In April 2024, the Mayo Clinic Proceedings, a peer-reviewed journal dating back nearly a century, published the study, “Circulating Docosahexaenoic Acid and Risk of All-Cause and Cause-Specific Mortality.” The study examined health data from 160,404 people in the United Kingdom and elsewhere who had data gathered on their health characteristics—and in the cases of 24,342 people, their causes of death—over periods averaging 14 years. The goal was to find the relationship between blood levels of the omega-3 fatty acid DHA and the risk of death from all causes. The study went a step further and correlated DHA blood levels against the likelihood of death caused specifically by cardiovascular disease, cancer, and other causes.
The study found that people who had the highest blood levels of DHA (greater than 2.48%), when compared against those with the lowest blood levels (lower than 1.47%), had a 17% lower risk of dying during the study.
On a more granular level, those with the highest DHA levels versus those with the lowest had a:
- 21% lower risk of death caused by cardiovascular disease,
- 17% lower risk of death caused by cancer, and
- 15% lower risk of death from other causes.
These significant findings are very exciting, but they are preliminary. This was not a clinical study in which researchers used DHA or other omega-3s to treat people with ailments. Below is a more detailed breakdown of how the study was conducted, and the takeaways.
Who were the participants in the DHA/risk of mortality study?
Most of the people included in the study (117,702 people) are participants in the United Kingdom Biobank Study (UKBB). The study began in 2006, and to date has enrolled more than 500,000 volunteers living in the United Kingdom. Volunteers range in age from 40 to 69 at time of enrollment, and agree to provide information on their lifestyles, nutritional and medical data, and blood and urine samples. Participants are being followed for 30 years or more, with information recorded on diseases, hospitalizations, and causes of death.
The goal is to create a database of information that researchers can utilize in research intended to “enable better understanding of the prevention, diagnosis, and treatment of a wide range of serious and life-threatening illnesses – including cancer, heart disease and stroke.”
As noted in the study, “On average, the UKBB participants were 57 years of age, nearly evenly split by biological sex (54% female), primarily Caucasian (94%) and were overweight.”
In addition to the UKBB participants, the study drew on freshly updated data from 42,702 individuals participating in 17 fatty-acid studies that were originally aggregated by the Fatty Acid and Outcome Research Consortium (FORCE) in a study published in Nature in 2021.
These two sets of data were pooled together, resulting in a total studied population of 160,404, of which 24,342 died during the approximately 14-year period they were studied.
What health data did the DHA/cause of death study examine?
The study took the 160,000+ people studied and divided them into five equal groups (“quintiles”). People were grouped according to the amount of DHA in their blood when they were first enrolled in their studies, as a percentage of their total fatty acids:
- Quintile 1. DHA range: < 1.47%; estimated omega-3 index: 3.75%
- Quintile 2. DHA range: 1.47% – 1.79%; estimated omega-3 index: 4.96%
- Quintile 3. DHA range: 1.79% – 2.08%; estimated omega-3 index: 5.86%
- Quintile 4. DHA range: 2.08% – 2.48%; estimated omega-3 index: 6.89%
- Quintile 5. DHA range: > 2.48%; estimated omega-3 index: 8.72%
The frequency of death in each quintile was then evaluated for deaths from all causes, and broken down by cause into cardiovascular disease, cancer, and “other mortality.” Quintile 1, the quintile with the lowest DHA levels, was established as the baseline for frequency of death, and then each quintile was evaluated in comparison to the baseline. Data was adjusted for relevant risk factors, such as age, sex, occupation, education, physical activity, smoking, high cholesterol (hyperlipidemia), high blood pressure (hypertension), etc., and it was noted that other unmeasured variables could have impacted the results.
What were the results of the DHA/cause of death study?
For every cause of death evaluated, those with the lowest DHA blood levels had the highest death rate. As noted at the beginning of this article, those with the highest DHA levels versus those with the lowest had a:
- 21% lower risk of death caused by cardiovascular disease,
- 17% lower risk of death caused by cancer, and
- 15% lower risk of death from other causes.
There was some variation in the trend of DHA levels versus mortality rate, but in general, the greater the DHA level, the lower the mortality rate.
What possible reasons did the study authors offer for the relationship between DHA levels and mortality?
The study’s authors put forward a few rationales for the relationship between higher DHA levels and lower death rates found in the study:
- Heart Health: The authors note that high levels of DHA and EPA can lower blood pressure and heart rate, and that lower blood pressure and heart rate are associated with reduced risk of cardiovascular disease and premature mortality.
- Nervous System: The authors point out that people with higher vagal tone—a measure of the activity of the vagus nerve, which regulates heart rate reduction, vessel dilation and constriction, glandular activity, and other processes—tend to have a lower risk of all-cause and cardiovascular mortality. According to the authors, omega-3 supplementation has been shown to improve vagal tone.
- Aging: The authors state that frailty and muscle loss “are strongly correlated with aging and mortality,” and that multiple studies have found that omega-3 supplementation (with both DHA and EPA) has a positive impact on muscle size and strength, and reduction of age-related muscle loss.
The study’s authors volunteered that these and other potential associations noted in the study could explain the “reduced risks for all-cause mortality, CVD mortality, and cancer mortality associated with high DHA blood levels” found in the study.
While more research is necessary, these findings imply the importance of omega-3 consumption through both diet and supplementation.
The study did make note of the frequency of fish oil supplement use, as reported by the participants, and found that those with greater DHA levels were more likely to use fish oil supplements:
- Quintile 1: 18.3% reported supplement use.
- Quintile 2: 23.8% reported supplement use.
- Quintile 3: 29.6% reported supplement use.
- Quintile 4: 37.9% reported supplement use.
- Quintile 5: 47.2% reported supplement use.
This highlights the necessity of making omega-3 nutrition more accessible and appealing through every means possible, particularly for those who can’t or prefer not to incorporate fish or marine omega-3 supplements into their diets. Developing Nutriterra DHA Omega-3 Canola, the first plant-based source of complete omega-3 nutrition, creates a new source of omega-3 nutrition for the many people who aren’t consuming the 8 or more ounces of fish per week recommended by the Dietary Guidelines for Americans, which delivers roughly 250mg per day of DHA plus EPA, supporting overall health.
We are deeply grateful to the authors of this and other recent studies who have sought to define and measure the potential health benefits of DHA and other omega-3 fatty acids. We look forward to reading and sharing the results of future studies.