The murky evidence about saturated fat

For decades, it has been accepted as truth that eating foods high in saturated fats  such as  full-fat milk products and fatty cuts of meat — lead to an increased risk of heart disease. Yet a small but growing body of evidence is raising questions about whether reducing saturated fat intake impacts health outcomes.

Let me start by saying, the U.S. government unequivocally recommends a diet low in saturated fat. The U.S. Department of Agriculture reviewed the evidence in 2011 and concluded that decreasing saturated fat in your diet reduces your risk of heart disease.

And it’s true – the evidence does seem to show that eating less saturated fat lowers the risk of having a heart attack or stroke. But there is very little evidence to show that eating less saturated fat reduces mortality.  In other words, eating less saturated fat leads to less heart disease, but doesn’t do anything to prolong a person’s lifespan.

A systematic review sponsored by the Cochrane Collaboration fully explains this point, and concluded:

“Despite decades of effort and many thousands of people randomized, there is still only limited and inconclusive evidence of the effects of modification of total, saturated, monounsaturated, or polyunsaturated fats on cardiovascular morbidity and mortality.”

The New York Times’ Well blog provided some interesting background on the issue last week. It explains that one of the pioneering studies on fat intake was never fully analyzed. Now the researchers have re-analyzed the data and have found that men who ate a diet rich in polyunsaturated fats found in foods such as nuts and fish ,had  lower cholesterol, but were also more likely to die of a heart attack than those who stuck with their usual diet.  They also reviewed the available evidence and concluded that there is no cardiovascular benefit for substituting polyunsaturated fats for saturated fats.

So what’s the bottom line?  The only thing that seems abundantly clear is that we still don’t understand the role that dietary fat plays in cardiovascular disease. We need more careful study of the mechanisms at work to fully understand what is the best diet for optimizing health.  In the meantime, a diet with plenty of fruits and vegetables and a variety of protein and fat sources is probably the most reasonable one to follow.

Comments

  1. Although, eating less saturated fats does not reduces mortality, it would seem to me that reducing your intake of saturated fats is still a healthy alternative and would create a more comfortable lifestyle. I have reduced my fat intake in recent years and as a result, my cholesterol level has been greatly reduced. Your conclusions of eating fruits, vegetables, protein, and fat sources are still the best way to go.

  2. Jose Carlos Souto says:

    Some other papers to corroborate your point of view:

    Hession, M. et al., 2009. Systematic review of randomized controlled trials of low-carbohydrate vs. low-fat/low-calorie diets in the management of obesity and its comorbidities. Obesity reviews: an official journal of the International Association for the Study of Obesity, 10(1), pp.36–50. Available at: http://pt.scribd.com/doc/4895150/Review-of-lowcarb-vs-highcarb-diets.

    Santos, F.L. et al., 2012. Systematic review and meta-analysis of clinical trials of the effects of low carbohydrate diets on cardiovascular risk factors. Obesity reviews: an official journal of the International Association for the Study of Obesity, 13(11), pp.1048–1066.

    Siri-Tarino, P.W. et al., 2010. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. The American Journal of Clinical Nutrition, 91(3), pp.535–546. Available at: http://ajcn.nutrition.org/content/91/3/535 [Accessed September 13, 2013].

  3. Tony Hakim says:

    I completely agree with this article, saturated fat has long been seen as a bad thing – but all of this started when one study funded by the US grain lobby went to prove that this was the cause of obesity.

    Since then the old food pyramid introduced and our waistlines have exploded!

    Here is a little something else I have written about it:

    http://www.tony-hakim.com.au/how-bad-is-saturated-fat-really/

  4. David M Driscoll says:

    Did you look at the comments associated with the Sydney Diet Heart Study?

    http://www.bmj.com/content/346/bmj.e8707?tab=responses

    and more specifically some of the criticisms especially re trans fats not to mention statistics used

    http://www.smc.org.au/2013/02/round-up-dietary-fats-and-heart-disease-bmj-experts-respond/

  5. Benison O'Reilly says:

    You are quoting a 2001 Cochrane review but this review was updated in 2010

    The authors’ conclusions from the updated review were:

    The findings are suggestive of a small but potentially important reduction in cardiovascular risk on modification of dietary fat, but not reduction of total fat, in longer trials. Lifestyle advice to all those at risk of cardiovascular disease and to lower risk population groups, should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturates. The ideal type of unsaturated fat is unclear.

    http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD002137.pub3/abstract

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