Disclaimer: This is about how food affects the brain. It is not health advice. Please consult your doctor before making any changes to your diet.
Your Expensive Brain
Your brain is an expensive organ. Despite being only 2% of your body weight, it consumes about 20% of your calories.1 Without sufficient calories, it cannot run at full capacity. Your brain needs food to fuel its functioning, its repair, and its growth, so not eating is not an option.
But what sort of calories does the brain want?
The fuel that normally runs your brain is glucose. All carbohydrates, whether they are bread, bean, blueberry, or broccoli, get broken down into glucose in the body. Since, under most circumstances, your brain needs glucose for energy, you must eat some kind of food with carbohydrate calories in it. This includes all fruits, vegetables, grains, potatoes, and legumes.1
When fuel levels drop in your brain, your capacity for clear thinking and careful decision-making is diminished. As Teresa Aubele and Susan Reynolds explain in an article titled “Have You Fed Your Brain Today?” published in Psychology Today, this is because
the frontal lobes, the area of the brain that acts like the CEO of you, are particularly sensitive to falling glucose levels. … Researchers at Roehampton University in England noted that, ‘When your glucose level drops, the symptom is confused thinking.’ … Another early sign of a glucose drop is a change in mood, irritability, and overall grumpiness.2
Aubele and Reynolds also point out that the “brain doesn’t store glucose, and thus needs a fresh batch each day to fire it up,”2 which is why breakfast is such an important meal for academic success. When you break the fast of a night’s sleep with a meal, you’re refilling the empty gas tank of your brain. Studies show that people who skip breakfast have diminished concentration and problem-solving abilities.2
But wait, you might be thinking, can’t your brain run on fat? Absolutely. When deprived of glucose, the body will switch into ketosis – a state in which your primary fuel is ketones, which are derived from fat. 3 Ketosis can be advantageous in certain athletic situations and for certain health problems, and it may even improve cognitive function.3
However, in practice, getting your brain and body to use fat as fuel is hard to pull off. Entering and remaining in ketosis is very challenging and should only be done under the supervision of a physician.3 For most people, most of the time, glucose will be the brain’s primary fuel source. Therefore, to be at your best, you need to eat sufficient carbohydrate calories.
There is, however, an important caveat you need to be aware of:
Anytime your body detects a high concentration of glucose in the blood stream – the sort of thing that happens after you drink a glass of fruit juice or eat some candy – it sees this as dangerous and releases insulin to get the sugar out of the bloodstream.1 The glucose is then stored for later use as fat, which the brain cannot easily use.1 The insulin response deprives your brain of glucose, resulting in what is known as a “sugar crash.”1
Admittedly, “no sugar” is a tall order, but we don’t have to completely cut out sugar in order to experience a brain-health benefit. At the end of this article, we’ll look at some reasonable, realistic techniques for reducing sugar consumption. For now, let’s explore the science of how sugar affects the brain.
Also, when I say “sugar,” I’m including corn syrup, high-fructose corn syrup, barley malt, dextrose, maltose, rice syrup, and the dozens of other additives that are really just sugar masquerading under a different name. The ingredients list might hide what’s in the product, but the nutritional information won’t: It will tally up all of these things under “sugars.”
Slow it Down
To properly fuel your brain, you have to eat foods with carbohydrates that don’t dump all their glucose into the bloodstream at once. Instead of sugar and simple carbohydrates, eat complex carbohydrates that digest slowly. “The healthier the carbohydrates you give your body, the better your body will be able to stabilize blood sugar levels and elevate brain function.”2
Foods that are high in sugar or simple carbohydrates are known as high-glycemic foods, whereas foods that have slowly-digesting carbohydrates are known as low-glycemic foods. Because they have fiber, whole grains, beans, and lentils have a better glycemic index than refined grains like white rice or white bread.
Whether a child eats high-glycemic meals or low-glycemic meals turns out to be a big deal. A 2015 article published in Clinical Pediatrics noted that:
In 2007, Benton et al studied the effects of 3 different breakfasts with either low, medium, or high glycemic index in normal, healthy children in school. When children received breakfasts with a low glycemic index, scores on memory, attention, and time spent on tasks were significantly better than scores after the medium- or high-glycemic-index breakfasts.4
Vegetables are important to eat because of their micronutrients, but many vegetables don’t have a lot of calories, so you can eat a lot of broccoli and not get much fuel for your brain. Starchy roots like carrots, beets, and sweet potatoes have more glucose to offer.
Fruits, too, are valuable because of their micronutrients, but they often have a high glycemic index because they contain a great deal of naturally occurring sugar. Fruit juice is even more problematic because it is digested so quickly. Combining fruits with foods that slow down digestion is good strategy for mitigating their sugar load.
Three things slow down the absorption of carbohydrates: fiber, fat, and protein. Foods that are high in fiber, fat, and protein take longer for the body to break down, slowing digestion.1 The result is that carbohydrates eaten at the same time break down more slowly, releasing their glucose into the bloodstream more gradually.1 This gives your brain a steady supply of fuel and decreases the likelihood of a crash-producing insulin response.1
My personal brain-fuel program is to eat a high-fat, high-protein breakfast, followed immediately by fruit and something high in fiber. I typically don’t feel hungry again for about five hours and experience a very steady level of mental energy. When I finally do eat lunch, it is most often coconut curry loaded with veggies, combining fat, protein, and complex carbohydrates.
Can Sugar Make You Dumber?
We’ve established that sugar causes an insulin response that deprives your brain of energy, but are there other negative effects as well? The answer appears to be yes.
Research out of the University of California, Los Angeles, suggests that sugar forms free radicals in the brain’s membrane and compromises nerve cells’ ability to communicate. This could have repercussions in how well we remember instructions, process ideas, and handle our moods, says Fernando Gómez-Pinilla, Ph.D., author of the UCLA study.5
Other research has found a link between sugar consumption and current memory problems, as well as a link between sugar consumption and dementia in old-age.6 This may be related to the finding that high-sugar diets reduce “the production of a brain chemical known as brain-derived neurotrophic factor (BDNF),” which is critical for learning and memory.7 BDNF also promotes neurogenesis,8 meaning that eating a lot of sugar will inhibit the growth of new brain cells.
Aubele and Reynolds add that “researchers at the Salk Institute in California found that high glucose levels resulting from quick, easy sugar intake slowly but surely damage cells everywhere in the body, especially those in the brain.”9
Most people are well-aware of how unhealthy sugar is for the body. Our nation suffers from an epidemic of obesity, type-2 diabetes, and heart disease, and sugar is high on the list of culprits. But surprisingly few people are aware of the problems sugar poses for the brain. The next time you’re weighing the pros and cons of eating a candy bar, you ought to consider the damage it does to your brain in addition to the harm it does to your body.
A Surprise Consensus in the Fad-Diet Debates
There is a wide range of opinions out there regarding what people should and shouldn’t eat: Whole-grain or low-carb? High-fat or low-fat? Paleo or vegetarian? Despite all the disagreement, no one is advising that we eat more sugar. No one.
Is Sugar Like an Addictive Drug?
Yes. Neuroscience research shows that when people eat sugary foods, particular areas of their brains activate – the same brain areas that light up when a drug addict consumes his substance of choice.5 Sugar also triggers the release of dopamine and serotonin – the same neurotransmitters released in the brain of a drug addict when he gets high.5 Many researchers are now calling for the government to regulate sugar the same way they regulate drugs.5
However, as Gary Taubes details in The Case Against Sugar, sugar producers, including corn-syrup producers, have powerful lobbyists to influence Congress,10 so I wouldn’t count on change coming from above anytime soon. Avoiding sugar is something we’ll have to take into our own hands.
So How Bad Is It?
According to the U.S. Department of Agriculture (USDA), the average American consumes 156 pounds of added sugar per year. That’s five grocery store shelves loaded with 30 or so one pound bags of sugar each. If you find that hard to believe, that’s probably because sugar is so ubiquitous in our diets that most of us have no idea how much we’re consuming.7
According to the University of California, San Francisco, food producers currently use a stunning 61 different names for sugar on food labels, and about 75% of packaged foods sold in supermarkets contain one or more of these added sugars.11 Furthermore, the products you love might have a lot more sugar than you think. A 16 ounce vanilla latte, for instance, typically contains your entire daily allowance of sugar.5
And our sugar consumption has escalated quickly in recent years:
The average American consumes somewhere between two to three pounds of sugar each week. Over the last twenty years, our national sugar consumption exploded from 26 pounds to 135 pounds of sugar—per person—annually. Compare that to sugar consumption in the late 1800s, when the average consumption was five pounds per person-per year.9
To give you a visual, here’s what the average American consumes each month:
It’s hard to imagine that eating over 10 of those bags per year is a good idea. We have a serious problem.
What About Sugar Alternatives?
“Natural” sugar, such as honey, isn’t significantly healthier than processed sugars.9
And fake sugar, for a variety of reasons, isn’t the answer.9
Many recovering sugar-junkies turn to diet soda or other products with artificial sweeteners, because they satisfy cravings for sweetness without the sugar. This, it turns out, is a poor choice. Artificial sweeteners can actually make a sugar addiction worse, not better, and are themselves addictive.12
Artificial sweeteners overstimulate our taste buds, desensitizing us to sweetness. Often the result is that
people who routinely use artificial sweeteners may start to find less intensely sweet foods, such as fruit, less appealing and unsweet foods, such as vegetables, downright unpalatable. In other words, use of artificial sweeteners can make you shun healthy, filling, and highly nutritious foods, while consuming more artificially flavored foods with less nutritional value. Artificial sweeteners may play another trick, too. Research suggests that they may prevent us from associating sweetness with caloric intake. As a result, we may crave more sweets, tend to choose sweet food over nutritious food, and gain weight.12
A Little Help From Healthy Fat
Foods high in omega-3 fatty acids, especially those with a high amount of docosahexaenoic acid (DHA) help protect the brain from sugar’s damaging effects.13 “Still planning to throw caution to the wind and indulge in a hot-fudge sundae? Then also eat foods rich in omega-3 fatty acids, like salmon, walnuts and flaxseeds, or take a daily DHA capsule.”13
A Culture of Sugar
Sugar is deeply ingrained in our culture. Desserts are served at most parties because we believe that’s part of being a good host. Nearly every holiday we celebrate has its own special, sugary treats. We even have one holiday – Halloween – which revolves almost entirely around candy.
Given all that, reducing our sugar intake is sure to be an uphill battle, but it is a battle we can win.
To avoid sugar, we need to read food labels carefully and try to choose foods that have little or no added sugar. Avoiding processed foods is a good rule of thumb. We’ll be better off buying whole-food ingredients and cooking for ourselves.
And we need to change the culture, one social gathering at a time.
Realistic Sugar-Reduction Techniques
Okay, let’s be real. Completely avoiding sugar is next-to-impossible in the modern world, and a lifetime of sugar-eating habits aren’t going to dissolve as easily as a cube of white crystals in your coffee. As I said earlier, complete abstinence is not required. Any reduction in sugar consumption is beneficial for brain health, not to mention physical health.
When trying to avoid sugar, perfectionism will actually be counterproductive. It’s more helpful to have a spectrum mindset and remember that every step in the right direction counts. Every piece of candy not eaten is progress.
Remember that behavioral change is slow and hard, but absolutely possible. In time, your brain will rewire. Recognize that slip-ups are inevitable, and you’ll have an easier time making a shift away from sugar if you give yourself permission to be human.
With all that in mind, let’s look at some concrete ways you can help yourself and your family reduce sugar consumption:
- Start small and the transition will be less harsh. Gradually reduce the amount and frequency of sugar consumption.
- Have “cheat days” – days where you allow yourself to indulge freely. It’s common for people to choose one day each week as a cheat day. It’s also common for people to make holidays cheat days, since these days are so often filled with desserts. Over time, though, the frequency of cheat days should decrease, and the severity of binging on cheat days should diminish.
- Stop buying desserts, candy, sodas, and fruit juice at the grocery store. If it’s in the house, it’s a lot harder to resist. Exercise willpower once – while at the store – to avoid having to use your willpower constantly at home.
- Swap out fruit for dessert. My own experience was that after a month of not eating desserts or added sugar, fruit started to taste better than candy or cake.
I’m not perfect about this. I still eat my mom’s apple pie and her famous Christmas cookies. And once in a while, dark chocolate finds its way into my shopping cart. But I usually do decline dessert, and I never keep any significant amount of sweets at home. Over time, avoiding sugar has become easier and easier.
While the gradual approach works very well for most people, it should be understood that a significant minority of people are true sugar addicts, and will probably have to quit cold turkey. Some sugar addicts are quite aware of the hold sugar has on their psyche, while others may need a professional psychological diagnosis. As with drug addicts, sugar addicts will probably find more success if they quit completely, once and for all, with 100% commitment.
(Do you struggle with unhealthy cravings in general? If so, read this: How to Respond to Unhealthy Cravings.)
The Bittersweet Truth
I hope by now you’ve seen that sugar is a serious issue for neurological health and academic performance, and I hope you’ll guide your family towards a diet with less sugar.
Sweets, it turns out, aren’t so sweet after all.
Chris Loper has been working as a tutor and academic coach since 2014, racking up over 10,000 hours of experience supporting students.
Along with Greg Smith, Chris is the cocreator of Parenting for Academic Success (and Parental Sanity) – a five-part course offered every summer.
Chris’s most recent endeavor combines his academic and habit-formation expertise to help students thrive in college. Visit SmartCollegeHabits.com to learn more.
In 2021, he published a humorous memoir titled Wood Floats and Other Brilliant Observations, a book that blends crazy stories with practical life lessons, available on Amazon and through most local bookstores.
He lives in Issaquah, WA where he is the owner of South Cove Tutoring.
1 MacDonald, Matthew. Your Brain: The Missing Manual. O’Reilly Media, 2008.
2 Aubele, Teresa, and Susan Reynolds. “Have You Fed Your Brain Today?” Psychology Today. September 7, 2011.
3 Ferriss, Tim. Tools of Titans: The Tactics, Routines, and Habits of Billionaires, Icons, and World-Class Performers. Houghton Mifflin Harcourt, 2016.
4 Stevens, Laura J., et al. “Amounts of Artificial Food Dyes and Added Sugars in Foods and Sweets Consumed by Children.” Clinical Pediatrics. 2015, Vol. 54(4) 309-321.
5 “Your Brain on Sugar.” WebMD.
6 Reas, Emilie. “Sugar May Harm Brain Health: High levels of blood glucose are linked to memory impairments.” Scientific American. June 12, 2014.
7 DiSalvo, David. “What Eating Too Much Sugar Does to Your Brain.” Forbes. April 1, 2012.
8 Perlmutter, David, MD. “Neurogenesis: How to Change Your Brain.” The Huffington Post. November 2, 2010.
9 Reynolds, Susan, and Teresa Aubele. “Why a Sugar High Leads to a Brain Low.” Psychology Today. October 18, 2011.
10 Taubes, Gary. The Case Against Sugar. Knopf, 2016.
11 “Hidden in Plain Sight.” University of California, San Francisco.
12 Strawbridge, Holly. “Artificial sweeteners: sugar-free, but at what cost?” Harvard Health Publications. July 16, 2012.
13 Schmidt, Elaine. “This is your brain on sugar: UCLA study shows high-fructose diet sabotages learning, memory.” UCLA Newsroom, May 15, 2012.
Title Image: Girdwood, Andrew. “Bloody brain cakes.” www.flickr.com. Creative Commons 2.0. Text added.
Empty: Creative Commons Public Domain. Courtesy of Pixabay. https://pixabay.com/en/fuel-petrol-gas-gauge-empty-full-2741/.
Coconut: Creative Commons Public Domain. Courtesy of Pixabay. https://pixabay.com/en/coconut-brown-food-ingredient-1123738/.
Complex Carbs: Creative Commons Public Domain. Courtesy of Pixabay. https://pixabay.com/en/carrot-kale-walnuts-tomatoes-1085063/.
Slow Down: Creative Commons Public Domain. Courtesy of Pixabay. https://pixabay.com/en/road-sign-asphalt-road-sign-90390/.
Curry: Creative Commons Public Domain. Courtesy of Pixabay. https://pixabay.com/en/green-curry-thai-food-2457236/.
Boy with Candy Cane: Creative Commons Public Domain. Courtesy of Pixabay. https://pixabay.com/en/child-kid-boy-snack-lollypops-164454/.
Sugar Bag: Loper, Chris.
Honey: Creative Commons Public Domain. Courtesy of Pixabay. https://pixabay.com/en/honey-sweet-tasty-food-delicious-823614/.
Salmon: Creative Commons Public Domain. Courtesy of Pixabay. https://pixabay.com/en/salmon-dish-food-meal-fish-518032/.
Pumpkins: Creative Commons Public Domain. Courtesy of Pixabay. https://pixabay.com/en/halloween-pumpkin-carving-face-1001677/.
Berries: Creative Commons Public Domain. Courtesy of Pixabay. https://pixabay.com/en/berries-fruit-fruits-mixed-1546125/.