Low-carb diet impairs mental performance

Published on Saturday 13 December 2008 18:48

DIETERS who cut out carbohydrates are more likely to lose their memory than those who eat balanced meals, new research has shown.

A study has found that people who avoid starchy foods perform worse in mental tests than those who eat bread, pasta and potatoes.

Scientists found mental performance drops after just a week on a low-carb diet.

The best-known low-carb diet is the Atkins, which bans carbohydrates such as flour, sugar and potatoes but allows protein and fat. Some fruit and vegetables are also restricted.

The Atkins diet, which follows the concept that a low-carbohydrate diet produces a metabolic advantage in which the body burns more calories, overall, than normal diets, led the "low-carb craze".

At the height of its popularity, an estimated three million people in Britain were thought to be on the Atkins diet and the no-carb and low-carb eating concept remains popular, with a number of similar plans following in its footsteps.

But Dr Holly Taylor, who led the research at Tufts University in Boston in the United States, warned yesterday that such a diet can also have a negative impact on memory and thinking.

She said: "The study demonstrates that the food you eat can have an immediate impact on cognitive behaviour.

"The popular low-carb and no-carb diets have the strongest potential for negative impact on thinking and cognition." She added: "Although this study only tracked participants for three weeks, the data suggests that diets can affect more than just weight.

"The brain needs glucose for energy, and diets low in carbohydrates can be detrimental to learning, memory and thinking."

The study looked at the impact of low-carb diets on the brain power of 19 women aged 22 to 55. The volunteers were put on either a low-calorie balanced diet or a low-carb diet.

After a week the 10 women eating the low-carb diet were far poorer at performing mental tests than those on the conventional low-calorie diet.

The women were tested on their attention, long-term and short-term memory, visual attention and spatial memory, the part of the memory that records information about an individual's environment.

Those on a low-carb diet showed a gradual decline in ability to perform mental tasks compared with the low-calorie dieters. The researchers found their reaction time was more sluggish and their visual memory was not as good as those eating a balanced diet.

The research, published in the scientific journal Appetite, found there was no difference in the hunger levels of the women.

The scientists behind the study believe that low-carb diets reduce the amount of glucose or blood sugar carried to the brain and used by nerve cells for energy.