Write your abstract here.Higher intake of fish and
vitamin D levels linked to lower risk of age-
related macular disease.
Individuals
who have higher dietary intake of foods with omega-3 fatty acids and
higher fish consumption have a reduced risk of advanced age-
related macular degeneration, while those with higher serum levels of
vitamin D
may have a reduced risk of the early stages of the disease, according
to two reports in the May issue of Archives of Ophthalmology, one of
the JAMA/Archives journals.
Age-related macular degeneration (AMD) occurs when the macula, the area
at the back of the retina that produces the sharpest vision,
deteriorates over time. It is the most common cause of blindness among
older adults in the United States, affecting more than 7 million
individuals older than 40 years, according to background information in
the articles. The prevalence of AMD is likely to increase as the
population ages. There is currently no known way to prevent the
condition, but research has begun to identify potentially modifiable
risk factors and nutrient-based treatments.
The Age-Related Eye Disease Study Research Group assessed 4,519
individuals who were age 60 to 80 when they enrolled in 1992 through
1998. At that time, photographs were taken of their retinas to
determine if they had AMD, and if so, to which of four stages the
condition had progressed. The participants also completed a food
frequency questionnaire that measured how often they consumed foods
rich in certain vitamins, minerals and other nutrients, such as omega-3
fatty acids commonly found in tuna, salmon and other fish.
A total of 1,115 participants did not have any symptoms of AMD at
the beginning of the study, and were compared with those who did,
including 658 individuals with neovascular (severe) AMD. “Dietary total
omega-3 long-chain polyunsaturated fatty acid intake was inversely
associated with neovascular AMD, as was docosahexaenoic acid,” or DHA,
a fatty acid that previous evidence suggests affects the retina, the
authors write. “Higher fish consumption, both total and broiled/baked,
was also inversely associated with neovascular AMD.” Eating more than
two medium (4-ounce) servings of fish per week or more than one medium
serving of broiled or baked fish was associated with the lowest risk
for advanced AMD.
Omega-3 fatty acids may influence processes involved in the
development of blood vessel– and nerve-related diseases of the retina,
the authors write. For instance, DHA may protect the retina by
influencing which genes turn on and off, while fatty acids overall may
eventually form compounds that promote cell survival and proper blood
vessel function, reduce inflammation and maintain energy balance.
“These results and those from other observational analytic
investigations suggest that modifying diet to include more foods rich
in omega-3 long-chain polyunsaturated fatty acids could result in a
reduction in the risk of having neovascular AMD,” the authors conclude.
Clinical trials would provide further information about whether diet
changes or supplements could prevent the development of advanced AMD.
In a related study, Niyati Parekh, Ph.D., R.D., of the University of
the Medicine and Dentistry of New Jersey, New Brunswick, and the
University of Wisconsin–Madison, and colleagues analyzed data from
7,752 individuals (including 11 percent with AMD) who were part of the
National Health and Nutrition Examination Survey, a large study
designed to represent the entire U.S. population. Participants were
enrolled in the study between 1988 and 1994. They had physical
examinations that included blood and urine samples, photographs of the
retinas, and interviews and questionnaires regarding sociodemographics,
lifestyle habits and food intake.
“Levels of serum vitamin D were inversely associated with early AMD
but not advanced AMD,” the authors write. When participants were split
into five groups based on level of vitamin D in the blood, those in the
highest group had a 40 percent lower risk of early AMD than those in
the lowest group. “Milk intake was inversely associated with early AMD.
Fish intake was inversely associated with advanced AMD.”
Vitamin D may reduce the risk of AMD by reducing inflammation or by
preventing the growth of new blood vessels in the retina, which
contributes to some forms of AMD, the authors speculate. “This study
provides evidence that vitamin D may protect against AMD,” the authors
conclude. “However, at this time there is insufficient epidemiologic
evidence of the relationship between vitamin D level and AMD to make
recommendations regarding optimum serum vitamin D levels or milk and
fish intake to protect against AMD or its progression. The results of
the present research warrant further investigation for confirmation of
the vitamin D-AMD association in other population studies.”
Source: JAMA and Archives Journals