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The link between physical health and mental health continues to be reinforced, as researchers make connections demonstrating that older adults who exercise regularly and eat a healthy diet seem to preserve cognitive function longer and are generally happier people.
Two recent studies underscore that association, but in very different ways. A study published in the Nov. 9, 2009 issue of Archives of Neurology found that muscle strength is associated with a lower risk of developing mild cognitive impairment, a precursor to Alzheimer's disease. "Muscle strength also is associated with the rate of decline in cognitive function among older persons," says Patricia Boyle, PhD, a neuropsychologist with the Rush Alzheimer's Disease Center in Chicago and an author of the study. "Decreased muscle strength may be an indicator of impending cognitive impairment."
A separate study, conducted by Grant Brinkworth, PhD, of Commonwealth Scientific and Industrial Research Organization in Adelaide, Australia, found that after one year, people on a low-calorie, low-fat diet reported a significantly more positive mood than those who ate a low-carbohydate diet with the same number of calories. The study, which appeared in the Nov. 9, 2009 issue of Archives of Internal Medicine, noted that weight loss among study subjects was similar in both groups, but after a temporary improvement in mood among the low-carb group, most of them eventually returned to what their mood was at the start of the year-long study.
"What we are seeing here is not increased negative mood overall following a low-carb diet, but increased duration of positive changes in the low-fat condition," says Kristen D'Anci, PhD, with the Human Nutrition Research Center on Aging at Tufts University. Dr. D'Anci, who did not participate in the Australian study, but has been a part of similar research, adds that the results are particularly noteworthy because they were achieved after a full year--an unusually long time for a dietary study.
FOOD AND MOOD. It's unclear exactly why the low-fat diet was associated with a more positive mood than the low-carbohydrate diet. One possible explanation suggested by researchers may be detrimental effects of higher fat intake on brain levels of serotonin, a neurotransmitter related to mood and psychological functioning. However, researchers also concluded that the challenge of maintaining a more restrictive diet, particularly one that meant less volume of food available for consumption (see chart), may have helped suppress the mood of the low-carb group.
"Eating and sharing meals is an important part of our lives," Dr. D'Anci says. "Highly specialized or restricted diets can be isolating, which can affect mood."
She adds that consumers shouldn't overanalyze every bite of food on their plate, but rather eat a balanced low-fat diet and talk with their doctors about calorie control if weight loss is a serious issue. "Chronic concern about the 'right foods' and maintaining a 'good food/bad food' mentality reduces the enjoyment of one of our most basic pleasures and can negatively impact mood," Dr. D'Anci says. "Eating a precise formula of macro-nutrients ... would, in the long-term, be counterproductive."
MUSCLE AND MEMORY. Just as the Australian study couldn't definitively explain why a low-fat diet improves one's mood more than a low-carb eating plan, Dr. Boyle's study linking muscle strength and Alzheimer's risk doesn't provide a specific cause-and-effect. She suggests that the disease process that leads to Alzheimer's also contributes to diminished muscle strength and that it may be related to the mitochondria that are involved in energy production in cells.
"It's possible that the pathology of Alzheimer's disease plays a role, as it is now becoming evident that Alzheimer's pathology affects motor and physical function as well as cognition," Dr. Boyle says. "More research is greatly needed to determine the neurobiologic basis of the association of muscle strength with Alzheimer's and cognition in old age. These findings, though, do support the idea that there is a strong link between physical and brain health in aging, and suggest that maintenance of physical function is important at all ages."
FAST FACTS ABOUT FOOD VOLUME
Consuming the same number of calories on a low-carbohydate diet as you would on a low-fat diet will result in significantly less volume of food consumed.
Fat contributes more kilocalories (the correct term for the more commonly used "calorie") than protein or carbs. If you're reducing your fat intake, you're going to eat more low-calorie carbs (e.g. fruits and whole-grain breads), while the low-carb dieter will eat more calorie-dense, high-fat foods (e.g. red meat and protein bars).
* One gram of carbs contributes 4 kilocalories.
* One gram of protein contributes 4 kilocalories.
* One gram of fat contributes 9 kilocalories.
In the study cited in the article, low-carb dieters got 61 percent of their energy from fat, while the low-fat group consumed 30 percent of its calories from fat.
Prevention Is the Key
"Both of these studies are pertinent and timely in an aging population. As the population ages the health care system is facing an explosion in cost and finding qualified providers for the increased numbers of patients expected to present with cognitive decline. By far the most cost-effective and patient-effective solution to this impending explosion in cases is prevention Both of these studies reinforce that exercise and a healthy diet favorably affect multiple organ systems, including the brain. Given the obesity epidemic in America, these studies also provide evidence that programs designed to improve conditioning and diet may have favorable impacts on mood and cognition in addition to the well documented cardiovascular benefits. Additional research is required to better understand these factors."
HAROLD GOFORTH, MD, Assistant Professor-Psychiatry & Behavioral Sciences-General, Department of Psychiatry, Duke
Goforth, Harold. "Memory and mood may depend on muscle strength and diet choices: research continues to solidify the link between physical fitness and cognitive health." Health News 16.2 (2010): 3+. Health Reference Center Academic. Web. 28 Feb. 2010.
Gale Document Number:A218660369
Disclaimer:This information is not a tool for self-diagnosis or a substitute for professional care.