The brain relies primarily on glucose as a source of fuel and it goes without saying that anything that interferes with the brain’s supply of glucose has the potential to impact the brain’s functioning. Indeed there is a large body of evidence that suggests a link between a person’s mood and blood sugar levels, more particularly blood sugar spikes and dips that may occur following the consumption of certain foods[mfn]1,2[/mfn]

The sugar levels in the blood is one of the key parameters that need to be maintained within healthy levels. The body has a system of hormones to do this (Fig. 1). This ensures, among other reasons, that the body gets the energy it needs. Of note, the brain is quite sensitive to fluctuations in blood sugar levels. 

Scientists have used diabetic individuals, who are more prone to experience blood sugar spikes and dips, to study the impact of blood sugar variations on mood[mfn]1[/mfn]. When blood sugar is imbalanced, either too high or too low, it can cause negative changes to mood as a secondary effect of brain cells shifting from normal function. Among diabetics, higher blood glucose (hyperglycemia) has been associated with a state of anger or sadness. Conversely, blood sugar dips (hypoglycemia) have been associated with feelings of nervousness or anxiety. These findings show the close inter-relatedness between blood sugar and mood. 

Interestingly, healthy individuals can also experience mood disturbances due to significant fluctuations in blood sugar[mfn]3[/mfn].  The diet plays a big role in this. Of note, individuals consuming a diet high in refined carbohydrates and added sugars may experience a sudden surge in their blood sugar, followed by an exaggerated insulin response, leading to reactive hypoglycemia. 

A 2017 prospective study[mfn]4[/mfn] found positive associations between high sugar consumption and common mental disorders, concluding that sugar intake from sweet foods and beverages has an adverse effect on long-term psychological health.

What is Reactive Hypoglycaemia and how does it impact mood? 

Reactive hypoglycemia happens when your blood sugar crashes and drop below normal levels. This manifests as psychiatric-like symptoms including: mood swings, irritability, “hanger,” anxiety, depression, bipolar, and those associated with ADHD. Cognitive symptoms like headaches, chronic fatigue, brain fog, dizzy spells, and fainting can also happen. There is a strong link between our diet and the occurrence of reactive hypoglycaemia. This is favoured by certain foods as follows: 

• When we consume a high sugar meal or a meal that’s rich in simple carbohydrates (e.g. a breakfast of orange juice, a bagel with jam), the blood sugar rises. 
• This stimulates the pancreas to release a massive spike of insulin to help bring down blood sugar levels by storing away excess glucose. 
• Insulin can overcorrect, causing blood glucose levels to drop too low (reactive hypoglycemia), which the body interprets as an emergency. 
• The nervous system then signals the release of neurotransmitters, followed by cortisol, to bring up blood sugar levels (Fig. 3) 
• The adrenaline rush can lead to symptoms such as anxiety, shakiness, and lack of concentration. 
• The same cycle can repeat again throughout the day. 

How to prevent Reactive Hypoglycaemia and stabilise mood? 

Reactive hypoglycemia usually doesn’t require medical attention and dietary changes often help lessen symptoms.

Try making small changes to the timing and composition of meals, such as:

1. Add some natural fats into each snack and meals: try to add in more of these fat sources like avocados, nuts or sugar-free nut butters. This is because fats slow down digestion speed and consequently moderates the blood sugar response (Fig. 4)
2. Consume low-glycaemic foods: this will lead to more stable blood sugar levels. Switch from instant oats, sweetened with sugar to a something like an omelet with cheese and vegetables with a fresh fruit. 
3. Consume proteins with each meal: lean protein of high biological value will both reduce post-meal glucose increases. Examples include eggs, fish, game meat (and other very lean red meats), skinless poultry breast meat, and whey protein.
4. Eat more whole-food sources for carbs like rice, oats, grains, and root vegetables, potatoes, etc. instead of refined white flours and sugars.
5. Choose high-fibre foods or a source of fibre with each meal: fibre tends to slow down digestion speed, leading to a more stable blood glucose response. Good sources of fibre include broccoli, spinach and whole fruits. 

It also helps to do some light exercise after a main meal, like taking a 10-15 minute stroll. Exercise activates glucose transporter molecules that function as channels to facilitate the uptake of glucose from the bloodstream, helping with blood sugar control after a meal.

Most of us don’t realise the power of good nutrition and how it can make us feel better. Most of us have been misled into believing that a healthy diet consists of foods like high-carbohydrate, fat-free foods (e.g fruit juices, cereals, fat-free milk). These may actually be affecting the body’s metabolism, hormones, neurotransmitters and mood.  Uncontrolled blood sugar, given its profound impact on mood, can negatively impact a teen’s work productivity and interpersonal relationships with teachers, classmates and family. Numerous behavioural and cognitive issues may be corrected by simple dietary changes.

References:

1. Herzer M, Hood KK. Anxiety symptoms in adolescents with type 1 diabetes: association with blood glucose monitoring and glycemic control. J Pediatr Psychol. 2010 May;35(4):415-25. (Source)
2. Rechenberg K, Whittemore R, Grey M. Anxiety in Youth With Type 1 Diabetes. J Pediatr Nurs. 2017 Jan-Feb;32:64-71. (Source)
3. Warren RE, Frier BM. Hypoglycaemia and cognitive function. Diabetes Obes Metab. 2005 Sep;7(5):493-503. (Source)
4. Knüppel A, Shipley MJ, Llewellyn CH, Brunner EJ. Sugar intake from sweet food and beverages, common mental disorder and depression: prospective findings from the Whitehall II study. Sci Rep. 2017 Jul 27;7(1):6287. (Source)