Contrasting DHA studies spark debate on omega 3 supplementation benefits

18 May 2021 --- The debate over omega 3’s health benefits has been reignited by new research from the Intermountain Healthcare Heart Institute (IHHI) in Salt Lake City, US. 

It found higher EPA blood levels alone lowered the risk of major cardiac events and death in patients, but DHA blunted the cardiovascular benefits of EPA. Higher DHA levels at any level of EPA worsened health outcomes.

“Based on these and other findings, we can still tell our patients to eat omega 3 rich foods, but we should not be recommending them in pill form as supplements or even as EPA and DHA-combined prescription products,” says the study’s principal investigator Viet Le, IHHI cardiovascular physician assistant.

Simultaneously, however, a study published in Lancet stresses early preterm births may be “dramatically decreased” with DHA supplements. 

A dose of 1000 mg was more effective for pregnant women with low DHA levels than the 200 mg found in some prenatal supplements.

“The dramatic decrease in early preterm birth with DHA supplementation will improve short- and long-term outcomes for children, families and society in a cost-effective fashion,” says co-author Dr. Carl Weiner, professor of obstetrics and gynecology at the University of Kansas School of Medicine. 

Doctors often recommend omega 3s to help patients lower their cholesterol and improve heart health. Omega 3s raise concerns
The IHHI study was presented this week at the 2021 American College of Cardiology’s Scientific Session. Researchers identified 987 patients who underwent their first documented coronary angiographic study at Intermountain Healthcare between 1994 and 2012. 

They then tracked those patients for ten years, looking for major cardiac adverse events, including heart attack, stroke, heart failure requiring hospitalization or death. 

The researchers found patients with the highest levels of EPA had a reduced risk of major heart events. When evaluating how EPA and DHA affect one another, they found that higher DHA blunts the benefit of EPA. In particular, they also found that those patients with higher levels of DHA than EPA were more at risk for heart problems.

“Our findings show that not all omega 3s are alike. EPA and DHA combined together, as they often are in supplements, may void the benefits that patients and their doctors hope to achieve,” says Le.

A study from late last year also suggested EPA and DHA play separate roles in conveying health benefits.

DHA beneficial for pregnant patients
In the US study on DHA, women who received the higher dose had fewer early preterm births overall. However, participants with low DHA levels at enrollment had half the rate of premature preterm birth – 2 percent compared to 4.1 percent – when they were given a supplement of 1000 mg compared with those given a 200 mg supplement during the last half of pregnancy. 

For women who began the study with high DHA levels, many of whom were already taking prenatal DHA, the rate of early preterm birth was 1.3 percent and there was no benefit of the higher dose.

“We knew from our previous work that US women eat very little food sources of DHA. We thought a higher dose might be needed to boost intake,” says co-lead study author Dr. Christina Valentine, neonatologist and RD at the University of Cincinnati.

The IHHI study found higher DHA levels in patients blunts EPA’s ability to reduce the risk of major heart events.Because preterm birth is associated with negative outcomes and high healthcare costs, having an option for women to prevent preterm birth reliably and inexpensively is significant, the study supports.

Previous findings 
The omega 3 sector is in the mature industry growth phase, meaning omega 3 supplements have become a household name in infant nutrition, cognition and heart health.

The debate on the safety and efficacy of omega 3s, however, is not new. 

A study just last month revealed an association between omega 3 supplements and an increased likelihood of developing atrial fibrillation. Industry experts emphasized the safety of omega 3 supplements to NutritionInsight, arguing that the benefits outweigh the risks.

Le from the IHHI study states omega 3 advice for heart health is “pervasive,” but previous studies “don’t back this up for every single omega 3.”

The Lancet-published study encourages pregnant US women to take DHA supplements to prevent early preterm births.At last year’s American Heart Association’s Scientific Sessions, several omega 3 studies casted doubt on the ingredient’s potential in supporting heart health. For example, fish oil-based medication, known as omega 3 carboxylic acids, did not decrease the risk of cardiac events compared to a placebo.

At the 2019 American Heart Association’s Scientific Sessions, two studies further shed light on omega 3 supplementation uncertainties. In one paper, researchers found no link between higher omega 3 levels and an increased risk of prostate cancer. Another found a link between higher plasma omega 3 levels and severe heart disease.

Le was also involved in both aforementioned 2019 studies. 

At the time, he stated: “While a seeming association between higher plasma omega 3 levels and the findings of severe heart disease upon initial angiogram might raise alarms that omega 3 isn’t beneficial, the patients did live to see a doctor and get diagnosed.”

By Anni Schleicher