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Study finds antioxidant supplements help protect against hearing loss
In research reported on February 18, 2009 at the Association for Research in Otolaryngology's annual conference, Colleen LePrell, PhD, of the University of Florida and her colleagues discovered that supplementing laboratory animals with vitamins C and E, beta-carotene, and magnesium helps prevent noise-induced hearing loss.
In their first experiment, Dr LePrell and scientists from the University of Michigan administered the antioxidants to guinea pigs before exposing them to 4 hours of noise at a decibel level similar to that reached at a loud concert, which can cause a temporary reduction in hearing. Measurement of sound-evoked neural activity determined that the nutrients prevented the temporary loss of hearing in the noise exposed animals.
In the second study, mice supplemented with antioxidants were protected from permanent hearing loss after being exposed to a single loud sound. It was discovered that cell loss in the inner ear’s lateral wall was prevented in the supplemented animals.
In addition to the intense vibrations caused by loud noise, damage to the inner ear’s structures is also caused by free radicals, whose activity is prevented in part by antioxidants. "The free radicals literally punch holes in the membrane of the cells," stated University of Michigan professor Josef Miller.
"What is appealing about this vitamin 'cocktail' is that previous studies in humans, including those demonstrating successful use of these supplements in protecting eye health, have shown that supplements of these particular vitamins are safe for long-term use," Dr Le Prell commented.
"Ear protection, such as ear plugs, is always the best practice for the prevention of noise-induced hearing loss, but in those populations who don't or can't wear hearing protection, for people in which mechanical devices just aren't enough, and for people who may experience unexpected noise insult, these supplements could provide an opportunity for additional protection," she added.
B vitamins decrease macular degeneration risk
In the February 23 issue of the American Medical Association journal Archives of Internal Medicine, Harvard researchers report the results of a clinical trial which found that women who received the B vitamins folic acid, vitamin B6 and vitamin B12 have a reduced risk of age-related macular degeneration (AMD) compared with women who received a placebo. Age-related macular degeneration is a major cause of vision loss in older men and women, and has been linked in recent studies with elevated levels of homocysteine, which can be lowered with specific B vitamins.
For the current trial, William G. Christen, ScD of Harvard Medical School and his associates enrolled 5,442 participants in the Women's Antioxidant and Folic Acid Cardiovascular Study of women at high risk for cardiovascular disease. The majority of the subjects did not have macular degeneration at the beginning of the study. The women were assigned a placebo or 2.5 milligrams folic acid, 50 milligrams vitamin B6 and 1 milligram vitamin B12 daily from April, 1998 through July, 2005.
One hundred thirty-seven new diagnoses of macular degeneration were documented during an average 7.3 years of treatment and follow-up. Seventy of these cases were considered visually significant. Women who received the B vitamins were found to have a 34 percent lower risk of developing age related macular degeneration and a 41 percent lower risk of visually significant disease compared with those who received a placebo.
In addition to reducing homocysteine, the authors suggest that antioxidant effects and improved blood vessel function may be responsible for the benefits observed in association with the B vitamins used in this study. They announce that "The trial findings reported herein are the strongest evidence to date in support of a possible beneficial effect of folic acid and B vitamin supplements in AMD prevention.”
Stroke risk doubled by unhealthy lifestyle
A report published online on February 19, 2009 in the British Medical Journal revealed the impact of an unhealthy lifestyle on the risk of stroke. Men and women who had poor compliance with four basic lifestyle factors were found to have double the risk of stroke compared with those who practiced the behaviors.
Researchers at the University of East Anglia and the University of Cambridge in England utilized data from 20,040 participants in the European Prospective Investigation into Cancer Study (EPIC) Norfolk for the current analysis. Health and lifestyle questionnaires completed upon enrollment were scored one point for the practice of each of the following lifestyle factors: not smoking, not being physically inactive, having a moderate alcohol intake of 1 to 14 units per week, and having plasma vitamin C levels of at least 50 micromoles per liter, which is a marker for fruit and vegetable intake of five or more servings per day. Nineteen percent of the men participating in the study and 29.7 percent of the women practiced all four healthy behaviors.
Over the 11.5 year average follow up period, 599 strokes occurred. Stroke risk was shown to increase with each point decline. Compared with participants who scored all 4 healthy lifestyle points, those who scored one point experienced a risk of stroke that was 2.18 times greater, and those with zero points had a 2.3 times greater risk.
“The fact that the lifestyle behaviours examined in this study are potentially achievable in the general population means that our findings are of relevance to middle aged and older populations worldwide,” the authors write. “These results provide further incentive and support for the notion that small differences in lifestyle can have a substantial potential impact on risk,” they conclude.
DHA supplements reduce inflammation in men with high triglycerides
In the March, 2009 issue of the Journal of Nutrition, researchers from the University of California, Davis and the U.S. Department of Agriculture report that supplementation with docosahexaenoic acid (DHA), one of the omega-3 fatty acids that is abundant in fish, is associated with a reduction in inflammation in men with elevated triglyceride levels, which increase the risk of cardiovascular disease. Inflammation has been shown to predict the risk of heart attack, stroke, and all-cause mortality in apparently healthy men.
The double-blind, randomized trial included 34 men between the ages of 39 and 66. The men were divided to receive 7.5 grams DHA per day or an olive oil placebo for 90 days. Blood samples collected prior to and at the end of the treatment period were analyzed for white blood cells, C-reactive protein (CRP, a marker of inflammation), and inflammatory cytokines.
At the treatment period’s conclusion, white blood cells known as neutrophils, which are increased in inflammation, were reduced by 10.5 percent, C-reactive protein by 15 percent, and the inflammatory cytokine interleukin-6 by 23 percent among those who received DHA. Matrix metalloproteinase-2, an anti-inflammatory enzyme, increased by an average of 21 percent in the DHA group.
“Our finding of a reduction in the concentration of CRP in response to DHA supplementation is comparable to the 15-25% reduction in CRP caused by statins and may have clinical relevance,” the authors write. “DHA supplementation may improve cardiovascular health in several ways. DHA decreases the concentrations of fasting and post-prandial triglycerides, small dense LDL particles, remnant-like chylomicron particles, and inflammatory markers and increases the concentrations of large HDL and LDL particles, anti-inflammatory markers, and the omega-3 index.”
An apple a day . . .
A series of experiments conducted by Cornell University associate professor of food science Rui Hai Liu add evidence to the protective effect of fruits and vegetables against the development of breast cancer.
In a study published in the January 14, 2009 Journal of Agricultural and Food Chemistry, Dr Liu and his associates at Cornell and Harbin Medical University confirmed earlier findings which demonstrated that varying concentrations of fresh apple extract dose-dependently inhibited the size of mammary tumors in rats that received the carcinogen DMBA. "We not only observed that the treated animals had fewer tumors, but the tumors were smaller, less malignant and grew more slowly compared with the tumors in the untreated rats," Dr Liu stated.
While adenocarcinomas were found in 81 percent of DMBA-treated animals that did not receive the extracts, these tumors occurred in only 23 percent of rats that received the highest concentration of apple, which was equivalent in human consumption to six apples a day. "That reflects potent antiproliferative activity," Dr Liu observed.
In another study, reported in the November 12, 2008 issue of the journal, Dr Liu and Xiangjiu He report their discovery of new phenolic compounds in apple peel that have strong antioxidant and antiproliferative effects on tumors. An additional article coauthored by Dr Liu, published in the December 24, 2008 issue, discusses the role of apple extracts in modulating cell cycle machinery, which is suggested as a mechanism of apple’s antiproliferative activities.
"These studies add to the growing evidence that increased consumption of fruits and vegetables, including apples, would provide consumers with more phenolics, which are proving to have important health benefits,” concluded Dr Liu. “I would encourage consumers to eat more and a wide variety of fruits and vegetables daily."
Fish oil protects the liver in obesity
In a study published online on February 11, 2009 in The Journal of the Federation of American Societies for Experimental Biology (FASEB Journal), Spanish researchers report a protective effect on the liver of omega-3 polyunsaturated fatty acids against the damage caused by obesity.
For their research, University of Barcelona professor Joan Claria and colleagues used mice bred to become diabetic and obese, while normal mice served as controls. The animals were divided to receive a diet rich in omega-3 fatty acids or a control diet containing fat from non-omega-3 sources for 5 weeks. Additional groups of mice received injections of the omega-3 fatty acid DHA, the lipid mediator resolvin (derived from omega-3 fatty acids), or a placebo for a 4 day period.
Obese mice that received the control diet had increased body and liver fat, higher serum cholesterol levels, and greater activity of the enzyme ALT, which increases with liver damage, compared to the "wild-type" control animals. Obese mice given the high omega-3 fatty acid diet experienced a reduction in cholesterol, liver fat and inflammation, and improved insulin tolerance due to the formation of resolvins and protectins from the fatty acids. Injection of resolvin was also found to be protective against hepatic steatosis and elevated serum ALT.
"Our study shows for the first time that lipids called protectins and resolvins derived from omega-3 fatty acids can actually reduce the instance of liver complications, such as hepatic steatosis and insulin resistance, in obese people," Dr Claria concluded.
"Doctors are always looking for simple and easy ways to counter the harmful effects of obesity, and the great thing about this study is that the information can be used at dinner tonight," noted FASEB Journal Editor-in-Chief Gerald Weissmann, MD. "It's not unlikely that eating lots more fish or a simple switch to canola oil will make a difference."
Meta-analysis finds efficacy for aspirin in colorectal adenoma prevention
The February 18, 2009 issue of the Journal of the National Cancer Institute published the results of a meta-analysis conducted by researchers at the University of Vermont, The University of Nottingham, and other research centers, which concluded that aspirin is effective for the prevention of colorectal adenomas (polyps), a precursor to colorectal cancer.
For their review, Bernard F. Cole, PhD, of the University of Vermont in Burlington, and his colleagues selected four randomized double-blinded placebo-controlled trials of colorectal adenoma prevention by aspirin that included a total of 2,698 participants who underwent colonoscopies during follow-up. Three of the trials involved individuals with a history of colorectal adenoma, and one included patients who had been treated for colorectal cancer. Aspirin doses ranged from 81 to 325 milligrams per day taken over a median follow-up of 33 months.
Of the subjects included in the meta-analysis, adenomas were detected in 37 percent of those who received a placebo and in 33 percent who received aspirin. Advanced adenomas occurred in 12 percent of those who received a placebo, but in only 9 percent of those in the treatment groups. For any dose of aspirin versus placebo, the pooled relative reduction in the risk of any adenoma was 17 percent, and for advanced lesions, the reduction increased to 28 percent. The greatest benefit for aspirin appeared during the first year of the studies.
"The substantial size of the relative reduction in risk seen in our analysis and seen in clinical trials that evaluated the effect of aspirin on colorectal cancer risk (26% reduction) indicates the potentially important health benefits of aspirin use," the authors write. "Of course, these benefits need to be considered in the context of all of the health effects of aspirin, positive and negative."
Mediterranean diet may help protect against mild cognitive impairment and Alzheimer’s disease
In the February, 2009 issue of the journal Archives of Neurology, Nikolaos Scarmeas, MD, and colleagues at Columbia University report an association between consumption of a Mediterranean diet and a reduced risk of developing mild cognitive impairment, which precedes Alzheimer’s disease in older individuals. A Mediterranean diet is characterized by increased intake of vegetables, fruits, legumes, cereals, fish and unsaturated fatty acids, and low intakes of dairy products, meat and saturated fats.
The study included 482 men and women with mild cognitive impairment and 1,393 who were cognitively normal upon enrollment in the Washington Heights–Inwood Columbia Aging Project. Participants completed dietary questionnaires and were screened for cognitive impairment at regular intervals during an average 4.5 year follow up period.
Two hundred seventy-five of the subjects who did not have mild cognitive impairment at the beginning of the study developed the condition during follow-up. For participants whose adherence to the Mediterranean diet as evaluated in the initial dietary assessment was among the top one-third of subjects, the risk of developing cognitive impairment was 28 percent lower than those whose scores were among the lowest third. For the 482 subjects who had cognitive impairment upon enrollment, those whose adherence to the diet was among the top third had a 48 percent lower risk of developing Alzheimer's disease during a 4.3 average period, and those whose scores were among the middle third experienced a 45 percent lower risk.
Potential protective mechanisms cited for the diet against cognitive impairment are improved cholesterol and glucose levels, better vascular health, and reduced oxidative stress and inflammation. "Exploration of such mechanisms and potential future interventional studies will provide a more complete and convincing picture of the conceivably important role of a healthy diet in the risk of cognitive impairment and Alzheimer's disease," the authors conclude.
Omega-3 fatty acids reduce arterial cholesterol absorption
In an article published online on February 5, 2009 in the journal Arteriosclerosis, Thrombosis, and Vascular Biology, researchers at Columbia University Medical Center report that supplementing the diet of mice with fish oil decreases the absorption of cholesterol in their arteries.
Institute of Human Nutrition Director Richard J. Deckelbaum, MD, and his colleagues at Columbia fed mice regular chow consisting of 4.5 percent fat, or diets that provided 42 percent of their calories in the form of saturated fat (resembling a Western diet) or fish oil for twelve weeks. At the end of the treatment period, the animals were injected with labeled human low density lipoprotein (LDL)cholesterol, and its uptake in the aorta (the main artery leaving the heart) was traced.
Mice that received the high saturated fat diet experienced greater weight gain than the other two groups of mice, and had higher plasma free fatty acid and triglyceride levels. In contrast, mice that received fish oil had 40 percent lower plasma free fatty acids and 70 percent lower triglyceride levels than animals that received the standard diet. While the high fat group had greater arterial uptake of LDL cholesterol than the control mice, those that received fish oil had significantly less entry of LDL cholesterol into their aortas. The researchers determined that the omega-3 fatty acids that are abundant in fish oil decrease lipoprotein lipase, a molecule that traps low density lipoprotein in the wall of the artery. "We hypothesize that the effect of omega-3 fatty acids in decreasing arterial wall cholesterol delivery is one important mechanism by which these bioactive omega-3 fatty acids may decrease the risk of cardiovascular disease," the authors conclude.
Dr. Deckelbaum suggests that people increase their omega-3 fatty acid intake by consuming more fish or by using supplements containing the fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
Vitamin D deficiency in mothers may increase children's risk of developing MS
An article published on February 6, 2009 in the journal PLoS (Public Library of Science) Genetics reports that women who have insufficient levels of vitamin D during their pregnancy may negatively impact a genetic variant in their offspring that increases the risk of multiple sclerosis (MS). A link between reduced levels of vitamin D and multiple sclerosis has been proposed due to the greater number of persons afflicted with the disease who reside in higher latitudes and receive less exposure to sunlight, yet the potential mechanism of vitamin D in protecting against the disease has not been defined.
Julian C. Knight and his colleagues at the University of Oxford in England and the University of British Columbia found that proteins in the body activated by vitamin D bind to a DNA sequence next to the DRB1*1501 variant on chromosome 6. DRB1*1501 is a variant which increases the risk of MS to 1 in 300 in those who carry a single copy and 1 in 100 in those carrying 2 copies, in contrast to a risk of 1 in 1000 in the rest of the population. The team believes that a mother's vitamin D deficiency could alter the expression of DRB1*1501 in their children. "In people with the DRB1 variant associated with MS, it seems that vitamin D may play a critical role," Dr Knight stated. "If too little of the vitamin is available, the gene may not function properly."
"Our study implies that taking vitamin D supplements during pregnancy and the early years may reduce the risk of a child developing MS in later life," lead author Dr Sreeram Ramagopalan noted. "Vitamin D is a safe and relatively cheap supplement with substantial potential health benefits. There is accumulating evidence that it can reduce the risk of developing cancer and offer protection from other autoimmune diseases."
Higher vitamin D levels predict greater strength in girls
An article published online on November 25, 2008 in the Journal of Clinical Endocrinology & Metabolism reported the discovery of Kate Ward, PhD, of the University of Manchester in England and her associates of a link between higher levels of vitamin D and greater strength in adolescent girls.
The study included 99 girls between the ages of 12 and 14 who attended school in Manchester. Prior screening had found low levels of vitamin D, defined as less than 37.5 nanomoles per liter, in over 70 percent of the schoolgirls, however, none of the girls had symptoms of deficiency. Muscle power and force were evaluated through the use of jumping mechanography, which measures performance in a series of jumping activities.
The research team observed that girls who were low in vitamin D performed worse on the jumping tests compared with girls whose levels of the vitamin were higher. Serum 25-hydroxyvitamin D levels were positively correlated with jump velocity, jump height, muscle power, fitness, and force. Higher parathyroid hormone levels were associated with decreased jump velocity.
"We know vitamin D deficiency can weaken the muscular and skeletal systems, but until now, little was known about the relationship of vitamin D with muscle power and force," stated Dr Ward, of the University of Manchester's Department of Imaging Science and Biomedical Engineering. "Our study found that vitamin D is positively related to muscle power, force, velocity and jump height in adolescent girls."
"Vitamin D affects the various ways muscles work and we've seen from this study that there may be no visible symptoms of vitamin D deficiency, she noted. "Further studies are needed to address this problem and determine the necessary levels of vitamin D for a healthy muscle system."
More potassium needed to lower blood pressure
An article published in the January 12, 2009 issue of the American Medical Association journal Archives of Internal Medicine reports that, in addition to lowering sodium intake, individuals who need to reduce their blood pressure should focus on increasing potassium, a mineral found in fruits, vegetables, dairy products and nutritional supplements.
For the current study, epidemiologist Dr Paul Whelton and colleagues utilized data from Trials of Hypertension Prevention (TOHP) I and II which included 2,974 adults with prehypertension aged 30 to 54 years upon enrollment. Twenty-four hour urine samples collected intermittently over the trials' respective 18 and 36 month courses were analyzed for sodium and potassium excretion levels. Follow-up data collected over a 10 to 15 year period tracked the development of cardiovascular disease and cardiovascular mortality.
Of 2,275 participants for whom follow-up data was available, 193 cardiovascular events occurred. While subjects whose urine sodium levels were among the top 25 percent of participants experienced an insignificant increase in cardiovascular event risk, those with the greatest sodium to potassium ratio had a 50 percent greater risk of cardiovascular disease compared to those whose ratios were in the lowest quarter.
"There isn't as much focus on potassium, but potassium seems to be effective in lowering blood pressure and the combination of a higher intake of potassium and lower consumption of sodium seems to be more effective than either on its own in reducing the risk of cardiovascular disease," stated Dr Whelton, who is one of the nation's experts on hypertension. Commenting on the fact that the study utilized urinary levels of sodium and potassium rather than estimating their intake levels from dietary questionnaire responses, he noted that the current investigation "is a quantum leap in the quality of the data compared to what we have had before."