Judging by the outcomes of many clinical trials, the benefits of fish oil to heart health present an obvious exception to the “whole foods rule” principle.
No doubt, this is because omega-3 fatty acids provide most of the heart benefits associated with fish.
Still, to us and many researchers, fatty fish remains the preferred source of omega-3s … if you eat fatty fish at least twice a week.
This is because fatty fish provides other beneficial nutrients, such as selenium, vitamin D, and—only in wild salmon—the highly healthful orange pigment called astaxanthin.
A common omega-3 misconception
With regard to heart health, we commonly see claims that the omega-3 called EPA is more important than DHA ... its companion omega-3 in fish fat.
The makers of standard, chemically refined fish oils sometimes alter the proportions of EPA and DHA in their supplements to raise their supplements' EPA content.
But there's no good evidence that chemically altering the proportions of EPA and DHA in fish oil supplements actually enhances their heart-health effects.
(We never chemically refine or manipulate our naturally pure, “virgin” Wild Alaskan Sockeye Salmon Oil … which is exactly why some leading omega-3 researchers choose to it for their own use.)
A careful search of the biomedical literature undermines assertions that EPA is more important to heart health, with DHA and EPA appearing to offer distinct (and overlapping) benefits with regard to cardiovascular risk factors and outcomes.
In fact, the available evidence suggests that the two omega-3s work synergistically to reduce cardiovascular risks, via unique and shared effects.
Heart muscle accumulates more DHA than EPA, and these two omega-3s appear to exert different effects on blood stickiness, blood fat profiles, and artery health (e.g., arterial flexibility and inflammation status).
For example, in an Australian study of diabetic patients, supplemental DHA—but not EPA—significantly reduced platelet aggregation (blood stickiness) … a major predictor and sign of cardiovascular disease (Woodman RJ et al. 2003).
And the same Aussie team found that DHA beat EPA when it came to enhancing artery health and reducing the closely associated risk of hypertension (Mori TA, Bao DQ, Burke V et al. 1999; Mori TA, Watts GF, Burke V et al. 2000).
When it comes to lowering triglyceride and oxidative stress levels, DHA and EPA exert similar beneficial effects (Mori TA, Burke V, Puddey IB et al. 2000; Mori TA, Woodman RJ, Burke V et al. 2003)
It's important to note the human body can convert DHA to EPA, but cannot convert EPA to DHA.
In this sense—and because DHA is far more important to brain, nerve, and eye health—it is always more important to ensure adequate intake of DHA … but for heart health, it's ideal to get both, as we shall see.
(Humans can make DHA—hence EPA as well—from the plant-source omega-3 called ALA. But this is a very inefficient process that's impaired by diets high in omega-6 fatty acids from vegetable oils … such as the standard American diet.)
Now, the results of two separate studies strengthen the idea that both of the two omega-3s in whole fish and fish oil—EPA and DHA—are needed for optimal heart health.
Only DHA was linked to men's artery health
A measure of artery-wall thickness called “carotid intima-media thickness” (CIMT) is linked to the presence and severity of atherosclerosis and the risk of cardiovascular disease.
A study in Spanish adults with unhealthful blood profiles (dyslipidemia) linked higher blood DHA levels to reduced CIMT (Sala-Vila A et al. 2010).
That finding was just confirmed by an “observational” study involving 310 middle-aged Japanese men and 298 U.S. caucasian men, all aged 40 to 49 and free of cardiovascular disease, but with some risk factors for CVD (Sekikawa A et al. 2011).
A team of researchers from Japanese and American universities compared the men's CIMT values (thickness measurements) to blood levels of EPA and DHA, and other CVD risk factors.
The results showed that in both groups, higher DHA blood levels—but not higher EPA levels—were linked to lower (healthier) CIMT values.
Having higher blood levels of the plant-source omega-3 called ALA was also linked to lower (healthier) CIMT values … but only in the US group, presumably because their EPA+DHA levels were so much lower than the Japanese levels, allowing dietary ALA to exert a more noticeable effect in the Americans.
Significantly, in this analysis, blood levels of DHA proved a reliable predictor of a man's CIMT values. That is, higher DHA levels were linked to having lower (healthier) CIMT values.
The analysis also linked higher total omega-3 (EPA+DHA) blood levels to healthier (lower) CIMT values … but this association only appeared in the Japanese men, who had less atherosclerosis and double the omega-3 levels, compared with their US counterparts
Only EPA was linked to reduced risk of congestive heart failure
As we've said, DHA is linked to lower risk of key heart disease risk factors … but a new study finds that it doesn't seem to reduce the risk of congestive heart failure.
In congestive heart failure (CHF), the heart is unable to pump sufficient blood … a condition that can develop from coronary artery disease, high blood pressure, obesity, or diabetes.
According to the American Heart Association, one in five people develop CHF after the age of 40, and about half will die within five years.
Harvard researchers recently compared the fatty acid content of blood in people with CHF to that of people who didn't develop heart failure, in a study involving 2,735 men and women who were followed for up to 14 years.
After seven years of follow-up, higher levels of EPA were linked to a significantly lower risk of CHF, with the risk being cut by about half in those with the highest EPA levels.
Smaller risk reductions were seen in those with the highest blood levels of DPA, and total long-chain omega-3s (EPA+DHA+DPA).
(DPA is a lesser known omega-3 that occurs at much lower levels in fish fat, compared with EPA and DHA. The body uses DPA to make DHA … or omega-6 fatty acids, if needed, which is rare among Americans. DPA's role in health is just beginning to be explored, with exciting indications already appearing.)
In contrast, higher blood levels of DHA were not associated with a lower risk of CHF.
Nor was higher fish intake linked to lower CHF risk. This is not too surprising, since term "fish" was not defined, so it included lean and fatty fish, which have low and high levels of total omega-3s, respectively.
Further, each seafood species has a different ratio of EPA to DHA ... though most fish and fish oil supplements (including our salmon oil) have more EPA than DHA.
The outcomes of these two studies bolster the growing evidence that both DHA and EPA are needed to maximally reduce the risk of cardiovascular disease ... which usually precedes development of heart failure.
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