teen diets, nutrition and health

© Food – a fact of life 2010

Teenage diets, nutrition and health

British Nutrition Foundation


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


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.


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.


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%)


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)


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)


Vitamin Boys 11-14 yrs

Girls 11-14 yrs

Boys15-18 yrs

Girls15-18 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


Mineral Boys 11-14 yrs

Girls 11-14 yrs

Boys15-18 yrs

Girls15-18 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


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.


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.


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).


• 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


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.


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).


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.


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.


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.


•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


• 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.


• 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


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


• 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


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.


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.


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.


Bulimia NervosaImpact 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.


• Binge Eating Disorder (BED);

• complusive overeating;

• eating disorders in sport;

• ‘Orthorexic’;

• ‘Drunkorexic’.

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

Other eating disorders


Teenagers - key issues

• Nutritional requirements• Dietary recommendations• Macronutrients• Micronutrients • Energy balance• Physical activity• Diet and cognitive ability• Diet and behaviour• Eating disorders


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.


For more information visit

www.nutrition.org.uk

www.foodafactoflife.org.uk

teen diets, nutrition and health

Health & Medicine

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