Sugar and the Brain: What is the Real Truth?

Twenty percent of our average daily calories come from refined sugars. Most hidden sugars consumed in the U.S. are found in soft drinks, soda, and boxed cereal. The caffeine and phosphates in soda pop are also health risks.

Is Sugar Addictive?

Sugar is addictive for many people. Long-term sugar consumption has been shown to reduce impulse control and lower the ability to resist high-fat and sugary foods. The mesocorticolimbic system regulates our hedonic impulses and motivations. Sucrose consumption activates the mesocorticolimbic system similarly to substances of abuse.¹

Research also shows that, for susceptible people, eating sugar produces characteristics of craving and withdrawal, along with chemical changes in the brain’s reward center, the limbic region. Using brain-scanning technology, scientists have demonstrated that sugar causes changes in peoples’ brains similar to those in people addicted to drugs such as cocaine and alcohol. These changes are linked to an increased craving for more sugar. This important evidence has encouraged more investigation on the potentially addictive properties of sugar.²

Hoebel and associates have demonstrated that rats eating large amounts of sugar actually undergo neurochemical changes in the brain that appear to mimic those produced by substances of abuse, including cocaine, morphine, and nicotine.³ To elaborate more: when these sugar-eating rodents were denied sugar for a prolonged period, they worked harder to get it when it was reintroduced to them. They consumed more sugar than they ever had before, suggesting craving and relapse behavior. The rats drank even more alcohol than normal once their sugar supply stopped. Liberal sugar consumption can become the gateway to other paths of destructive behavior, such as increased alcohol intake. Unfortunately, it was worse than that. After receiving a dose of amphetamine, normally so minimal that it usually has no effect, the rats became significantly hyperactive. The increased sensitivity to the psychostimulant has a long-lasting brain effect that is indicative of an addiction.

Dr. C.P. Richter is well-known for his cafeteria experiments. He showed that rodents will usually select a healthy, balanced diet by carefully selecting the appropriate food to eat and maintaining a normal weight. However, in other studies, researchers showed that when a 10 percent sugar solution was hung in one corner of the cage, the rodents gradually came to prefer it to the exclusion of the healthier chow. Ultimately, the rodents literally drank themselves to death.⁴

Researcher B.A. Gosnell summarized it this way. “A number of studies have indicated a relationship between the intake of palatable foods or fluids and drug self-administration.”⁵

A 2023 study found that foods high in sugar and fat can actually rewire the brain to need more in the future.⁶

Sugar Impairs Cognitive Performance

Sugar consumption can decrease your ability to see your options and solve problems Sudden rises and dips in blood sugar decrease mental performance. It is therefore very unwise to eat sugar or drink a sugary drink on an empty stomach.

Gut bacteria produce compounds that affect our brains. A healthful diet encourages the growth of friendly bacteria that produce useful compounds. In contrast, consumption of a poor diet increases the number of harmful bacteria that produce damaging inflammatory compounds. Overeating fat and/or sugar can impair various memory functions. Both a high-fat diet and a high-sugar diet, compared to a normal diet, produces deleterious changes in gut bacteria that appear related to a significant loss of mental flexibility. Cognitive flexibility is the power to adapt and adjust to changing situations. Rats who consumed the high-sugar diet showed an impairment of early learning for both long-term and short-term memory.^7,8

An interesting experiment showed that just five days of consuming the typical cafeteria rat chow, rats experienced mental deterioration. Thirty days of consuming this diet produced large inflammation within the brain.⁹  A single meal of sweets and other high glycemic foods can impair memory performance in children and healthy young adults.^10,11

In older individuals, the higher intake of total sugars, free sugars, sucrose, lactose, sugar-sweetened beverages, sugar-sweetened cakes, and dessert was found to be significantly associated with a lower Mini Mental State Examination score after adjusting for confounding variables. In contrast, fruit consumption improve the scores.¹²

Sugar and Executive Performance

There is some evidence that frequent sugar consumption adversely affects the prefrontal cortex and its executive functions—decision making, the ability to plan and organize, self-control and self-monitoring, and mental flexibility. For example, sucrose-exposed rats failed to show context-appropriate responding during a mental challenge.¹³ This suggests that the excessive use of sugar may impair decision making and memory, and increase the risk of mental diseases.¹⁴

Sugar consumption has been linked to worse executive functions in children and adolescents.¹⁵ Studies suggest that a high-fat and sugar diet heightens anxiety.¹⁶ In one study, a daily 2 hour consumption of a high-fat/high-sugar diet is linked to impaired fear inhibition and high anxiety in young adult rats.¹⁷ Researchers found that soda consumption had the strongest link to aggression, withdrawal behavior, and poor attention in five year olds (after controlling for other potential confounders, such as television viewing and a stressful home environment), ¹⁸

Sugar Could Increase Your Risk for Depression

In a study including more than 70,000 postmenopausal women, researchers found that a diet high in refined carbohydrates, such as sweets, sweetened beverages, and white rice may lead to an increased risk for new-onset depression. The investigators found that consumption of foods that scored high on the glycemic index, and consumption of added sugars and refined grains were associated with increased risk of new-onset depression in post-menopausal women. However, there was some good news. Greater consumption of dietary fiber, whole grains, vegetables, and non-juice fruits were associated with decreased risk. This suggests that dietary interventions for many individuals could serve as treatment and preventive measures for depression.¹⁹ Depression is a complicated, multi-faceted disease with many causes. While eating junk foods can contribute to and magnify depression, other possible causes need to be explored and dealt with adequately. A healthful diet is essential in the treatment of depression.

How Much Sugar?

The average American consumes 19.5 teaspoons (82 grams) every day. That translates into about 66 pounds of added sugar consumed each year, per person. Many refined sugars are “hidden” in processed foods. The American Heart Association (AHA) recommends no more than 6 teaspoons (25 grams) of added sugar per day for healthy women and 9 teaspoons (38 grams) for men. The AHA limits for children vary depending on their age and caloric needs, but range between 3-6 teaspoons (12 – 25 grams) per day.²⁰ Even that amount can compromise the immune system for about five hours.²¹

Positive Solutions:

• When you eat sugar, eat the treat in the morning with whole-plant based protein. Consume no more than 6 teaspoons of sugar a day. Much less, if you are immune compromised or have inflammatory conditions. Avoid sugar if you are addicted to it!
• Eat fruit based desserts. Blended frozen fruits in non-dairy milk can taste as delicious as ice cream if you include a tropical fruit. Use just one tropical fruit along with low-glycemic fruits such as berries and apples.
• Avoid the high-sugar with high fat combo. 
• Eat whole fruits; do not gulp down fruit juice. Fruit juice should be a treat. Habitually drinking it often raises triglycerides or blood fats which increase the risk of heart attack and stroke in at risk persons.
• Use organic whole cane sugar to avoid herbicide exposure if you do use sugar occasionally. Glyphosate is an herbicide commonly detected on sugarcane. Glyphosate may stimulate hormone-dependent cancers even at extremely low amounts.
• Dark raw honey contains phytochemicals. Since honey is twice as sweet as sugar, you can use less of it.
• Gradually taper off and stay off of caffeine. Why? Caffeine make foods and drinks seem less sweet, so to compensate, we become more easily tempted to eat more sweets.²²

 

1. Angela Jacques, et al., The impact of sugar consumption on stress-driven, emotional and addictive behaviors/ Neuroscience & Biobehavioral Reviews, Volume 103,2019, Pages 178-199, ttps://www.sciencedirect.com/science/article/pii/S0149763418308613↩
2. sugarscience.ucsf.edu/the-growing-concern-of-overconsumption/#.Wq-5X-jwYd↩
3. Princeton University. “Sugar Can Be Addictive: Animal Studies Show Sugar Dependence.” ScienceDaily. 11 December 2008. www.sciencedaily.com/releases/2008/12/081210090819.htm↩
4. Baldwin B. Griffin V. Kissinger E. Food for Thought. ARENA. 2004↩
5. Gosnell, B.A., et al., Sucrose-intake predicts rate of acquisition-of-cocaine self-administration, Psychopharmacology (Berl). 2000 Apri; 149(3):286-92↩
6. Sharmili Edwin, et al.  Habitual daily intake of a sweet and fatty snack modulates reward processing in humans. Cell Metabolism, 2023; DOI: 10.1016/j.cmet.2023.02.015 ↩
7. Magnusson K.R. Relationships between diet-related changes in the gut microbiome and cognitive flexibility.Neuroscience, 2015; 300: 128 DOI:10.1016/j.neuroscience.2015.05.01↩
8. Oregon State University. “Fat, sugar cause bacterial changes that may relate to loss of cognitive function.” ScienceDaily. ScienceDaily, 22 June 2015.↩
9. Beilharz J. Diet-Induced Cognitive Deficits: The Role of Fat and Sugar, Potential Mechanisms and Nutritional Interventions. Nutrients. 2015 Aug; 7(8): 6719–6738↩
10. Nabb S.The influence on cognition of the interaction between the macro-nutrient content of breakfast and glucose tolerance. Physiol Behav. 2006 Jan 30; 87(1):16-23↩
11. Micha R.Glycaemic index and glycaemic load of breakfast predict cognitive function and mood in school children: a randomised controlled trial. Br J Nutr. 2011 Nov; 106(10):1552-61↩
12. Habitual sugar intake and cognitive impairment among multi-ethnic Malaysian older adults. Clin Interv Aging. 2019 Jul 22;14:1331-1342.↩
13. Reichelt AC. impact of adolescent sucrose access on cognitive control, recognition memory, and parvalbumin immunoreactivity. Learn Mem. 2015 Mar 16; 22(4):215-24↩
14. Reichelt AC. Impact of adolescent sucrose access on cognitive control, recognition memory, and parvalbumin immunoreactivity. Learn Mem. 2015 Mar 16; 22(4):215-24.↩
15. Cohen JF. The effect of healthy dietary consumption on executive cognitive functioning in children and adolescents: a systematic review. Br J Nutr. 2016 Sep;116(6):989-1000.↩
16. Ibid. Reichelt↩
17. Baker KD. Impaired fear extinction retention and increased anxiety-like behaviours induced by limited daily access to a high-fat/high-sugar diet in male rats: Implications for diet-induce prefrontal cortex dysregulation. Neurobiol Learn Mem. 2016 Dec; 136:127-138.↩
18. Fuhrman Joel. Fast Food Genocide. Harper. 2017. Pg. 47-49.↩
19. Gangwisch JE. High glycemic index diet as a risk factor for depression: analyses from the Women’s Health Initiative. Am J Clin Nutr. 2015 Aug; 102(2): 454–463↩
20. (sugarscience.ucsf.edu/the-growing-concern-of-overconsumption/#.Wq-5X-jwYdU↩
21. Nedley, N. Proof Positive, Nedley Publishers, Ardmore, OK, 1998↩
22. Cornell University. “Caffeine tempers taste, triggering temptation for sweets.” ScienceDaily. 24 August 2017. www.sciencedaily.com/releases/2017/08/170824101747.htm↩