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Clinician Article

Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis.



  • Chowdhury R
  • Warnakula S
  • Kunutsor S
  • Crowe F
  • Ward HA
  • Johnson L, et al.
Ann Intern Med. 2014 Mar 18;160(6):398-406. doi: 10.7326/M13-1788. (Review)
PMID: 24723079
Read abstract Read evidence summary Read full text
Disciplines
  • Family Medicine (FM)/General Practice (GP)
    Relevance - 7/7
    Newsworthiness - 6/7
  • General Internal Medicine-Primary Care(US)
    Relevance - 7/7
    Newsworthiness - 6/7
  • Cardiology
    Relevance - 6/7
    Newsworthiness - 6/7
  • Internal Medicine
    Relevance - 6/7
    Newsworthiness - 6/7
  • Public Health
    Relevance - 6/7
    Newsworthiness - 6/7

Abstract

BACKGROUND: Guidelines advocate changes in fatty acid consumption to promote cardiovascular health.

PURPOSE: To summarize evidence about associations between fatty acids and coronary disease.

DATA SOURCES: MEDLINE, Science Citation Index, and Cochrane Central Register of Controlled Trials through July 2013.

STUDY SELECTION: Prospective, observational studies and randomized, controlled trials.

DATA EXTRACTION: Investigators extracted data about study characteristics and assessed study biases.

DATA SYNTHESIS: There were 32 observational studies (530,525 participants) of fatty acids from dietary intake; 17 observational studies (25,721 participants) of fatty acid biomarkers; and 27 randomized, controlled trials (103,052 participants) of fatty acid supplementation. In observational studies, relative risks for coronary disease were 1.02 (95% CI, 0.97 to 1.07) for saturated, 0.99 (CI, 0.89 to 1.09) for monounsaturated, 0.93 (CI, 0.84 to 1.02) for long-chain ω-3 polyunsaturated, 1.01 (CI, 0.96 to 1.07) for ω-6 polyunsaturated, and 1.16 (CI, 1.06 to 1.27) for trans fatty acids when the top and bottom thirds of baseline dietary fatty acid intake were compared. Corresponding estimates for circulating fatty acids were 1.06 (CI, 0.86 to 1.30), 1.06 (CI, 0.97 to 1.17), 0.84 (CI, 0.63 to 1.11), 0.94 (CI, 0.84 to 1.06), and 1.05 (CI, 0.76 to 1.44), respectively. There was heterogeneity of the associations among individual circulating fatty acids and coronary disease. In randomized, controlled trials, relative risks for coronary disease were 0.97 (CI, 0.69 to 1.36) for α-linolenic, 0.94 (CI, 0.86 to 1.03) for long-chain ω-3 polyunsaturated, and 0.89 (CI, 0.71 to 1.12) for ω-6 polyunsaturated fatty acid supplementations.

LIMITATION: Potential biases from preferential publication and selective reporting.

CONCLUSION: Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.

PRIMARY FUNDING SOURCE: British Heart Foundation, Medical Research Council, Cambridge National Institute for Health Research Biomedical Research Centre, and Gates Cambridge.


Clinical Comments

Cardiology

The problem is that the meta-analysis is based on observational rather than randomized studies, and the logic to avoid saturated fats seems pretty sound.

Family Medicine (FM)/General Practice (GP)

I am highly skeptical of self-reported questionnaires as it is well known that people may under-report what they eat and over-report the amount of exercise they do. In the NHS, we spend more than £500 per year per patient in prescribing omega 3 supplements. In my opinion, this would be better spent toward an exercise subscription to encourage healthier exercise habits. A capsule or two a day will not achieve the same benefits as exercising 3-4 times per week.

Family Medicine (FM)/General Practice (GP)

This is important. It challenges the assumed benefits of poly-unsaturated fat diets and the harms of saturated fats. Since it is observational data in the main, there is a risk of bias, but I imagine this is likely to be in the direction of the assumed state of play. Knowing what to recommend to patients to maintain optimal health is difficult. The best advice seems to be a `Mediterranean` diet.

General Internal Medicine-Primary Care(US)

This is a puzzling/challenging publication. It appears to demonstrate a fact about nutrient fat type and CV outcomes that runs counter to the prevailing paradigm. Despite the very large numbers of participants, one wonders whether the statistical methods are sufficient to validate any meaningful differences that otherwise have meaningful clinical belief.

General Internal Medicine-Primary Care(US)

The results observed in this study bring up more discussion about the effects of polyunsaturated fatty acids and saturated fats in cardiovascular outcomes. The large scale of this meta-analysis gives the study great strength, even though clear biases are observed and recognized by the authors. The study used a smart approach to evaluate fatty acid impact based on serum fatty acid levels, although this in itself introduced bias in the results. The study does not support current recommendations for the consumption of different types of fatty acids. It is definitely worth looking further into these results since public health policy has been affected in recent years based on current diet recommendations. The study will definitely stir the debate on this matter.

Internal Medicine

It`s going to take more evidence than this to convince me that guidelines calling for lower intake of saturated fatty acids are all wrong.

Internal Medicine

Given the years of publicity about dietary fat components and CAD, this is a useful meta-analysis that suggests that there are no strong data on these relationships.

Internal Medicine

This area has been very confusing; useful to have a summary of data.

Public Health

An article that challenges strongly held beliefs that is likely to be controversial. I can`t fault the methodology, so I believe the conclusions are likely to be valid. However, I suspect it will be insufficient to change the minds of those with a vested interest in the received wisdom (dogma?), so it is unlikely to change practice. In this regard, it will fulfill a similar role for dietetics as the Cochrane review that questioned the value of mammography did for screening. Very interesting material for debate!

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