Tobacco and alcohol use independently increase risk of head and neck cancer
Cigarette smoking is more strongly associated with head and neck cancers than drinking alcohol, according to a study in the May 16 issue of the Journal of the National Cancer Institute. The study found that smoking is responsible for a quarter of head and neck cancers among individuals who do not drink alcohol.
At least 75 percent of head and neck cancers are caused by a combination of cigarette smoking and drinking alcohol, but researchers have not known the individual contributions of these risk factors because people who smoke are more likely to drink than the general population and vice versa. In a new study, researchers sought to tease out the independent effect of each risk factor on head and neck cancer development.
Mia Hashibe, Ph.D., of the International Agency for Cancer Research in Lyon, France, and colleagues examined head and neck cancer risk among smokers who never drank alcohol and people who drink but never used tobacco products. They pooled data from 15 case–control studies, which included 10,244 head and neck cancer patients and 15,227 controls. About 16 percent of the patients and 27 percent of the controls never drank, and about 11 percent of the patients and 38 percent of the controls never smoked.
Cigarette smoking was associated with an increased risk of head and neck cancer—especially cancer of the larynx—among patients who never drank alcohol. About 24 percent of head and neck cancers were due to smoking among patients who never drank.
Drinking alcohol was also associated with greater risk of head and neck cancers among never smokers, but mainly for patients who drank three or more drinks per day. They had twice the risk of head and neck cancers as people who never drink. Only seven percent of head and neck cancers were due to drinking among never smokers.
Wednesday, May 16, 2007
Boiling Broccoli Ruins Its Anti Cancer Properties
Researchers at the University of Warwick have found that the standard British cooking habit of boiling vegetables severely damages the anticancer properties of many Brassica vegetables such as broccoli, Brussel sprouts, cauliflower and green cabbage.
Past studies have shown that consumption of Brassica vegetables decreases the risk of cancer. This is because of the high concentration in Brassicas of substances known as glucosinolates which are metabolized to cancer preventive substances known as isothiocyanates. However before this research it was not known how the glucosinolates and isothiocyanates were influenced by storage and cooking of Brassica vegetables.
The researchers, Prof Paul Thornalley from Warwick Medical School at the University of Warwick and Dr Lijiang Song from the University of Warwick’s Department of Chemistry bought Brassica vegetables, (broccoli, Brussel sprouts, cauliflower and green cabbage) from a local store and transported them to the laboratory within 30 minutes of purchasing. The effect of cooking on the glucosinolate content of vegetables was then studied by investigating the effects of cooking by boiling, steaming, microwave cooking and stir-fry.
Boiling appeared to have a serious impact on the retention of those important glucosinolate within the vegetables. The loss of total glucosinolate content after boiling for 30 minutes was: broccoli 77%, Brussel sprouts 58%, cauliflower 75% and green cabbage 65%.
The effects of other cooking methods were investigated: steaming for 0–20 min, microwave cooking for 0–3 min and stir-fry cooking for 0–5 min. All three methods gave no significant loss of total glucosinolate analyte contents over these cooking periods.
Domestic storage of the vegetables at ambient temperature and in a domestic refrigerator showed no significant difference with only minor loss of glucosinolate levels over 7 days.
However the researchers found that storage of fresh vegetables at much lower temperatures such as −85 °C (much higher than for storage in a refrigerator at 4–8 °C) may cause significant loss of glucosinolates up to 33% by fracture of vegetable material during thawing.
The researchers found that preparation of Brassica vegetables had caused only minor reductions in glucosinolate except when they were shredded finely which showed a marked decline of glucosinolate levels with a loss of up to 75% over 6 hours after shredding.
Professor Thornalley said: "If you want to get the maximum benefit from your five portions-a-day vegetable consumption, if you are cooking your vegetables boiling is out. You need to consider stir frying steaming or micro-waving them."
Past studies have shown that consumption of Brassica vegetables decreases the risk of cancer. This is because of the high concentration in Brassicas of substances known as glucosinolates which are metabolized to cancer preventive substances known as isothiocyanates. However before this research it was not known how the glucosinolates and isothiocyanates were influenced by storage and cooking of Brassica vegetables.
The researchers, Prof Paul Thornalley from Warwick Medical School at the University of Warwick and Dr Lijiang Song from the University of Warwick’s Department of Chemistry bought Brassica vegetables, (broccoli, Brussel sprouts, cauliflower and green cabbage) from a local store and transported them to the laboratory within 30 minutes of purchasing. The effect of cooking on the glucosinolate content of vegetables was then studied by investigating the effects of cooking by boiling, steaming, microwave cooking and stir-fry.
Boiling appeared to have a serious impact on the retention of those important glucosinolate within the vegetables. The loss of total glucosinolate content after boiling for 30 minutes was: broccoli 77%, Brussel sprouts 58%, cauliflower 75% and green cabbage 65%.
The effects of other cooking methods were investigated: steaming for 0–20 min, microwave cooking for 0–3 min and stir-fry cooking for 0–5 min. All three methods gave no significant loss of total glucosinolate analyte contents over these cooking periods.
Domestic storage of the vegetables at ambient temperature and in a domestic refrigerator showed no significant difference with only minor loss of glucosinolate levels over 7 days.
However the researchers found that storage of fresh vegetables at much lower temperatures such as −85 °C (much higher than for storage in a refrigerator at 4–8 °C) may cause significant loss of glucosinolates up to 33% by fracture of vegetable material during thawing.
The researchers found that preparation of Brassica vegetables had caused only minor reductions in glucosinolate except when they were shredded finely which showed a marked decline of glucosinolate levels with a loss of up to 75% over 6 hours after shredding.
Professor Thornalley said: "If you want to get the maximum benefit from your five portions-a-day vegetable consumption, if you are cooking your vegetables boiling is out. You need to consider stir frying steaming or micro-waving them."
Mediterranean Diet Halves Risk of Lung Disease
A Mediterranean diet halves the chances of developing progressive inflammatory lung disease (COPD), reveals a large study, published ahead of print in Thorax.
COPD (chronic obstructive pulmonary disease) is an umbrella term for chronic progressive lung disease, such as emphysema and bronchitis. It is expected to become the third leading cause of death worldwide by 2020, with cigarette smoking the primary factor in its development.
The researchers tracked the health of almost 43,000 men, who were already part of the US Health Professionals Follow up Study. This began in 1986 and involved more than 50,000 US health care professionals aged between 40 and 75, who were surveyed every two years.
They were asked questions about lifestyle, including smoking and exercise, diet and medical history. Dietary intake was assessed in detail every four years.
Eating patterns fell into two distinct categories: those who ate a diet rich in fruit, vegetables, whole grains and fish (Mediterranean diet); and those who ate a diet rich in processed foods, refined sugars, and cured and red meats (Western diet).
Between 1986 and 1998, 111 cases of COPD were newly diagnosed.
The Mediterranean diet was associated with a 50% lower risk of developing COPD than the Western diet, even after adjusting for age, smoking, and other risk factors.
And men who ate a predominantly Western diet were more than four times as likely to develop COPD, even after taking account of other influential factors.
The higher the compliance with a Mediterranean diet, the lower was the risk of developing COPD over the 12 year period.
Conversely, the higher the compliance with the Western diet, the higher was the risk of developing COPD.
To view the paper in full: http://press.psprings.co.uk/thx/may/tx74534.pdf
COPD (chronic obstructive pulmonary disease) is an umbrella term for chronic progressive lung disease, such as emphysema and bronchitis. It is expected to become the third leading cause of death worldwide by 2020, with cigarette smoking the primary factor in its development.
The researchers tracked the health of almost 43,000 men, who were already part of the US Health Professionals Follow up Study. This began in 1986 and involved more than 50,000 US health care professionals aged between 40 and 75, who were surveyed every two years.
They were asked questions about lifestyle, including smoking and exercise, diet and medical history. Dietary intake was assessed in detail every four years.
Eating patterns fell into two distinct categories: those who ate a diet rich in fruit, vegetables, whole grains and fish (Mediterranean diet); and those who ate a diet rich in processed foods, refined sugars, and cured and red meats (Western diet).
Between 1986 and 1998, 111 cases of COPD were newly diagnosed.
The Mediterranean diet was associated with a 50% lower risk of developing COPD than the Western diet, even after adjusting for age, smoking, and other risk factors.
And men who ate a predominantly Western diet were more than four times as likely to develop COPD, even after taking account of other influential factors.
The higher the compliance with a Mediterranean diet, the lower was the risk of developing COPD over the 12 year period.
Conversely, the higher the compliance with the Western diet, the higher was the risk of developing COPD.
To view the paper in full: http://press.psprings.co.uk/thx/may/tx74534.pdf
A Walk a Day Might Help Keep the Doctor Away
New research reported in the Journal of the American Medical Association shows daily, mild exercise - walking or bike riding - improves the fitness of post-menopausal women who are currently sedentary, overweight or obese.
Timothy Church, M.D., Ph.D., of the Pennington Biomedical Research Center, led a team of researchers who examined the effect of various amounts of walking on more than 460 women. The results showed that as little as 15 minutes a day, five days a week of walking on a treadmill or riding a stationary bike improved fitness.
"The level of walking we studied was so light most people would not consider it exercise," Church said, "The message for women here is just get up and walk. You don't need a gym, you don't need fancy clothes or a stop-watch. All you need is a pair of comfortable shoes that you can walk in."
The women were randomly placed into one of four groups: a control group that did not exercise and groups that exercised 72 minutes, 135 minutes, or 191 minutes of exercise per week. Church's team found that the more exercise performed the greater the increase in fitness, which was expected. However, the lowest exercise groups also saw improvements in fitness, which the team did not expect.
"The surprising news," Church said, "is that the lowest exercise group showed significant improvement. We continue to recommend 30 minutes a day of walking at least five days a week, but the data suggests just doing something - even 15 minutes a day - is better than nothing.
Timothy Church, M.D., Ph.D., of the Pennington Biomedical Research Center, led a team of researchers who examined the effect of various amounts of walking on more than 460 women. The results showed that as little as 15 minutes a day, five days a week of walking on a treadmill or riding a stationary bike improved fitness.
"The level of walking we studied was so light most people would not consider it exercise," Church said, "The message for women here is just get up and walk. You don't need a gym, you don't need fancy clothes or a stop-watch. All you need is a pair of comfortable shoes that you can walk in."
The women were randomly placed into one of four groups: a control group that did not exercise and groups that exercised 72 minutes, 135 minutes, or 191 minutes of exercise per week. Church's team found that the more exercise performed the greater the increase in fitness, which was expected. However, the lowest exercise groups also saw improvements in fitness, which the team did not expect.
"The surprising news," Church said, "is that the lowest exercise group showed significant improvement. We continue to recommend 30 minutes a day of walking at least five days a week, but the data suggests just doing something - even 15 minutes a day - is better than nothing.
Monday, May 14, 2007
Calcium plus vitamin D may help prevent weight gain
Calcium plus vitamin D supplements may help prevent weight gain in postmenopausal women
Postmenopausal women who take calcium and vitamin D supplements may gain less weight than those who do not, although the overall effect is small, according to a report in the May 14 issue of Archives of Internal Medicine, one of the JAMA/Archives journals. The benefit is greater in those who had not previously been getting the daily recommended amount of calcium.
"Because weight loss or prevention of weight gain is likely to have significant health benefits for middle-aged women, early to middle menopause may be a critical period of life in which to slow the trajectory of weight gain," the authors note as background information in the article. Some evidence suggests that calcium and vitamin D may play a role in effective weight management. These nutrients may stimulate the breakdown of fat cells and suppress the development of new ones.
Bette Caan, Dr.P.H., of Kaiser Permanente Northern California, Oakland, and colleagues studied 36,282 postmenopausal women age 50 to 79 who were enrolled in the Women's Health Initiative clinical trial. The women were randomly assigned to receive a dose of 1,000 milligrams of calcium plus 400 international units of vitamin D (18,176 women) or placebo (18,106 women) daily. They were weighed each year for approximately seven years.
At the beginning of the study, 39.63 percent of the women met current recommended daily intake of 1,200 milligrams of calcium, 53.94 percent reported taking any calcium supplements and 28.95 percent reported taking supplements of 500 milligrams of calcium or more. At the end of the study, women who took the supplements weighed an average of 0.28 pounds less than those who did not.
Among women who were getting less than the recommended amount of calcium daily before the study, those who took the supplements weighed an average of 0.42 pounds less than those who did not. After three years, when compared to women taking placebo, these women had a lower risk of gaining weight in both small amounts (2.2 to 6.6 pounds) and moderate amounts (more than 6.6 pounds) and had a higher likelihood of maintaining a stable weight (within 2.2 pounds of starting weight) or losing weight (more than 2.2 pounds).
"Prevention of weight gain is an important public health goal, and caloric restriction and daily physical activity should still be considered the basic tenets of weight management," the authors conclude. "Further research should be undertaken to address the effect of calcium supplementation combined with caloric restriction and physical activity on weight gain prevention."
Postmenopausal women who take calcium and vitamin D supplements may gain less weight than those who do not, although the overall effect is small, according to a report in the May 14 issue of Archives of Internal Medicine, one of the JAMA/Archives journals. The benefit is greater in those who had not previously been getting the daily recommended amount of calcium.
"Because weight loss or prevention of weight gain is likely to have significant health benefits for middle-aged women, early to middle menopause may be a critical period of life in which to slow the trajectory of weight gain," the authors note as background information in the article. Some evidence suggests that calcium and vitamin D may play a role in effective weight management. These nutrients may stimulate the breakdown of fat cells and suppress the development of new ones.
Bette Caan, Dr.P.H., of Kaiser Permanente Northern California, Oakland, and colleagues studied 36,282 postmenopausal women age 50 to 79 who were enrolled in the Women's Health Initiative clinical trial. The women were randomly assigned to receive a dose of 1,000 milligrams of calcium plus 400 international units of vitamin D (18,176 women) or placebo (18,106 women) daily. They were weighed each year for approximately seven years.
At the beginning of the study, 39.63 percent of the women met current recommended daily intake of 1,200 milligrams of calcium, 53.94 percent reported taking any calcium supplements and 28.95 percent reported taking supplements of 500 milligrams of calcium or more. At the end of the study, women who took the supplements weighed an average of 0.28 pounds less than those who did not.
Among women who were getting less than the recommended amount of calcium daily before the study, those who took the supplements weighed an average of 0.42 pounds less than those who did not. After three years, when compared to women taking placebo, these women had a lower risk of gaining weight in both small amounts (2.2 to 6.6 pounds) and moderate amounts (more than 6.6 pounds) and had a higher likelihood of maintaining a stable weight (within 2.2 pounds of starting weight) or losing weight (more than 2.2 pounds).
"Prevention of weight gain is an important public health goal, and caloric restriction and daily physical activity should still be considered the basic tenets of weight management," the authors conclude. "Further research should be undertaken to address the effect of calcium supplementation combined with caloric restriction and physical activity on weight gain prevention."
Grain fiber and magnesium = lower risk for diabetes
Grain fiber and magnesium intake associated with lower risk for diabetes
Higher dietary intake of fiber from grains and cereals and of magnesium may each be associated with a lower risk of type 2 diabetes, according to a report and meta-analysis in the May 14 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
Projections indicate that the number of people diagnosed with diabetes worldwide may increase from 171 million in 2000 to 370 million by 2030, according to background information in the article. The associated illness, death and health care costs emphasize the need for effective prevention, the authors write. Fiber may help reduce the risk of diabetes by increasing the amount of nutrients absorbed by the body and reducing blood sugar spikes after eating, among other mechanisms. Current American Diabetes Association guidelines include goals for total fiber intake, but research suggests that some types of fiber may be more beneficial than others. Findings regarding magnesium and diabetes risk remain unclear.
Matthias B. Schulze, Dr.P.H., and colleagues at the German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, conducted a study of 9,702 men and 15,365 women age 35 to 65 years. Participants completed a food questionnaire when they enrolled in the study between 1994 and 1998, then were followed up through 2005—an average of seven years—to see if they developed diabetes. In addition, the researchers performed a meta-analysis of previously published work related to intake of fiber or magnesium and risk of diabetes.
During the follow-up period, 844 individuals in the study developed type 2 diabetes. Those who consumed more fiber through cereal, bread and other grain products (cereal fiber) were less likely to develop diabetes than those who ate less fiber. When the participants were split into five groups based on cereal fiber intake, those who ate the most (an average of 17 grams per day) had a 27 percent lower risk of developing diabetes than those in the group that ate the least (an average of 7 grams per day). Eating more fiber overall or from fruits and vegetables was not associated with diabetes risk, nor was magnesium intake.
In the meta-analysis, the researchers identified nine studies of fiber and eight studies of magnesium intake. Based on the results of all the studies, in which participants were classified into either four or five groups according to their intake of fiber or magnesium, those who consumed the most cereal fiber had a 33 percent lower risk of developing diabetes than those who took in the least, while those who consumed the most magnesium had a 23 percent lower risk than those who consumed the least. There was no association between fruit or vegetable fiber and diabetes risk.
"In conclusion, the evidence from our study and previous studies, summarized by means of meta-analysis, strongly supports that higher cereal fiber and magnesium intake may decrease diabetes risk," the authors conclude. "Whole-grain foods are therefore important in diabetes prevention."
Higher dietary intake of fiber from grains and cereals and of magnesium may each be associated with a lower risk of type 2 diabetes, according to a report and meta-analysis in the May 14 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
Projections indicate that the number of people diagnosed with diabetes worldwide may increase from 171 million in 2000 to 370 million by 2030, according to background information in the article. The associated illness, death and health care costs emphasize the need for effective prevention, the authors write. Fiber may help reduce the risk of diabetes by increasing the amount of nutrients absorbed by the body and reducing blood sugar spikes after eating, among other mechanisms. Current American Diabetes Association guidelines include goals for total fiber intake, but research suggests that some types of fiber may be more beneficial than others. Findings regarding magnesium and diabetes risk remain unclear.
Matthias B. Schulze, Dr.P.H., and colleagues at the German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, conducted a study of 9,702 men and 15,365 women age 35 to 65 years. Participants completed a food questionnaire when they enrolled in the study between 1994 and 1998, then were followed up through 2005—an average of seven years—to see if they developed diabetes. In addition, the researchers performed a meta-analysis of previously published work related to intake of fiber or magnesium and risk of diabetes.
During the follow-up period, 844 individuals in the study developed type 2 diabetes. Those who consumed more fiber through cereal, bread and other grain products (cereal fiber) were less likely to develop diabetes than those who ate less fiber. When the participants were split into five groups based on cereal fiber intake, those who ate the most (an average of 17 grams per day) had a 27 percent lower risk of developing diabetes than those in the group that ate the least (an average of 7 grams per day). Eating more fiber overall or from fruits and vegetables was not associated with diabetes risk, nor was magnesium intake.
In the meta-analysis, the researchers identified nine studies of fiber and eight studies of magnesium intake. Based on the results of all the studies, in which participants were classified into either four or five groups according to their intake of fiber or magnesium, those who consumed the most cereal fiber had a 33 percent lower risk of developing diabetes than those who took in the least, while those who consumed the most magnesium had a 23 percent lower risk than those who consumed the least. There was no association between fruit or vegetable fiber and diabetes risk.
"In conclusion, the evidence from our study and previous studies, summarized by means of meta-analysis, strongly supports that higher cereal fiber and magnesium intake may decrease diabetes risk," the authors conclude. "Whole-grain foods are therefore important in diabetes prevention."
More fish and vitamin D = less macular disease
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."
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."
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