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Your Brain on Sugar

Research suggests sweet tooth can hurt your head, long before symptoms appear


Sugar in the morning, sugar in the evening, sugar at suppertime... that 1958 pop tune could easily have served as the American dietary anthem in recent decades. Even as the medical establishment and media took a hard line against cholesterol and fats - blaming them as the primary cause of cardiovascular disease - sugar got a pass. Our taste for the sweet stuff only continued to grow as food manufacturers cut the fat content in their products but increased the sugar.

It turns out that refined simple sugar (sucrose, dextrose, high fructose corn syrup, etc.) consumed in excess can lead to more than tooth decay, weight gain, and diabetes, however. Numerous studies show that excess sugar also boosts the risk of cardiovascular disease and certain cancers. Now researchers are taking a closer look at the effects of high sugar intake on the brain.

Sugar, insulin, and the brain

According to Dr. Robert Lustig, a pediatric endocrinologist at the University of California, and his colleagues at, our bodies can metabolize a maximum of 6 teaspoons of added sugar per day. Trouble is, the average American consumes at least 15 teaspoons of added sugar per day (American Journal of Clinical Nutrition, 2011) - more than double the amount that the body can manage - and athletes who use sugar-based fuels consume far more than that! Regular intake of all that sugar puts a major stress on the pancreas and liver.

"When the pancreas, which produces insulin to process sugars, becomes overworked, it can fail to regulate blood sugar properly," says Lustig. Eventually the body becomes resistant to insulin - causing blood glucose levels to rise - leading to diabetes.

Insulin also plays an important role in brain signaling. But when the brain is regularly exposed to excess insulin, this signaling can become disrupted, leading to memory and thinking problems.

A recent analysis by Australian researchers strongly supports the link between excess sugar, insulin resistance, and dementia. In their review of 14 studies involving 2 million people, diabetes was associated with a 60% increased risk for dementia in men and women (U.S. News and World Report, Dec. 2015).

Even more worrisome, research suggests that sugar-related changes to the brain begin long before any obvious signs of cognitive decline. In a University of Arizona study published in 2013, higher fasting blood sugar levels were associated with lower gray matter volume in brain areas associated with AD in cognitively normal, non-diabetic adults.

Citing a study published in the New England Journal of Medicine in 2013, neurologist David Perlmutter, M.D., says "Alzheimer's is directly related to elevation of blood sugar... even mild elevation of blood sugar, 105 or 110, these levels were dramatically associated with the risk for becoming demented." Perlmutter believes 85-95 to be a healthy range for fasting blood sugar.

What to do

Athletes already have a leg up, since exercise is one of the best ways to prevent insulin resistance. But there's much more you can do. Reduce your intake of added dietary sugars by avoiding sugary sodas; choose whole fruit over fruit juices; and avoid processed and packaged foods, which often contain large amounts of hidden sugar. (Check the label!)

When it comes to endurance fuels, avoid those that contain added simple sugars (dextrose, fructose, glucose, sucrose), which cause blood sugar levels to spike and then crash. Instead opt for fuels made with a complex carbohydrate, such as the maltodextrin used in Hammer Nutrition's HEED, Hammer Gel, Perpetuem, and Recoverite.

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