Fish oil supplements too have been shown to have no benefit in clinical trials

Fish oil supplements too have been shown to have no

This preview shows page 37 - 39 out of 60 pages.

Fish oil supplements, too, have been shown to have no benefit in clinical trials, despite dozens of observational studies claiming the opposite. Yet dietary advice in many countries, including Australia, the UK and the US is still that people should eat oily fish regularly. Even the linchpins of today’s dietary advice fail to translate into unambiguous benefits when put to the test. “There are no randomised controlled trials showing whole grains, fruit and veg or fibre affect mortality or heart attacks or cancer rates,” says Levy. “It’s just not plausible to do a trial following a large enough group over a sufficient period to see enough deaths.” That’s right. Despite all the urging that we should “eat a rainbow” of different-coloured plant foods, aiming for five portions a day – or maybe seven or even nine, depending on who you listen to – no trial has shown that doing so makes us live longer. The same goes for eating wholegrain versions of foods such as bread, pasta and rice, which is recommended for the fibre content. The best support that randomised trials have given us here is that a type of fibre found in oats, called beta-glucan, brings small improvements in blood pressure and cholesterol levels. But these effects are so small that it is unclear they would protect you from a heart attack, and to achieve them requires eating the equivalent of three bowls of porridge a day – something most people would find hard to swallow. Then we come to the shambles over advice on fat. Numerous national guidelines say we can prevent heart attacks by avoiding saturated fat, mainly found in red meat and dairy products. Again, not one single randomised trial has shown that doing this saves lives, says Susan Jebb at the University CLAUDIA TOTIR/GETTY “The problem is serious enough that we should be sceptical of all dietary advice” РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS
Image of page 37
13 July 2019 | New Scientist | 35 folic acid supplements, and that people with high blood pressure can bring it down by cutting salt intake. Interestingly, these last two findings have been demonstrated in randomised trials, showing that they can be done, when there is a real effect to find. But these successes came some time ago. “Nutrition science did an amazing job in terms of addressing deficiencies,” says Warner. “But when we started having enough to eat, that science tends not to give as many clear answers.” Ioannidis says nutrition researchers need to universally adopt the good research practices seen elsewhere, such as pre-registering all studies, including stating which confounders they will use, to prevent cherry-picking after the results come in. Prasad goes further, saying there should be a moratorium on observational studies until the problems are fixed. “The public is becoming so fatigued with flip-flopping advice that they are losing faith in science more broadly.” In the meantime, common sense and moderation feel like an unsatisfyingly vague set of dietary principles. And of course, many
Image of page 38
Image of page 39

You've reached the end of your free preview.

Want to read all 60 pages?

  • Fall '19
  • Science, Srinivasa Ramanujan, New Scientist

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture