Reported by: Dr. Venkat S. Karra, Ph.D.
Coronary heart disease (CHD) is a condition caused by a build-up of fatty deposits on the inner walls of the blood vessels that supply the heart, causing the affected person to experience pain, usually on exertion (angina). A complete occlusion of the vessel by deposits causes a heart attack (myocardial infarction).
Lifestyle factors, such as diet (particularly one high in fat), contribute to causing CHD.
There are different types of fat, some of which are thought to increase risk of CHD, such as saturated fat, typically found in meat and dairy foods. However, others, such as unsaturated fats (polyunsaturated and monounsaturated fats) found in foods such as vegetable oils, fish, and nuts, may actually help prevent this condition.
Although there have been many studies investigating the role of different types of dietary fat in coronary heart disease, it is still not clear whether coronary heart disease can be prevented by changing the type of dietary fat consumed from saturated to unsaturated fats or by lowering all types of dietary fat. Furthermore, many of these studies have relied on participants recalling their dietary intake in questionnaires, which is an unreliable method for different fats.
So in this study, the researchers used an established UK cohort to measure the levels of different types of fatty acids in blood to investigate whether a diet high in saturated fatty acids and low in unsaturated fatty acids increases CHD risk.
These findings suggest that plasma concentrations of saturated fatty acids are associated with increased risk of CHD and that concentrations of omega-6 poly-unsaturated fatty acids are associated with decreased risk of CHD.
These findings are consistent with other studies and with current dietary advice for preventing CHD, which encourages substituting foods high in saturated fat with n-6 polyunsaturated fats. The results also suggest that different fatty acids may relate differently to CHD risk and that the overall balance between different fatty acids is important. However, there are limitations to this study, such as that factors other than diet (genetic differences in metabolism, for example) may cause changes to blood fatty acid levels so a major question is to identify what factors influence blood fatty acid concentrations.
Nevertheless, these findings suggest that individual fatty acids play a role in increasing or decreasing risks of CHD.
Related articles
- Revisiting the association between saturated fat intake and coronary heart disease (medicalxpress.com)
- Revisiting the association between saturated fat intake and coronary heart disease (eurekalert.org)
- Heart Healthy Essential Fatty Acids (jasoncroce.me)
- Why a low-fat diet might not be helping your heart… unless you eat ‘good fats’ as well (dailymail.co.uk)
- Are Dietary Saturated Fats Dangerous? (diabeticmediterraneandiet.com)
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I’m surprised at the emphasis of n-6 PUFAs without mention of n-3 PUFAs. n-6 PUFAs are readily available from meat sources, and they are tied to linoleic acid and arachidonic acid, considered proinflammatory. This means that a diet rich in good, tasty, well marbled beef rib fed with corn (wink), would promote diabetes or metabolic syndrome, a know risk factor for CHD. Linolenic acid is the essential FA and PUFA that is anti-inflammatory. It has a good source from salmon, tuna, ocean white fish, sardines, but not plant sources, except for Flax Seed. This may present a problem for strict vegans, although supplements are easily obtained. The ratio of n-3/n-6 is actually the most important measure of balance, and it was reported many years ago, when LC/MS was not advanced to where it is today.
There is still more to the story based on the studies of amino acid on metabolic pathways done by Vernon Young (deceased) and Yves Ingenbleek. Plant sourced amino acids are poor in sulfur and selenium compared with animal sources, which ties in with homocysteine, cystathionine, and Coenzyme A. That’s another story.
Interesting comment Larry! There is definitely more to the story. You are correct in emphasizing that the ratio of n-3/n-6 PUFA has been reported long back to contribute to the balance for good fatty acids in diet. Dr. Karra has also mentioned in his blog post that “…different fatty acids may relate differently to CHD risk and that the overall balance between different fatty acids is important.”
There was a lot of excitement regarding the benefits of n-6 fatty acids when the correlation of their beneficial effects on reducing cardiovascular diseases was discovered. Infact, the American Heart Association (AHA) started recommending n-6 PUFA intake that would account of upto 10% of dietary energy. However, the relevance of the ratio of the two PUFA has been in question in the past few years with the obvious recognition that the use of a ratio can disguise extremely low or very high intakes of n-6 and/or n-3 fatty acids. As discussed in an article by Deckelbaum et al, 2010 (http://journals.lww.com/co-clinicalnutrition/Fulltext/2010/03000/Dietary_n_3_and_n_6_fatty_acids__are_there__bad_.2.aspx), authors question “what should be included when considering using a ratio has also been questioned: linoleic acid to α-linolenic acid, total n-3 to total n-6 fatty acids, arachidonic acid to EPA or something else” and conclude “extremely low intakes of either might be harmful. We should encourage adequate intakes of both n-6 and n-3 fatty acids.”