DHA supplementation improves memory in older individuals
The Alzheimer's Association 2009 International Conference on Alzheimer's Disease held in Vienna was the site of a presentation on July 12, 2009 by Karin Yurko-Mauro, PhD concerning the finding of a positive effect for the omega-3 fatty acid docosahexaenoic acid (DHA) on memory and heart rate in older men and women. Docosahexaenoic acid, the main omega-3 fatty acid found in brain, is involved in neural function, and decreases have been associated with cognitive decline and a greater risk of Alzheimer's disease.
Acting on the discovery in an animal model of Alzheimer's disease of reduced levels of amyloid beta and tau following DHA supplementation, Dr Yurko-Mauro and her associates randomized 485 healthy older men and women with age related cognitive decline to receive 900 milligrams DHA from algae or a placebo daily for 6 months. The participants, whose average age was 70, were enrolled at 19 sites across the United States. Memory tests were administered before supplementation and at the study's conclusion. Heart rate, blood pressure, body weight, plasma phospholipid DHA levels, and other factors were also assessed.
At the end of the treatment period, plasma phospholipid DHA levels had doubled in the group that received the supplement. Participants who received DHA experienced significantly fewer errors on a visuospatial episodic memory test compared to pretreatment testing than did those who did not receive DHA. Heart rate decreased in the DHA group, and blood pressure and body weight remained unchanged in both groups. No serious treatment-related adverse effects were observed.
"In our study, healthy people with memory complaints who took algal DHA capsules for six months had almost double the reduction in errors on a test that measures learning and memory performance versus those who took a placebo," stated Dr Yurko-Mauro, who is Associate Director of Clinical Research at Martek Biosciences. "The benefit is roughly equivalent to having the learning and memory skills of someone three years younger."
In another study reported at the conference, DHA supplementation was not associated with cognitive improvement in Alzheimer's disease patients. "These two studies – and other recent Alzheimer's therapy trials – raise the possibility that treatments for Alzheimer's must be given very early in the disease for them to be truly effective," noted William Thies, PhD, who is the Chief Medical & Scientific Officer at the Alzheimer's Association. "For that to happen, we need to get much better at early detection and diagnosis of Alzheimer's, in order to test therapies at earlier stages of the disease and enable earlier intervention."
Researchers have identified a number of factors that may contribute to cognitive decline:
Diet. In one prospective study, more than 500 participants age 55 or older without clinical symptoms of dementia were evaluated. Their diets were assessed at the onset of the study, and participants were screened for symptoms of dementia an average of two years later. After adjusting for other factors, participants with the highest total fat intake were found to have a significantly elevated relative risk of dementia. An increased risk of dementia was also associated with a high dietary intake of saturated fat and cholesterol. On the other hand, a high intake of fish was associated with a significantly lower risk of dementia (Kalmijn V et al 1997). These findings have been supported in several other studies (Solfrizzi V et al 2005; Solfrizzi V et al 2003; Solfrizzi V et al 1999; Panza F et al 2004; Capurso A et al 2000).
Inflammation. The theory linking inflammation to cognitive decline is relatively new, but it appears to be consistent with our increasing understanding of the damage of chronic inflammation (as measured by C-reactive protein or interleukin-6 levels). Various studies have examined the association between inflammation and mild cognitive impairment and found compelling evidence. For example, one study of 2632 participants (mean age: 74 years) found that people who had both metabolic syndrome and high inflammation levels were more likely to experience cognitive impairment than were patients who suffered from neither. Metabolic syndrome is a cluster of abnormalities including high blood pressure, high insulin levels, obesity, and abnormal blood lipid levels. It is closely associated with increased risk of heart attack and stroke. In contrast, those with metabolic syndrome and low inflammation were not at increased risk of mild cognitive impairment (Yaffe K et al 1998).
Free radical damage. Free radicals are highly unstable molecules that react with other molecules in a damaging process known as oxidation. Areas of the body with high energy output, such as the brain, are particularly vulnerable to damage from free radicals. The body normally defends itself against the harmful effects of free radicals with antioxidants, including superoxide dismutase and glutathione peroxidase, as well as vitamins C and E. Animal studies have suggested that diets high in antioxidants can delay age-related memory loss (Joseph JA et al 1998; Perrig WJ et al 1997).
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