Saturated Fat Not Linked to Heart Disease – What Do You Think?
The latest research published in the American Journal of Clinical Nutrition found that saturated fat is not linked to heart disease as we’ve always be told. This latest study was a meta-analysis and did not find significant evidence linking dietary saturated fat with increased risk of heart disease.
A meta-analysis combines the results of several studies completed with similar theories. In this particular analysis, 21 studies were compared in regards to dietary fat and heart disease risk. I do like meta-analysis results, because they can provide a big picture look at the overall findings. However, there are weaknesses.
Here are three known weaknesses:
- Reliance on published studies – Studies that do not show significant results have difficulty getting published. If a meta-analysis only includes studies showing a positive or negative association there could be many unpublished studies finding no link.
- Studies included are not controlled – A meta-analysis may include studies with a poor design which can skew results inaccurately. The studies included in a meta-analysis is a subjective design made by the researchers – they get to decide.
- Simpson’s Paradox – This deals with statistics and how study results are interpreted. There are different ways to measure results and there is no one agreed upon measurement method – with is of particular importance in the field of medicine.
Why am I sharing this information with you?
Because the results of this latest meta-analysis are interesting, but I do not recommend you throw out your olive oil and replace it with lard. It’s likely saturated fat does not deserve the “bad rap” it has received; however, that doesn’t mean excess amounts are good. Everything comes back to moderation.
Please let me know what you think by adding a comment below.
All the best,
Lisa Nelson RD
Heart Healthy Tips
http://www.hearthealthmadeeasy.com
What are your thoughts on saturated fat from nuts and nut butter, not meats or cheese.
Hi James,
Nuts do contain some saturated fat, but they are a great source of heart healthy unsaturated fats. Nuts, seeds, and nut butters can be a great addition to a heart healthy diet. However, they are high in calories so moderation is important.
All the best,
Lisa Nelson RD
http://www.lisanelsonrd.com
The health authorities are fully aware of the serious flaws and omissions in this meta-analysis. This study was funded by the National Dairy Council, dairy being the number one contributor of saturated fat in the U.S. and many other parts of the world. It was also conveniently published just before the USDA lowered the dietary recommendations of saturated fat for the first time in 20 years, from 10% to 7% of total calories.
Below is a section from the statement released by the European Heart Network in regards to their opinion of this meta-analysis, titled “European Heart Network position piece: Impact of saturated fat on cardiovascular disease obscured by over‐adjustment in recent meta‐analysis”
“However, the meta‐analysis (and an accompanying opinion piece by the same authors (4)) is compromised by a number of serious flaws and omissions. These are enumerated and discussed in detail in an editorial from Jeremiah Stamler (5). The most serious of these flaws is an over‐adjustment for serum cholesterol levels. The meta‐analysis involves data from 16 studies that evaluate the impact of saturated fat intake on CHD incidence or mortality, and 8 studies that evaluate the impact of saturated fat intake on stroke incidence or mortality. The authors state that ‘wherever possible, risk estimates from the most fully adjusted models were used in the estimation of the pooled [relative risks]’. It is well‐established that saturated fat intake is associated with increased level of serum cholesterol (6), and that serum cholesterol levels are associated with CHD and CVD (7). Therefore, serum cholesterol levels lie on the causal chain between saturated fat intake and CHD and CVD, and to adjust for serum cholesterol levels in a meta‐analysis will obscure the impact of saturated fat intake on these health outcomes. Yet 7 of the 16 studies included in the meta‐analysis of CHD events, and 4 of the 8 studies included in the meta‐analysis of stroke events were adjusted for serum cholesterol levels. These studies accounted for nearly half of all CHD and CVD events included in the meta‐analyses. Adjustment for serum cholesterol levels will inevitably bias the results of the meta‐analyses towards finding no association between dietary saturated fat intake and cardiovascular disease, but the authors do not mention this limitation in their article. As Jeremiah Stamler asserts in his editorial, what was actually found by the meta‐analysis was ‘a statistically non‐significant relation of SFA [saturated fat] to CHD… independent of other dietary lipids, serum lipids, and other covariates’ (5). A more appropriate and informative analysis would have included non‐adjusted associations between saturated fat and cardiovascular disease. An examination of the forest plots provided in the article shows that those cohort studies that did not adjust for serum cholesterol levels were more likely to find a positive association between saturated fat intake and cardiovascular disease, suggesting that a meta‐analysis of unadjusted data would likely produce positive results. “
References 5-7
(5) Stamler J. Diet‐heart: a problematic revisit. American Journal of Clinical Nutrition, 2010; 91: 497‐499.
(6) Clarke R, Frost C, Collins R, Appleby P, Peto R. Dietary lipids and blood cholesterol: quantitative meta‐analysis of metabolic ward studies. BMJ, 1997; 314: 112.
(7) Prospective Studies Collaboration. Blood cholesterol and vascular mortality by age, sex, and blood pressure: a meta‐analysis of individual data from 61 prospective studies with 55,000 vascular deaths. The Lancet, 2007; 370: 1829‐1839.
The full statement from the European Heart Network can be found here:
http://www.sydan.fi/lehtiarkisto/sydan_210/artikkelit/fi_FI/elainrasvat/_files/83538765767049682/default/EHN%20position%20piece%20-%20sats%20meta%20analysis.pdf
Below is a published study showing reversal of severe heart disease backed up with angiogram evidence.
http://www.heartattackproof.com/resolving_cade.htm