boys

11-14 yrs

Girls

11-14 yrs

Boys

15-18 yrs

Girls

15-18 yrs

Iron 3% 44% 3% 48%

Calcium 13% 24% 9% 19%

Magnesium 28% 51% 11% 53%

Potassium 10% 19% 15% 38%

Zinc 14% 37% 9% 10%

Micronutrients

- percentage of older children and teenagers with

intakes below the LRNI

Source: National Diet and Nutrition Survey 2003

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What about salt?

• NDNS survey results - average salt intakes above

recommendations in teenagers:

- Boys (11-14 years) 6.75 g/day

(15-18 years) 8.25 g/day

- Girls (11-18 years) 5.75 g/day

(excluding salt added in cooking or at the table)

• Recommended maximum daily salt intake:

- 11 years and over: up to 6 g/day.

© Food – a fact of life 2010

Teenagers and iron

• Teenagers have increased iron requirements.

• Girls need more iron than boys to replace menstrual

losses (RNI: boys 11.3 g/day, girls 14.8 g/day).

• Low iron intakes (< LRNI) in 44% of girls (11-14 years)

and 48% of girls (15-18 years).

• 9% of girls (15-18 years) were found to have poor iron

status (Hb < 12g/dl).

• Lack of iron leads to an increased risk of iron

deficiency anaemia and associated health

consequences.

• Teenagers who follow a vegetarian diet or restrict

food intake (e.g. to lose weight) particularly at risk.

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Iron absorption

• Good sources: meat (especially lean red meat),

liver and offal, green leafy vegetables, pulses

(beans, lentils), dried fruit, nuts and seeds, bread

and fortified breakfast cereals.

• Iron from meat sources (haem iron) is readily

absorbed by the body.

• Vitamin C helps the body to absorb iron from other

sources (non-haem iron).

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• Teenagers have high calcium requirements.

• Around 50% of the adult skeleton is formed during

the teenage years (RNI - boys 1000 mg/day, girls

800 mg/day).

• Low calcium intakes (< LRNI) found in 24% of 11-14

year-old girls and 19% of 15-18 year-old girls.

• A lack of calcium may have consequences for

future bone health e.g. increased risk of

osteoporosis.

Teenagers and calcium

© Food – a fact of life 2010

Teenagers and energy balance

• Levels of overweight and obesity are increasing: 35%

of teenagers (12-15 years) are classified as

overweight or obese (Scottish Health Survey 2009).

• Teenagers, especially girls, often try to control their

weight by adopting very low energy diets or smoking.

• Restricted diets may lead to nutrient deficiencies and

other health consequences.

• Teenagers of unhealthy weight may need guidance

on lifestyle changes to help them achieve a healthy

weight.

© Food – a fact of life 2010

Teenagers – physical activity

• Physical activity through life is important for

maintaining energy balance and overall health.

• At least 60 mins of moderate-intensity physical

activity each day is recommended.

• Include activities that improve bone health, muscle

strength and flexibility at least twice per week.

• 68% of boys and 41% of girls (13-15 year-olds) achieve

the recommended 60 mins per day (Scottish Health

Survey 2005).

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Diet and cognitive ability

• Food eaten at school can make up a substantial

proportion of the diet and have a significant effect on

functions such as learning, memory, information

processing and mood.

• Cognition represents a complex multidimensional set

of abilities and cognitive performance is affected by

many influencing factors.

• Nutritional effects are difficult to measure.

Stevenson J (2006) Dietary influences on cognitive

development and behaviour in children Proct Nutr Soc 65(4):361-5.

Bellisle F (2004) Effects of diet on behaviour and cognition in children Br J Nutr 92 Suppl 2: S227-32.

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Glycaemia

The brain appears to be sensitive to short-term

fluctuations of glucose supply and therefore it

might be beneficial to maintain glycaemia at

adequate levels to optimise cognition.

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Eating breakfast

• Starting each day with breakfast will supply energy

to the brain & body.

• Eating breakfast leads to improved energy and

concentration levels throughout the morning.

• Breakfast consumption may improve cognitive

function related to performance in school.

• Other benefits of breakfast include better nutrient

intakes and weight control.

Hoyland A et al. (2009) A systematic review of the effect of breakfast on the cognitive performance of children and adolescents Nutr Res Rev 22(2): 220-43.

© Food – a fact of life 2010

•Even mild dehydration (1-2%) can lead to headaches,

irritability and loss of concentration. This level is not

enough to cause feelings of thirst.

•The recommendation is to drink 6-8 glasses/day (1.2

litres) to prevent dehydration. People need to drink

more when the weather is hot or when they have

been active.

•All drinks count in terms of fluid intake but those

without sugar are best between meals.

Fluids and hydration

© Food – a fact of life 2010

• Brain health depends on optimal intakes of nutrients

from the diet.

• Much speculation about the importance of long

chain omega-3 fatty acids to behavioural and

cognitive development, including IQ.

• Supplementation studies show the best outcome

observed in children with learning disabilities.

• Current recommendation is one portion of oily fish

(140g) per week.

Diet and IQ

Willatts P. (2002) Long chain polyunsaturated fatty

acids improve cognitive development J Fam Health

Care 12(6 suppl):5.

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• There are a number of foods that have a

pharmacological effect in the body which affects

mood:

* caffeine;

* vaso-active amines, such as histamine;

* tryptophan and serotonin.

• There is evidence to suggest that poor vitamin and

mineral status may be associated with poor

educational attainment and antisocial behaviour.

Diet and mood/behaviour

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Food additives and hyperactivity

• The Southampton study suggested that

consumption of mixes of certain artificial food

colours and the preservative sodium benzoate

could be linked to increased hyperactivity in some

children. The colours are:

sunset yellow FCF (E110)

quinoline yellow (E104)

carmoisine (E122)

allura red (E129)

tartrazine (E102)

ponceau 4R (E124)

• An EU-wide mandatory warning must be put on any

food and drink (except drinks with more than 1.2%

alcohol) that contains any of the six colours.

Bateman B et al. 2007

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• Defined as: an eating pattern that becomes harmful to

health.

• Can affect anyone but most likely young women.

• It is estimated that there are 1 million people affected

in the UK, with the majority being 12 to 25 year-old

women.

• Trigger is multi-factorial and often linked to emotions.

• New evidence to suggest genetic makeup may have

a small impact.

Eating disorders

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Anorexia Nervosa

• Defined as: the refusal to eat enough to maintain a

normal body weight.

• Sufferers have the impression that they are overweight

and often picture themselves as being fat even though

they are already underweight.

• If it occurs before puberty, anorexia may lead to stunted

growth. In teenage girls and young women, menstrual

abnormalities may occur including amenorrhoea (the

cessation of periods), which can pose a significant risk to

bone health.

• Other physical symptoms include: constipation, stomach

pains; dry, patchy skin; low body temperature and loss

of hair.

© Food – a fact of life 2010

Anorexia Nervosa

Impact on mental health:

• intense fear of gaining weight and obsessive interest in

what others are eating;

• distorted perception of body shape or weight;

• denial of the existence of a problem;

• changes in personality and mood swings;

• becoming aware of an ‘inner voice’ that challenges

views on eating and exercise.

Impact on behaviour:

• rigid or obsessive behaviour with eating, mood swings;

• restlessness and hyperactivity;

• wearing big baggy clothes;

• vomiting.

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Bulimia Nervosa

• Sufferers are obsessed with the fear of gaining weight

and undergo a recurring pattern of binge eating,

which is usually followed by self-induced vomiting.

• People with bulimia often feel a lack of self-control

and have an excessive concern with their body

weight and shape.

• Sufferers may also use large quantities of laxatives,

slimming pills or strenuous exercise to control their

weight.

• Many bulimics have poor dental health due to

regular vomiting; vomit is acidic and can erode teeth

in a characteristic way.

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Bulimia Nervosa

Impact on mental health

• uncontrollable urges to eat vast amounts of food;

• an obsession with food, or feeling ‘out of control’ with food;

• distorted perception of body weight and shape;

• emotional behaviour and mood swings;

• anxiety and depression; low self-esteem, shame and guilt;

Impact on behaviour

• disappearing to the toilet after meals to vomit food eaten;

• excessive use of laxatives, diuretics or enemas;

• frequent periods of fasting;

• excessive exercise;

• secrecy and reluctance to socialise;

• shoplifting for food;

• abnormal amounts of money spent on food;

• food disappearing unexpectedly or being secretly hoarded.

© Food – a fact of life 2010

• Binge Eating Disorder (BED);

• complusive overeating;

• eating disorders in sport;

• ‘Orthorexic’;

• ‘Drunkorexic’.

Visit www.b-eat.co.uk for further information.

Other eating disorders

© Food – a fact of life 2010

Teenagers - key issues

• Nutritional requirements

• Dietary recommendations

• Macronutrients

• Micronutrients

• Energy balance

• Physical activity

• Diet and cognitive ability

• Diet and behaviour

• Eating disorders

© Food – a fact of life 2010

Teenagers - dietary improvements needed

• More fruit and vegetables, pulses, wholegrain foods.

• More milk and diary foods.

• More iron-rich foods.

• More oily fish.

• Less foods high in saturated fat and added sugars.

• Less salt.