The body breaks down carbohydrates into glucose, which is then transported to brain cells and is used as fuel by the brain; however, in individuals adhering to a low-carb diet, glucose is limited, and the brain switches to using ketones as energy. This has raised the question whether low-carb diets have adverse effects on brain function, since the body isn't using glucose as its primary energy source.
Low-Carb Diets
A low-carb diet limits the use of carbohydrates, such as bread, fruit and pasta, while increasing the intake of both protein and fats. This forces the body to enter ketosis, a metabolic state in which the body is using ketones as its main energy source. Beginners usually experience brain fog and lack of energy, but the body adapts and symptoms usually disappear. Low-carb diets vary on the carbohydrate amount allowed, but it's typically between 50 to 150 g per day, according to the Mayo Clinic.
Mood
Scientists from the University of Australia investigated the long-term effects of a very low-carbohydrate, high-fat diet versus a high-carbohydrate, low-fat diet on mood and cognitive function in overweight and obese participants for one year. They reported in the November 2009 issue of the "Archives of Internal Medicine" that subjects following a high-carbohydrate, low-fat diet experienced improvements in mood, whereas those adhering to a very low-carbohydrate diet migrated toward negative levels on mood measuring scales. Both groups experienced similar changes in cognitive function for memory and word processing.
Cognitive Function
Another study conducted by researchers from the University of Adelaide in Australia found different results regarding mood and cognitive function. Scientists compared the effects of a low-carbohydrate, high-fat diet versus a high-carbohydrate diet in overweight and obese adults for eight weeks. They found that both groups experienced increases in mood and memory; however, the low-carbohydrate diet group improved their word processing compared to the high-carbohydrate group, according to findings reported in the September 2007 issue of the "American Journal of Clinical Nutrition." (reference 3)
Mild Cognitive Impairment
Low-carb diets might enhance memory in older adults with mild cognitive impairment, according to a study conducted by researchers from the University of Cincinnati. Participants with mild impairment followed a six-week low-carbohydrate diet and underwent memory performance tasks. Scientists reported in the December 2010 issue of "Neurobiology & Aging" that subjects experienced improvements in memory performance tasks.
References
- Mayo Clinic: Low-Carb Diet
- "Archives of Internal Medicine"; Long-term Effects of a Very Low-Carbohydrate Diet and a Low-Fat Diet on Mood and Cognitive Function; G.D. Brinkworth et al.; November 2009
- "American Journal of Clinical Nutrition"; Low-And High-Carbohydrate Weight-Loss Diets Have Similar Effects on Mood But Not Cognitive Performance; A.K. Halyburton et al.; September 2007
- "Neurobiology of Aging"; Dietary Ketosis Enhances Memory in Mild Cognitive Impairment; R. Krikorian et al.; December 2010
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