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How Does Sugar Affect the Brain? Insights from a Registered Dietitian

Kara Collier, RDN, LDN, CNSC

Published in Health & Wellness

11 min read

October 23, 2023
a person holding a spoon full of sugar
a person holding a spoon full of sugar

As a registered dietitian, I'm no stranger to the impact that our food choices have on our health. Sugar, in particular, is a hot topic in the world of nutrition, and for good reason: The global intake of sugar has risen by over 24 million metric tons since 2010, and it's estimated that the average American consumes over 17 teaspoons of added sugar each day, which equates to almost 57 pounds per person every year! 

The effects of sugar on different areas of your health can be surprising to uncover, but I believe the connection between sugar consumption and brain health is especially important to be aware of. As someone who has the APOE4 gene, a known risk factor for Alzheimer's disease, my interest in how nutrition may affect my cognitive function and risk of neurological diseases is personal. 

So let’s explore the relationship between sugar and the brain, taking both scientific research and practical dietary advice into account along the way. I’ll uncover the ways sugar can influence your brain health and share practical steps we can all take to make informed, health-conscious decisions when it comes to sugar consumption.

The Relationship Between Sugar and Brain Function

Kara Collier, RDN out on a hike

Understanding how sugar impacts the human brain is an important step in making informed dietary choices. Our brains actually require sugar, specifically glucose, to function. 

Glucose is a type of sugar that serves as the primary source of energy for our brain cells. The food we consume gets broken down into metabolites, like glucose, that get transported by the body to fuel various cognitive functions, including thinking, memory, and decision-making.

Our brains are able to get this glucose from the foods we eat, including those found in whole grains, fruits, and vegetables. It is an excessive intake of added sugars, those that aren’t found naturally in foods like fruits and vegetables, that can negatively affect brain function. 

Neuroscience research shows that, through a combination of biochemical reactions and intricate signaling pathways, excess sugar can impact memory, mood, and concentration, and even lead to inflammation in the brain. Eating too much sugar has the power to affect our cognitive function, influence our cravings, and even contribute to the onset of neurological conditions. Understanding this relationship is key to making informed decisions about our dietary choices.

4 Ways Sugar Negatively Impacts the Brain

how sugar can negatively impact the brain

Now that we’ve learned about the profound impact a high-sugar diet can have on different aspects of cognitive health function, let’s dive deeper into four ways sugar can negatively impact the brain:

1) Can Impact Cognitive Function

Research suggests that excessive sugar consumption may have detrimental effects on memory and learning. High sugar intake has been associated with impaired synaptic plasticity, or the process by which connections between brain cells are strengthened or weakened in response to learning experiences. This, in turn, can compromise our ability to retain information and adapt to new challenges.

Research has also highlighted the potential link between elevated blood sugar levels and cognitive decline in later life. Chronic high blood sugar levels, which can be caused by an excessive intake of added sugars, among other factors, can increase your risk of type 2 diabetes, which in turn is associated with an increased risk of cognitive impairment.

2) May Impact Mood and Mental Health

The impact of sugar on mental health is complex to unpack. While sugar consumption can provide a temporary mood lift due to its effect on dopamine levels, this surge is often followed by a crash, potentially exacerbating feelings of irritability, depression, and anxiety.

Emerging evidence also suggests a connection between high sugar intake and an increased risk of mood disorders such as depression and anxiety. This may be due to sugar’s influence on the body’s inflammatory response, which may play a role in disrupting the delicate balance of neurotransmitters in the brain.

3) May Lead to Cravings or Addiction

Sugar impacts your brain’s reward system, leading to cravings and for some people, even sugar addiction. This is because consuming sugar triggers the release of dopamine and may impact opioid receptors and serotonin function as well.

This surge in dopamine reinforces the desire for sweet foods, potentially leading to cravings and a repeated cycle of consumption, which can lead to other symptoms such as overeating, energy crashes, brain fog, and weight gain.

This destabilization of the brain’s reward pathways is similar to what is observed in addiction and can lead to other health problems over time, such as heart disease or type 2 diabetes. One animal study even found that the reward response for sugar can be even stronger than that of cocaine

4) May Have Links to Alzheimer's Disease

Long-term, excessive sugar intake has also emerged as a potential risk factor in the development and progression of Alzheimer's disease. Prolonged exposure to high levels of sugar can lead to insulin resistance, which can impair the brain's ability to efficiently utilize glucose. 

This disruption in glucose metabolism may contribute to the accumulation of toxic substances called amyloid plaques, which are characteristic of Alzheimer's. Excessive sugar consumption is also associated with chronic inflammation, including inflammation in the brain, a factor that may increase the risk of neurodegenerative diseases like Alzheimer’s. 

In light of this research, a healthy diet that minimizes excessive sugar intake may be an important strategy in reducing the risk of Alzheimer's disease and supporting brain health in the long term, particularly for people like myself who carry the APOE4 gene.

Can Sugar Be Good for Brain Health?

a graph of high and low GI foods

The short answer is no. When it comes to sugar, there are no inherent benefits for brain health. With that said, it's important to distinguish between added sugars and carbohydrates.

Carbohydrates are a vital macronutrient that our bodies rely on for glucose, the main source of energy for the brain. Both simple and complex carbs can be found in a variety of whole foods, including:

  • Fruits
  • Starchy vegetables
  • Whole grains
  • Legumes

Many complex carbs, like beans and whole grains, are also lower glycemic foods and a healthy choice for supplying a steady, sustained release of glucose to the brain and other parts of the body. However, some complex carbs like white rice and white potatoes have a higher glycemic index and may cause a rapid spike in glucose. 

Similarly, different sources of simple carbs may also have a different impact on glucose. For example, some low glycemic fruits like berries contain simple carbs but in moderate amounts have a low glycemic load and are far less likely to spike your glucose compared to sugary processed desserts. 

Added sugars, like those found in ultra-processed foods, sweet and sugary foods, and sweetened beverages, offer little nutritional value and lack the fiber and nutrients found in whole food sources of unprocessed or minimally processed carbs. 

So, while carbohydrates are a necessary component of a balanced diet, added sugar itself is not an added benefit for brain health. Opting for nutrient-dense, whole food sources of lower glycemic carbohydrates is a wiser choice in supporting both overall health and cognitive function.

My Easy Tips for Reducing Your Added Sugar Intake

Kara Collier's tips for reducing your sugar intake

Over the years, I’ve seen firsthand that making an effort to reduce added sugar intake is one of the most impactful decisions we can make for our health. In this section, I'll share my personal tips for reducing your added sugar intake. These strategies will empower you to take charge of your nutrition and pave the way for a healthier lifestyle.

1) Opt for Sugar-Free Coffee or Tea

Choosing black coffee or tea is a simple and effective strategy for reducing your sugar intake. Tea and coffee on their own contain zero calories and zero grams of added sugars, making them a great alternative to sugary coffee drinks and flavored teas. 

However, if black coffee isn’t for you, a splash of whole milk or half-and-half with no sweetener added is another great alternative.

2) Choose Sugar-Free Drinks

Choosing sugar-free beverages is a smart move when you’re trying to reduce the amount of sugar you’re consuming. While it's widely known that sugary sodas and fruit juices can contribute significant amounts of added sugars to your daily intake, lesser-known culprits can also be hidden sources of added sugars. These can include:

  • Oat milk
  • Sports drinks
  • Favored nut milks
  • Certain brands of coconut water

Opting for sugar-free alternatives in these categories can help you make more health-conscious choices.

3) Opt for Plain Greek Yogurt and Sweeten With Whole Fruit

a bowl of greek yogurt with strawberries
Photo by Monika Grabkowska on Unsplash

Sweetening plain yogurt with whole fruit is a great way to reduce your sugar intake while still enjoying a creamy, flavorful treat. Unlike flavored yogurts, which often contain significant amounts of added sugars, choosing plain yogurt allows for greater control over the sweetness level. 

By adding whole fruits like berries or sliced bananas, you can enhance the natural sweetness and nutritional value of the yogurt without resorting to refined sugars.

4) Avoid Sugary Desserts and Opt for Fruit or Unsweetened Dark Chocolate Instead

Replacing sugary desserts with fruit is another smart way to cut down on your sugar intake while still satisfying your sweet tooth. Fruits offer a naturally sweet and flavorful alternative to processed sugars, and the natural sugars found in fruits like berries, watermelon, apples, and citrus fruits come packaged with a wealth of essential nutrients and antioxidants.

If your sweet tooth still isn’t satisfied, unsweetened dark chocolate is another great alternative. Don’t forget to pair with protein for a balanced glucose response! 

5) Eat Full-Fat Foods Instead of No-Fat Foods

When manufacturers remove fat from their products, they often compensate for the loss of flavor by adding extra sugar or artificial sweeteners. This can be especially prevalent in products like low-fat or fat-free salad dressings, yogurt, and baked goods. Choosing full-fat versions of these items can help sidestep the hidden sugars often found in their leaner counterparts.

6) Make Your Own Salad Dressing

someone pouring salad dressing on a salad
Photo by Getty Images on Unsplash

Many store-bought dressings, even those marketed as "low-fat" or "light," often contain hidden sugars to enhance flavor. When you opt to make your own dressings at home, you have complete control over the ingredients, allowing you to omit added sugars altogether and savor the true flavors of fresh ingredients without the unnecessary and often excessive sugar content found in commercial options.

7) Opt for a Savory Breakfast

Traditional sweet breakfast options, like cereals, pastries, and flavored yogurts, often contain hidden sugars that can lead to spikes and crashes in blood sugar levels. In contrast, savory breakfasts like omelets or whole grain toast with salmon and avocado provide a hearty and satisfying start to the day without the unnecessary sugar content. This choice sets a positive tone for your overall dietary habits, helping to regulate appetite and energy levels.

8) Check Nutrition Labels and Ingredient Lists

When it comes to reducing sugar intake, reading nutrition labels and ingredients lists is a great habit to get into. Manufacturers often use various terms to conceal added sugars, making it important to examine labels closely. 

By reviewing the nutrition facts of a product, you can identify the total sugar content and distinguish between naturally occurring sugars and those that have been added during processing, helping you steer clear of products that may appear healthy but harbor hidden sugars.

9) Don’t Keep Ultra-Processed Foods at Home

a bowl of cheesy pretzels
Photo by Haley Truong on Unsplash

Highly-processed foods, particularly those labeled as "low-fat" or "diet," often contain hidden sugars to compensate for flavor lost during processing. When healthier, whole foods are the only option you have at home, rather than sweet treats or snacks, you may be more likely to reach for fruits, vegetables, lean proteins, and whole grains instead of easy, ultra-processed options.

This not only reduces your sugar intake but also provides a greater array of essential nutrients, keeping you on track with your health and diet goals.

10) Choose Restaurant Meals Wisely

Restaurants often use added sugars to enhance the flavor and appeal of their dishes, even in savory items like sauces, dressings, and marinades. By preparing meals at home, you have control over the ingredients used, allowing you to minimize or completely avoid added sugars. 

If you do dine out, all is not lost! Simple hacks such as requesting sauces or dressings on the side, avoiding sugary drinks, and choosing a whole food-based protein-rich main course with fiber-rich lower glycemic carbs is a great place to start. 

This conscious choice can empower you to select whole, unprocessed ingredients, and opt for healthier cooking methods that don't rely on excessive sugar content.

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Heather Davis, MS, RDN, LDN

Reviewed by: Heather Davis, MS, RDN, LDN

Heather is a Registered and Licensed Dietitian Nutritionist (RDN, LDN), subject matter expert, and technical writer, with a master's degree in nutrition science from Bastyr University. She has a specialty in neuroendocrinology and has been working in the field of nutrition—including nutrition research, education, medical writing, and clinical integrative and functional nutrition—for over 15 years.