As parents leave sugar-filled birthday parties they are often commenting to others about the effects of sugar. The public perception appears to be that with sugar comes loud, silly and extra-active behaviour from their child, otherwise referred to by many as 'hyperactive' behaviour.
However, current research doesn't seem to support this public perception that sugar causes negative changes to a child's behaviour and cognition.
Grab a coffee, tea or smoothie and let's unpack this.
*Trigger warning. This article briefly discusses eating disorder statistics.
Why is this important to discuss?
In science, it is important that anecdotal observations are explored scientifically to see if there really is a link. This is important for several reasons, and one that stands out to me is the impact unsubstantiated claims may have on a child's (or parent's) relationship with food.
If we believe (based on public perception) that sugar causes hyperactivity and is 'bad', but there is no evidence to support this belief, we risk damaging relationships with food and may contribute to disordered eating. Eating disorders, when combined with disordered eating, are estimated to affect 16.3% of the Australian population (Hay et al., 2015).
WHAT DOES THE RESEARCH SAY?
Is there a causal link between sugar and hyperactivity?
Decades of research on the topic of sugar and its impact on behaviour and cognition suggest the same outcome: sugar does not appear to impact most children's behaviour or cognition negatively. Let's explore the research further.
In research, quality of evidence is important. Case studies are the bottom tier of evidence, whist meta analyses are the top tier of evidence, with randomised controlled trials (RCTs) and systematic reviews layered in between.
A 1995 META ANALYSIS (top tier of evidence) of 16 studies that looked into the effects of sugar on cognition and behaviour concluded that sugar doesn't appear to negatively impact children's behaviour or cognitive performance (Wolraich et al., 1995).
A more recent 2019 cohort study of 2924 6-11 year old children reviewed whether there was an association between a change in sugar consumption in childhood and the incident of attention-deficit/hyperactivity disorder (ADHD) (Del-Ponte et al., 2019). While cohort studies using dietary recall have their limitations, no association between high sugar intake and a higher incidence of ADHD was found.
In fact, there is evidence to suggest sugar may actually improve performance, both athletic and non athletic, including academic work (Benton & Stevens, 2008). This makes sense when we consider that the brain uses glucose (a sugar) as its preferred fuel source. Glucose utilisation for a 4 year old, per unit of weight of brain, is double that of an adult and this remains until around 9-10 years, reaching adult utilisation by around 16-18 years.
Finally, a 2013 psychological review concluded that limiting sugar consumption as a behaviour management strategy should not be a treatment focus and may be counter productive (Flora and Polenick, 2013).
Is it our EXPECTATION that sugar causes negative effects at play?
This is where things get interesting (for me, at least). A small clinical trial found that mums who were told their 5-7 year old boys had consumed large amounts of sugar rated their children as significantly more hyperactive than mums who had been told their children had received the (sugar free) placebo (Hoover et al., 1994). Interestingly, ALL children in the trial received a sugar free placebo.
It is suggested that confirmation bias may also play a role in a child's behaviour following excess sugar intake. The mothers in the above study who were told their children had consumed large amounts of sugar were observed to criticise, look at and talk to their children more than mothers who were told their children did not consume sugar. This behaviour may negatively reinforce misbehaviour following sugar intake, making it more likely to occur next time the child consumes sugar.
Is there something else at play?
ENVIRONMENT: In my experience as a parent as well as a family nutritionist, excess sugar most commonly surrounds exciting and fun events - think Halloween, Christmas, parties, Easter, holidays and grandma's house, to name a few.
ADDITIVES/PRESERVATIVES: The purpose of this article is not to address additives and preservatives and thus, it has not been the focus of literature review. However, at present there is limited evidence to support elimination diets for behaviour management. The Feingold hypothesis suggested that food additives such as artificial colours and flavours, as well as naturally occurring salicylates were to blame for hyperactivity in children. A critical review concluded that a number of double-blind studies have failed to prove that elimination diets (removing additives and salicylates) provide any benefit beyond normal placebo effect (Krummel et al., 1996).
It is important to note here that elimination diets in childhood should ALWAYS be supervised by a practicing paediatric dietician as there are serious risks that accompany a reduced range of foods (such as nutritional deficiencies), in addition to the impact restrictive diets can have on a child's relationship with food.
Current research does not support a causal link between sugar and 'hyperactive' behaviour or cognition.
Limiting sugar as a behaviour management strategy is unfounded and may be counter productive.
It's important to be mindful of our food language, especially in relation to effects that are largely unfounded. Such language may contribute to confirmation bias and restriction.
Whilst unlikely, we can't rule out that some children may be more sensitive to sugar or that other factors may be at play.
Excess added sugar (more than around 4-6 teaspoons per day) can displace other important nutrients and contribute to tooth decay. It's still a great idea to focus on a varied diet rich in fruit, vegetables, beans and legumes, wholegrain, lean proteins and dairy/alternatives.
Added sugar (the recommendations)
How to improve vegetable consumption
(1996). Hyperactivity: Is candy causal?, Critical Reviews in Food Science and Nutrition, 36:1-2, 31-47.
Del-Ponte et al., (2019). Sugar consumption and attention-deficit/hyperactivity disorder (ADHD): A birth cohort study. J Affective Disorders. 243, 290-296.
Hoover et al. (1994). Effects of sugar ingestion expectancies on mother-child interactions. J Abnorm Child Psychol. 22:501-15.
Wolraich et al., (1995) The Effect of Sugar on Behaviour or Cognition in Children. A Meta-Analysis. JAMA. 274:1617-1621.