Finetune your focus with good nutrition

Finetune your focus with good nutrition

If I received a penny for each time my dad told me to eat my fish because it’s ‘brain food’, I would be a wealthy woman! The teenage years are considered to be a time of significant physical, social, and emotional development and are characterised by a number of neurobiological changes. Certain components of a healthy diet have been found to support optimal brain development while others have been found to exacerbate nutritional deficiencies linked to poorer cognitive outcomes.


The body needs up to 40 nutrients daily in order to function optimally¹. When making poor food choices, one of the biggest risks is that healthier nutrients are displaced by processed or ultra-processed foods (aka junk food) containing ‘empty’ calories. Usually weight remains unaffected (or starts to creep upwards) while nutrient status suffers. These sub-standard dietary choices can not only impair cognition but also alter the way your teen’s reward system functions. This can predispose your teen to dysregulated eating and even an increase in impulsive behaviour².


It is vitally important for the family unit to work with teenagers to help them adopt some of these healthy dietary habits and this includes being a great role model that your kids can follow by example. Let’s explore which nutrients are important and how we can practically include these in your teens diet.


Limit added/ free sugars

There are two main forms of sugar that we consume, intrinsic sugar and added/ free sugar. Intrinsic sugar is found naturally inside fruit (as fructose) and dairy (as lactose). These sugars form part of what is known as the food matrix and when eaten in their natural state, form part of a healthy diet and can contribute quite significantly to nutrient intake. On the other hand, added/ free sugars are usually a concentrated form of sugar (which can negatively affect blood sugar level) and are often low or devoid of beneficial nutrients. Examples of added sugars include table/ white sugar, brown sugar, beet sugar, cane sugar and raw sugar³ while examples of free sugar include honey, syrups, fruit juices and fruit juice concentrate⁴. It’s important to understand that added sugar itself is not linked to poor concentration⁵, but replacing foods that are high in added sugar with nutrient dense options will go a long way towards helping your child meet their nutrients needs on a regular basis.



The World Health Organization recommends that all adults and children reduce their intake of added/ free sugars to less than 10% of their total daily energy, but ideally to less than 5%³. Energy needs vary depending on your teen height and weight, sex, age and activity levels but to give you a rough estimate of what this sugar recommendation looks like let’s use average values for a teenage boy and girl. The average energy intake is about 2870 kCal and 2240 kCal for a teenage boy and girl respectively¹. Thus, teenage boys should aim to reduce their added sugar intake to between 35-70g sugar/ day and teenage girls should aim for less than 28-55g sugar/ day. To put this into perspective, let’s have a look at how much sugar is found in some commonly eaten foods and drinks⁶:


Food/drink Sugar(g)
Low fat, sweetened yoghurt, 1 cup</td 45</td
Sugar sweetened beverage (like cola), 330ml</td 39</td
Energy drink, 500ml 31.5
Sweet chili sauce, 2 Tbsp 16
BBQ sauce, 2 Tbsp</td 9</td


Ramp up iron intake (especially for girls)

As your teen matures, their iron needs naturally increase due to an increased deposition of lean body mass (muscles) as well as increased red blood cell volume and loss of blood (when girls have their period). Iron needs are at their highest during active growth phases (like during puberty and growth spurts) as well as directly after menstruation starts¹.


To give you an example of how high these requirements become, a girl before the age of 13 only needs 8 mg iron/ day and once she starts her period, her needs almost double to 15 mg/ day. If a teens iron needs outweigh their intake, they can suffer from physiologic anaemia of growth⁷. The effects of iron deficiency anaemia (specifically in adolescents) include an impaired immune response, decreased resistance to infections, fatigue and decreased cognitive functioning and short-term memory. All these symptoms can have serious effects on your child’s ability to learn. For example, if they are frequently ill they may miss school days or if they are tired all the time and can’t concentrate they may lose motivation to get their school work done.



There are two forms of iron in the foods that we eat, heme iron and non-heme iron. Heme iron is generally found in animal foods and non-heme iron in plant foods. Heme iron is more bioavailable (or better absorbed), but absorption of non-heme iron can be improved through pairing these food sources with vitamin C containing foods¹.


Iron food sources

Heme Iron Non-Heme Iron
Organ meat (e.g. liver)</td Soybeans</td
Oysters/td White beans</td
Beef/td> Lentils/td>
Sardines/td Spinach</td


Make smart fat swaps

The type of fat that your teen eats on a regular basis not only affects future heart health, but can also affect intelligence and mental capacity⁸ ⁹. The link probably boils down to the fact that the brain is composed mainly of fat. Diets that are high in saturated fats (found in fast foods, fatty cuts of meat, skin on the chicken, butter, cream and coconut oil etc) have been associated with cognitive deterioration. While a diet high in polyunsaturated fats (like oily fish, nuts and seeds) has been shown to have protective effects.


Diets like the Mediterranean diet, which are high in the polyunsaturated fats known as omega 3’s, have also been associated with better memory capacity and a lower risk of cognitive deterioration⁸. Similar to the advice given above, the Mediterranean diet encourages the consumption of plenty of unprocessed and minimally processed foods including lots of fresh fruits and vegetables, legumes and wholegrains as well as some oil fish and healthy fats like olive oil, avo, nuts and seeds¹.



Seems like some foods are worthy of the ‘brain food’ badge of honour. This being said, eating a variety of foods is always the best way to ensure that all your nutrient needs are met. We know that helping our teens to get all the nutrient they need is easier said than done but at Bioteen we are as committed as you are to seeing your teen thrive That’s why we have developed a range of supplements to suit your teens individual needs, not to mention that our entire range is not only nutritious, but tasty too!



1. Mahan LK, Escott-Stump S, Raymond J. Krause’s Food and the Nutrition Care Process. 13th ed.: Elsevier; 2012.
2. Reichelt C, Rank MM. The impact of junk foods on the adolescent brain. Birth Defects Res. 2017.
3. Guideline: sugars intake for adults and children [Internet]. 2015 [cited 12 July 2021]. Available from:
4. More Key Topics | MyPlate [Internet]. [cited 12 July 2021]. Available from:
5. Wolraich ML, Wilson DB, White JW. The effect of sugar on behavior or cognition in children. A meta-analysis. JAMA. 1995 Nov 22-29;274(20):1617-21.
6. U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, 2019.
7. Institute of Medicine. Dietary reference intakes: the essential guide to nutrient requirements 2006; National Academies Press Washington, DC.
8. García RMM, Ortega AIJ, Sobaler AML. Nutrition strategies that improve cognitive function. Nutr Hosp. 2018.
9. O’Neil A, Quirk SE, Housden S, Brennan SL, Williams LJ, Pasco JA, et al. Relationship Between Diet and Mental Health in Children and Adolescents: A Systematic Review. Am J Public Health. 2014.

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