What is the Link Between Sugar, ADHD and IBS?

What is the Link Between Sugar, ADHD and IBS?

ADHD has a strong genetic component. Many studies have investigated the role of certain genes and enzymes such as catechol-O-methyltransferase (COMT) and the dopamine transporter (DAT1) genes on ADHD symptoms,(1).

This is because COMT may play a role in degradation of dopamine, which is a key deficiency in the case of ADHD. The two enzymes involved in the breakdown of dopamine are monoamine oxidase (MAO) and catechol O-methyltransferase (COMT), (3).

Studies contain considerable evidence supporting this low dopamine hypothesis, whereby an underlying dopamine deficit would be responsible for at least part of the ADHD spectrum,(4).

One study suggests that a higher amount of COMT and DAT1 genetic alleles may predict increasing symptoms of hyperactivity and inattention in boys from the general population assessed at 11 and 15 years of age. The presence of both alleles was also associated with full ADHD diagnosis at age 18 years in boys from this cohort. It has also been reported that oestrogen has an antagonistic effect on DAT1 activity, which may protect against ADHD by delaying dopamine reuptake,(4).

But how can diet influence mental health in relation to ADHD? This is where we turn our attention to the gut-brain–microbiome axis. Diets rich in vegetables, fibre and micronutrients such as vitamins D and C, probiotics and prebiotics, fermented foods, anti-inflammatory and omega-3-rich foods that are low in bad fats, and low in refined carbohydrate promote positive mental health.

They can increase beneficial trains of bacteria such as Bacteroidetes, Prevotella, and help to create short-chain fatty acids (which increase colon health) via the production of other beneficial gut microbiome species such as Bifodobacteria, Akkermansia, Roseburia, Lactilobacillus, and the anti-inflammatory immune cytokine interleukin (IL)-10 while also decreasing levels of un-beneficial gut bacterial species such as Firmicutes, Escherichia coli, Ruminococcus, Coprococcus and their toxic byproducts known as lipopolysaccharides,(5).

High-fat, high-sugar, and ultra-processed foods increase Bacteroides, bile acids, Bilophila wadsworth, Enterobacteriaceae, Firmicutes, Enterobacteriaceae, Escherichia, Klebsiella, and Shigella, which are problematic for our gut and brain health, (5).

But how does this relate so strongly to the sugar – dopamine – ADHD – IBS – connection? Well, genetically low dopamine, in the case of ADHD, may cause sugar cravings, as those individuals look to seek out ways to ‘fill’ the dopamine receptors that are low in dopamine, giving a calming effect in the short-term, but possibly causing downstream negative effects on the health of the digestive system.

While glucose is a primary fuel for the brain which does increase brain focus, we want to be careful of consuming too much sugar, in particular high sugar items and items containing large amounts of fructose. Fructose is found in fruit much lower than high-fructose corn syrup which is up to 50% fructose, and fruit contains other beneficial components such as enzymes and fibre that help to ‘package up’ the fructose.

We want to be focusing on food that is low in glycemic load for many reasons, mainly to manage our blood sugar levels, but also to help minimise disruptions to our gut health and the microbial diversity due to consuming high amounts of sugar, (6).

This is partly because fructose is handled very differently to glucose by the body. It may actually increase ghrelin, which is the hunger hormone, so ingesting a lot of fructose may lead to more feelings of hunger and cravings for sweet foods. After a hard workout like HIIT our bodies are more efficient at metabolising sugar, so then may be a good time to eat, say, a mango which is high in glucose and fructose, (6).

Parallel pathways are neural pathways that enable the opposite to happen, for example a flex of the arm. The parallel pathway for sugar is for us to seek more sugar containing foods, and the other is the degree that a specific food will raise blood glucose. The sweet pathway is hardwired in us, and this is to do with the nervous system’s need for it. When we taste something sweet the neural pathways shift our entire self towards seeking more sugar and food in general, (6).

The mesolimbic reward pathway creates an increase in dopamine that goes to the striatum, which places us into modes of action to pursue particular things. Sugar has a big capability to induce this pathway, especially sweet liquids. The perception of that sweet thing increases dopamine in the mesolimbic reward pathway, which induces the need to seek out more of that sweet thing, (6).

So, it is not the sensation of satiety, but the sensation of wanting more that helps to fill the dopamine receptors, which in turn want more of that ‘thing’. It is a pleasure/pain balance (7).

When we increase our levels of dopamine, it also increases our sensation of frustration or lack of it. So, if you savour the taste of the chocolate, just as you swallow it, you may notice that you actually want more. That is actually the neural circuits that are of pain and are pushing dopamine down. (6), so that is why we seek more, either sugar, or something to get that dopamine back up. The follow up is never going give us the same level of dopamine as the first mouthful, but the greater the dopamine increases, the greater the dopamine pain/need seek level increases. And so, this is the chicken and egg, perpetual cycle that someone with genetically low dopamine may find themselves in, regarding a need to find ways to fill that gap.

This is a natural urge that we all need for survival, but these dopamine pathways should be known about, as the cascade for more sweet stuff links to possible gut issues due to un-beneficial bacteria and yeast ‘feasting’ on the high sugar and also an increase blood glucose, neither of which are beneficial to our health.

So, it is recommended to cut down slowly with some of these suggestions, (8).

  1. Limit processed foods as many processed foods have added sugars.
  2. Remove sugary drinks as they often contain lots of added sugar.
  3. Read nutrition labels to watch out for ‘hidden’ or “added sugar”.
  4. Experiment with substitutions from sugar and honey such as cinnamon, nutmeg, lemon, and other natural extracts.

To summarise: craving sugar is a natural response as the brain craves glucose to function, but this craving may be heightened in ADHD, (9).

The ADHD brain becomes easily unsatisfied and bored with tasks that offer no challenges, attention wanders and there may be irritation, temper-tantrums and frustration, (9). These are the signals to indicate that the ADHD brain is in distress, and it begins to demand glucose to activate dopamine secretion. When the ADHD individual consumes foods such as carbohydrates, (bread, pasta, cookies, sweets, etc) they are converted into glucose rapidly and the individual may experience suppression of restlessness, (9).

These are just some of the findings so far within the global research of ADHD. While ADHD can often be a positive skill for many people who are often able to ‘hyper-focus’ and are often much more likely to have a certain amount of ‘drive’ and determination due to their specific personality type, ADHD can also come with what is termed as ‘emotional dysregulation’ which can make it hard for a person with ADHD to regulate their emotions. This can lead to a person overreacting, taking risks, feeling depressed or anxious and this ‘may’ also be what then contributes to the physiological occurrence of IBS in many people with ADHD. For this reason, it is always good to inform yourself as much as possible as to whether you or anyone that you know may have ADHD, so that you can help to manage the symptoms using a blend of lifestyle and natural interventions.

  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5082511/
  2. https://link.springer.com/article/10.1007/s12035-013-8516-5
  3. https://pressbooks.lib.vt.edu/neuroscience/chapter/neurotransmitters-ach-glutamate-gaba-and-glycine/
  4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5082511/
  5. https://doi.org/10.3390/ijms23126643
  6. https://open.spotify.com/episode/0H5VEVRJAU8NCsrPvLlE7Q?si=Re-6-yi7SmGkmuVI8C2GHQ&nd=1
  7. https://www.amazon.com/Dopamine-Nation-Finding-Balance-Indulgence/dp/152474672X
  8. https://www.razcoaching.com/the-adhd-brain/
  9. https://www.healthline.com/health/adhd/sugar-and-adhd#talk-with-a-doctor