This article was first published in the November 2018 edition of NHD magazine.

The teenage years are usually defined as starting at the age of 13 and ending at the age of 18. As children are beginning to transition towards adulthood, significant hormonal and developmental changes occur.

This article will cover the main nutritional factors to consider for teenagers.

Important Nutrients

The recommended intake and average intake of key nutrients for teenagers in the UK are outlined in table one.

Table One: Results of NDNS survey of teenagers aged 11 – 18 years (Table devised using references 3, 4, 5 and 8)

As the body is rapidly maturing during the teenage years, requirements for energy and protein increase accordingly¹.

Boys have slightly higher protein requirements than girls, as they tend to be larger and have more muscle².

Carbohydrates are the main source of energy for teenagers, and the majority of teenagers in the UK meet the recommended total carbohydrate intake^4-5.

Fibre intake was recently found to be low, and sugar intake was almost triple the recommended amount in those between the age of 11 and 18³.

A high intake of sugar in teenagers is associated with a higher calorie intake and an increased risk of tooth decay⁵. And a survey from 2013 in the UK found that 46% of 15 year olds had tooth decay⁶. A high intake of sugary drinks is also linked with weight gain in teenagers, and a higher risk of type 2 diabetes⁵.

Total fat and trans fat intake were both found to be within recommended levels for teenagers in the most recent NDNS, but saturated fat intake was found to be above the recommended limit³. This is concerning, as a high intake of saturated fat is associated with an increased risk of heart disease in later life⁷.  

Meeting vitamin D requirements is important for bone and muscle health, and so that calcium can be properly absorbed to reduce the risk of osteomalacia in later life⁸.

The average intake of vitamin D for teenagers is well below the recommended amount, even when supplements are taken into account³.

As dietary sources of vitamin D are limited, it is important for teenagers to consider taking a daily supplement containing 10mcg of vitamin D, especially when there is less exposure to sunlight from October to March⁹.

The rapid growth and increase in bone mass that occurs during the teenage years means that calcium intake increases¹. It is important to meet these requirements to promote good bone health in later life, but recent UK data has found that teenagers were consuming less than the recommended calcium intake³.

Therefore, sources of calcium should be encouraged for teenagers, such as: milk, cheese, yoghurt, calcium-fortified plant-based milks, tofu, green leafy vegetables, tinned salmon, tinned sardines and calcium fortified bread or juice.

Iron requirements increase for teenagers in order to support growth and muscle development². When menstruation begins, girls have a higher iron requirement than boys due to menstrual losses¹.

NDNS data shows that teenagers are not reaching iron requirements, with intakes being particularly low in teenage girls³.

This increases the risk of iron deficiency anaemia which can have serious medical consequences. To avoid this, a good intake of iron should be encouraged from foods such as: red meat, offal, green leafy vegetables, dried fruit, beans, fortified breakfast cereals, wholegrains and nuts².

Including sources of vitamins C, like a glass of orange juice, along with iron-rich foods can help to boost the absorption of iron, whereas the tannins present in tea and coffee can reduce iron absorption if consumed along with a meal.

Iodine is important for thyroid health, which effects metabolism and growth⁹. Teenage boys in the UK have an intake of iodine which is close to the recommended amount, whereas intake for teenage girls is lower than this³.

Urinary iodine levels also show that teenage girls of childbearing age aren’t meeting the cut-offs for sufficient iodine levels for pregnancy³. This is worrying as iodine has an important role in the development of a baby’s brain during pregnancy¹⁰.

This pattern of low iodine intake may be related to a reduced intake of dairy products, as this is our main source of iodine in the UK⁹. Other sources of iodine include: fish, shellfish, iodised salt, seaweed and eggs.

Folate is important for forming red blood cells and DNA¹¹. Most teenage boys in the UK meet the folate requirements, however teenage girls were recently found to have a slightly lower intake³.

To reduce the risk of neural tube defects, any woman who is considering becoming pregnant needs to have a dietary intake of 200μg of folate, as well as taking a supplement which contains 400μg of folic acid (the synthetic form of folate)¹¹.

Requirements for a number of other vitamins and minerals increase for girls and boys during their teenage years, such as:¹

• Thiamine
• Niacin
• Riboflavin
• Vitamins B6
• Vitamin B12
• Vitamin C
• Magnesium
• Potassium
• Copper
• Selenium
• Iodine

However, zinc requirements increase for boys but decrease for girls during teenage years, and similarly vitamin A requirements increase in teenage boys but not teenage girls¹.  

Intake of salt and salty foods should be limited, as on average UK teenagers exceed the recommended limit of 6 g of salt per day (average intake for teenage girls: 6.2 g per day, average intake for teenage boys: 7.1 g per day)¹².

Drinks:

Encouraging six to eight glasses of fluid per day can help teenagers to stay hydrated.

Water is usually the best choice, but milk is another great way to hydrate while also boosting calcium intake.

Fruit juice and shop-bought smoothies can be a good source of vitamin C, but it is advised to have no more than 150ml of these per day, as this provides excess sugar otherwise.

The teenage years are a time when people may experiment with alcohol. It is important that teenagers are aware of the health risks associated with underage drinking, such as a higher risk of: ¹³

• Liver damage
• Injuries
• Alcohol poisoning
• Sleep problems
• Headaches
• Mental health problems
• Memory problems
• Reduced attention span
• Learning problems

Underage drinking can also put teenagers in vulnerable situations. For example, 12%  of teenagers who have had an alcoholic drink have experienced physical, medical or criminal harm related to this¹⁴.

Vegetarian and Vegan Diets:

Teenagers may experiment with plant-based diets for a variety of reasons.

It is important that those who follow these types of diets do so in a balanced way, by ensuring they consume a variety of protein sources as well as a good intake of: iron, calcium, iodine, vitamin B12, omega 3 and selenium.  

It is also important to be aware that a dietary change which involves cutting out food groups can sometimes be a sign of disordered eating¹⁵.

Maintaining a Healthy Relationship With Food:

As teenagers begin to take more responsibility of their lives, this can be a great time to encourage cooking skills and more independence with food choice.

However, large number of eating disorders emerge during the teenage years¹.

So discussions related to food should be approached carefully, to avoid promoting an obsessive relationship with food and healthy eating.

There is a higher prevalence of eating disorders in teenage girls, but 11% of those with an eating disorder are male².

Numerous factors can contribute to developing an eating disorder, such as genetics, or body image issues (which can often be influenced by messages in the media and social media)^16-17.

In a bid to change their body, achieve a particular aesthetic or a perceived vision of ‘health’, teenagers may also try fad diets at this time, which runs the risk of nutritional deficiencies and excess.

Meal pattern may also start to falter at this age, as some teenagers prefer to lie in rather than have breakfast, and may want to spend time with their friends after school rather than with sitting at the family dinner table.

Trying to maintain a good meal pattern at this time can help to ensure nutritional requirements are met and encourages good eating habits for later life.

Conclusion:

There are numerous factors which can affect nutrition during the teenage years, including: physical and hormonal changes, increased independence, and phases of experimentation with food and drink.

Although getting the nutritional balance right is important, this is also a vital phase for fostering a long-term healthy relationship with food.  

References:

1. Manual of Dietetic Practice. edited by Joan Gandy in conjunction with The British Dietetic Association (5th Edition, 2014).
2. British Nutrition Foundation (2015) ‘Teenagers’ [accessed August 2018 via: https://www.nutrition.org.uk/nutritionscience/life/teenagers.html?showall=1].
3. Department of Health. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. London. HMSO,1991.
4. Results of the National Diet and Nutrition Survey (NDNS) rolling programme for 2014 to 2015 and 2015 to 2016 [accessed August 2018 via: https://www.gov.uk/government/statistics/ndns-results-from-years-7-and-8-combined].
5. SACN (2015) “Carbohydrates and Health” [accessed August 2018 via: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/445503/SACN_Carbohydrates_and_Health.pdf].  
6. “Child Dental Health Survey 2013, England, Wales and Northern Ireland” [accessed August 2018 via: https://digital.nhs.uk/data-and-information/publications/statistical/children-s-dental-health-survey/child-dental-health-survey-2013-england-wales-and-northern-ireland]
7. NICE (2014) “Cardiovascular disease: risk assessment and reduction, including lipid modification” [accessed August 2018 via: https://www.nice.org.uk/guidance/cg181/chapter/1-recommendations#lipid-modification-therapy-for-the-primary-and-secondary-prevention-of-cvd-2]
8. SACN (2016) “Vitamin D and Health” [accessed August 2018 via: https://www.gov.uk/government/publications/sacn-vitamin-d-and-health-report]
9. “PHE publishes new advice on vitamin D” [accessed August 2018 via: https://www.gov.uk/government/news/phe-publishes-new-advice-on-vitamin-d]  
10. BDA Food Fact Sheet ‘Iodine’ [accessed August 2018 via:  https://www.bda.uk.com/foodfacts/Iodine.pdf]  
11. BDA Food Fact Sheet ‘Folic Acid’ [accessed August 2018 via:  https://www.bda.uk.com/foodfacts/FolicAcid.pdf]   
12. Results of the National Diet and Nutrition Survey (NDNS) rolling programme for 2008-2009 to 2011-2012 [Accessed August 2018 via: https://www.gov.uk/government/statistics/national-diet-and-nutrition-survey-results-from-years-1-to-4-combined-of-the-rolling-programme-for-2008-and-2009-to-2011-and-2012]
13. Dinkaware “Know the risksof drinking alcoholunderage” [Accessed August 2018 via: https://www.drinkaware.co.uk/advice/underage-drinking/know-the-risks-of-drinking-alcohol-underage/]
14. Ipsos MORI (2015) “Drinkaware Monitor 2014: Young people’s and their parents’ drinking behaviour and attitudes in the UK” [Accessed August 2018 via: https://www.drinkaware.co.uk/media/1469/drinkaware_monitor_2014_young_people_reportcompressed__1_.pdf].
15. Sullivan and Damani “Vegetarianism and eating disorders — partners in crime?” [Accessed August 2018 via: https://onlinelibrary.wiley.com/doi/abs/10.1002/1099-0968(200008)8:4%3C263::AID-ERV367%3E3.0.CO;2-2].
16. Rogers et al. (2015) “Longitudinal relationships among internalization of the media ideal, peer social comparison, and body dissatisfaction: Implications for the tripartite influence model” [Accessed August 2016 via:https://www.ncbi.nlm.nih.gov/pubmed/25751099]
17. Tiggemann and Slater (2016) “Facebook and body image concern in adolescent girls: A prospective study“ [Accessed August 2018 via: https://onlinelibrary.wiley.com/doi/abs/10.1002/eat.2264]