麻豆AV

听

Consider omega-3 pills, which outside of vitamins, are probably the most widely consumed dietary supplements. We take them hoping to reduce our risk of heart disease, prevent cancer, save us from depression, protect us from Alzheimer鈥檚 disease and to boost our brain power. We give them to our children to improve their school performance, and should they be hyperactive, we ply them with omega-3s to calm them down. We do these things because we have so often heard that omega-3s can help with all these things. The argument usually begins with the statement that omega-3 fats are essential in the diet because our bodies cannot make them, and that they play important roles as constituents of cell membranes, particularly in the brain and the retina. We鈥檙e informed that they also have anti-inflammatory effects, they raise HDL, the good cholesterol, they reduce the risk of irregular heart beats. They make arteries more supple. They can improve memory and maybe reduce the risk of dementia.听But to justify claims that taking omega-3s in pill form is beneficial, we need more than hearsay, we need evidence.

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There is some, but way less than what one might expect in light of all the publicity that has been generated. The best evidence is for protection against heart disease, though even that is pretty weak. An analysis of all the studies published in this area suggests a reduction in cardiovascular disease by some 10% if adequate amounts of fish oils are incorporated into the diet. Surveys have indeed linked higher blood levels of one specific omega-3, with the foreboding name of docosahexaenoic acid, with protection from dementia.听Of course there is the question of what constitutes an adequate amount. Current thinking is that about 200 mg a day of docosahexaenoic acid (DHA) and 100 mg of eicosapentaenoic acid (EPA), the famous fats found in fish oil, are enough.听Where does our body get the omega-3 fats? From the same source as it gets anything else, it gets it from- food. The term 鈥渙mega-3鈥� is a general one that describes a whole family of compounds with similar molecular structures and properties, but not with identical properties. Docosahexaenoic acid, or DHA, is the one found mostly in the brain, eicosapentaenoic acid, or EPA, is the one that affects the suppleness of arteries and reduces the risk of blood clot formation, and alpha-linolenic, or ALA, is thought to have some anti-inflammatory properties. But the body is also capable of using ALA to make the other two omega-3s. The best dietary source of these fats is fish oil. Interestingly, fish cannot make these fats, they must eat them. And they do. Microscopic algae, abundant in natural waters, is the source of all omega-3 fats in the flesh of fish. Larger fish that feast on smaller ones will ave more of these fats. Farmed fish have to be given appropriate food, either fish meal or algae, otherwise they will be devoid of these healthy fats. A couple of bites of tuna will do it. Non fish eaters can get omega-3s from flax, walnuts, soy or canola, as these actually contain alpha-linolenic acid (ALA).听The conversion is only about 2-5%, but since these foods are rich in ALA, that is enough. It takes less than a tablespoon of canola oil to provide adequate amounts.

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Now, what about the other claims? There is virtually no evidence for protection against cancer or Alzheimer鈥檚 disease. A recent study of subjects aged between 70 and 80 showed absolutely no improvement in cognitive ability with omega-3 supplements. A large trial in England failed to support the preconceived notion that supplements would improve students鈥� performance on exams. While there was some improvement, it was less than the improvement seen the year before when no supplements were used. There may be some effect on hyperactivity, but studies are conflicting. As far as depression goes, there is evidence that countries with a high intake of omega-3 have lower levels of depression. But this is not seen in randomized controlled trials, so some other factor seems to be involved. When it comes to arthritis, the literature does present some support for helping with morning stiffness and reducing the amount of anti-inflammatory drugs needed. So what鈥檚 the conclusion here? The evidence for benefits of omega-3s beyond what is available from a proper balanced diet is very skimpy. Of course if one wants to present supplements in a positive light, one can always fish for, and find, a study to support it. But chances are that the study has been supported by some company that has a vested interest. They would probably say that my analysis is faulty because I have not been taking enough omega-3s to boost my brain power.