For years, many health experts have hailed foods rich in omega-3 fatty acids as being good for the lowering of stroke risk, as well as for the reduction of the risk of mild cognitive impairment. But other studies have suggested that omega-3 fatty acids -- and fish oil supplements in particular -- actually don't lower one's risk of stroke or heart attack.

With so many contrasting opinions, it's been difficult to determine what's true and what's not.

Now new research is clouding the picture even further by suggesting that omega-3 fatty acids -- found in fatty fish such as salmon and in nuts -- may not benefit thinking skills, as some earlier studies have indicated.

The study is published in the Sept. 25 online issue of Neurology®, the medical journal of the American Academy of Neurology.

“There has been a lot of interest in omega-3s as a way to prevent or delay cognitive decline, but unfortunately our study did not find a protective effect in older women. In addition, most randomized trials of omega-3 supplements have not found an effect,” said study author Eric Ammann of the University of Iowa in Iowa City, in a press release. “However, we do not recommend that people change their diet based on these results. Researchers continue to study the relationship between omega-3s and the health of the heart, blood vessels, and brain. We know that fish and nuts can be healthy alternatives to red meat and full-fat dairy products, which are high in saturated fats.”

Researchers studied 2,157 women between the ages of 65 and 80 who were enrolled in the Women's Health Initiative clinical trials of hormone therapy. The women were given annual tests of thinking and memory skills for an average of six years. Blood tests were taken to measure the amount of omega-3s in the participants’ blood before the start of the study.

The researchers found no difference between the women with high and low levels of omega-3s in the blood at the time of the first memory tests. There was also no difference between the two groups in how quickly their thinking skills declined over time.

The study was supported by the National Heart, Lung, and Blood Institute, National Institutes of Health, and U.S. Department of Health and Human Services.

What does appear to be good for the brain is chocolate. In a small study conducted earlier this year, Harvard researchers found that drinking two cups of hot chocolate a day for 30 days was linked with improved blood flow to the brain and better scores on memory and thinking skill tests for elderly people.

Earlier on HuffPost50:

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  • The Alzheimer's Prevention Cookbook

    <a href="http://www.amazon.com/The-Alzheimers-Prevention-Cookbook-Recipes/dp/1607742470">The Alzheimer's Prevention Cookbook</a> by Dr. Marwan Sabbagh and Beau MacMillan. Published by Ten Speed Press. (The following slides were reprinted with permission from The Alzheimer’s Prevention Cookbook: Recipes to Boost Brain Health by Dr. Marwan Sabbagh and Beau MacMillan, copyright © 2012. Published by Ten Speed Press, an imprint of the Crown Publishing Group)

  • Sweet Peach Smoothie

    The key to this recipe is using a ripe, in-season peach. It’s always good to get to know the produce guys at your local grocery store because they will let you know when peaches are in their prime. Peaches contain numerous nutrients that are good for your body, including niacin, thiamin, potassium, and calcium. They are also high in beta-carotene, which promotes healthy hearts and eyes. The darker the peach’s color, the more vitamin A it has in its pulp. Peaches may also help in maintaining healthy urinary and digestive functions. There’s some evidence that flaxseed oil may help reduce your risk of heart disease, cancer, stroke, and even diabetes.

  • Sweet Peach Smoothie

    MAKES ABOUT 3 CUPS 11/2 cups apple juice 1 ripe peach, peeled, pitted, and chopped (about 3/4 cup) 3/4 ripe banana, peeled and chopped 1 tablespoon vanilla yogurt 6 ice cubes 2 teaspoons honey 2 teaspoons flaxseed oil Combine the apple juice, peach, banana, yogurt, and ice in a blender and puree until smooth. Add the honey and flaxseed oil and puree briefly to incorporate. Pour into glasses and serve right away.

  • Breakfast Fried Rice with Scrambled Eggs

    Think outside the (cereal) box: fried rice is a great way to fuel up with carbs in the morning. With brown rice, lots of fresh vegetables, and a minimal amount of fat, this recipe is a healthy take on fried rice and is high in vitamin B6. <em>Lop chong</em> is a dried, cooked Chinese sausage with a slightly sweet and smoky flavor; it will require a trip to the Asian grocery store, but you can choose to leave it out.

  • Breakfast Fried Rice with Scrambled Eggs

    MAKES 4 SERVINGS Fried Rice 2 tablespoons chopped lop chong (Chinese sausage; optional) 1/4 cup vegetable oil 1 tablespoon chopped garlic 1 tablespoon peeled, chopped fresh ginger 1 green onion, white and green parts, chopped 2 tablespoons diced red onion 1 or 2 leaves baby bok choy, thinly sliced 1/4 cup shredded red cabbage 5 sugar snap peas, cut into thin strip on the diagonal 2 cups cooked and cooled brown rice 4 tablespoons soy sauce 4 tablespoons mirin Eggs and Garnishes 2 large eggs, beaten 1 teaspoon sesame seeds 2 tablespoons toasted cashews, chopped 1 green onion, white and green parts, sliced thin on the diagonal 2 tablespoons chopped fresh cilantro To make the fried rice, in a large wok or large skillet over high heat, fry the lop chong until rendered, less than a minute. Transfer the lop chong to a paper towel–lined plate and discard the fat. Set the wok over high heat and heat until very hot. Add the oil to the wok. Add the garlic, ginger, chopped green onion, red onion, bok choy, cabbage, and snap peas. Cook, stirring, for 1 minute, or until the vegetables have softened and you can smell the ginger. Add the rice and continue to cook, stirring, until everything is coated, 2 to 4 minutes. Add the soy sauce and mirin and toss well. Remove the wok from the heat. To cook the eggs, heat a small nonstick skillet over medium heat. Spray the pan with nonstick cooking spray, and then pour in the beaten eggs. Cook, gently stirring the eggs, until scrambled but still moist. Transfer fried rice to a serving bowl and top with the scrambled eggs. Sprinkle with the sesame seeds, toasted cashews, and diagonally cut green onion and serve right away.

  • Ahi Tuna on Rye with Spinach Pesto Yogurt

    This is not your average tuna sandwich. For one thing, it’s more like tuna tartare on bread. For another, it’s a very brain-healthy meal. Spinach Pesto Yogurt, not mayonnaise, holds the tuna mixture together, which keeps the amount of saturated fat to a minimum. Tuna is an excellent source of omega-3 fatty acids, the pistachios provide vitamin E, and the raisins are a good source of polyphenol antioxidants. Because the tuna is not cooked in this recipe, be sure to purchase sashimi-grade tuna; ask the fishmonger if you aren’t sure about the quality of the tuna on offer at the seafood counter.

  • Ahi Tuna on Rye with Spinach Pesto Yogurt

    MAKES 2 SANDWICHES 8 ounces sashimi-grade ahi tuna, diced small 2 tablespoons Spinach Pesto Yogurt 2 tablespoons golden raisins 1/4 cup shelled unsalted roasted pistachios, chopped Juice of 1/2 lemon 4 slices rye bread, toasted 1/2 cup alfalfa sprouts 1 teaspoon extra-virgin olive oil Spinach Pesto Yogurt Makes about 3 cups 2 cups loosely packed baby spinach 1 cup extra-virgin olive oil 1/4 cup pine nuts 2 tablespoons grated 
Parmigiano-Reggiano cheese 1 clove garlic, peeled Juice of 1 lemon Pinch of salt Pinch of freshly ground black pepper 1 cup low-fat or nonfat plain yogurt In a medium bowl, combine the tuna, Spinach Pesto Yogurt, raisins, pistachios, and lemon juice, and mix well. Lay out two of the bread slices on a work surface and divide the tuna mixture evenly among them. Put the alfalfa sprouts into a small bowl, drizzle with the olive oil, and toss to combine. Top each portion of tuna with half of the alfalfa sprouts and top with the remaining slices of bread. Cut each sandwich in half and serve right away. Combine the spinach, olive oil, pine nuts, cheese, garlic, lemon juice, salt, and pepper in a blender and puree until well blended. Pour the mixture into a bowl, add the yogurt, and whisk until incorporated. Serve slightly chilled. The mixture will keep in an airtight container in the refrigerator for 3 to 4 days.

  • Striped Bass with Golden Tomato 
and Sweet Pepper Stew

  • Striped Bass with Golden Tomato 
and Sweet Pepper Stew

    MAKES 4 SERVINGS Tomato and Sweet 
Pepper Stew 3 tablespoons olive oil 1 tablespoon finely chopped garlic 1 small shallot, finely chopped 1 fennel bulb, diced large 2 yellow bell peppers, seeded and diced large 3 yellow tomatoes, cored and diced large Pinch of saffron threads 2 tablespoons Pernod or other anise liqueur, such as ouzo or anisette 1 cup white wine 2 cups Brain-Boosting Broth Salt and freshly ground black pepper Fish 2 tablespoons olive oil 4 (6-ounce) skin-on striped bass fillets Salt and freshly ground pepper 11/2 tablespoons chopped fresh flat-leaf parsley leaves, for garnish Preheat the oven to 350°F. To make the stew, in a large saucepan over medium heat, warm the olive oil. Add the garlic, shallot, fennel, and bell peppers and cook, stirring occasionally, until the vegetables soften, about 
10 minutes. Add the tomatoes and saffron and continue to cook until the tomatoes soften slightly, about 2 minutes. Pour in the Pernod, bring to a simmer, and cook, stirring, until almost evaporated. Add the white wine, bring to a simmer, and cook until the liquid is reduced by about half, about 
5 minutes. Pour in the broth, season with salt and pepper, and simmer uncovered for 15 minutes to bring the flavors together. While the stew is simmering, cook the fish. In a large ovenproof skillet over medium-high heat, warm the olive oil. Score the fish fillets with a knife and season them with salt and pepper. Add the fish fillets to the skillet skin side down and cook until the skin is golden brown and crisp, about 3 minutes. Slide the skillet into the oven and cook until the fish skin is opaque and flaky, about 5 minutes. Divide the stew among four plates and place a fish fillet on top. Sprinkle with parsley and serve right away. Brain-Boosting Broth Makes 2 quarts 8 quarts water 3 carrots, coarsely chopped 2 white onions, coarsely chopped 2 celery stalks, coarsely chopped 2 bulbs fennel, coarsely chopped 1 parsnip, coarsely chopped 12 cloves garlic, chopped 1/4 cup fresh ginger, peeled and chopped Stems from 1/2 bunch fresh flat-leaf parsley 1 bunch green onions, green and white parts 1 stalk fresh lemongrass, 
cut in half lengthwise 1 tablespoon salt 1 teaspoon black peppercorns 2 cloves 1 teaspoon dried oregano 1 teaspoon dried rosemary 1 bay leaf Combine all of the ingredients in a large stockpot and bring to a boil over high heat. Turn down the heat to maintain a gentle simmer and cook, uncovered, for 2 hours. Strain the broth through a fine-mesh sieve. Use immediately, refrigerate for up to 5 days, or freeze for up to 1 month.

  • Spaghetti Squash with 
Caramelized Onion and Tomato

    Spaghetti squash is an often-overlooked vegetable. But it’s a very powerful ingredient from a brain-health perspective: it’s low in saturated fat, very low in cholesterol, and a good source of niacin, vitamin B6, and pantothenic acid--plus spaghetti squash is a very good source of vitamin C. In this recipe, strands of baked spaghetti squash are the backdrop for sweet caramelized onions that contrast against salty, savory Parmesan cheese. This dish will appeal to adults and kids alike, and it’s a great way to get pasta lovers to eat more vegetables.

  • Spaghetti Squash with 
Caramelized Onion and Tomato

    MAKES 4 SERVINGS Olive oil 1/2 spaghetti squash (about 
2 pounds), seeded 1 tablespoon unsalted butter 1 medium yellow onion, thinly sliced Curry Salt 1/2 cup grated Parmigiano-Reggiano cheese 1/3 cup chopped fresh chives 1 ripe tomato, cored, seeded, and diced Fresh cilantro leaves, for garnish Preheat the oven to 350°F. Drizzle a rimmed baking sheet and the flesh of the squash with a little olive oil. Set the squash half cut side down on the baking sheet. Sprinkle 2 tablespoons of water over the squash and bake, uncovered, until a fork inserted into the thickest part of the flesh meets no resistance, 30 to 45 minutes. Let cool to room temperature. In a large nonstick skillet over medium heat, melt the butter. Add the onion and cook, stirring occasionally, until lightly caramelized, about 5 minutes. Set aside. Using a fork, scrape the squash from the skin into a medium bowl; the flesh will separate into spaghetti-like strands (you should have about 
21/2 cups). Return the skillet with the onion to medium heat and add the squash. Cook, tossing gently, just until heated through, 1 to 2 minutes. Season to taste with Curry Salt; go easy because the cheese will add salt, too. Toss in the cheese and chives and transfer to a serving bowl. Sprinkle with the tomatoes and cilantro and serve right away. Curry Salt Makes about 1/2 cup 1/2 cup fleur de sel 4 teaspoons curry powder Mix the salt and curry powder until well combined. Store in an airtight container in a cool, dark place (the flavor of the salt gets better with age). This recipe will not go bad over time.

  • Curried Quinoa with Green Onions and Basil

  • Curried Quinoa with Green Onions and Basil

    MAKES 4 SERVINGS 11/2 cups Brain-Boosting Broth 3/4 cup quinoa, rinsed 1 teaspoon curry powder 1 teaspoon minced fresh ginger 5 to 7 green onions, white and green parts, chopped 1/4 cup chopped fresh basil leaves 1/4 cup slivered almonds, toasted 1/4 cup dried cherries, chopped Pinch of salt Pinch of freshly ground black pepper Juice of 1 lemon 2 tablespoons extra-virgin olive oil In a medium saucepan over high heat, bring the broth to a boil. Add the quinoa, curry powder, 
and ginger. Turn down the heat to medium-low, cover, and simmer until the quinoa is tender, about 20 minutes. Transfer the quinoa to a rimmed baking sheet, distribute in an even layer, and let cool to room temperature. When cooled, put the quinoa into a medium bowl and add the green onions, basil, almonds, and cherries. Sprinkle with the salt and pepper and toss to combine. Drizzle with the lemon juice and olive oil and toss again. Serve at room temperature or lightly chilled. Brain-Boosting Broth Makes 2 quarts 8 quarts water 3 carrots, coarsely chopped 2 white onions, coarsely chopped 2 celery stalks, coarsely chopped 2 bulbs fennel, coarsely chopped 1 parsnip, coarsely chopped 12 cloves garlic, chopped 1/4 cup fresh ginger, peeled and chopped Stems from 1/2 bunch fresh flat-leaf parsley 1 bunch green onions, green and white parts 1 stalk fresh lemongrass, 
cut in half lengthwise 1 tablespoon salt 1 teaspoon black peppercorns 2 cloves 1 teaspoon dried oregano 1 teaspoon dried rosemary 1 bay leaf Combine all of the ingredients in a large stockpot and bring to a boil over high heat. Turn down the heat to maintain a gentle simmer and cook, uncovered, for 2 hours. Strain the broth through a fine-mesh sieve. Use immediately, refrigerate for up to 5 days, or freeze for up to 1 month.