Researchers in the US found that people whose diet is closer to a Mediterranean diet are at lower risk of developing MCI or Mild Cognitive Impairment (a stage between normal aging and dementia) and also have a reduced risk of MCI turning into Alzheimer’s disease.
The study was the work of Dr Nikolaos Scarmeas and colleagues at Columbia University Medical Center, New York and is published in the February issue of Archives of Neurology, one of the JAMA/Archives journals.
Previous studies have found that sticking to a Mediterranean diet may protect people from Alzheimer’s disease, but not much is known about its possible ties with MCI.
A Mediterranean diet is high in fish, vegetables, legumes (beans and lentils), fruits, cereals and unsaturated fatty acids, and low in dairy products, meat and saturated fats, plus moderate amounts of alcohol.
For the study, the researchers asked 1,875 people to fill in questionnaires about their food consumption between 1992 and 1999. From the responses, the researchers then calculated a score for the extent to which each person’s food intake most closely resembled a Mediterranean diet.
At the start of the study, 1,393 of the participants had no cognitive problems and 482 of them had MCI, and they were all examined, interviewed and screened for MCI.
The results showed that:
- Over an average follow up period of 4.5 years, 275 of the 1,393 participants without MCI developed the condition.
- Comparing the one third with the lowest scores for Mediterranean diet adherence with the one third that had the highest scores, showed that having a high score was linked to a 28 per cent lower risk of developing MCI.
- The middle third had a 17 per cent lower risk.
- Among the 482 participants who had MCI at the start, 106 developed Alzheimer’s over an average follow up of 4.3 years.
- Among these participants, sticking to a Mediterranean diet was linked with a lower risk of MCI converting to Alzheimer’s.
- In this group, the one third of participants with the highest scores for Mediterranean diet adherence had a 48 per cent lower risk of developing Alzheimer’s compared to the one third with the lowest scores.
- The middle third had a 45 per cent lower risk.
The authors concluded that:
” Higher adherence to the MeDi [Mediterranean diet] is associated with a trend for reduced risk of developing MCI and with reduced risk of MCI conversion to AD [Alzheimer’s disease].”
They also wrote that more studies were needed to confirm these findings.
Speculating on their findings, they suggested that the Mediterranean diet may improve levels of cholesterol and blood sugar, as well as keep blood vessels healthier. It may also reduce inflammation. All these factors have been linked to MCI. They said that individual foods in the Mediterranean diet are also linked to lower risk of MCI. Examples of such foods include:
“Alcohol, fish, polyunsaturated fatty acids (also for age-related cognitive decline) and lower levels of saturated fatty acids,” they wrote.
Alzheimer’s is the most common form of dementia, which is a general term for loss of memory and other intellectual skills that impair quality of life. Alzheimer’s is a progressive and fatal brain disease that destroys brain cells, resulting in decline of memory, thinking and behaviour that eventually stops people from being able to work and have an independent life; their quality of life gradually diminishes as the disease progresses.
According to the Alzheimer’s Assocation (US), the disease is the sixth leading cause of death among Americans.
“Mediterranean Diet and Mild Cognitive Impairment.
Nikolaos Scarmeas; Yaakov Stern; Richard Mayeux; Jennifer J. Manly; Nicole Schupf; Jose A. Luchsinger.
Arch Neurol. Vol. 66 No. 2, pp 216-225, February 2009.
Sources: Journal abstract, JAMA/Archives press release, Alzheimer’s Association.
Written by: Catharine Paddock, PhD