Flavonoids, compounds which exist in plants, are extremely powerful antioxidants and anti-inflammatory substances. Scientists say inflammation and stress play a major role in cognitive decline, and that consuming plenty of flavonoids helps reduce their effects.
Previous studies had already shown that consuming flavonoids, especially anthocyanidins, can improve cognitive functions. However, they were all either animal studies or very small human ones.
The US elderly population - people aged at least 65 years - rose by 15% during the first ten years of this century, compared to an overall population increase of 9.7%, according to the 2010 US Census.
Team leader, Dr. Elizabeth Devore, said:
"As the U.S. population ages, understanding the health issues facing this group becomes increasingly important. Our study examined whether greater intake of berries could slow rates of cognitive decline."
The researchers gathered data from the Nurses Health Study, which has information on 121,700 female, registered nurses. They had all completed questionnaires which included data on their health and lifestyle. The nurses were aged between 30 and 55 when they were questioned. The study started in 1976. From 1980 onwards, the participants were monitored every four years regarding their dietary habits. 16,010 of them had their cognitive function assessed between 1995 and 2001 at two-yearly intervals. All of the 16,010 were aged at least 70 years. In the present study, the women's average age was 74 and their BMI (body mass index) was 26.
The authors found that those whose consumption of blueberries and strawberries were high had slower cognitive decline, compared to the other participants. A reduction in cognitive decline was also found among those with a greater consumption of anthocyanidins and total flavonoids.
The elderly females whose berry consumption was higher had an average 2.5 year slower cognitive decline, compared to their counterparts whose berry intake was low.
The researchers emphasized that despite having taken some factors into account, there might still be others which are linked to higher berry intake which could affect their findings. For example, possibly those who eat more berries also exercise more.
Dr. Devore said:
"We provide the first epidemiologic evidence that berries may slow progression of cognitive decline in elderly women. Our findings have significant public health implications as increasing berry intake is a fairly simple dietary modification to test cognition protection in older adults."
What are berries?According to strict botanical definition, a berry is a fleshy fruit produced from a single ovary, such as a grape. However, in everyday "layman's" English, a berry refers to any small, edible fruit - they are typically round or semi-oblong, juicy, brightly colored, and have no pit (stone).
Several types of "berries". By strict botanical definition, the only real berry in this picture is the blueberry. In everyday "layman's" English, they are all berries.