You already know that eating fish is healthy for your heart, but new research suggests it may also be good for your head. In a study presented at a meeting of the Radiological Society of North America, older adults who ate fish at least once a week-baked or broiled, not fried-had a greater volume of gray matter in the brain in areas important in Alzheimers disease. Fish consumption was also associated with sharply lower rates of developing mild cognitive impairment or dementia.
The findings add to the mounting array of evidence that eating more fish is one of the healthiest changes you can make to your diet. The 2010 Dietary Guidelines for Americans recognized the health benefits of fish consumption by recommending eating two servings per week, about eight ounces total. Fish deliver lean protein and are a good source of omega-3 fatty acids. Boosting your fish consumption also means that many fewer servings of red meat and other entre options higher in calories and saturated fat.
The advantages of eating fish are many, says Alice H. Lichtenstein, DSc, director of Tufts HNRCA Cardiovascular Nutrition Laboratory. Fish offers heart-healthy omega-3 fatty acids and is low in calories and saturated fat.
But too few Americans are taking advantage of the health benefits of putting fish on their plates. Says Lichtenstein, Unfortunately, fish consumption in the United States, especially if you exclude breaded deep-fried fish, is extremely low. On average, Americans barely eat 16 pounds of seafood a year (including fish sticks). Compare that to Iceland, with the worlds highest per capita seafood consumption at a whopping 220 pounds a year. Iceland also has a higher average life expectancy, almost 81 years, than the US 78 years.
Feeding Your Head
Maybe those striking new findings about fish consumption and the brain will inspire more Americans to visit the seafood counter. Cyrus Raji, MD, PhD, of the University of Pittsburgh, and colleagues focused on 260 people, average age 71, who enrolled in the Cardiovascular Health Study. According to initial dietary questionnaires, 163 of those participants ate fish at least once a week. Fish consumption was also assessed about five years later, and showed little change. After 10 years, participants underwent an MRI scan to measure their brain volume; another five years later, they had followup cognitive testing.
The MRI scans revealed that people eating broiled or baked fish, but not fried, on a weekly basis had greater volumes of gray matter in the brains frontal and temporal lobes, including the hippocampus. These areas, Dr. Raji noted, are responsible for memory and learning, which are severely affected in Alzheimers disease.
In subsequent cognitive testing, only 3.2% of those with the highest fish intake and greatest preservation of gray matter were found to have developed mild cognitive impairment or dementia. That was a stark contrast to the 30.8% of non-fish eaters whod suffered such cognitive decline. Average scores for working memory, a brain function seriously impaired in Alzheimers, were significantly better among weekly fish eaters.
Scientists speculated that the brain benefits of fish could be credited to the omega-3 fatty acids found in fish oils, which could increase blood flow to the brain, combat inflammation and prevent the accumulation of amyloid plaques associated with Alzheimers. But the study, which has not yet been published in a peer-reviewed journal, wasnt designed to identify the mechanism of seafoods effects on the brain or to prove cause and effect. It could be that eating fish is simply a marker of a healthy lifestyle thats good for the brain.
Nonetheless, Dr. Raji felt confident enough in the results to conclude, Consuming baked or broiled fish promotes stronger neurons in the brains gray matter by making them larger and healthier. This simple lifestyle choice increases the brains resistance to Alzheimers disease and lowers risk for the disorder.
Omega-3s for Heart, Eyes
The simple lifestyle choice of eating more fish can deliver a wealth of benefits for your body as well. The best-known connection between fish consumption and health dates from the 1970s, when epidemiological studies noted the low cardiovascular mortality in Eskimos eating lots of fish. That led to the realization that omega-3 fatty acids could help protect the heart and arteries. Subsequent research has found that omega-3s may lower triglycerides, improve blood pressure, prevent blood clots that can trigger strokes, and reduce heart arrthymia, the leading cause of sudden cardiac death.
Research published last year in Archives of Ophthalmology also supports the possibility that fish high in omega-3s might protect against age-related macular degeneration (AMD), the leading cause of blindness in older Americans. The study of 38,022 participants in the Womens Health Study linked regular consumption of fish and the omega-3s found in fish (DHA and EPA) to reduced risk of AMD. Over 10 years of follow-up, 235 of the women were diagnosed with AMD. Based on food questionnaires at the start of the study, those eating fish at least once a week were 42% less likely to develop AMD than women eating fish less than once a month. Consumption of fish oil from the diet was also associated with lower risk, with the highest intake of DHA, for example, linked to a 38% lower likelihood of AMD.
Americans have been slow to take advantage of the well-established nutritional benefits of omega-3s, however. Most of us consume 10 times as much omega-6 fatty acids-typically from vegetable oils-as we do omega-3s like those in fish. When scientists at the Tufts Medical Centers Evidence-Based Practice Center reviewed nationwide data on US dietary habits, they found that on any given day only a quarter of the population reported consuming any DHA or EPA, the omega-3s in fish, at all.
If you want to buck that trend, keep in mind that all seafood is not the same in delivering omega-3s. Among the best sources, according to the Dietary Guidelines, are salmon, anchovies, herring, sardines, Pacific oysters, trout, and Atlantic and Pacific mackerel. Although there is no official Reference Daily Intake (RDI) for omega-3s, the Dietary Guidelines recommend that a person eating a 2,000-calorie daily diet should aim for 1.75 grams of EPA/DHA per week, or 250 milligrams a day. A four-ounce serving of wild salmon contains almost as much EPA/DHA as that recommended weekly total. Or you could get most of the recommended total of those omega-3s by eating half a can of tuna four times a week. (What about fish-oil pills? The American Heart Associations currently recommends fish-oil supplements only for individuals with established heart disease or hypertriglyceridemia, under the guidance of a doctor.)
While its good to increase your omega-3 consumption, dont fret too much about whether the fish you prefer-or can most easily afford-is packed with omega-3s. Its still better to eat more fish than less fish. Last year, the New York Times took aim at tilapia, one of the most affordable fish choices that many novice fish eaters also find less fishy, as being nutritionally inadequate. But Tufts Lichtenstein says, Tilapia happens to be lower in fat and calories than some other fish, so it has less of all types of fatty acids, including omega-3s. Tilapia is, however, more affordable than most other fish in the market today. Splitting hairs over whether one fish has less omega-3 fatty acids per serving than other types of fish when the total fat content is low seems to miss the point. Lets get people eating more fish, and then worry about fine-tuning either the fishs diet or our diet to edge up the omega-3 content.
Yes, You Can
Another affordable seafood option, which also skirts questions of seasonal availability, is canned fish. Omega-3s arent destroyed in the canning process, and many of the varieties most often canned or preserved in handy pouches are those highest in omega-3s. Opt for water-packed fish when possible, however, as some of the omega-3s can migrate into the canning oil and are lost when the fish are drained.
Americas most popular canned fish, tuna, is not naturally as high in omega-3s, but you can get more by smart shopping. A three-ounce serving of the most common canned tuna, skipjack (often sold as light), packed in water and then drained, contains only a about a quarter-gram of EPA/DHA. But albacore tuna (white) has nearly three-quarters of a gram in the same size serving.
Some fragile nutrients such as vitamin C are damaged by the heat of canning, but otherwise canned fish is as nutritious as fresh or frozen. Besides being an excellent source of low-calorie protein, some canned varieties such as salmon, sardines and mackerel (but not tuna) actually contain extra calcium, because theyre canned with the bones. The heat of cooking and canning makes these fish bones soft enough to eat. So three ounces of canned salmon contain 325 milligrams of calcium (about the same as a cup of milk), compared to almost none in fresh salmon fillets.
Studies have also shown that canned fish can be added to dishes such as casseroles, as in many recipes, with almost no further loss of nutrients from cooking. What you see on the label is what you get on the plate.
Some canned fish also contains unwanted ingredients, however-notably sodium. Salty anchovies pack one and a half times your recommended daily sodium total in just three ounces, while canned herring are typically salted and smoked (kippered), which also makes them high in sodium. If you like these fish, try rinsing and soaking anchovies or herring in water for 30 minutes before using to remove some of the salt. Watch out for added salt in all canned fish by checking the label and looking for low sodium or reduced salt. When buying canned tuna, for instance, you can avoid more than 200 milligrams per serving of excess sodium by savvy shopping.
For more on canned fish, see our complete coverage in the May 2010 newsletter.
Other unwanted extras in seafood that have caused concern are mercury and polychlorinated biphenyls (PCBs). According to the Environmental Protection Agency (EPA), Mercury occurs naturally in the environment and can also be released into the air through industrial pollution. Mercury falls from the air and can accumulate in streams and oceans and is turned into methylmercury in the water.… Fish absorb the methylmercury as they feed in these waters and so it builds up in them. It builds up more in some types of fish and shellfish than others, depending on what the fish eat, which is why the levels vary.
PCBs are highly toxic industrial compounds that were banned in US manufacturing in 1977 but are slow to break down and can accumulate in sediment at the bottoms of streams, rivers, lakes and coastal areas. From there, PCBs can build up in the fatty tissues of fish.
In 2006, however, an expert panel of the Institute of Medicine (IOM) weighed all the evidence to date and concluded that the health benefits of eating fish generally outweigh the risks.
Confusion may have scared people out of eating something that is beneficial for them and maybe for their offspring, says Jose M. Ordovas, PhD, director of Tufts HNRCA Nutrition and Genomics Laboratory, who served on the panel. Our goal was to put both the benefits and risks into perspective and see where is the balance. People should not be scared about eating seafood.
The experts report, Seafood Choices: Balancing Benefits and Risks, made recommendations for specific population groups:
Females who are or may become pregnant or who are breast-feeding as well as children up to age 12: May benefit, especially from seafood high in omega-3 fatty acids EPA and DHA. Can reasonably consume two three-ounce (cooked) servings but can safely consume 12 ounces per week. Can consume up to six ounces of white (albacore) tuna per week. Should avoid large predatory fish such as shark, swordfish, tilefish or king mackerel.
Healthy adolescents and most adults: May benefit by reducing their risk of cardiovascular disease. If consuming more than two servings a week, should select a variety of seafood to reduce risk of contaminants from a single source.
Adults at risk of coronary heart disease: May benefit by consuming seafood regularly, especially from fish high in EPA/DHA. If consuming more than two servings a week, should select a variety of seafood to reduce risk of contaminants from a single source.
Since the IOM report, new insight into the potential risks of mercury in seafood has come from an unlikely source: thousands of people who donated their toenail clippings for science. In findings published in the New England Journal of Medicine, Harvard scientists who analyzed mercury in toenails-a more accurate measure of long-term exposure than blood testing-report no link between even the highest levels of mercury and increased risk of heart disease or stroke. In fact, they found a slight protective association, probably because of other nutritional benefits of fish, even varieties higher in mercury such as shark and swordfish. The scientists cautioned that pregnant and nursing women and children should still exercise caution about exposure to mercury from fish.
As for PCBs, the US Food and Drug Administration (FDA) says levels in fish are well below safety limits. Another look at the evidence, published in JAMA about the same time as the Institute of Medicine report, concluded, Levels of dioxins and PCBs in fish are low, and potential carcinogenic and other effects are outweighed by potential benefits of fish intake and should have little impact on choices or consumption of seafood. For those nonetheless concerned about PCB content, the authors suggested that it can be reduced up to 40% by discarding skin and trimming off belly and back fat. The report also promoted eating a variety of fish.
Thats good advice in any case. Our Seafood Sampler chart (previous page) can help you make smart choices at the fish counter, frozen-food aisle or canned-fish section, but there are few truly bad choices when it comes to seafood. As long as you dont fry it or load it up with buttery sauces, you can hardly lose. When eating out or buying prepared fish, of course you should avoid seafood deep-fried in partially hydrogenated fat.
Sample a wide variety, discover what you like best and whats most affordable, and keep seafood on your menu all year long. It could be the easiest nutritional decision youll make in 2012.