This Is Your Brain on Sugar: A Dietitian Details How a Love for Sweets May Worsen Your Memory
The sweet tooth was once an evolutionary advantage. Only recently have researchers begun to discover what this still-lingering trait means for our long-term brain health today.
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There may be no love-hate relationship quite as conflicted as the one between us humans and sugar. On the one hand, we physiologically cannot live without this sweet substance—in fact, the human brain and many of our metabolic processes rely on sugar to fuel some of our key cognitive and internal functions. But, as with just about anything upon which the survival of our species depends (like, say, sex), nature designed sugar to bring us such great pleasure that, at times, it can seem impossible to resist.
The tough part is that regardless of your sugar source—whether it’s fruits and vegetables, a package of Chips Ahoy (ah, nostalgia), or a glass of pinot—our bodies are hardwired to crave more. So, thanks to the effects of sugar on the human brain, the American Heart Association reports that most of us consume at least three times as much sugar every day as we really should.
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Does the brain need sugar?
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Ellen Albertson, PhD—a registered dietitian, nutritionist, and psychologist—explains that glucose, often referred to as “blood sugar,” is the brain’s main energy source.
Maybe it’s tempting to hear that as an excuse to whip up a package of Ghirardelli brownies, but Albertson says not so fast: your brain “doesn’t need regular table sugar to run properly,” she advises. Healthier carbohydrate sources provide more than enough glucose—and, failing that, your body can make glucose from the fat and protein you eat.
Then why does a sugar craving sometimes feel like a compulsion? Well, while sugar is everywhere today (and our diets aren’t in short supply of fats or proteins, either), it was pretty scarce in prehistoric times. And because naturally sugary foods like fruits are such an efficient source of calories, the survival-oriented ancestors’ brains came to crave this chemical.
Today, we have yet to evolve past this. Add to this that many of our ancestors spent their entire days engaged in ongoing physical activity. For the most part, the typical modern lifestyle is very different from that—our bodies aren’t processing our sugar consumption.
Meanwhile, having sugar in the system often leads to wanting more—in fact, researchers for a lauded 2008 psychology study asserted that consuming sugar can activate “neurochemical changes in the brain that also occur with addictive drugs.”
How does sugar affect your brain?
This part explains a lot: Albertson reveals that when we eat something sweet, it activates our brain’s reward system. The feel-good neurotransmitter, dopamine, gives us a short-term high, signaling that what we just experienced was positive—reinforcing our desire to do it again. (Makes sense, right? Learn more on this from nutrition professionals’ recent takes on the science behind cravings.)
Research published in Current Biology in 2016 illustrated the sheer strength of this reward system. The study demonstrated that just seeing something associated with a past reward triggers a massive dopamine hit. This subconscious activity can help drive good habits, like exercising or working toward a goal. But that’s also why it’s so easy to mindlessly reach into the cookie drawer…even when you’re full.
Can sugar change the brain?
Albertson says the brain is constantly rewiring itself, thanks to a phenomenon called “neuroplasticity.” This activity optimizes how well the brain functions, supporting processes like learning and memory. But constantly flooding your brain with dopamine through a high-sugar diet will also provoke it to adapt to your habits. “What this means is that we need larger amounts of sweet foods to get the same pleasant feelings,” she says.
Love ways to help keep your mind sharp? Read 16 Memory-Boosting Tips from Brain Scientists
What can happen to your brain when you eat too much sugar?
Here’s the irony: even as the brain seeks more and more sugar, excessive amounts start to reduce its neuroplasticity, according to 2019 research in Neuroscience & Behavioral Reviews. This means your sweet tooth may diminish your brain’s capacity for tasks like learning and memory formation.
Albertson also points to another 2019 review, published in Alzheimer’s & Dementia, which concluded that individuals who had reported consuming more than one sugary beverage per day actually had a lower average total brain volume, particularly in the hippocampus—the part of the brain that’s involved in learning and memory processes.
Over time, these effects may even lead to neurocognitive deficits, like problems with decision-making, good judgment, attention, and language, according to research published in Frontiers in Neuroscience. And in the long-term, this damage may raise the risk of cognitive decline—including developing Alzheimer’s disease or dementia.
“Can eating sugar affect my mood?”
A quick sugar fix might seem to lift your spirits in the moment…but over time, eating too much sugar can actually take an emotional toll. The Neuroscience & Behavioral Reviews research suggested that a high-sugar diet was associated with greater rates of mood disorders, like anxiety and depression. The researchers found that over-consuming sugar may also interfere with your ability to handle stress and anxiety.
In a nutshell: it looks like a high-sugar diet can leave us moody, stressed, forgetful, and prone to bad decisions (like, eating more sugar).
What happens when you quit sugar?
Now for the good news: the learning and memory problems and the cognitive deficits associated with a high-sugar diet are reversible, according to a study published in Appetite. The key is to reduce your sugar intake and turn to foods with a low glycemic index, like healthy carbs.
This choice may also help you look on the bright side. A 2017 public health study at University College London found that reducing dietary sugar appeared to improve mental health—the researchers reported “that lower intake of sugar may be associated with better psychological health.”
It’s just that you may encounter a bit of discomfort in getting there. While some scientists are split over whether sugar is a truly addictive substance the same way nicotine and alcohol are, the sweet stuff is clearly habit-forming. And if you’re not feeding your healthier dopamine-driven habits, you may experience symptoms like cravings and a low mood. (Get inspired: A Trainer Says This Under-$30 Resistance Band Will Transform Your At-Home Workouts)
That’s why swearing off sugar now and forever isn’t always the most sustainable approach. Instead, start with these 12 easy swaps to reduce your sugar intake.
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- Ellen Albertson, PhD, a registered dietician, nutritionist, and psychologist
- American Heart Association: "How much sugar is too much?"
- Current Biology: "The Role of Dopamine in Value-Based Attentional Orienting."
- Neuroscience & Behavioral Reviews: "The impact of sugar consumption on stress driven, emotional and addictive behaviors."
- Alzheimer's & Dementia: "Sugary beverage intake and preclinical Alzheimer's disease in the community."
- Frontiers in Neuroscience: "Long-Term Overconsumption of Sugar Starting at Adolescence Produces Persistent Hyperactivity and Neurocognitive Deficits in Adulthood."
- Diabetes, Obesity and Metabolism: "HbA1c and brain health across the entire glycaemic spectrum."
- Appetite: "A high-fat high-sugar diet-induced impairment in place-recognition memory is reversible and training-dependent."
- Scientific Reports: "Sugar intake from sweet food and beverages, common mental disorder and depression: prospective findings from the Whitehall II study."
- British Journal of Sports Medicine: "Sugar addiction: Is it real? A narrative review."