Hi! Welcome. You being here means more than you know. Knowing it lands with someone like you keeps me going. I'm Lavena Xu-Johnson. I write about psychology for founders. Why? Because scaling a business means scaling ourselves first.
Happy Thursday, founders,
Last weekend, I had an interesting encounter: an acquaintance offered my son some candies, and he naturally refused them. One, because most of the time, he never really enjoyed sweets since day one. Two, because I always told him the effect of sugar on our bodies: ‘It’s bad for us.’ His little 4-year-old face would look very serious when he refuses candy (not on the days when he’s in the mood for some ice cream, though).
I don’t believe in banning sweet stuff altogether (because the mystery would make sugar even more appealing). My son could safely eat sugar-free cookies, for example, with stevia sweeteners. And I always leave room for him to make his own choice when he’s offered sugary content, and most of the time he makes the right choice without my involvement.
“He doesn’t want sweets?” The acquaintance was surprised.
“No, I ‘brainwashed’ him about how bad sugar is for us. I guess it’s working!” I grinned.
“Oh no! What’s fun about life then!”
Hm.. It’s a lot more fun when we’re not addicted to sugar uncontrollably, actually... I thought.
I don’t blame her for making the judgment. I only became very aware and mindful of added and processed sugar two years ago, and before that, I was a malted-milk-cookie addict. Never have I ever read the label that states it has 17g of added sugar per 100g. It didn’t even taste sweet to me at that time!
Most of us aren’t aware of how sugar actually affects us - mental performance, gut health, inflammation, and how fast we age. It is nearly impossible to avoid sugar and processed food these days. Not to mention, additive-free, no-added-sugar, and unprocessed ingredients are often priced unreasonably high.
The effects of sugar on adult and children’s brain health are evident in research, so why do we want to feed addictive content to our own bodies, let alone condition and reward the future generation with sugary content, getting them hooked early?
This issue, let’s dive into the effect of sugar on our brain health. At the end of the day, how can we build and lead with clarity when what we eat undermines our health and our ability to maintain mental clarity and stability?
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Sugar and cocaine ‘lit’ our brain the same way?
Our body doesn’t “process sugar” in one single way; it depends on the type - we get pushed into the spike-and-drop rhythm differently.
Glucose: Found in starchy foods, rice, potatoes, fruits, honey, and derived from breaking down cornstarch. It goes straight into your blood and becomes the quick fuel your brain and body can use.
Fructose: Found in fruit, honey, and root vegetables. It follows a very different route - it’s metabolised through the liver and (as described in the research) does not traverse the blood - brain barrier, leading to a slower rise in blood glucose compared with glucose.
Sucrose: Manufacturers create it by processing sugar cane and sugar beets. It is a “combo sugar”: your body breaks it down into glucose and fructose, then handles each separately.
The perpetual cycle of sugar addiction looks like this:
Sugar consumption: You consume sugar because of cravings, and its addictive properties
Blood sugar spikes rapidly: Dopamine spikes, mass insulinis secreted to drop blood sugar levels
Blood sugar falls rapidly: High insulin levels cause immediate fat storage, and your body craves the lost sugar ‘high.’
Hunger & cravings: Low blood sugar levels cause increased appetite and cravings, and the cycle repeats itself.
Whole-brain activity maps in mice after sucrose vs cocaine, showing overlapping activation in reward circuitry (notably the nucleus accumbens). (Bijoch et al., 2023)
A 2023 study on mice mapped what happens in the brain after and found both switch on the same reward center: the nucleus accumbens. At the cell level, a lot of the same neurons lit up for sugar and cocaine, and both triggered similar “rewiring” signals linked to reinforcement and craving. The difference is: sugar created a big spike early on, while cocaine kept recruiting more of the brain’s reward network (even silent synapses, which are responsible for creating new memories) with repeated exposure.
Sugar and brain health
High-sugar diets have become the default of a modern diet - sweetened drinks, desserts, processed snacks. This surge fuels obesity, diabetes, and cardiovascular disease, but it is not widely known that a high sugar diet is also increasingly tied to mental health outcomes. People often reach for something sweet for relief and comfort, and studies repeatedly show higher rates of depression among those who consume more sugar.
Here is some of the evidence showing the link between sugar and depression:
A 2024 systematic review and meta‑analysis included 40 studies with 1,212,107 participants and found sugar intake associated with a higher risk of depression - every additional 100g/day of dietary sugar intake was associated with a 28% higher incidence of depression.
The Whitehall II study (Scientific Reports, 2017) analysed repeated measures and found that in men, the highest tertile of sugar intake from sweet foods/beverages was linked with higher odds of incident common mental disorder after 5 years (23% increased odds).
A large 2019 review pulled together 300+ studies and concludes that long-term high sugar intake is linked to cognitive impairments, worse neuroplasticity, and a higher risk of anxiety/depression-type outcomes: with sugar activating the brain’s reward circuitry in a way that resembles substances of abuse, and increasing impulsivity around feeding.
A Frontiers review lays out several mechanisms that line up with what many people feel day‑to‑day:
Blood sugar swings → mood volatility + stress signalling (cortisol)
HPA-axis disruption → stress system gets less stable over time
Inflammation → linked to depressive symptoms and reduced neuroplasticity
Gut microbiota shifts → gut–brain signalling changes
Lower Brain-Derived Neurotrophic Factor → weaker support for emotional regulation and learning
Dopamine disruption → reward feels “blunted,” cravings get louder
How to reduce sugar intake
First, we need to clear our sugar blind spots:
Sugar is in your diet much more than you think.
Packaged juice, sugary yogurt, and soda drinks: If you see packaged juice. Run the other direction. On average, there are 20–26 grams of sugar per cup (240 ml) of packaged fruit juice. Both packaged juices and soft drinks are bad for your health.
Sauces and cooking ingredients: Ketchup, Mayonnaise, Takayuki sauce, oyster sauce and salad dressings…
Packaged snacks and cereal: “Protein” bars, Granola, and Cereal
White flour food: Your body breaks its starch into glucose fast, so it behaves like sugar in your bloodstream - quick spike, quick drop, and the same cravings loop.
High sugar fruits: These are not bad for you, but if you’re in the process of lowering glucose volatility and unwinding cravings, it’s best to avoid them early, because it does not help with your body adjusting to the new norm.
Learn to read labels like you read term sheets.
Added sugar, syrups, concentrates - same story, different costume. You’ll be surprised to find most of the food in your corner shop is not healthy, full of sugar, additives, and chemicals our bodies don’t need.
Trust the process.
It has been almost two years since I consciously avoided sugar at all costs, and I still remember how my body and my brain reacted in the first few weeks. You may feel similar:
Week 1: During the first week of cutting down on sugar, you may feel faint and even fatigued. Your body is adjusting to a new ‘normal’ without constant spikes.
Week 2: The second week will be full of cravings. Your body has adjusted to the new levels of stable glucose, but your brain really wants to give in.
Week 3: You may feel balanced; the efforts from the first two weeks are paying off. Very few cravings from the body or the brain, easy to put off.
At first, it will not be easy, but once you’ve done it, you will never look back.
After 2-3 months of removing the lists above, take a tiny bite of your old favourite sugary snack - your taste buds will tell you the truth: it tastes far more artificial than you remember.
That moment, will feel like freedom.
Bonus: A few documentaries to watch about the sugar industry
Junk food, sugar, and additives - The dark side of the food industry by DW Documentary
Sugar is Not a Treat TEDx
How's the depth of today's edition?
As always, hit reply if something in here hits home.
Until next week,
Lavena
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