Food affects us in so many ways – physically, emotionally, intellectually and cognitively. In our society, high-fat, high-sugar foods, meat and alcohol are associated with celebration and comfort, but when we look at the scientific studies, we see overwhelming evidence that adhering to an unhealthy eating style, such as the standard American diet (SAD), has serious consequences.
In this post, we’ll look at one of the biggest culprits in the Western diet:1 added sugars. Regular and excessive consumption of sugar is associated with poorer cognitive function, increased risk of depression or dementia, or reduced brain volume.2-7 Even in short-term studies, detriments to learning, memory, or attention have been detected.
Brain function, including learning, memory, mood, attention, processing speed, and motor function, is profoundly affected by the foods we eat. Over decades, a poor diet can impair brain health through nutrient insufficiencies, oxidative stress, inflammation, and vascular damage. This can lead to depression, dementia, or a decline in cognitive function. In contrast, vitamins, minerals, antioxidant nutrients, and other phytochemicals have protective effects.
Omega-3 fatty acids are structural components of brain cell membranes that influence learning, memory, and mood. Fast food and commercial baked goods are associated with depression,8 whereas vegetable, fruit, and phytochemical intake is associated with reduced risk of depression,9-12 and dietary interventions effective at improving mood and reducing depression symptoms.13-15 It is true when they say, "good food, good mood."
Neuroinflammation could underlie the deficits in attention, learning, and memory that are associated with a poor diet. There is growing consensus among researchers that pro-inflammatory diet components, such as added sugars and saturated fats, lead to insulin resistance, systemic inflammation, and neuroinflammation. The good news is that phytochemicals in vegetables and fruits may help to prevent or slow loss of cognitive function with age by lowering oxidative stress and inflammation.16-19
Related: Omega-3 fatty acids, DHA and EPA, are crucial for brain health through all stages of life
Related: Short-term dietary intervention improves depression symptoms
Position Paper: Treating Depression Naturally (free for members)
Loaded with sugars, salt, and oils, “highly palatable” junk foods have drug-like, addictive effects. These foods stimulate reward systems in the brain.20-24 Eating a little makes you desire more.
Overeating and substance abuse share some common characteristics. People often build a tolerance to junk food and have unsuccessful efforts to cut back or eliminate the substance. There is continued use despite negative consequences, quite similarly to drugs. Adding sugars to foods to maximize reward in the brain leads to cravings for more and more sugar; over time, the level of sweetness in natural foods (such as berries and carrots) no longer has any appeal.
Excess intake of sugars, leading to elevated blood glucose (hyperglycemia) damages blood vessels, including those in the brain. There is evidence that this damage contributes to a progressive decline in brain function. The cognitive effects of hyperglycemia, most extensively studied in patients with diabetes, are likely due to a combination of hyperglycemia, hypertension, insulin resistance, and elevated cholesterol associated with diabetes.2-4, 25
In patients with diabetes, even after just a single instance of hyperglycemia, studies reported slowed cognitive function, increased number of errors, and deficits in attention, speed of information processing, working memory, and some aspects of attention.3, 26, 27
Patients with type 2 diabetes reportedly experience increased feelings of sadness, agitation, lethargy, and anxiety during acute hyperglycemia.26 However, this is not limited to patients with diabetes. In healthy young people as well, a brain imaging study suggested that in a hyperglycemic state, the brain’s ability to process emotion is compromised.28
Trying to control your addiction to sugary foods by eating them in moderation never works. You have to kick sugar to the curb.
Follow one of my 20-day detox programs or utilize the free Beginner’s Guide to the Nutritarian diet and begin the process of detoxing and resetting your palate to appreciate the natural sweetness and flavor of whole plant foods.
Try our most-loved dessert recipes in the member center to learn to bake with dates and other whole foods, plant-based sweetners. Once your tastebuds reset to enjoy the taste of natural foods you will be amazing by the sweet and carmel flavor from dates and other fruits.
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Kroner Z. The relationship between Alzheimer's disease and diabetes: Type 3 diabetes? Altern Med Rev 2009, 14:373-379.
Kodl CT, Seaquist ER. Cognitive dysfunction and diabetes mellitus. Endocr Rev 2008, 29:494-511.
Starr VL, Convit A. Diabetes, sugar-coated but harmful to the brain. Curr Opin Pharmacol 2007, 7:638-642.
Ye X, Gao X, Scott T, Tucker KL. Habitual sugar intake and cognitive function among middle-aged and older Puerto Ricans without diabetes. Br J Nutr 2011, 106:1423-1432.
Knuppel A, Shipley MJ, Llewellyn CH, Brunner EJ. Sugar intake from sweet food and beverages, common mental disorder and depression: prospective findings from the Whitehall II study. Sci Rep 2017, 7:6287.
Beilharz JE, Maniam J, Morris MJ. Diet-Induced Cognitive Deficits: The Role of Fat and Sugar, Potential Mechanisms and Nutritional Interventions. Nutrients 2015, 7:6719-6738.
Sanchez-Villegas A, Toledo E, de Irala J, et al. Fast-food and commercial baked goods consumption and the risk of depression. Public Health Nutr 2012, 15:424-432.
Chang SC, Cassidy A, Willett WC, et al. Dietary flavonoid intake and risk of incident depression in midlife and older women. Am J Clin Nutr 2016, 104:704-714.
Molendijk M, Molero P, Ortuno Sanchez-Pedreno F, et al. Diet quality and depression risk: A systematic review and dose-response meta-analysis of prospective studies. J Affect Disord 2018, 226:346-354.
Beezhold BL, Johnston CS, Daigle DR. Vegetarian diets are associated with healthy mood states: a cross-sectional study in Seventh Day Adventist adults. Nutrition Journal 2010, 9:26.
Blanchflower DG, Oswald AJ, Stewart-Brown S. Is Psychological Well-Being Linked to the Consumption of Fruit and Vegetables? Social Indicators Research 2012.
Beezhold BL, Johnston CS. Restriction of meat, fish, and poultry in omnivores improves mood: A pilot randomized controlled trial. Nutr J 2012, 11:9.
Francis HM, Stevenson RJ, Chambers JR, et al. A brief diet intervention can reduce symptoms of depression in young adults - A randomised controlled trial. PLoS One 2019, 14:e0222768.
Firth J, Marx W, Dash S, et al. The Effects of Dietary Improvement on Symptoms of Depression and Anxiety: A Meta-Analysis of Randomized Controlled Trials. Psychosom Med 2019, 81:265-280.
Spencer SJ, Korosi A, Laye S, et al. Food for thought: how nutrition impacts cognition and emotion. NPJ Sci Food 2017, 1:7.
Lamport DJ, Saunders C, Butler LT, Spencer JP. Fruits, vegetables, 100% juices, and cognitive function. Nutr Rev 2014, 72:774-789.
Devore EE, Kang JH, Breteler MM, Grodstein F. Dietary intakes of berries and flavonoids in relation to cognitive decline. Ann Neurol 2012.
O'Brien J, Okereke O, Devore E, et al. Long-term intake of nuts in relation to cognitive function in older women. J Nutr Health Aging 2014, 18:496-502.
Avena NM, Gold JA, Kroll C, Gold MS. Further developments in the neurobiology of food and addiction: update on the state of the science. Nutrition 2012, 28:341-343.
Fortuna JL. The obesity epidemic and food addiction: clinical similarities to drug dependence. J Psychoactive Drugs 2012, 44:56-63.
Gearhardt AN, Yokum S, Orr PT, et al. Neural Correlates of Food Addiction. Arch Gen Psychiatry 2011.
Taylor VH, Curtis CM, Davis C. The obesity epidemic: the role of addiction. CMAJ 2010, 182:327-328.
Volkow ND, Wang GJ, Fowler JS, et al. Food and drug reward: overlapping circuits in human obesity and addiction. Curr Top Behav Neurosci 2012, 11:1-24.
Moreira PI. Alzheimer's disease and diabetes: an integrative view of the role of mitochondria, oxidative stress, and insulin. J Alzheimers Dis 2012, 30 Suppl 2:S199-215.
Sommerfield AJ, Deary IJ, Frier BM. Acute hyperglycemia alters mood state and impairs cognitive performance in people with type 2 diabetes. Diabetes Care 2004, 27:2335-2340.
Cox DJ, Kovatchev BP, Gonder-Frederick LA, et al. Relationships between hyperglycemia and cognitive performance among adults with type 1 and type 2 diabetes. Diabetes Care 2005, 28:71-77.
Schopf V, Fischmeister FP, Windischberger C, et al. Effects of individual glucose levels on the neuronal correlates of emotions. Front Hum Neurosci 2013, 7:212.
Barnard ND, Bunner AE, Agarwal U. Saturated and trans fats and dementia: a systematic review. Neurobiol Aging 2014, 35 Suppl 2:S65-73.
Andre P, Laugerette F, Feart C. Metabolic Endotoxemia: A Potential Underlying Mechanism of the Relationship between Dietary Fat Intake and Risk for Cognitive Impairments in Humans? Nutrients 2019, 11.
Erridge C. The capacity of foodstuffs to induce innate immune activation of human monocytes in vitro is dependent on food content of stimulants of Toll-like receptors 2 and 4. Br J Nutr 2011, 105:15-23.
Erridge C, Attina T, Spickett CM, Webb DJ. A high-fat meal induces low-grade endotoxemia: evidence of a novel mechanism of postprandial inflammation. Am J Clin Nutr 2007, 86:1286-1292.
Madison AA, Belury MA, Andridge R, et al. Afternoon distraction: a high-saturated-fat meal and endotoxemia impact postmeal attention in a randomized crossover trial. Am J Clin Nutr 2020.
Joel Fuhrman, M.D. is a board-certified family physician, seven-time New York Times bestselling author and internationally recognized expert on nutrition and natural healing, who specializes in preventing and reversing disease through nutritional methods. Dr. Fuhrman coined the term “Nutritarian” to describe his longevity-promoting, nutrient dense, plant-rich eating style.
For over 30 years, Dr. Fuhrman has shown that it is possible to achieve sustainable weight loss and reverse heart disease, diabetes and many other illnesses using smart nutrition. In his medical practice, and through his books and PBS television specials, he continues to bring this life-saving message to hundreds of thousands of people around the world.
*There is no guarantee of specific results. Results can vary. All material provided on the DrFuhrman.com website is provided for informational or educational purposes only. Consult a physician regarding the applicability of any opinions or recommendations with respect to your symptoms or medical condition.