Heart health depends on artery health; new research illuminates the important protective role played by omega-3s
by Craig Weatherby
Last June, we reported on research that expanded our understanding of why diets high in omega-3s have been linked to reduced rates of stroke, second heart attack, and sudden cardiac death.
The heart benefits of omega-3s have been attributed to two major factors: reduced triglyceride levels and reduced risk of arrhythmia's.
But the research we covered last summer added key, inflammation-related explanations for the documented heart benefits of omega-3s. (See “Omega-3 Findings Point to Greater Cardiovascular Potential”).
Those findings were preceded by other intriguing indications of how omega-3s from fish help support artery health, which we summarized in “Omega-3s Ease Artery-Stiffening Impacts of Fatty Meals” and “DHA Helps Heal Arteries in High-Cholesterol Kids”.
Now, innovative research into the condition of people’s arteries reveals even more about the ways in which omega-3s enhance vascular health… hence cardiovascular health as well.
Clinical tests reveal link between omega-3s and better artery health
The results of the new study come from the National Heart, Lung, and Blood Institute and the medical schools of eight top academic institutions: Wake Forest University, Northwestern University, Columbia University, Johns Hopkins University, and the state universities of North Carolina, Vermont, Minnesota, and Washington.
Their goal was to fill a big hole in the medical literature.
As the authors wrote, researchers have known very little about the relationships between people’s intake of fish and omega-3s and the presence of early clinical signs of atherosclerosis.
(For a quick primer on atherosclerosis and its relationship to heart disease, see “What is “Heart Disease”, Exactly?”.)
The nationwide team recruited 5,488 adults aged 45 to 84 from various ethnic groups, who were free of cardiovascular disease.
The volunteers recorded their diets – including their intakes of different types of fish meals (fried, broiled, steamed, baked, or raw) – via questionnaires.
What makes this study so unusual and significant is that the participants also underwent standard tests designed to detect early, so-called “sub-clinical signs” of developing atherosclerosis.
Sub-clinical signs are internal markers that appear in the absence of any outward signs of disease.
The key step in the study was to compare the participants’ diets to four standard measures of atherosclerosis:
- Common carotid intima–media thickness (cCIMT)
- Internal CIMT (iCIMT)
- Coronary artery calcium score (CAC)
- Ankle-brachial index (ABI)
After being adjusted to account for potential confounding factors, the test results proved encouraging.
Findings make fish (except fried) look good
The results from three tests (iCIMT, CAC, and ABI) did not show any diet-related differences among the volunteers.
But, compared to the participants with the lowest estimated intakes of omega-3s, the volunteers with the highest estimated omega-3 intakes were 31 percent less likely to show signs of sub-clinical atherosclerosis as determined by cCIMT.
This outcome is highly significant, because cCIMT is the test most commonly used to determine the effectiveness of statins and other cardiovascular drugs intended to reduce atherosclerosis.
Those with the highest intake of non-fried fish were 20 percent less likely to show signs of sub-clinical atherosclerosis as determined by cCIMT.
Finally, the volunteers with the highest intake of fried fish were 10 percent less likely to show signs of sub-clinical atherosclerosis as determined by cCIMT.
In other words, people who reported eating fried fish were only half as likely to enjoy healthy cCIMT scores, compared with people who reported eating non-fried fish.
And people who reported eating fried fish were only one-third as likely to enjoy healthy cCIMT scores, compared with people with the highest estimated omega-3 intake.
The authors’ conclusion was clear: “This study indicates that the dietary intake of long-chain [omega-3s] or non-fried fish is associated with a lower prevalence of sub-clinical atherosclerosis classified by cCIMT...”
And they noted an important caveat: “Our findings also suggest that the association of fish and atherosclerosis may vary depending on the type of fish meal consumed and the measures of atherosclerosis.”
The superior health impact of non-fried fish compared with fried fish almost certainly stemmed from the presence in fried fish batter of loads of pro-inflammatory omega-6 fatty acids, which compete with omega-3s for placement in cell membranes.
Omega-6 fats predominate in common frying oils – soy, cottonseed, corn, safflower, sunflower, and soy – which contain virtually no omega-3s. This is actually necessary, because omega-3s get badly damaged by the high temperatures used for deep-frying foods.
In fact, diets high in fried fish actually raise the risk of stroke.
For more on the unhealthful effects of diets high in omega-6s, see “Omega-6/Omega-3 Imbalance Pushes Heart/Diabetes Perils”, “Stroke: An Update on Fish and other Factors”, “Report Finds Americans Need More Omega-3s and Less Omega-6s”, and “Farmed Salmon's Diet Yields Unhealthful Cardiovascular Effects”.
- He K, Liu K, Daviglus ML, Mayer-Davis E, Jenny NS, Jiang R, Ouyang P, Steffen LM, Siscovick D, Wu C, Barr RG, Tsai M, Burke GL. Intakes of long-chain n-3 polyunsaturated fatty acids and fish in relation to measurements of subclinical atherosclerosis. Am J Clin Nutr. 2008 Oct;88(4):1111-8.
- Mozaffarian D, Lemaitre RN, Kuller LH, Burke GL, Tracy RP, Siscovick DS; Cardiovascular Health Study. Cardiac benefits of fish consumption may depend on the type of fish meal consumed: the Cardiovascular Health Study. Circulation. 2003 Mar 18;107(10):1372-7.