Teenage diets, nutrition and health
British Nutrition Foundation
© Food – a fact of life 2010
Teenagers (12-18 years)
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Nutritional requirements
Dietary recommendations
Macronutrients
Micronutrients
Energy balance
Physical activity
Diet and cognitive ability
Diet and behaviour
Eating disorders
Summary - key issues
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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.
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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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Dietary recommendations
Teenagers should consume a variety of foods from each
of the four main food groups:
Fruit and vegetables (33%)
Meat, fish, eggs, beans
and other non-dairy
sources of protein (12%)
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Bread, rice, potatoes,
pasta and other starchy
foods (33%)
Milk and dairy foods (15%)
Macronutrients
- average intakes
(Scottish NDNS and Survey of Sugar Intake data)
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%
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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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Micronutrients
- percentage of older children and teenagers with
intakes below the LRNI
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%
Source: National Diet and Nutrition Survey 2003
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Micronutrients
- percentage of older children and teenagers with
intakes below the LRNI
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%
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.
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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 and calcium
• 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.
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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.
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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.
Bellisle F (2004) Effects of diet on behaviour and
cognition in children Br J Nutr 92 Suppl 2: S227-32.
Stevenson J (2006) Dietary influences on cognitive
development and behaviour in children Proct Nutr Soc
65(4):361-5.
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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.
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Fluids and hydration
•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.
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Diet and IQ
• 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.
Willatts P. (2002) Long chain polyunsaturated fatty
acids improve cognitive development J Fam Health
Care 12(6 suppl):5.
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Diet and mood/behaviour
• 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.
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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)
Bateman B et al. 2007
• 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.
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Eating disorders
• 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.
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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.
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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.
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Other eating disorders
• Binge Eating Disorder (BED);
• complusive overeating;
• eating disorders in sport;
• ‘Orthorexic’;
• ‘Drunkorexic’.
Visit www.b-eat.co.uk for further information.
© 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.
© Food – a fact of life 2010
For more information visit
www.nutrition.org.uk
www.foodafactoflife.org.uk
© Food – a fact of life 2010