Which Omega 3 oils are best – DHA is Better than EPA at Reducing Inflammation

DHA and EPA are long-chain omega-3 fatty acids that are well known for their health benefits.

Both are found in fatty fish, as well as fish oil supplements. Most research has examined their combined health effects, but few studies have compared them.

Recently, a large Canadian study compared the effects of DHA and EPA on inflammatory markers and blood lipids.

Here is a detailed summary of its findings.

Plant And Animal Sources Of Omega 3 Fatty Acids

Background

Many scientists believe that chronic, low-grade inflammation is a key factor in the development of lifestyle diseases, such as heart disease (12).

Several unhealthy lifestyle habits contribute to inflammation. One of them is the excessive consumption of omega-6 oils, relative to omega-3.

Excessive omega-6 intake is a consequence of the modern, processed diet. If you eat a lot of processed food and vegetable oils — mainly soybean, sunflower or corn oil — you are almost certainly getting too much omega-6.

Unlike omega-6, long-chain omega-3 fats are anti-inflammatory. There are two main types of long-chain omega-3 fats (34):

  • Eicosapentaenoic acid (EPA)
  • Docosahexaenoic acid (DHA)

Both EPA and DHA are found in seafood, fatty fish, fish oil and certain types of marine microalgae.

The body can also produce them from alpha-linolenic acid (ALA), which is found in many plant oils. However, the conversion of ALA to EPA and DHA is inefficient. It’s best to get EPA and DHA from your diet or supplements, rather than relying on ALA.

Few studies have compared the anti-inflammatory potential of EPA and DHA. Most have investigated mixtures of EPA and DHA or included only one of them (4).

Some studies suggest that DHA may be more effective at improving the blood lipid profile, but little is known about their individual effects on inflammation (5).

Article Reviewed

This study compared the effects of EPA or DHA supplementation on inflammatory markers and blood lipids.

Randomized, crossover, head-to-head comparison of EPA and DHA supplementation to reduce inflammation markers in men and women: the Comparing EPA to DHA Study.

Study Design

This was a double-blind, randomized controlled trial examining the effects of supplementing with EPA or DHA on markers of inflammation in healthy men and women.

The study recruited 48 men and 106 women with abdominal obesity and low-grade chronic inflammation.

They were randomly assigned to three groups:

  • EPA: This group took three 1-gram capsules, providing a total of 2.7 grams of eicosapentaenoic acid (EPA) every day for 10 weeks.
  • DHA: This group took three 1-gram capsules, providing a total of 2.7 grams of decahexaenoic acid (DHA) every day for 10 weeks.
  • Control: This group took three 1-gram capsules, providing a total of 3 grams of corn oil every day for 10 weeks. Corn oil is rich in omega-6 but contains very low amounts of omega-3.

The study had a crossover design, which means that the participants were assigned to all three treatments in a random order. Each treatment period was separated by a 9-week washout period.

During the study, the participants were asked to exclude all major sources of omega-3 from their diet.

At the start and end of each study period, the researchers measured the following:

  • Inflammatory markers: C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-18 (IL-18) and adiponectin.
  • Blood lipids: Triglycerides, total cholesterol, HDL-cholesterol and apolipoprotein B (apoB). LDL-cholesterol was calculated using the Friedewald equation.

Bottom Line: This was a randomized controlled trial comparing the effects of the omega-3 fats DHA and EPA on inflammatory markers and blood lipids.

Finding 1: DHA Reduced Inflammation More Than EPA

Supplementing with DHA caused a significantly greater reduction in inflammatory markers than EPA.

Specifically, DHA and EPA supplementation had the following effects, compared to the control (corn oil):

  • Interleukin-18 (IL-18): -7.0% with DHA, while EPA had no significant effects.
  • Interleukin-6 (IL-6): -12.0% with DHA and -13.4% with EPA.
  • Tumor necrosis factor-α (TNF-α): -14.8% with DHA, but EPA had no effects.
  • C-reactive protein (CRP): -7.9% with DHA, while EPA had no significant effects.
  • Adiponectin (AN): +3.1% with DHA, while EPA had no significant effects.

These findings are presented in the charts below:

IL 18

CRP IL6 TNF AN

Three previous trials have compared the effects of supplementing with DHA or EPA on inflammatory markers. Supplementing with EPA or DHA did not affect any inflammatory markers (678).

However, those studies recruited only 25 or fewer participants for each group and had far less statistical power than the present study.

Bottom Line: Supplementing with DHA had a stronger anti-inflammatory effect than EPA.

Finding 2: DHA Improved the Blood Lipid Profile More Than EPA

Supplementing with DHA improved the blood lipid profile more than supplementing with EPA.

Specifically, DHA and EPA supplementation had the following effects, compared to control (corn oil):

  • Triglycerides (TG): -13.3% with DHA and -11.9% with EPA.
  • Total cholesterol (TC): +3.8% with DHA, while EPA had no significant effects.
  • HDL-cholesterol (HDL-C): +7.6% with DHA, while EPA had no effects.
  • LDL-cholesterol (LDL-C): +6.9% with DHA and +2.2% with EPA. DHA had a stronger effect on LDL-cholesterol in men (+12.5%), compared to women (+4.4%).
  • Apolipoprotein B (apoB): +4.5 with DHA, but EPA had no significant effects.
  • Cholesterol to HDL-cholesterol ratio (TC:HDL-C): -2.5% with DHA, but EPA had no significant effects.

These findings are presented in the chart below:

TG TC HDL LDL APOB TCHDL

The results are consistent with the findings of a previous meta-analysis showing that supplementing with DHA leads to a greater decrease in triglycerides and greater increases in LDL and HDL-cholesterol, compared to EPA (5).

DHA supplementation led to changes in triglycerides, apoB and LDL-cholesterol, which may suggest an increase in LDL particle size (a good change). However, future studies are needed to confirm this finding using proper measurements.

Bottom Line: Supplementing with DHA had greater effects on blood lipids than EPA. These changes appeared beneficial.

Limitations

The study had an excellent design and few methodological issues. However, the authors pointed out some minor limitations.

Circulating levels of DHA and EPA weren’t measured at the beginning of each study period. For this reason, it is unclear if the washout between treatment periods was long enough to eliminate all effects from the previous treatment period.

However, the levels of blood lipids and inflammatory markers were similar at the start of each of the periods, indicating that there were no residual effects from the previous treatment period.

Summary and Real-Life Application

In short, supplementing with 2.7 grams of DHA for 10 weeks was more effective than a similar dose of EPA at decreasing markers of chronic inflammation and improving the blood lipid profile in men and women with excessive belly fat.

However, more research is needed before we can claim that DHA is healthier than EPA. In fact, a recent study concluded that EPA may have greater benefits when it comes to heart disease prevention (9).

For the time being, it may be best to eat fatty fish, which provides both DHA and EPA, or choose mixed long-chain omega-3 supplements.