Fish, tuna, fresh, skipjack, raw
Tuna fish are truly a nutrient-dense food. An excellent source ofhigh quality protein, tuna are rich in a variety of important nutrientsincluding the minerals selenium, magnesium, and potassium; the Bvitamins niacin, B1 and B6; and perhaps most important, the beneficialomega-3 essential fatty acids. Essential fatty acids are so namedbecause they are essential for our health but cannot be made by thebody; they must therefore be obtained from foods. Cold-water fish liketuna are a rich source of the omega-3 essential fats, a form ofessential fatty acids in which the standard American diet is sorelydeficient. (The other form of essential fatty acids, the omega-6s, areplentiful in a variety of commonly consumed oils such as corn andsafflower oil. In fact, the omega-6s are so plentiful in the typicalAmerican diet that too much omega-6 is consumed in proportion toomega-3s--an imbalance that promotes inflammation, thus contributing tovirtually every chronic disease in which inflammation is a keycomponent.)
Omega-3 fatty acids provide a broad array of cardiovascularbenefits. Omega-3s benefit the cardiovascular system by helping toprevent erratic heart rhythms, making blood less likely to clot insidearteries (which is the ultimate cause of most heart attacks), andimproving the ratio of good (HDL) cholesterol to potentially harmful(LDL) cholesterol. And, as mentioned above, omega-3s reduceinflammation, which is a key component in the processes that turncholesterol into artery-clogging plaques. In a recent population-basedprospective study, modest consumption of tuna was actually found to beassociated with lower risk of death from ischemic heart disease inindividuals 65 years and older.
Tuna is also a very good source of vitamin B6, which, along with folic acid,lowers levels of homocysteine. Homocysteine, an intermediate compoundproduced during the methylation cycle, is directly damaging to arterywalls, and elevated blood levels of homocysteine are considered animportant risk factor for atherosclerosis.
Increases Heart Rate Variability-A Measure of Heart Muscle Function
Yet another way in which consuming fish rich in omega-3 fats, suchas tuna, promotes cardiovascular health is by increasing heart ratevariability (HRV), a measure of cardiac function, in as little as threeweeks, according to a study published in the April 2005 issue of Chest.
By providing greater variability between beats, the marine omega3 fatty acids, EPA and DHA, reduce the risk of arrhythmia and/or suddendeath.
Researchers from Atlanta, GA, Boston, MA, and Cuernavaca,Mexico, took the HRV of 58 elderly patients every other day for twomonths to establish an HRV baseline for each participant. For the next11 weeks, half of the study participants took a daily 2 gram supplementof fish oil and the other half took a daily 2 gram supplement of soyoil.
Patients in both groups experienced a significant increase inHRV, with those who took fish oil achieving a greater increase in ashorter time period. Patients who received fish oil experiencedincreased HRV within the first 2.7 weeks, whereas it took 8.1 weeks fora significant increase in HRV to be seen in the group taking soy oil.
On the other hand, while none of the study participantsexperienced significant negative side effects, 41% of participants inthe fish oil group reported belching, compared to 16% in the soy oilgroup.
"Our findings contradict the current belief in the medicalcommunity that increasing the intake of omega-3 fatty acids producesonly long-term cardiac benefits," said the study's lead author,Fernando Holguin, MD, Emory University School of Medicine, Atlanta, GA."In fact, our study group showed improvements in heart function in aslittle as two weeks.""Studies like this demonstrate that there are additional approaches wecan take to protect ourselves from heart attacks," said Paul A. Kvale,MD, FCCP, President of the American College of Chest Physicians. "It'sexciting to see the potential for omega-3 fatty acids in improvingheart function when it complements a healthy lifestyle of exercising,maintaining a healthy weight, and getting eight hours of sleep." We'dadd eating healthful foods to this proactive list. Rather than pop adaily pill, we'd rather enjoy a daily "dose" of delicious tuna, salmon or soyfoods. For recipes certain to not only increase your heart rate variability but also your delight in eating, click Recipes.
Just Two Servings of Omega-3-rich Fish a Week Can Lower Triglycerides
Triglycerides are a form in which fat is carried in yourbloodstream. In normal amounts, triglycerides are important for goodhealth because they serve as a major source of energy. High levels oftriglycerides, however, are associated with high total cholesterol,high LDL (bad) cholesterol and low HDL (good) cholesterol), andtherefore, with an increased risk of cardiovascular disease.In addition, high triglycerides are often found along with a group ofother disease risk factors that has been labeled metabolic syndrome,a condition known to increase risk of not only heart disease, butdiabetes and stroke. (Metabolic syndrome is the combined presence ofhigh triglycerides, increased blood pressure, high blood sugar, excessweight, and low HDL (good) cholesterol.)
|Less than 150 mg/dL||Normal|
|500 mg/dL||Very High|
*Note: Triglycerides are most accurately measured after an 8-12 hour fast.
In this 6-month study involving 142 overweight men and womenwith high triglycerides, subjects were divided into 5 groups, one ofwhich served as a control group, 2 of which ate 2 servings of fish highin omega-3s while also replacing their normal household fats with fathigh in sunflower (Group 1) or canola oil made from rapeseed (Group 2),and 2 of which ate 2 weekly servings of white fish while also replacingtheir normal household fats with ones high in sunflower (Group 3) orcanola oil made from rapeseed (Group 4).
Canola oil also provides some omega-3 fats, with anomega-6:omega-3 ratio of 2:1, while sunflower oil contains omega-6, butno omega-3 fats.
At the end of the study, triglyceride levels had dropped 6.6%in the omega-3-rich fish groups combined. Triglycerides droppedmost-10.4%-in those consuming omega-3-rich fish and canola oil. Inthose eating omega-3-rich fish and sunflower oil, triglycerides dropped2.8%.Bottomline: A healthy way of eating that incorporates at least 2 weeklyservings of fish and other food sources of omega-3 fats, such asflaxseed or canola oil, may significantly lower triglyceride levels.Replacing normal household fats with flaxseed oil, in which the ratioof omega-6:omega:3 fats is 1:4, might result in an even larger drop intriglyceride levels.
Stroke PreventionA recent study showed that eating fish lowers the risk of certain typesof strokes. The study, which involved almost 80,000 nurses during a15-year period revealed that those women who ate fish 2 to 4 times perweek had a 27% reduced risk of stroke compared to women who ate fishone a month. Eating fish five or more times per week reduced the riskof certain strokes 52%.
A meta-analysis of eight studies published in the July 2004 issue of Strokeprovides further support that eating fish is protective against strokein men as well as women. Eating fish, such as tuna, as little as 1 to 3times per month may protect against ischemic stroke (a stroke caused bylack of blood supply to the brain, for example, as a result of a bloodclot), suggests
Data on nine independent groups participating in eightdifferent studies found that, compared to those who never consumed fishor ate fish less than once per month, risk of ischemic stroke dropped:
- 9% in those eating fish 1 to 3 times per month
- 13% in those eating fish once per week
- 18% in those eating fish 2 to 4 times per week
- 31% in those eating fish 5 or more times each week
Protection Against Atrial Fibrillation (Heart Arrhythmia)Eatingtuna that's broiled or baked, but not fried, may reduce risk of atrialfibrillation, the most common type of heart arrhythmia, especially inthe elderly, according to a Harvard study published in the July 2004issue of Circulation.In the 12-year study of 4,815 people 65 years of age or older, eatingcanned tuna or other broiled or baked fish 1 to 4 times a weekcorrelated with increased blood levels of omega-3 fatty acids and a 28%lower risk of atrial fibrillation. Eating broiled or baked fish 5 timesa week lowered risk even more- a drop in atrial fibrillation risk of31%.
Eating fried fish, however, provided no similar protection. Not only isfried fish typically made from lean fish like cod and Pollack thatprovide fewer omega-3 fatty acids, but in addition, frying results inthe production of damaged, free-radical-laden fats in the fish as wellas the frying oil.
In further research to determine if the omega-3 fats found in fishoil were responsible for fish's beneficial effects on the heart'selectrical circuitry, Dariush Mozaffarian and colleagues from HarvardMedical School analyzed data on fish intake and electrocardiogramresults from 5096 adults, aged 65 or older, who were enrolled in theCardiovascular Health Study from 1989-1990.
Eating tuna or other broiled or baked fish at least once a weekwas associated with lower heart rate (-3.2 beats/minute) and a 50%lower likelihood of prolonged ventricular repolarisation (the period oftime it takes the heart to recharge after it beats, so it can beatagain), compared to those consuming fish less than once a month.
Consuming 1 gram/day of omega-3 fatty acids from fish wasassociated with 2.3 beats/minutes lower heart rate and a 46% lower riskof prolonged ventricular repolarisation.Eating fish at least 5 times per week was associated with an evenhealthier heart rhythm. However, eating fried fish (typically sold inthe U.S. as fish burgers or fish sticks) was not associated withincreased blood levels of omega 3 fats or any beneficialelectrocardiogram results. In fact, a previous study led by the sameresearcher (Mozaffarian, Am J Cardiol 2006 Jan) found that while eatingbaked or broiled fish was linked to a slower but more powerful heartbeat and lower blood pressure, eating fried fish was associated withheart muscle motion abnormalities, a reduced ejection fraction, lowercardiac output, and higher blood pressure. Since irregular heart beatsare a major precipitating factor in sudden death due to cardiac arrest,promoting a healthy heart rhythm by eating baked or broiled-notfried-fish several times a week makes very good sense. Happily, as ourrecipes, such as 15 Minute Asian Tuna show, it's a quick, easy and most importantly, delicious prescription.
Eating Fish Daily Provides Substantially More Protection against Heart Attack
While as little as a weekly serving of fish lowers risk of ischemicstroke, enjoying a daily serving omega-3-rich fish, such as tuna,provides significantly greater reduction in the risk of coronary heartdisease than eating fish even as frequently as a couple of times aweek, show the findings of a study published in the January 17, 2006issue of Circulation, the journal of the American Heart Association.
Researchers in Japan followed 41,578 men and women aged 40 to59, none of whom had cardiovascular disease or cancer when the studybegan, from 1990-1992 to 2001. Food frequency questionnaires completedat the beginning of the study and in 1995, provided information onweekly fish intake, which was analyzed for omega-3 content.
When individuals whose fish consumption was in the topone-fifth of participants at 8 times per week were compared to thosewhose intake was in the lowest fifth at once per week, they were foundto have a 37% lower risk of developing coronary heart disease and a 56%percent lower risk of heart attack.
When the effect of omega-3 fatty acid intake on cardiovascularrisk was analyzed, coronary heart disease risk was lowered by 42% amongthose whose intake was the highest at 2.1 grams per day or morecompared to those whose intake was the lowest at 300 milligrams perday. Those whose intake of omega 3s was in the top fifth received a 65%reduction in the risk of heart attack compared to those whose omega 3intake was lowest.
The authors theorize that daily fish consumption is highlyprotective largely due to the resulting daily supply of omega-3 fattyacids, which not only reduce platelet aggregation, but also decreasethe production of pro-inflammatory compounds called leukotrienes.Lowering leukotrienes reduces damage to the endothelium (the lining ofthe blood vessels), a key factor in the development of atherosclerosis."Our results suggest that a high fish intake may add a furtherbeneficial effect for the prevention of coronary heart disease amongmiddle-aged persons," note the study's authors.
Fish, Fruit and Vegetables Protective against Deep Vein Thrombosis, Pulmonary Embolism
Deep vein thrombosis is a dangerous condition in which blood clotsdevelop in the deep veins of the legs, thighs or pelvis, causingswelling and pain. An embolism is created if a part or all of the bloodclot in the deep vein breaks off from the site where it was created andmoves through the venous system. If the clot lodges in the lung, a veryserious condition, pulmonary embolism, arises.
Fortunately, a healthy way of eating offers significantprotection, as demonstrated by a prospective study over 12 years thatinvolved almost 15,000 middle-aged adults. While those eating the mostred and processed meat doubled their risk of deep vein thrombosis(DVT), those in the upper 3 quintiles of fruit and vegetable intake hada 41-53% lower risk of DVT. And those eating fish, such as tuna, atleast once each week were found to have a 30-45% lower DVT risk.(Steffen LM, Folsom AR, et al.,Circulation)Practical Tip: For protection against deep vein thrombosis, increaseyour consumption of fruit and vegetables; eat fish at least once aweek; and decrease consumption of red and processed meats.
Special Cardiovascular Protection for Postmenopausal Women with Diabetes
Eating omega-3 rich fish, such as tuna, at least twice each weeksignificantly reduces the progression of atherosclerosis inpostmenopausal women with diabetes, suggests a Tufts University studypublished in the September 2004 issue of the American Journal ofClinical Nutrition.
The three year study included 229 women with atherosclerosis,42% of whom also had diabetes. Although new atherosclerotic lesionswere seen in all the women, regardless of fish intake, those whoconsumed 2 or more servings of fish per week had significantly fewerlesions-especially if at least one serving was chosen from those highin omega-3 fatty acids, such as tuna, salmon, mackerel or sardines.
Women with diabetes eating less than 2 servings of fishexperienced an average 4.54% increase in stenosis (thickening andrestriction) in their arteries, compared to an average increase of only0.06% in women eating 2 servings of any fish per week.
In diabetic women eating less than 1 serving of omega-3-richfish per week, stenosis increased 5.12% compared to a 0.35% increase inthose who ate 1 or more servings of omega-3-rich fish each week.
Eating fish rich in omega-3s is so beneficial because these fats:
- lower the amount of lipids (fats such as cholesterol and triglycerides) circulating in the bloodstream
- decrease platelet aggregation, preventing excessive blood clotting
- inhibit thickening of the arteries by decreasing endothelialcells' production of a platelet-derived growth factor (the lining ofthe arteries is composed of endothelial cells)
- increase the activity of another chemical derived fromendothelial cells (endothelium-derived nitric oxide), which causesarteries to relax and dilate
- reduce the production of messenger chemicals calledcytokines, which are involved in the inflammatory response associatedwith atherosclerosis
Omega 3s Help Prevent Obesity and Improve Insulin ResponseSalmonis particularly beneficial not just for women with type 2 diabetes, butfor men with this condition as well, due to its high content of omega 3fats.
Research presented December 2004 at the 6th Congress of theInternational Society for the Study of Fatty Acids and Lipids suggeststhat while saturated fats appear to promote weight gain, the omega 3fats found in cold water fish, such as tuna, reduce the risk ofbecoming obese and improve the body's ability to respond to insulin.
The reason why? The omega 3 fatty acid, eicosapentaenoic acid (EPA)stimulates the secretion of leptin, a hormone that helps regulate foodintake, body weight and metabolism, and is expressed primarily byadipocytes (fat cells).
EPA, an Omega-3 Fat found in Tuna, Reduces Inflammation
A recently identified lipid (fat) product our bodies make from EPA,called resolvins, helps explain how fish oils' provide theiranti-inflammatory effects on our joints and improve blood flow.
Resolvins, which have been shown to reduce inflammation inanimal studies, are made from EPA by our cellular enzymes, and work byinhibiting the production and regulating the migration of inflammatorycells and chemicals to sites of inflammation.Unlike anti-inflammatory drugs, such as aspirin, ibuprofen and theCOX-2 inhibitors, the resolvins our bodies produce from EPA do not havenegative side effects on our gastrointestinal or cardiovascular systems.
Fish and Whole Grains Highly Protective against Childhood Asthma
According to the American Lung Association, almost 20 millionAmericans suffer from asthma, which is reported to be responsible forover 14 million lost school days in children, and an annual economiccost of more than $16.1 billion.
Increasing consumption of whole grains and fish could reducethe risk of childhood asthma by about 50%, suggests the InternationalStudy on Allergy and Asthma in Childhood (Tabak C, Wijga AH, Thorax).
The researchers, from the Dutch National Institute of PublicHealth and the Environment, Utrecht University, University MedicalCenter Groningen, used food frequency questionnaires completed by theparents of 598 Dutch children aged 8-13 years. They assessed thechildren's consumption of a range of foods including fish, fruits,vegetables, dairy and whole grain products. Data on asthma and wheezingwere also assessed using medical tests as well as questionnaires.
While no association between asthma and intake of fruits,vegetables, and dairy products was found (a result at odds with otherstudies that have supported a link between antioxidant intake,particularly vitamins C and E, and asthma), the children's intake ofboth whole grains and fish was significantly linked to incidence ofwheezing and current asthma.
In children with a low intake of fish and whole grains, theprevalence of wheezing was almost 20%, but was only 4.2% in childrenwith a high intake of both foods. Low intake of fish and whole grainsalso correlated with a much higher incidence of current asthma (16.7%).compared to only a 2.8% incidence of current asthma among children witha high intake of both foods.
After adjusting results for possible confounding factors, suchas the educational level of the mother, and total energy intake, highintakes of whole grains and fish were found to be associated with a 54and 66% reduction in the probability of being asthmatic, respectively.
The probability of having asthma with bronchialhyperresponsiveness (BHR), defined as having an increased sensitivityto factors that cause narrowing of the airways, was reduced by 72 and88% when children had a high-intake of whole grains and fish,respectively.Lead researcher, CoraTabak commented, "The rise in the prevalence ofasthma in western societies may be related to changed dietary habits."We agree. The Standard American Diet is sorely deficient in thenumerous anti-inflammatory compounds found in fish and whole grains,notably, the omega-3 fats supplied by cold water fish and the magnesiumand vitamin E provided by whole grains. One caution: wheat may need tobe avoided as it is a common food allergen associated with asthma.
Protection against Sunburn
Another benefit of omega-3s anti-inflammatory effects may be theirability to protect our skin against sunburn, and possibly, skin cancer.
Although our increased susceptibility to skin cancer is usuallyblamed on damage to the ozone layer, dietary changes over the last 75years, which have resulted in excessive consumption of omega-6 fattyacids and insufficient consumption of omega-3 fats, may also be causinghuman skin to be more vulnerable to damage from sunlight.
Research by Dr Lesley Rhodes, Director of the Photobiology Unitat the University of Manchester, UK, suggests that eating moreomega-3-rich fish, such as tuna, could lessen the inflammation inducedby UV-B radiation and help prevent not only the damaging effects ofsunburn, but possibly skin cancer as well.
In a paper published in January 2005 in the Journal of Investigative Dermatology,Rhodes explored the ability of omega-3s to protect epidermal and dermalskin cells against UV-B-induced triggering of tumor necrosisfactor-alpha, a molecule that induces the production of thepro-inflammatory cytokine, IL-8. Both EPA and DHA significantlysuppressed TNF-?-induced IL-8 secretion-by 54% in the case of EPA and42% by DHA.In an earlier one of Dr Rhodes studies, published in the May 2003 issueof Carcinogenesis,42 healthy volunteers were given a measured dose of ultraviolet light,then divided into two groups. One group was given a daily 4 gramomega-3 fish oil supplement, while the other group received olive oil.After three months, when their responses to ultraviolet light wereagain measured, the skin cells of volunteers receiving fish oilexperienced significantly less DNA damage, leading Rhodes to suggestthat increasing consumption of omega-3-rich fish might reduce skincancer in humans.
Grumpy Teenagers? Tuna May Help Reduce Hostility and Protect Hearts
Feeling really grumpy? Eating more cold water fish such as salmon,tuna, or sardines may help. A study published in the January 2004 issueof the European Journal of Clinical Nutrition found astatistically significant relationship between consuming fish rich inomega-3 fats and a lower hostility score in 3581 young urban white andblack adults. Those with the highest intake of omega 3 fats had only a10% likelihood of being among those with the highest hostility scores.Eating any fish rich in omega 3 fats compared to eating no omega-3-richfish was also found to drop subjects' chances of being hostile by 12%.One reason this finding is important: hostility has been shown topredict the development of heart disease, and the young adults in thisstudy were already also enrolled in the CARDIA (Coronary Artery RiskDevelopment in Young Adults) study-a study that is examining how heartdisease develops in adults.
In addition to tuna's omega-3s, the seleniumit contains is a necessary component in one of the body's mostimportant antioxidants--glutathione peroxidase--which is critical for ahealthy liver, the organ responsible for detoxifying and clearingpotentially harmful compounds such as pesticides, drugs, and heavymetals from the body. Selenium also helps prevent cancer and heartdisease.
Eating even small amounts of fish may protect against ovarian anddigestive tract cancers. A total of 10,149 cancer patients with 19different types of cancer and 7,990 controls were included in a recentstudy conducted in Spanish hospitals. The researchers determined thateating more fish correlates with a reduced risk of certain cancers.Fish eaters had less cancer in the ovaries, pancreas, and all parts ofthe digestive tract including the mouth, pharynx, esophagus, stomach,colon and rectum.Eating fish rich in omega-3 fatty acids, suchas tuna, may also help protect against breast cancer, suggest animaland lab culture studies published in the November 2005 issue of the International Journal of Cancer.
In the animal experiments, mice were fed diets rich in eitheromega-3 (fish oil) or omega-6 (corn oil) fatty acids after which breastcancer cells were implanted. Three weeks later, tumor volume and weightwas significantly lower in mice on the omega-3 rich diet.In the lab culture experiments, when cells were treated with DHA orEPA, sphingomyelinase activity increased by 30-40%, and breast cancercell growth dropped 20-25%.
Why? Dietary fatty acids are incorporated into cell membranes, and thetype of fatty acids dictates how a cell responds and grows. Researchersfound that omega-3 fatty acids affect cell growth by activating anenzyme called sphingomyelinase, which then generates the release ofceramide, a compound that induces the expression of the human tumorsuppressor gene p21, which ultimately causes cancer cell death.
Lower Your Risk of Leukemia, Multiple Myeloma, and Non-Hodgkins Lymphoma
Fishermen have, in epidemiological studies, been identified ashaving a lower risk of leukemia, multiple myeloma and non-Hodgkinlymphoma, an occupational benefit that researchers thought might be dueto the fact that they eat more fish.Now, a Canadian study published in the April 2004 issue of Cancer Epidemiology Biomarkers & Preventionsuggests that persons whose diet includes more weekly servings of freshfatty fish have a much lower risk of these three types of cancer. Datadrawn from a survey of the fish eating habits of 6,800 Canadiansindicates that those consuming the most fatty fish decreased their riskof leukemia by 28%, their risk of multiple myeloma by 36%, and theirrisk of non-Hodgkin lymphoma by 29%. Overall, frequent eaters of fattyfish reduced their risk for all forms of lymphomas by 30%.
Some of the cancer protective effects of fish, such as tuna, maycome from its being a great source of omega 3 fatty acids, which havethemselves shown impressive anticancer effects, especially important inprotection against breast cancer. Recent in vitro (test tube) evidencesuggests that this beneficial effect is related to the fact that whenomega-3s are consumed in the diet, they are incorporated into cellmembranes where they promote cancer cell apoptosis via severalmechanisms including: inhibiting a pro-inflammatory enzyme calledcyclooxygenase 2 (COX 2), which promotes breast cancer; activating atype of receptor in cell membranes called peroxisomeproliferator-activated receptor (PPAR)-ã, which can shut downproliferative activity in a variety of cells including breast cells;and, increasing the expression of BRCA1 and BRCA2, tumor suppressorgenes that, when functioning normally, help repair damage to DNA, thushelping to prevent cancer development.
Tuna and Other Fatty Fish Highly Protective against Kidney Cancer
Consumption of fatty fish, such as tuna, offers significantprotection against renal cell carcinoma, the most common form of kidneycancer, suggests evidence presented in a 15.3-year epidemiologicalstudy involving 61,433 women who participated in the SwedishMammography Cohort Study (Wolk A, Larsson SC, JAMA).
Renal cell carcinoma (RCC), the 10th most common form of cancerwith a male:female ratio of 5:3, accounts for more than 80% per cent ofall kidney cancers. Although an earlier review of prospective cohortstudies (MacLean et al, JAMA) did not support the hypothesis that fish consumption is protective, the authors of the new JAMAstudy point out that virtually all the other studies on the subject,including MacLean's, did not take into account whether the fishconsumed were fatty or lean fish.(Fatty fish contain 20 to 30 timesmore omega-3 (DHA and EPA) than lean fish, which provide 3-5 times morevitamin D.)
When this distinction was considered, the researchers foundthat those who consumed one or more serving of fatty fish each week hada 44% decreased risk of RCC compared with those who consumed no fattyfish.
Plus, those who reported long-term consumption between thebeginning of the study and the 10-year follow-up had a dramatic 74%lower risk.
In contrast, no association was found between consumption oflean fish or other seafood and incidence of RCC.Wolk notes,"Our results support the hypothesis that frequentconsumption of fatty fish may lower the risk of RCC, possibly due toincreased intake of fish oil rich in EPA and DHA, as well as vitamin D."
Reduce Risk of Macular Degeneration
A diet high in omega-3 essential fatty acids, especially from fishsuch as tuna, offers significant protection against both early and lateage-related macular degeneration (AMD), show two studies published inthe July 2006 issue of the Archives of Opthalmology.
In age-related macular degeneration, the area at the back of theretina called the macula, which controls fine vision, deteriorates,resulting in central vision loss and even blindness. AMD is the leadingcause of blindness in people over 50, affecting more than 30 millionpeople worldwide.
In the first study, Brian Chua and colleagues in Sydney,Australia, utilized data from the Blue Mountains Eye Study, whichenrolled 3,654 men and women aged 49 and older between 1992 and 1994.Dietary questionnaires completed by 2,895 participants at the beginningof the study provided information on fatty acid intake.
Participants among the top one-fifth in terms of omega-3-richfish consumption had a 42% lower risk of early AMD compared to thosewhose fish intake placed them in the lowest fifth. Enjoyingomega-3-rich fish at least once a week provided a a 42% reduction inrisk for early AMD.
Eating omega-3-rich fish at least three times a week was associated with a 75% reduction in late AMD.
In the second study, Johanna M. Seddon and colleagues at theMassachusetts Eye and Ear Infirmary, Harvard Medical School, Boston,looked at modifiable and protective factors for AMD among elderly maletwins enrolled in the National Academy of Sciences-National ResearchCouncil World War II Veteran Twin Registry. Of the 681 twins examined,222 were found to have intermediate or late stage AMD, and 459 twinshad no signs of AMD.
Current smokers had a 1.9-fold (almost double) increased riskof AMD. Even past smokers' risk was highly elevated-a 1.7 increasecompared to men who never smoked.
Eating more fish, however, greatly reduced AMD risk. Among themen whose fish consumption put them among the top 25% of dietaryomega-3 fatty acid intake, risk of AMD was 45% lower compared to thosewith the lowest fish / omega-3 intake.
Eating fish at least twice a week reduced AMD risk by 36%compared to those who ate less than one serving of fish per week.The authors noted that AMD is highly preventable simply by following ahealthy lifestyle: "About a third of the risk of AMD in this twin studycohort could be attributable to cigarette smoking, and about a fifth ofthe cases were estimated as preventable with higher fish and omega-3fatty acid dietary intake."
Fend Off Dry Eyes
Dry eye syndrome (DES) afflicts more than 10 million Americans.Artificial tears offer only temporary relief. Expensive prescriptiondrugs promise help, but at the cost of potentially serious sideeffects.
Could Mother Nature provide a cure? Yes, suggests research published in the October 2005 issue of the American Journal of Clinical Nutrition involving nearly 40,000 female health professionals aged 45-84 enrolled in the Women's Health Study.
Researcher Biljana Miljanovic, MD, MPH, and colleagues atBrigham and Women's Hospital looked at whether essential fattyacids-the omega-3 fats (found in high amounts in cold water fish andflaxseeds), and the omega-6 fats (found in red meat, safflower,sunflower, soy and corn oils)-play a role.
They do. Women whose diets provided the highest amounts ofomega-3 fatty acids had a 17% lower risk of dry eye syndrome comparedwith those consuming the least of these beneficial fats.
In contrast, a diet high in omega-6 fats, but low in omega-3s,significantly increased DES risk. Women whose diets supplied a highratio of omega-6 to omega-3 fatty acids had a 2.5-fold higher risk ofDES syndrome compared to those with a more balanced intake of fattyacids.
Researchers specifically looked at eating tuna fish- a main source of omega-3 fatty acids in the American diet.
Compared with women eating less than one 4-ounce serving of tuna a week:
- Women who ate 2 to 4 servings of tuna per week had a 19% lower risk of DES.
- Women eating 5 to 6 servings of tuna per week had a 68% lower risk of DES.
"These findings suggest that increasing dietary intake of omega-3fatty acids may reduce the risk of dry eye syndrome, an important andprevalent cause of ocular complaints," Miljanovic and colleaguesconclude.In addition to tuna fish, omega-3 fatty acids are richly supplied byother fatty fish (such as salmon, mackerel, halibut, sardines, andherring), flaxseeds and flaxseed oil. Due to concerns about mercurylevels in tuna, to lower your risk of DES we recommend enjoying avariety of cold-water fish and adding flaxseeds and flaxseed oil toyour Healthiest Way of Eating.
Protect against Alzheimer's and Age-related Cognitive Decline
Research published in the August 2004 issue of the Journal ofNeurology, Neurosurgery and Psychiatry indicates regular consumption ofniacin-rich foods like yellowfin tuna provides protection againstAlzheimer's disease and age-related cognitive decline.
Researchers from the Chicago Health and Aging Projectinterviewed 3,718 Chicago residents aged 65 or older about their diet,then tested their cognitive abilities over the following six years.Those getting the most niacin from foods (22 mg per day) were 70% lesslikely to have developed Alzheimer's disease than those consuming theleast (about 13 mg daily), and their rate of age-related cognitivedecline was significantly less.
The significant amounts of the omega-3 fatty acid, DHA(docosahexaenoic acid) found in cold-water fish, such as tuna, may alsotranslate into protection against Alzheimer's disease. In a paperpublished in the September 2004 issue of the journal Neuron,researchers at the University of California, Los Angeles School ofMedicine reported that a diet rich in DHA reduced the impact of a genelinked to the development of Alzheimer's disease.Using mice bred to have genetic mutations that cause lesions typical ofAlzheimer's, the researchers found that those fed a diet containingomega-3-rich fish did not develop the expected memory loss or braindamage. In contrast, mice fed safflower oil, which is low in theomega-3 fats and high in the omega-6 fatty acids, showed signs ofsynaptic damage in their brains that closely resemble those of peoplewith Alzheimer's.