Excess sugar is toxic to the brain

Researchers have known for some time that excess sugar consumption can harm the brain. Chronically elevated blood sugar levels—even if they are only moderately elevated—can negatively affect communication between neurons and can cause the brain to shrink, specifically in the hippocampus, the brain’s memory center.^{2 3} Additionally, diets high in refined sugar have been implicated in mental health disorders such as schizophrenia,⁴ depression, and anxiety⁵ because sugar can interfere with normal neurotransmitter production.⁶ Irritability, mood swings, brain fog, and fatigue can also ensue after you consume too much sugar. And now, the science is telling us that sugar can also play a role in the development of Alzheimer’s.

Depression

Depression is a major health problem, with some experts predicting it will become the second cause of morbidity in the world by the year 2020. We know that what we eat can significantly impact our mental health in both positive and negative ways, so what types of food are thought to contribute to depression? Namely, sugars and refined carbs.⁷

An investigation conducted at Baylor College of Medicine in Texas looked at sugar consumption rates and how they correlated with the annual rates of major depression in a variety of locations. They found that in six different countries there was “a highly significant correlation between sugar consumption and the annual rate of depression.”8 Additionally, a recent long-term study published in 2017 links sugar consumption from sweet drinks and food to an increased chance of mood disorders, particularly in male subjects.⁹

Diets high in refined sugars are harmful to your brain because they promote inflammation and oxidative stress. Conversely, eating well can actually protect our brains from mental health problems. Research has shown that eating a healthy whole food-based diet like the Mediterranean diet may actually reduce the inflammatory, vascular, and metabolic processes that increase clinical depression risk.¹⁰

Anxiety

Anxiety is another disabling mental health condition that is accompanied by depression in 40 to 67 percent of cases. When you consume high-sugar food and drinks, your blood sugar skyrockets only to crash shortly thereafter. This not only makes you feel physically lousy, but it can also make the symptoms of mood disorders like anxiety even worse. And when you are on a blood sugar rollercoaster, it makes it harder for your body to cope with stress, makes mood swings more likely, and makes it that much harder to get anxiety symptoms under control.

Scientific research has demonstrated how bingeing on sugar leads to anxiety in animal subjects.¹¹ Other animal research published in the journal Physiology & Behavior demonstrates how sucrose (a form of sugar) likely affects the brain differently than a healthier sweetener like antioxidant-rich honey. Overall, the subjects fed honey showed significantly less anxiety at all stages of ageing compared to those fed sucrose. In addition, the honey-fed animals displayed better spatial memory over the course of the 12-month long study.¹²

Eating a “Western-style diet” (which typically includes lots of sweets, refined grains, fast food, fried foods, processed meats, and a reduction of fruit and vegetable intake) has been independently associated with an increased risk for the development of both anxiety and depression.¹³ This type of diet also leads to clear negative effects on the mental health of today’s teenagers. Research has shown that the quality of teenagers’ diets in adolescence may even affect their mental health for the rest of their lives.¹⁴

Dementia

In the landmark Rotterdam study¹⁵ 6,370 elderly subjects were studied for two years. During the follow up period it was observed that 126 patients developed dementia, 89 of whom had Alzheimer’s disease. The researchers concluded that type-2 diabetes was found to double the risk of developing dementia. We know that in type-2 diabetes, blood sugar levels are chronically elevated. All of that excess blood sugar floating around damages proteins, creating harmful substances called advanced glycation end products (AGEs) that contribute to oxidative damage and inflammation, both underlying factors in the development of Alzheimer’s disease. AGEs also play a role in the formation of neurofibrillary tangles and amyloid beta plaques—also well-known pathogenic factors of Alzheimer’s.¹⁶

But it is not just diabetics’ brains that are at risk. A study published in The New England Journal of Medicine examined whether higher glucose levels raise the risk for dementia in non-diabetics. The result? Researchers found that both diabetics, as well as those without diabetes, had an increased risk for dementia if they had higher-than-average glucose levels the five years before their dementia diagnosis.¹⁷ A longitudinal study published in the journal Diabetologia in 2018 tracked the blood sugar levels, diabetes status, and cognitive function of 5,189 people over a 10-year period. The researchers found that people with high blood sugar had a faster rate of cognitive decline than those with normal blood sugar, and this was true whether or not their blood-sugar level technically qualified them as diabetic.¹⁸ So overall, the higher the blood sugar, the faster the cognitive decline.

Two other issues that come with elevated blood sugar levels, even with only modest elevations, are elevated insulin levels and decreased production of brain-derived neurotrophic factor (BDNF).¹⁹ While insulin activates signaling pathways associated with learning and long-term memory,²⁰ chronically elevated levels of insulin (in the case of insulin resistance or pre-diabetes) also play a role in the formation of neurofibrillary tangles and amyloid plaques.²¹ Additionally, amyloid beta neurotoxins have been shown to disrupt insulin signaling in the brain, leading to oxidative damage, reduced plasticity, and eventually, the development of Alzheimer’s.²² Impairments in insulin signaling lead to a deficiency in energy metabolism, increased oxidative stress, inflammation, and mitochondrial dysfunction—all underlying factors in Alzheimer’s disease.²³ BDNF plays a key role in the survival and growth of neurons, and it serves as a neurotransmitter modulator while also playing a role in neuronal plasticity, which is essential for learning and memory. The less BDNF found in the brain, the harder it is to learn and remember things. Elevated insulin and reduced BDNF both go back to too much sugar and refined carbohydrate consumption.

A problem years in the making

You don’t have to be diagnosed with type-2 diabetes for your brain to be affected by blood sugar. Even slight elevations, levels that sit in the higher range of “normal,” can cause problems. You can have slightly elevated blood sugar and insulin levels for years and not know it, and in fact, some of your seemingly unrelated symptoms could actually be caused by elevated blood sugar and insulin. These symptoms can include fatigue, irritability, depression, anxiety, brain fog, mood swings, achy joints and other aches and pains, headaches, and elevated cholesterol and triglycerides. Maintaining healthy blood sugar levels is crucial for maintaining good health—the two go hand-in-hand.

What you can do to protect your brain

You can have chronically elevated levels of blood sugar and insulin for years before any illness manifests, so controlling your insulin and blood sugar now is the first step to lower your risk of depression and anxiety and to prevent cognitive decline. Maintain healthy blood sugar levels by consuming fiber, healthy fat, and protein at every meal and snack. Strictly reducing refined carbohydrates (think grain-based baked goods and cereals) and sugar is a must. Keep an eye out for the many forms sugar can appear in packaged food—fructose, high fructose corn syrup, cane sugar, rice syrup, maple syrup, corn sugar, juice concentrates, etc. Instead, aim to get your carbohydrates from whole food sources such as vegetables, legumes, and low-glycemic fruits.

One area of study that’s gaining traction is in ketogenic diets for Alzheimer’s sufferers. As much as our brains love glucose for fuel they can also use ketone bodies as a back-up fuel source. Ketones are molecules produced by the liver from fatty acids during periods of low food intake or carbohydrate-restrictive diets. This may have been an evolutionary mechanism that benefited our ancestors when food was scarce because when we convert stored fat into ketones we are able to use these ketones in order to go many days without a meal. Researchers^{24 25} have investigated the benefits of a ketogenic diet for those with Alzheimer’s and indeed, it seems to be able to improve memory and cognition.^{26 27}

Dramatically reducing carbohydrate consumption as well as consuming medium chain triglycerides (MCTs) are ways in which you can shift into healthy ketosis. Coconut oil is 65 percent MCTs²⁸—the highest percentage of any food, so it can be very helpful. Drinking coffee—minus the sugar—has also been shown to significantly stimulate ketone production.²⁹ Unless you’re struggling with anxiety, a cup of coffee with a tablespoon of coconut oil is an ideal way to start your day.  

Exercise is important too, as it increases the body’s sensitivity to insulin and has been shown³⁰ to prevent or slow down cognitive decline. Move on a daily basis. Stress management is also crucial for optimal brain function. When we’re stressed, cortisol levels rise and one of cortisol’s main roles in the body is to increase blood sugar. In this way, stress can imbalance your blood sugar and lead to insulin issues.

Supplements can also play a vital role in balancing blood sugar and protecting your brain. Some important ones include:

Those that Reduce Sugar Cravings

Magnesium, zinc and l-glutamine may all help to curb sugar cravings and ward off that intense desire for sugar-laden foods.

B Complex

The B vitamins are crucial for converting glucose into energy. Biotin, in particular, regulates genes involved in glucose metabolism, and when paired with chromium, has been shown to decrease fasting glucose levels in type-2 diabetics.³¹

Chromium Picolinate

This is an important nutrient for blood sugar control as well as insulin sensitivity.^{32 33 34} It has been suggested that chromium may³⁵ improve insulin sensitivity directly in the brain—making this one of the most important dietary supplements for those concerned about brain function. Dietary chromium is poorly absorbed and chromium decreases with age,³⁶ therefore taking chromium in supplement form is recommended.

Alpha Lipoic Acid

This supplement exerts antioxidant^{37 38} and anti-inflammatory effects³⁹ in the body, which can be protective against⁴⁰ diabetes as well as neurological decline. It has also been shown to have the ability to decrease fasting glucose levels and improve insulin sensitivity.^{41 42 43 44 45}

Vitamin E

Vitamin E is a powerful antioxidant⁴⁶ that may play a role in protecting the brain against Alzheimer’s disease.⁴⁷ The antioxidant effects of vitamin E protect cell membranes from oxidation, which is a crucial aspect of cognitive health. In a landmark study⁴⁸ published in the Journal of the American Medical Association, vitamin E was shown to significantly delay the progression of Alzheimer’s disease.

Berberine

This plant extract has been shown to be as effective at controlling blood sugar in type-2 diabetics as metformin, a common prescription drug.⁴⁹ It also improves insulin sensitivity.⁵⁰

Cinnamon

Both as a spice and supplement, cinnamon has been shown to help lower blood sugar levels. It may also improve sensitivity to the hormone insulin.

Your brain can suffer major collateral damage from excessive sugar (and refined carb) consumption. The damage sugar can cause over the long term is significant, and can potentially lead down the path to Alzheimer’s disease. Restricting your sugar and refined carbohydrate consumption and doing all you can to maintain healthy blood sugar balance is crucial. A balanced diet, smart supplement routine, and healthy lifestyle habits are key for keeping your brain in tiptop shape. A functional and proactive approach goes a long way in giving yourself the best chance of maintaining your cognitive health now and well into your later years of life.

References

1. Cristin E. Kearns, DDS, MBA, Laura A. Schmidt, PhD, MSW, MPH, Stanton A. Glantz, PhD. (2016 Nov 1). Sugar Industry and Coronary Heart Disease Research. JAMA Intern Med. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5099084/ 
2. http://neuro.hms.harvard.edu/harvard-mahoney-neuroscience-institute/bra…
3. http://www.drperlmutter.com/study/higher-glucose-levels-associated-lowe…
4. https://www.ncbi.nlm.nih.gov/pubmed/15123503
5. https://www.newscientist.com/article/2141967-mens-sweet-tooth-may-incre…
6. http://brainhealthbook.com/brain-sugar/
7. TA Popa, M Ladea. (2012 Dec 15). Nutrition and depression at the forefront of progress. J Med Life. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3539842/
8. Westover AN, Marangell LB. (2002). A cross-national relationship between sugar consumption and major depression? Depress Anxiety. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/12415536
9. Anika Knüppel, Martin J. Shipley, Clare H. Llewellyn, Eric J. Brunner. (2017 July 27). Sugar intake from sweet food and beverages, common mental disorder and depression: prospective findings from the Whitehall II study. Scientific Reports. Retrieved from https://www.nature.com/articles/s41598-017-05649-7
10. Sánchez-Villegas A, Delgado-Rodríguez M, Alonso A, Schlatter J, Lahortiga F, Serra Majem L, Martínez-González MA. (2009 Oct). Association of the Mediterranean dietary pattern with the incidence of depression: the Seguimiento Universidad de Navarra/University of Navarra follow-up (SUN) cohort. Arch Gen Psychiatry. Retrieved from
    https://www.ncbi.nlm.nih.gov/pubmed/19805699
11. Avena NM, Bocarsly ME, Rada P, Kim A, Hoebel BG. (2008 Jun 9). After daily bingeing on a sucrose solution, food deprivation induces anxiety and accumbens dopamine/acetylcholine imbalance. Physiol Behav. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/18325546
12. Chepulis LM, Starkey NJ, Waas JR, Molan PC. (2009 Jun 22). The effects of long-term honey, sucrose or sugar-free diets on memory and anxiety in rats. Physiol Behav. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/19296910
13. Monique Aucoin, Sukriti Bhardwaj. (2016 Jul 14). Generalized Anxiety Disorder and Hypoglycemia Symptoms Improved with Diet Modification. Case Rep Psychiatry. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4963565/
14. Jacka FN, Kremer PJ, Berk M, de Silva-Sanigorski AM, Moodie M, Leslie ER, Pasco JA, Swinburn BA. (2011 Sep 21). A prospective study of diet quality and mental health in adolescents. PLoS One. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/21957462
15. https://www.ncbi.nlm.nih.gov/pubmed/10599761
16. http://www.acam.org/blogpost/1092863/185761/The-Relationship-Between-Al…
17. Paul K. Crane, M.D., M.P.H., Rod Walker, M.S., Rebecca A. Hubbard, Ph.D., Ge Li, M.D., Ph.D., David M. Nathan, M.D., Hui Zheng, Ph.D., Sebastien Haneuse, Ph.D., Suzanne Craft, Ph.D., Thomas J. Montine, M.D., Ph.D., Steven E. Kahn, M.B., Ch.B., Wayne McCormick, M.D., M.P.H., Susan M. McCurry, Ph.D., James D. Bowen, M.D., Eric B. Larson, M.D., M.P.H.. (2013 August 8). Glucose Levels and Risk of Dementia. N Engl J Med. Retrieved from http://www.nejm.org/doi/full/10.1056/NEJMoa1215740
18. Zheng, F., Yan, L., Yang, Z. et al.. (25 January 2018). HbA1c, diabetes and cognitive decline: the English Longitudinal Study of Ageing. Diabetologia. Retrieved from https://doi.org/10.1007/s00125-017-4541-7
19. Molteni R, Barnard RJ, Ying Z, Roberts CK, Gómez-Pinilla F. (2002) A high-fat, refined sugar diet reduces hippocampal brain-derived neurotrophic factor, neuronal plasticity, and learning. Neuroscience. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/12088740
20. http://www.acam.org/blogpost/1092863/185761/The-Relationship-Between-Al…
21. http://www.sciencedirect.com/science/article/pii/S0925443916302150
22. https://www.ncbi.nlm.nih.gov/pubmed/24402880
23. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2769828/
24. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2604900/
25. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2731764/
26. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2367001/
27. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2604900/
28. https://examine.com/supplements/coconut-oil/
29. https://www.ncbi.nlm.nih.gov/pubmed/28177691
30. https://www.ncbi.nlm.nih.gov/pubmed/21878600
31. https://www.ncbi.nlm.nih.gov/pubmed/17506119
32. https://www.ncbi.nlm.nih.gov/pubmed/18234131
33. http://care.diabetesjournals.org/content/29/8/1826
34. https://www.ncbi.nlm.nih.gov/pubmed/15208835
35. https://www.ncbi.nlm.nih.gov/pubmed/7838011
36. https://www.ncbi.nlm.nih.gov/pubmed/15208835
37. https://www.ncbi.nlm.nih.gov/pubmed/21666939
38. http://www.sciencedirect.com/science/article/pii/0891584996001724
39. https://examine.com/supplements/alpha-lipoic-acid/
40. https://examine.com/supplements/alpha-lipoic-acid/
41. https://examine.com/supplements/alpha-lipoic-acid/
42. https://www.ncbi.nlm.nih.gov/pubmed/22374556
43. https://www.researchgate.net/profile/Najmeh_Hejazi/publication/51213226…
44. http://www.webmd.com/vitamins-supplements/ingredientmono-767-alpha%20li…)
45. https://www.ncbi.nlm.nih.gov/pubmed/21666939
46. https://www.ncbi.nlm.nih.gov/pubmed/16477766
47. https://examine.com/supplements/vitamin-e/
48. http://www.drperlmutter.com/study/effect-vitamin-e-memantine-functional…
49. https://www.ncbi.nlm.nih.gov/pubmed/18442638
50. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3310165/