Most people know that eating too much dessert and processed food can contribute to physical health problems like obesity and type 2 diabetes. Far less attention, however, has been given to the impact of a high-sugar diet on mental health, even though numerous studies have shown the deleterious effects a sweet tooth can have on mood, learning and quality of life. In addition to inflating waistlines, sugar and other sweeteners, including high fructose corn syrup, honey, molasses and maple syrup, may contribute to a number of mental health problems:
The roller coaster of high blood sugar followed by a crash may accentuate the symptoms of mood disorders. Research has tied heavy sugar consumption to an increased risk of depression and worse outcomes in individuals with schizophrenia. There are a couple theories explaining the link. For starters, sugar suppresses activity of a hormone called BDNF that is low in individuals with depression and schizophrenia. Sugar is also at the root of chronic inflammation, which impacts the immune system, the brain, and other systems in the body; inflammation has also been implicated in depression. Interestingly, countries with high sugar intake also have a high rate of depression.
Although controversial, a growing body of evidence points to the addictive potential of sugar. Both drugs and—to a lesser extent—sugar and processed junk foods flood the brain with the feel-good chemical dopamine, which, over time, changes the function of the brain. In a study by researchers at Yale University, the simple sight of a milkshake activated the same reward centers of the brain as cocaine among people with addictive eating habits. A 2007 study showed that rats actually prefer sugar water to cocaine. Rats given fatty and sugary products demonstrated classic symptoms of addiction, including tolerance and withdrawal symptoms when the products were taken away.
The standard American diet, which is full of sugar and fat, does not necessarily cause anxiety, but it does appear to worsen anxiety symptoms and impair the body’s ability to cope with stress. Individuals who suffer from panic attacks, for example, are hyper-alert to signs of impending danger. Sugar can cause blurry vision, difficulty thinking, and fatigue, all of which may be interpreted as signs of a panic attack, thereby increasing worry and fear. A sugar high and subsequent crash can cause shaking and tension, which can make anxiety worse.
Research has established a correlation between sugar intake and anxiety. In a 2008 study, rats that binged on sugar and then fasted displayed anxiety; in a 2009 study, rats fed sucrose compared to high-antioxidant honey were more likely to suffer anxiety. While dietary changes alone cannot cure anxiety, they can minimize symptoms, boost energy and improve the body’s ability to cope with stress.
4. Learning and Memory
Sugar may also compromise cognitive abilities such as learning and memory. In an animal study by researchers at the University of California, Los Angeles, six weeks of taking a fructose solution (similar to soda) caused the rats to forget their way out of a maze, whereas rats that ate a nutritious diet and those that consumed a high-fructose diet that also included omega-3 fatty acids found their way out faster. The high sugar diet caused insulin resistance, which in turn damaged communications between brain cells that fuel learning and memory formation.
Recognizing these and other risks, the trends in sugar consumption seem to be changing. People are consuming less sugar—about 13 percent of their daily calories—which is still far too much, but clear progress from 18 percent just over a decade ago. Our bodies were never intended to handle the amount of sugar that has become the norm in the American diet, but at least now we’re beginning to recognize that the mind and body are intricately connected and both must be nurtured to achieve optimal health.