Eating a handful of walnuts per day may help reduce the risk, delay the onset, slow the progression of, or prevent Alzheimer’s disease due to the anti inflammatory and anti-oxidative properties of the dry fruit, a study led by an Indian-American scientist has claimed.
These yet to be published findings are very promising and help lay the groundwork for future human studies on walnuts and Alzheimer’s - a disease for which there is no known cure, researchers said. “One in 10 people over the age of 65 suffer from Alzheimer’s. However, the awareness about the disease is very less. It takes 10 years to show the symptoms. It is not diagnosed properly; people think it is just an old age symptom and they have started forgetting things,” said Dr Abha Chauhan from New York State Institute for Basic Research in Developmental Disabilities (IBR) in the US.
“Oxidative damage and inflammation are two prominent features in the pathology of Alzheimer’s disease and many other neurodegenerative diseases. Walnuts are very rich in anti-inflammatory components and antioxidants,” said Chauhan, lead researcher of the study and head of the Developmental Neuroscience Laboratory at IBR.
Demographic ageing is a global phenomenon. India’s population is undergoing a rapid demographic transition now. With demographic ageing comes the problem of dementia, researchers said. According to the Dementia India Report 2010, India is home to more than 70 million people older than 60 years as per the 2001 census. The number of persons with dementia double every five years of age and so India will have one of the largest numbers of elders with this problem.
In 2010, there were 3.7 million Indians with dementia and it is expected to double by 2030. The number of persons with dementia double every 5 years of age and so India will have one of the largest numbers of elders with this problem, the report said.
According to the new study, walnuts are rich in antioxidant and anti-inflammatory components. “We have previously reported protective effects of walnut extract against A beta-induced oxidative stress and cell death and beneficial effects of dietary supplementation of six per cent (T6) or nine per cent walnuts (T9) (equivalent to one or 1.5 ounce of walnuts per day in humans) on the memory, anxiety and learning skills in a transgenic mouse model of AD,” researchers said.
One ounce is considered to be one serving of walnuts, and loosely translates to 12 to 14 halves, or 1/4 cup (about a handful). In the latest study, researchers compared A beta levels in the brain and blood samples of the AD mice with a walnut diet and without walnut diet and those of wild-type mice on diet without walnuts.
A previous study found significant improvement in learning skills, memory, reducing anxiety, and motor development in mice fed a walnut-enriched diet.
At the age of four months (before starting diet with walnuts), A beta levels (brain and blood) were similar in mice without walnut diet and with walnut diet groups. At the age of 14.5 and 19 months, mice without walnut diet had significantly higher A beta levels than mice with walnut diet. In the brain, mice with dietary supplementation of six per cent walnuts and those with nine per cent walnuts had significantly lower levels of soluble A beta oligomers compared to mice without walnut diet.
In the blood samples, A beta levels were increased in mice with dietary supplementation of six per cent walnuts and those with nine per cent walnuts compared to mice without walnuts, suggesting that walnuts in the diet can increase the clearance of A beta from brain to the blood. “These findings suggest that dietary supplementation with walnuts may have a beneficial effect in reducing the risk, delaying the onset, or slowing the progression of AD,” said researchers, including Pankaj Mehta and Ved Chauhan also from NYS Institute for Basic Research in Developmental Disabilities.
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Walnuts are beneficial because of their ability to inhibit A beta fibrillisation, A beta-induced oxidative stress and A beta-mediated cytotoxicity, and also by reducing the levels of soluble A beta oligomers in the brain and increasing A beta clearance, they said in the study funded by the California Walnut Commission (CWC).
A previous study also led by Chauhan and published in the Journal of Alzheimer’s Disease found significant improvement in learning skills, memory, reducing anxiety, and motor development in mice fed a walnut-enriched diet. In that study, the researchers suggested that the high antioxidant content of walnuts (3.7mmol/ounce) may have been a contributing factor in protecting the mouse brain from the degeneration typically seen in Alzheimer’s disease.