Is Sugar Bad for Your Brain?

Sugar candies
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5.3 million Americans currently have Alzheimer's disease, and that number is projected to sharply increase as our population ages. As we look at various ways to reduce the risk of developing Alzheimer's disease and other types of dementia, including mild cognitive impairment, one of the many areas that has been studied frequently is that of sugar.

We Americans, in general, love our sugar. But is it possible that sugar increases our likelihood of developing dementia?

Research on Sugar and Cognitive Functioning

There's an already established link between type 2 diabetes and the development of dementia. But how does sugar affect people who don't have diabetes?

Multiple studies have been conducted on how sugar, or more specifically, glucose levels in our blood, impact cognition. A few of them include the following:

  • In 2008, the journal Neuroepidemiology published research that measured the fasting insulin levels of more than 1,400 middle-aged women who did not have diabetes. Beginning 10 years later, the researchers measured the cognitive ability of these women over the next four years. They found that the women who had higher insulin levels in mid-life were more likely to experience cognitive decline later in life.
  • In 2013, the journal Neurology reported on a study where researchers again found that higher blood sugar levels were associated with significantly poorer performance on cognitive tests measuring delayed recall, memory, and learning. This study involved 141 participants with an average age of 63 years old, none of whom had diabetes.
  • An article published in 2013 in the Physiology and Behavior journal described research involving 98 participants without diabetes. The scientists measured each person's cognition by using the Stroop test, which is widely considered to be an accurate measure of the brain's executive functioning ability. The results indicated that participants with an inability to regulate their glucose levels achieved lower scores on the Stroop test, indicating decreased cognitive ability. The researchers stated, "Our results indicate that even mild hyperglycemia in the non-diabetic range is associated with attentional processing difficulties in a sample of younger adults." 

    How About Sugar Intake?

    The British Journal of Nutrition in 2011 outlined a study that sought to determine if sugar intake (not blood glucose levels) affects cognitive functioning. 737 people without diabetes, ages 45 to 75, were involved in this study, which was part of the Boston Puerto Rican Health Study conducted from 2004-2009. The participants' cognition was measured by a variety of tests including the Stroop test, clock-drawing test, digit span test, and verbal fluency tests. These results were compared to the amount of sugar ingested by each person. The researchers found that in general, higher levels of sugar intake were correlated with lower cognitive scores.

    Effect on the Brain

    Not only does research show a connection between cognitive functioning and blood sugar levels, it also has demonstrated a correlation to actual brain size and structure. A study reported in Neurology found that higher blood glucose levels in people without diabetes were correlated with brain atrophy (shrinkage) in the hippocampal areas and the amygdala.

    So, No More Sugar?

    As with many other foods, moderation and balance are important factors in our diets. Unfortunately, it appears that it may be wise to avoid consistently high levels of sugar in light of the research outlined above in order to decrease your risk of cognitive impairment.

    Instead of sugar, enjoy these 11 tasty foods that have repeatedly been connected with a lower risk of dementia.

    Sources:

    Tucker KL, Ye X, Gao X, Scott T. Habitual sugar intake and cognitive function among middle-aged and older Puerto Ricans without diabetes.  British Journal of Nutrition2011;106(9):1423-32.

    Grodstein F, van Oijen M, Okereke OI et al. Fasting Insulin Levels and Cognitive Decline in Older Women without Diabetes. Neuroepidemiology. 2008; 30(3): 174–179.

    Anstey KJ, Cherbuin N, Sachdev P. Higher normal fasting plasma glucose is associated with hippocampal atrophy: The PATH Study. Neurology. 2012; 79(10):1019-1026.

    Floel A et al. Higher glucose levels associated with lower memory and reduced hippocampal microstructure. Neurology. 2013;81:1746-1752.

    Krakoff J et al. Impaired glucose regulation is associated with poorer performance on the Stroop Task. Physiology and Behavior. 2013;122:113-9. 

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