Recent studies show that taking supplements to increase vitamin D and omega-3 levels may not reduce systemic inflammation.

The new research, which drew from the VITAL study, aimed to determine the biomarker levels of several inflammation indicators in people either taking or not taking vitamin D and omega-3 fatty acid supplements, or fish oil.

After 1 year, the study found no marked difference in levels between the two groups.

Dr. Karen Costenbader — the director of the Lupus Program in the Division of Rheumatology, Inflammation, and Immunity at the Brigham and Women's Hospital in Boston, MA — is the corresponding author of the study.

The results now appear in the journal Clinical Chemistry.

Why are markers of inflammation important?

Inflammation is a key prognostic marker of several life threatening conditions — especially those associated with aging and obesity.

These include cardiovascular disease, heart failure, osteoporosis, some neurodegenerative conditions (including Alzheimer's disease), diabetes, and some cancers.

Many people use vitamin D supplements and fish oil to reduce systemic inflammation and help prevent the onset of such conditions.

However, the researchers behind the new study found that neither vitamin D nor fish oil can reduce systemic inflammation, and in some cases, inflammation markers were actually higher in people taking these supplements than in those not taking them.

Dr. Costenbader and team looked at interleukin 6 (IL-6), tumor necrosis factor-receptor 2 (TNFR2), and high sensitivity C-reactive protein (hsCRP).

Individually, these markers have pivotal roles in the onset of inflammation. Being able to detect increased levels of these markers in the blood can be a prognostic tool to inform healthcare professionals about a person's levels of inflammation.

What was the purpose of the study?

Many people take vitamin D and fish oil supplements believing that they can help reduce inflammation. However, healthcare professionals may find it difficult to determine how to advise their patients about which supplements to take, and which dosages may be best.

This is because there is a lack of clinical trial data to inform treatment. The VITAL study aimed to provide the clinical data necessary to help healthcare professionals better inform their patients.

The ongoing VITAL study is a randomized, double-blind, placebo-controlled trial in which researchers investigate the effects of vitamin D, omega-3, or both on the levels of IL-6, TNFR2, and hsCRP in the blood.

For this research, the participants took 2,000 international units of vitamin D, 1 gram of omega-3, or both per day. Some received a placebo instead.

The scientists took an initial measurement at the beginning of the trial, which they compared with measurements they took a year later.

In the future, this trial will also investigate the effects of supplementation on the risks of cardiovascular disease and cancer.

What did the study find?

The results revealed that after 1 year of taking these supplements, blood levels of one type of vitamin D (25-OH) and one type of omega-3 (n-3 FA) were 39% and 55% higher in those taking the supplements, respectively, compared with those taking a placebo, in whom changes were minimal.

This suggests that the participants' bodies were successfully absorbing the supplements.

Surprisingly, in those taking vitamin D supplements, levels of IL-6 were 8.2% higher.

Levels of hsCRP were 35.7% higher in people with lower baseline vitamin D, suggesting that those who take supplements because they have low vitamin D levels may actually be increasing their levels of this particular inflammatory marker.

Also, among those receiving omega-3, the levels of hsCRP did decline in those with lower baseline n-3 FA, but not in those with higher fish oil intake.

Conclusively, over 1 year of the study, neither supplement decreased the levels of biomarkers of inflammation.

"While the bottom line is that we didn't see a reduction in markers of inflammation for those who took either supplement, we did see that people whose fish [oil] intake was low at baseline had a reduction in one of the biomarkers of inflammation." Dr. Karen Costenbader

"It will be interesting and important to see the results of future VITAL analyses, especially those that look at risk of diseases rather than biomarkers."

Although these results seem to suggest no clinical benefit of taking supplementation to reduce systemic inflammation, there were a number of limitations to the trial.

For example, the cohort was a small snapshot of the initial recruits; the team tested only 1,500 of a potential 25,000. Had the cohort been larger, the results may have been clearer.

In addition, they only tested one form of vitamin D and one form of omega-3. Other formulations of these supplements could be more effective at decreasing systemic inflammation.

For these reasons, further investigation is necessary.