Of the two omega-3 fatty acids that are best explored, EPA and DHA, it is likely DHA that exerts the most blood pressure- and heart rate-reducing effects. Here are the data of Mori et al in which 4000 mg of olive oil, purified EPA only, or purified DHA only were administered over 6 weeks:
In this group of 56 overweight men with normal starting blood pressures, only DHA reduced systolic BP by 5.8 mmHg, diastolic by 3.3 mmHg.
While each omega-3 fatty acid has important effects, it may be DHA that has an outsized benefit. So how can you get more DHA? Well, this observation from Schuchardt et al is important:
DHA in the triglyceride and phospholipid forms are 3-fold better absorbed, as compared to the ethyl ester form (compared by area-under-the-curve). In other words, fish oil that has been reconstituted to the naturally-occurring triglyceride form (i.e., the form found in fresh fish) provides 3-fold greater blood levels of DHA than the more common ethyl ester form found in most capsules. (The phospholipid form of DHA found in krill is also well-absorbed, but occurs in such small quantities that it is not a practical means of obtaining omega-3 fatty acids, putting aside the astaxanthin issue.)
So if the superior health effects of DHA are desired in a form that is absorbed, the ideal way to do this is either to eat fish or to supplement fish oil in the triglyceride, not ethyl ester, form. The most common and popular forms of fish oil sold are ethyl esters, including Sam’s Club Triple-Strength, Costco, Nature Made, Nature’s Bounty, as well as prescription Lovaza. (That’s right: prescription fish oil, from this and several other perspectives, is an inferior product.)
What sources of triglyceride fish oil with greater DHA content/absorption are available to us? My favorites are, in this order:
CEO and founder, Marc St. Onge, is a friend. Having visited his production facility in Nova Scotia, I was impressed with the meticulous methods of preparation. At every step of the way, every effort was made to limit any potential oxidation, including packaging in a vacuum environment. The Ascenta line of triglyceride fish oils are also richer in DHA content. Their NutraSea High DHA liquid, for instance, contains 500 mg EPA and 1000 mg DHA per teaspoon, a 1:2 EPA:DHA ratio, rather than the more typical 3:2 EPA:DHA ratio of ethyl ester forms.
Pharmax (now Seroyal) also has a fine product with a 1.4:1 EPA:DHA ratio.
Nordic Naturals has a fine liquid triglyceride product, though it is 2:1 EPA:DHA.