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Fat and Disease

Part 1
So what’s the story with saturated fat and how does it affect our health? Has everything we’ve been told about nutrition a lie as a recent article featured in the Guardian led us to believe. For the lay person nutritional science can be a confusing subject, with mixed and often contradictory message. Venturing online in an attempt to gain a grasp of the facts is like a trip into the old Wild West. Internet bloggers, fitness columnist, journalists, coaches, teachers and housewives all mingle with experts. Often those with most persuasive arguments or impressive website have the largest following regardless of the content.

So what’s the story with fat have we been lied to? The fitness industry is largely thickle and hypocritical and just like the high street things go in and out of fashion. So around a month ago the internet nearly exploded after a newspaper article proclaimed eating a high protein diet was almost as dangerous as smoking. I wrote a short blog on my facebook page about it. High protein advocates quickly dismissed the article and the research paper, after all what would a bunch of nerdy scientists, with years of research experience, sophisticated lab equipment and a publication in a highly prestigious journal know. The paper was after all based on observational data rather than the gold standard randomised control trial (RCT), essentially it couldn’t prove anything, more steak and eggs anyone?
If any of them bothered to read it though they’d have realised it was more than simply an observational paper. The internet has a short memory and the same high protein advocates jumped on an article earlier this month when it was proclaimed that high fat diet is perhaps not as bad for cardiovascular disease as first thought. The research paper1 in question once again was based largely on observational research. The very same kind of research the protein paper published a month before got panned for. It did contain a large subset of data on RCTs but this was actually data based on supplementation trials, the only real difference was it justified large intakes of protein. More steak and eggs anyone?

So first off what did the paper in question actually find? Based on the data they found a non-significant increase in risk of disease for saturated fatty acids, trans fatty acids increased the risk of disease, omega -3 fatty acids decreased the risk, there was also a non significant decrease in risk with omega-6 fatty acids. The main outcome measure of the trial was coronary events so things like heart attacks and death caused by heart disease. When you look at the data from the RCTs you can see there was a trend towards lower risk of cardiovascular events when subjects were supplemented with polyunsaturated fatty acids. So they investigated what happens when fish oils were added to the diet rather than when saturated fats were removed. The authors concluded that more trials were needed to establish the effect of fatty acid intake on cardiovascular events, and at this time there evidence didn’t support current guidelines, even though there evidence was largely observational.

In spite of this, there was a fairly comprehensive review published by the Cochrane Library on fat intake and cardiovascular disease recently2. Cochrane reviews are considered the gold standard in research reviews and employ stringent criteria to the evidence reviewed. The review found that reducing saturated fat or replacing saturated fat, mono or polyunsaturated fats reduced the risk of cardiovascular disease by as 14% across 65,508 participants in RCTs. Modifying fatty acid intake had a positive effect on cholesterol and circulating fat. In the longer term trials (over 2 years) the authors found modifying fat was more effective than simply reducing fat. The authors concluded replacing animal fats with those from plant oils and unsaturated fats may reduce the risk of cardiovascular disease and it was unclear if polyunsatureated fats or monounastaruated fats were more beneficial. Some will argue that the current dietary recommendations to reduce saturated fat intake and increase wholegrain food consumption has failed. Metabolic associated diseases like obesity, cardiovascular disease and type 2 diabetes have been on the increase since the 70s and show no signs of slowing down. However this has more to do with the over consumption of energy dense, nutrient poor foods and lack of exercise. People quite simply have failed to head healthy eating advice, they’ve chosen chips over carrot sticks. Where people have been offered support and counselled during dietary regimes the current dietary recommendations have proved to be effective3.

So modifying our fat intake may reduce the risk of heart disease, but what happens if we simply eat less food and still consume the same amount of fat? Or what happens if we eat more fat and eat less carbohydrate. What happens to our risk of cardiovascular disease or diabetes and what about other disease like cancer? Such questions will be addressed in the next article, until then rest assured you’ve not been lied to all along.

References

  1. Chowdury et al. (2013) Association of Dietary, Circulating, and Supplement Fatty Acids With Coronary Risk. Annals Of Internal Medicine.
  2. Hooper et al. (2012) Reduced or modified dietary fat for preventing cardiovascular disease. Cochrane Heart Group.
  3. Rees et al. (2013) Dietary advice for reducing cardiovascular risk. Cochrane Heart Group
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