Another Study Questions US Nutritional Recommendations

ImageFindings from the most recent review comparing the effects of fatty acids on heart disease do not agree with the current US nutritional recommendations. Current recommendations encourage replacing saturated fat intake with monounsaturated and polyunsaturated fats to reduce heart disease risk. The meta-analysis, published in the Annals of Internal Medicine, finds no association of saturated fat intake with heart disease. 

The new review is robust, including 600,000 individuals in 76 observational and randomized controlled studies from multiple countries. Many of the studies measured biomarkers of fatty acid consumption to confirm the validity of food questionnaires submitted by participants.

Contrary to US nutritional recommendations, the study did not find saturated fat consumption to be correlated with heart disease risk. Monounsaturated fat consumption also had no impact on heart disease risk.

Effects of polyunsaturated fatty acids were less clear. Consumption of omega-3 or omega-6 fatty acids was not significantly associated with altered risk of heart disease (although there was a trend of reduced heart disease with increased omega-3 consumption). However, when specific polyunsaturated fats in the blood were measured there were some significant correlations. High levels of circulating eicosapentaenoic acid (EPA) and docosahexaenoic (DHA) together produced a 25% reduction in heart disease risk.  These are the omega-3 fatty acids found in fish oil. However, the review did not find an impact of supplementation with omega-3 fatty acids on heart disease risk in at-risk populations. The authors conclude that more studies of omega-3 fatty acids in healthy populations are needed to determine if they prevent heart disease.

The only type of fat in the study associated with an increased risk of heart disease was trans fat, which increased risk by 16%.

The authors conclude that the findings from their analysis do not support the US guidelines that encourage low consumption of saturated fats and that the recommendations may require reappraisal.

In summary, the only type of fat that we should avoid is trans fat. Trans fats are man-made and not present in nature. Natural fats, whether they come from animals or plants, do not appear to increase heart disease risk.

Food manufacturers often alter serving sizes to hide the presence of trans fat in their product. If you see an ingredient that is “hydrogenated” or “partially hydrogenated,” it is a trans fat and is best to avoid.

7 thoughts on “Another Study Questions US Nutritional Recommendations

    • Will, I did check out the letter to the editor. Walter Willett certainly is not happy about the findings of this study but I think he goes too far in saying the study should be retracted. These are the key points that I found:

      1. Willett seems to be in agreement that substitution of saturated fat with carbohydrate does not reduce heart disease risk. I agree.

      2. Willett, however, believes that eating polyunsaturated fats instead of saturated fats will reduce heart disease risk. The data for this argument is mixed. I think omega-6 polyunsaturated fats should be minimized because we already get a lot of them in our diets, while omega-3’s should be increased to balance out the omega-3 to 6 ratio. If a person getting enough omega-3 and omega-6 to satisfy their body’s needs, I don’t see evidence that further increasing amounts of those fats in place of saturated fat will reduce heart disease risk.

      3. Willett believes that omega-3 fatty acids will reduce heart disease risk, but the meta-analysis was unclear as to the effects of omega-3’s on heart disease. I think Willett is correct. There does seem to be evidence that increasing omega-3 to balance the omega-3 to 6 ratio is beneficial.

  1. Bill,

    First, thanks for putting time and effort into this blog — I just discovered it as part of an ongoing process in understanding the latest nutrition science in practical terms. Reading your work has been helpful!

    Your synopsis indicates that higher levels of omega-3 fatty acids in the bloodstream are correlated with lower risk of heart disease. Later on, however, you indicate that “the review did not find an impact of supplementation with omega-3 fatty acids on heart disease risk in at-risk populations.” Are you saying that taking omega-3 supplements (like fish oil) didn’t result in lowered risk of heart disease, even though earlier you say that higher levels of omega-3 fatty acids result in lowered risk of heart disease? I’m currently interpreting this to mean that taking fish oil wouldn’t actually reduce my chances of heart disease.

    Keep up the good work!

    • Hi Michael,

      Correct, this study did not find a reduction in heart disease risk when consuming omega-3 fatty acids. However, when we look at all the studies on omega-3’s and heart disease there is a strong association between omega-3 consumption and heart disease risk. Sometimes a study does not find a significant effect because of variation in the data. But, on the whole I still think the benefit of omega-3’s is backed by solid evidence.

      Fish oil is the one supplement that I think can benefit people most because of this strength of the data behind omega-3’s and the low amount of omega-3’s in most diets.

      Thanks for reading,

      Bill

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