Advice from scientists and doctors to aging adults has been consistent: get plenty of physical activity and mental stimulation to help maintain memory and preserve the thinking (cognitive) abilities that naturally decline with age. A new study adds calorie restriction to this list of good habits for the mind. The study, published in the Proceedings of the National Academy of Sciences, found that a low-calorie diet was more effective than a diet high in unsaturated fats at preventing memory loss in seniors.
Comparing diets
The three-month study included 50 healthy people between 50 and 80 years old. They were divided into three diet groups: the first was instructed to reduce their daily caloric intake by 30%, to a minimum of 1,200 calories per day; the second was instructed to increase their daily intake of mono- and poly-unsaturated fats by 20%; and the third ate their usual diet. Blood and memory tests were done at the beginning and end of the study.
The people in the calorie-restriction group lost weight and their C-reactive protein (CRP, a marker of inflammation, high levels of which are a known risk factor for heart disease) and fasting insulin levels decreased over the course of the study. Their performance on memory tests improved by nearly 30%, and improvements were most pronounced in the people who followed the diet most closely. There were no changes in weight, blood tests, or memory test scores in either the high-unsaturated fat diet group or the usual diet group.
The insulin connection
The benefits of calorie restriction on brain function seen in this study are similar to those seen in previous research. Although the reasons are not fully understood, one likely explanation is the drop in insulin levels that is associated with calorie cutting, as rising insulin levels have been linked to cognitive impairment and dementia. Other possible explanations include the anti-inflammatory effect of calorie restriction demonstrated by the reduction in CRP levels, and brain cell stimulation by the chemical changes that accompany calorie restriction.
“The current results suggest that caloric restriction may improve memory in healthy elderly individuals,” said study co-author Dr. Agnes Flöel at the University of Münster in Germany. “Our findings further point to increased insulin sensitivity and reduced inflammatory activity as mechanisms by which reducing calories might protect neurons and lead to better brain cell functioning.” She added that more research is needed to confirm these early observations and to explore the effect of a fat-modulated diet that aims to specifically increase omega-3 fatty acids on memory.
Cut carefully
Cutting calories may a healthy step for many people, but those who are underweight or have any chronic health problems should seek advice from a healthcare provider before making significant cuts. Seniors have a tendency to be undernourished, and are especially susceptible to protein, vitamin B12, folic acid, and other nutrient deficiencies, so care must be taken to keep nutrient-dense foods in the diet, and to keep caloric intake above the 1,200-calorie-per-day minimum. In addition, bear in mind the two cornerstones of memory preservation and enhancement:
• Keep your brain active—Older people who spend leisure time playing board games, reading, and playing musical instruments have a lower risk of dementia.
• Keep your body active—Dancing in particular has been linked to better cognitive health in seniors.
(Proc Natl Acad Sci 2009;online publication)
Maureen Williams, ND
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