多吃草莓或藍莓可能延緩失智症的發生

Eating Berries Linked to Delay in Cognitive Decline Fran Lowry

May 1, 2012 — Increased consumption of blueberries and
strawberries appears to slow cognitive decline in older women, according to an
analysis of data from the Nurses' Health Study (NHS).

"Increasing
berry intake appears to slow memory decline by up to 2.5 years," lead
author, Elizabeth E. Devore, ScD, from the Channing Laboratory, Brigham and
Women's Hospital and Harvard Medical School, Boston, Massachusetts, told Medscape Medical News. "By
this, we mean that women eating the most berries vs. little to no berries had
memory differences equivalent to women 2.5 years apart in age."

The news study was
published online April 25 in the Annals of Neurology.

Berries and
Flavonoids

In their
prospective, observational study, which was funded by the National Cancer
Institute and the California Strawberry Commission, Dr. Devore and her team
evaluated long-term intake of berries and flavonoids in relation to memory decline
in 16,010 older women who were participants in the NHS.

The NHS
encompasses a large population cohort of 121,700 female registered nurses aged
30 to 55 years who completed health and lifestyle questionnaires starting in
1976.

Between 1995 and
2001, cognitive function was measured every 2 years in study participants aged
70 and older. The mean age of the women in the current analysis was 74, and
their mean body mass index was 26 kg/m².

"Experimental
data show that berry supplementation enhances neuronal function and survival
and ameliorates age-related cognitive impairment in rodents," Dr. Devore
noted.

Berries are particularly high in a
subclass of flavonoids called anthocyanidins, which can cross the blood-brain
barrier and localize in the hippocampus, known to be an area of the brain
involved in learning and memory, she said.

"Flavonoids
have powerful antioxidant and anti-inflammatory properties, and both oxidative
stress and inflammation are thought to be important contributors to cognitive
impairment. So increased flavonoid consumption could be a potential
strategy for reducing cognitive decline in older adults," she said.

The researchers
found that greater intakes of blueberries and strawberries were associated with
slower rates of cognitive decline.

After adjustment
for age and education, greater consumption of blueberries was highly
associated with slower decline in the global score (P
trend = .010), the verbal score (P trend = .016),
and the Telephone Interview of Cognitive Status (P
trend = .027).

The mean
difference in rate of global decline was 0.04 standard unit over the study
period (95% confidence interval [CI], 0.01 - 0.07) in women who had 1 or more
servings of blueberries per week vs those who ate less than 1 serving per week.

They also found
that a greater intake of strawberries was related to slower decline in the
global and verbal scores after adjustment for age (P
trend for global score = .021) and education (P
trend for verbal score = .014).

Women who ate 2 or
more servings of strawberries per week had an average decline in the global
score that was 0.03 standard unit less over the study follow-up period compared
with women who had less than 1 serving per week (95% CI, 0.00 - 0.06).

Overall in the
study population, the researchers found that 1 year of age was associated with
a mean decline of 0.02 standard unit on the global score over the follow-up
period.

"Thus, the
mean differences that we observed comparing extreme categories of blueberry and
strawberry intakes were equivalent to approximately 1.5 to 2.5 years of
cognitive aging," Dr. Devore explained. "Women with higher berry
intake appeared to have delayed their cognitive aging by up to 2.5 years."

However, she
cautioned that although the study controlled for other health factors, the
possibility that the preserved cognition in those who ate more berries may be
also influenced by other lifestyle choices, such as exercising more, cannot be
ruled out.

The study does,
however, have strengths, she said. "It is the first large epidemiologic
study of long-term berry and flavonoid intake in relation to memory decline,
utilizing information from over 16,000 older women. In addition, we collected
information on berry intake over 20 years prior to initial memory testing,
which enabled us to analyze long-term patterns of berry intake."

For now, however,
doctors can tell their patients that eating berries may delay memory decline.
"Specifically, eating 1 or more servings per week of blueberries or 2 or
more servings per week of strawberries appears to be associated with memory
benefits," Dr. Devore said.

Remain
Skeptical

Commenting on this
study for Medscape Medical News, David
Knopman, MD, from the Mayo Clinic, Rochester, Minnesota, and a spokesperson for
the American Academy of Neurology, agreed that the study did have its
strengths, including the fact that mid-life dietary practices were assessed at
the time, not retrospectively, and its inclusion of a very large number of
women who had had 3 cognitive assessments.

However, he said
he still has concerns about the study.

"The concerns
that I have about the report stem primarily from the fact that studies of
associations between dietary habits and health outcomes are notoriously
difficult to replicate," Dr. Knopman said. "Second, the possibility
of residual confounding by general health behavior, levels of physical
activity, socioeconomic status is a possibility that cannot be discounted. The
authors acknowledge this.

I would note that inclusion of
physical activity and household annual income in the statistical models that
they used attenuated the associations to the point that they were no longer
significant.

"Further, I
would note that inclusion of physical activity and household annual income in
the statistical models that they used attenuated the associations to the point
that they were no long significant at the p < 0.05 level for 2 of 3 of the
cognitive outcomes," he said.

"The authors
presented the results but did not comment on these analyses in the text of
their article or in the abstract. I think that the authors should have said:
'When controlling for other health-related variables, the associations were
attenuated and raise questions about the specificity of our findings.'
Therefore, I remain skeptical that these results reflect what the authors say
they do," Dr. Knopman said.

The study was funded by the National Cancer
Institute and the California Strawberry Commission. Dr. Devore and Dr. Knopman
have disclosed no relevant financial relationships.

Ann Neurol. Published online April
25, 2012. Abstract